title: Stephen Harper

text: Under Harper, the annual budget of Veterans Affairs Canada increased from $2.85 billion in 2005–2006 to $3.55 billion in 2014–2015, while the quantity of veterans served has declined from 219,152 in 2008–2009 to 199,154 in 2015. Nine Veterans Affairs offices were closed between 2012 and 2015, and 900 positions were phased out from the department since 2009. Former-minister of veterans affairs Erin O'Toole stated that the closures were made to modernize the department, by moving services online and to Service Canada locations. In 2006, Harper implemented the New Veterans Charter passed with all party support by the previous Liberal government. This charter gave veterans the option to select a lump-sum payment, an annual installment over the number of years of a Veteran's choosing, or a combination of these two payment options. Under Harper, the Canadian government spent $700,000 fighting a class-action lawsuit brought by a group of wounded Afghan veterans who argued that the new charter was discriminatory.


title: Stephen Harper

text: During his term, Harper dealt with many foreign policy issues relating to the United States, the War on Terror, the Arab–Israeli conflict, free trade, China, and Africa.


title: Stephen Harper

text: In 2009, Harper visited China. During the visit Chinese Premier Wen Jiabao publicly scolded Harper for not visiting earlier, pointing out that "this is the first meeting between the Chinese premier and a Canadian prime minister in almost five years"; Harper in response said that, "it's almost been five years since we had yourself or President Hu in our country." In 2008, former-prime minister Jean Chrétien had criticized Harper for missing opening ceremonies for the 2008 Summer Olympics in Beijing; in response, Dimitri Soudas, a spokesperson for Harper, called the remarks hypocritical, pointing out that Chrétien "attended one of six Olympic opening ceremonies during his 13 years as prime minister".


title: Stephen Harper

text: During mid-2015, Harper repeatedly voiced his opinion that Russia should be excluded from association with the G7 group of nations because of Russia's support for Russian-speaking Ukrainian dissidents. On June 8, Harper said,"Mr. Putin ... has no place at the [G7] table, and I don't believe there's any leader who would defend Mr. Putin having a place."


title: Stephen Harper

text: Michael Ignatieff criticized Harper for cutting foreign aid to Africa by $700 million, falling short of the UN Millennium Development Goals, and cutting eight African countries from the list of priority aid recipients.


title: Stephen Harper

text: On March 11 and 12, 2006, Harper made a surprise trip to Afghanistan, where Canadian Forces personnel had been deployed as part of the NATO-led International Security Assistance Force since late 2001, to visit troops in theatre as a show of support for their efforts, and as a demonstration of the government's commitment to reconstruction and stability in the region. Harper's choice of a first foreign visit was closely guarded from the press until his arrival in Afghanistan (citing security concerns), and is seen as marking a significant change in relationship between the government and the military. Harper returned to Afghanistan on May 22, 2007, in a surprise two-day visit which included visiting Canadian troops at the forward operating base at Ma'Sum Ghar, located south of Kandahar, making Harper the first prime minister to have visited the front lines of a combat operation.


title: Stephen Harper

text: Harper has shown admiration for Israel since the early 1990s. Friends and colleagues describe his views as being the product of thinking and reading deeply about the Middle East. Toronto rabbi Philip Scheim, who accompanied Harper to Israel in 2014 said, "I sense that [Harper] sees Israel as a manifestation of justice and a righting of historical wrongs, especially in light of the Holocaust."


title: Stephen Harper

text: At the outset of the 2006 Israel–Lebanon conflict, Harper defended Israel's "right to defend itself" and described its military campaign in Lebanon as a "measured" response, arguing that Hezbollah's release of kidnapped Israel Defense Force (IDF) soldiers would be the key to ending the conflict. Speaking of the situation in both Lebanon and Gaza on July 18, Harper said he wanted "not just a ceasefire, but a resolution" but such a thing would not happen until Hezbollah and Hamas recognize Israel's right to exist. Harper blamed Hezbollah for all the civilian deaths. He asserted that Hezbollah's objective is to destroy Israel through violence.


title: Stephen Harper

text: The media noted that Harper did not allow reporters opportunities to ask him questions on his position. Some Canadians, including many Arab and Lebanese Canadians, criticized Harper's description of Israel's response.


title: Stephen Harper

text: In December 2008, the Conference of Presidents of Major American Jewish Organizations recognized Harper's support for Israel with its inaugural International Leadership Award, pointing out Harper's decision to boycott the Durban II anti-racism conference, and his government's "support for Israel and [its] efforts at the U.N. against incitement and... the delegitimization of Israel".


title: Stephen Harper

text: In March 2009, Harper spoke at a Parliament Hill ceremony organized by Chabad-Lubavitch to honour the Jewish victims of the 2008 Mumbai attacks, which included an attack on the Nariman House. He expressed condolences over the murder at Chabad's Mumbai centre of Rabbi Gavriel Holtzberg and his wife Rivka. Harper described the killings as "affronts to the values that unite all civilized people". Harper added that the quick instalment of a new rabbi at the Chabad centre in Mumbai as a signal that the Jewish people will "never bow to violence and hatred".


title: Stephen Harper

text: In 2010, Canada lost a bid for a seat on the UN Security Council. While initially blaming the loss on his rival Ignatieff, Harper later said that it was due to his pro-Israeli stance. Harper then said that he would take a pro-Israeli stance, no matter what the political cost to Canada. Ignatieff criticized Harper's stance as a "mistake", saying Canada would be better able to defend Israel through the Security Council than from the sidelines and pointed out that it is the Security Council that will determine if sanctions are imposed on Iran. Ignatieff also accused Harper of steering the discussion away from implementing the two-state solution, and instead of rendering all discussion into a competition "about who is Israel's best friend".


title: Stephen Harper

text: Harper backed Israel's 2014 war in Gaza and condemned Hamas. Harper said, "It is evident that Hamas is deliberately using human shields to further terror in the region."


title: Stephen Harper

text: On June 7, 2007, the Conservative government announced it had finalized free trade negotiations with the European Free Trade Association (EFTA). Under this agreement, Canada increased its trade ties with Iceland, Norway, Switzerland and Liechtenstein. In 2006, the value of trade between these partners was $10.7 billion. Canada had originally begun negotiations with the EFTA on October 9, 1998, but talks broke down because of a disagreement over subsidies to shipyards in Atlantic Canada.


title: Stephen Harper

text: Shortly after being congratulated by George W. Bush for his victory, Harper rebuked US Ambassador David Wilkins for criticizing the Conservatives' plans to assert Canada's sovereignty over the Arctic Ocean waters with armed forces. Harper's first meeting as prime minister with the US president occurred at the end of March 2006.


title: Stephen Harper

text: The government received American news coverage during the Democratic Party's 2008 presidential primaries after the details of a conversation between Barack Obama's economic advisor Austan Goolsbee, and Canadian diplomat Georges Rioux were revealed. Reportedly Goolsbee was reassuring the Canadians that Obama's comments on potentially renegotiating the North American Free Trade Agreement (NAFTA) were more political rhetoric than actual policy. The accuracy of these reports has been debated by both the Obama campaign and the Canadian government. The news came at a key time nearing the Ohio and Texas primaries, where perceptions among Democratic voters was (and is) that the benefits of the NAFTA agreement are dubious. Thus the appearance that Obama was not being completely forthright was attacked by his opponent Hillary Clinton.


title: Stephen Harper

text: ABC News reported that Harper's chief of staff, Ian Brodie was responsible for the details reaching the hands of the media. Harper has denied that Brodie was responsible for the leak, and launched an investigation to find the source. The Opposition, as well as Democratic strategist Bob Shrum, criticized the government on the issue, stating they were trying to help the Republicans by helping Hillary Clinton win the Democratic nomination instead of Obama. They also alleged the leak would hurt relations with the United States if Obama ever were to become President. Obama was elected president in November. In February, Obama made his first foreign visit as the US president to Ottawa, in which he affirmed support for free trade with Canada, as well as complimenting Canada on its involvement in Afghanistan.


title: Stephen Harper

text: Since Harper's government took office in 2006, Canadian greenhouse gas emissions fell from 749 to 726 Mt of carbon dioxide equivalent (CO eq). From 1993 until 2006, during the previous Liberal government greenhouse gas emissions increased from 600 to 749 Mt of CO eq. The reduction corresponded Canada's decreased economic output during the Great Recession and emissions began increasing slightly in 2010, when the economy began recovering. Other significant factors in Canada's decreased emissions during Harper's tenure are initiatives such as the carbon tax in British Columbia, the cap and trade system in Quebec, Ontario discontinuing use of coal-fired power plants, and the Clean Air Regulatory Agenda which regulates emissions for automobiles and light trucks. In 2006, a Clean Air and Climate Change Act was proposed to address air pollution as well as greenhouse gas emissions; it never became law. In 2006, the Clean Air Regulatory Agenda (CARA) was established to "support Government of Canada efforts to reduce greenhouse gas (GHG) and air pollutant emissions in order to improve the environment and health of Canadians". In December 2011, the Harper government announced that Canada would formally withdraw from the Kyoto Protocol. Environment Minister Peter Kent stated, "It's now clear that Kyoto is not the path forward for a global solution to climate change." In December 2012, Canada became the first signatory to formally withdraw from the Kyoto Protocol.


title: Stephen Harper

text: Other federal initiatives include the 2011 loan guarantee towards the Lower Churchill Project in Labrador, which is scheduled for completion in 2017. The Lower Churchill's two hydroelectric installations at Gull Island and Muskrat Falls will have a combined capacity of over 3,074 MW and have the ability to provide 16.7 TW·h of electricity per year, which is enough to "reduce greenhouse gas emissions equivalent to taking 3.2 million vehicles off the road each year".


title: Stephen Harper

text: In 2006, Harper introduced a Public Transit Tax Credit, where individuals could claim 15 per cent of the cost of a transit pass each year. From 2006 to 2013, the Harper government invested over $5 billion towards public transit projects in Canada. In 2006, the federal government provided $697 million towards the Toronto York–Spadina Subway Extension. In September 2013, Finance Minister Jim Flaherty announced a federal contribution of $660 million towards the Scarborough Subway Extension.


title: Stephen Harper

text: Starting in 2006, the Harper government implemented policies that had the effect of reducing transparency. During this government, scientists employed by the government were not able to speak with the media and inform the public of their findings without government permission, the government made significant cuts to research and other forms of data collection, and significant destruction and inaccessibility of government-held data and documents occurred.


title: Stephen Harper

text: During the Harper government, it was not possible for government-employed scientists to openly speak about the government policy that prohibited communication with the media. However, following the election of a new government in 2015, several scientists who were or had been employed by the government came forward to confirm the allegations made by anonymous sources during the Harper years.


title: Stephen Harper

text: The government made drastic cuts to scientific research and data collection. Over 2,000 scientists were dismissed and funding was cut from world renowned research facilities. Cuts were also made to many essential programs, some so deep that they had to shut down entirely, including the monitoring of smoke stack emissions, food inspections, oil spills, water quality, and climate change. During this time, the long form census was also discontinued as a mandatory part of the census. This was ostensibly due to privacy concerns, however, the number of complaints about privacy proved to be minimal.


title: Stephen Harper

text: The government closed a number of government libraries without consultation on the closings or the process involved. The manner in which it was done received significant criticism because it left the remaining information in disarray, inaccessible for research.


title: Stephen Harper

text: Harper chose the following jurists to be appointed as justices of the Supreme Court of Canada by the governor general:


title: Stephen Harper

text: Harper returned to Ottawa as a Conservative backbencher and addressed a meeting of the Conservative caucus that included defeated MPs in November 2015. Interim leader Rona Ambrose stated that Harper would be in the House for key votes as the member for Calgary Heritage, but had earned the right to keep a low profile after his service as the prime minister. In February 2018, Harper stated that he could have still "easily" been leader of the Conservative Party, but he chose not to amass too much power in order to secure the party's fortunes in the future.


title: Stephen Harper

text: In December 2015, Harper had set up Harper & Associates Consulting Inc., a corporation that lists him a director alongside close associates Ray Novak and Jeremy Hunt.


title: Stephen Harper

text: Harper announced in May 2016 that he planned to resign his seat in the House of Commons during the summer before the fall session of Parliament. On May 26, 2016, he was named as a board member for the Conservative Party’s fundraising arm. The Conservative Fund is noted to have influence on the party operations. Harper and other directors played a role in the removal of Harper–appointed Conservative executive director Dustin Van Vught to avoid backlash from donors and grassroots conservatives. In the same month, Harper delivered a speech to the 2016 Conservative Party convention where his accomplishments as party leader and prime minister were honoured by the party.


title: Stephen Harper

text: In October 2017, Harper received media attention for criticizing Prime Minister Justin Trudeau's handling of the renegotiation of the North American Free Trade Agreement started by the United States under President Donald Trump, stating that Trudeau was too unwilling to make concessions to the U.S., sided too closely with Mexico, and tried to advance left-wing policies through the renegotiations.


title: Stephen Harper

text: On February 2, 2018, Harper revealed in a statement that he knew about the sexual assault allegations against then Conservative MP Rick Dykstra during the 2015 election but could not justify removing him as a candidate because the investigation was closed by police a year before the election.


title: Stephen Harper

text: On March 26, 2018, Harper attended the international Fellowship of Christians and Jews Gala at Mar-a-Lago where he stated that he expressed support for US President Donald Trump's speech on Jerusalem. On May 9, he expressed support for Trump's decision to withdraw from the Iran deal by lending his signature to an ad that appeared in "The New York Times" a day after the decision.


title: Stephen Harper

text: On November 19, 2018, Harper appeared on a show hosted by Ben Shapiro, where he made comments on issues such as populism, immigration and nationalism. The "National Post" noted that they "echo the argument made in his recently released book, "Right Here, Right Now: Politics and Leadership in the Age of Disruption", which urges conservatives to listen to populist grievances, rather than focus on other priorities like tax cuts for the wealthy."


title: Stephen Harper

text: In January 2019, Harper appeared on a PragerU video explaining why Donald Trump was elected to the presidency in the 2016 United States election. Then in May 2019, he appeared on another PragerU video explaining reasons to support Israel amid the Israeli–Palestinian conflict.


title: Stephen Harper

text: On March 11, 2021, during a virtual gathering hosted by the Conference of Defence Associations Institute, Harper claimed that the world has entered into a Second Cold War between the United States and China, and that middle-power countries such as Canada are also a part of the rivalry between the two main powers.


title: Stephen Harper

text: In 2021, Harper appeared on the podcast American Optimist, hosted by Joe Lonsdale. In the interview, Harper criticized the Trudeau government's large-scale deficit spending during the COVID-19 pandemic, calling it "overkill". He also criticized "woke culture".


title: Stephen Harper

text: On July 25, 2022, Harper endorsed his former cabinet minister Pierre Poilievre for the leadership of the Conservative Party. This was the first time Harper endorsed a federal Conservative leadership candidate; he previously chose not to in the 2017 and 2020 leadership elections.


title: Stephen Harper

text: In September 2022, Harper attended Elizabeth II's state funeral, along with other former Canadian prime ministers.


title: Stephen Harper

text: Harper received the Woodrow Wilson Award on October 6, 2006, for his public service in Calgary. The awards ceremony was held at the Telus Convention Centre in Calgary, the same place where he made his victory speech.


title: Stephen Harper

text: "Time" magazine also named him as Canada's Newsmaker of the Year in 2006. Stephen Handelman wrote "that the prime minister who was once dismissed as a doctrinaire backroom tactician with no experience in government has emerged as a warrior in power".


title: Stephen Harper

text: On June 27, 2008, Harper was awarded the Presidential Gold Medallion for Humanitarianism by B'nai B'rith International. He is the first Canadian to be awarded this medal.


title: Stephen Harper

text: On July 11, 2011, Harper was honoured by Alberta's Blood tribe. He was made Honorary Chief of the Kainai Nation during a ceremony, in which they recognized him for making an official apology on behalf of the Government of Canada for the residential schools abuse. Harper issued this apology in 2008. The chief of the tribe explained that he believes the apology officially started the healing and rebuilding of relations between the federal and native councils. Lester B. Pearson, John Diefenbaker, and Jean Chrétien are the only other prime ministers of Canada to have been awarded the same honorary title.


title: Stephen Harper

text: On September 27, 2012, Harper received the World Statesman of the Year award. This award was offered through a US group of various faith representatives. This occurred at a black tie banquet in New York. Jean Chrétien was one of the previous recipients from Canada.


title: Stephen Harper

text: In August 2016 President Petro Poroshenko of Ukraine awarded Stephen Harper with the highest award for foreigners–the Order of Liberty.


title: Stephen Harper

text: In December 2019, it was announced by Governor General Julie Payette that Harper had been appointed as a Companion of the Order of Canada. He was formally invested on September 18, 2022, by Governor General Mary Simon in London in a ceremony attended by incumbent Prime Minister Justin Trudeau, and former prime ministers Kim Campbell, Jean Chrétien, Paul Martin and former Governors-General Michaëlle Jean and David Johnston.


title: Stephen Harper

text: Harper married Laureen Teskey on December 11, 1993. Laureen was formerly married to New Zealander Neil Fenton from 1985 to 1988. The Harpers have two children: Benjamin and Rachel. Harper is the third prime minister, after Pierre Trudeau and John Turner, to send his children to Rockcliffe Park Public School, in Ottawa. He is a member of the evangelical Christian and Missionary Alliance and attends church at the East Gate Alliance Church in Ottawa.


title: Stephen Harper

text: An avid follower of ice hockey, he has been a fan of the Toronto Maple Leafs since his childhood in the Leaside and Etobicoke communities in Toronto. Harper is also a fan of the Calgary Flames. He published a book, "" (2013), which chronicles the growth of professional hockey, particularly in Toronto, and writes articles occasionally on the subject. Harper appeared on The Sports Network (TSN) during the broadcast of the Canada–Russia final of the 2007 World Junior Ice Hockey Championships. He was interviewed and expressed his views on the state of hockey and his preference for an overtime period in lieu of a shoot-out. In February 2010, Harper interviewed former National Hockey League greats Wayne Gretzky and Gordie Howe for a Saskatoon Kinsmen Club charity event.


title: Stephen Harper

text: Harper had a cameo appearance in an episode of the television show "Corner Gas," which aired March 12, 2007. He owns an extensive vinyl record collection and is a fan of The Beatles and AC/DC. In October 2009, he joined Yo-Yo Ma on stage in a National Arts Centre gala and performed "With a Little Help from My Friends". He was also accompanied by Herringbone, an Ottawa band with whom he regularly practices. He received a standing ovation after providing the piano accompaniment and lead vocals for the song.


title: Stephen Harper

text: In October 2010, Harper taped a cameo appearance in an episode of the television show "Murdoch Mysteries", which aired July 20, 2011, during the show's fourth season.


title: Stephen Harper

text: He was the first prime minister to employ a personal stylist, Michelle Muntean, whose duties range from coordinating his clothing to preparing his hair and makeup for speeches and television appearances. While she used to be on the public payroll, she has been paid for by the Conservative Party since "some time [in] 2007".


title: Stephen Harper

text: As of 2013, the Harper family had two cats, Stanley and Gypsy. They have fostered other cats as well.


title: Manufacturing

text: Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of secondary sector of the economy. The term may refer to a range of human activity, from handicraft to high-tech, but it is most commonly applied to industrial design, in which raw materials from the primary sector are transformed into finished goods on a large scale. Such goods may be sold to other manufacturers for the production of other more complex products (such as aircraft, household appliances, furniture, sports equipment or automobiles), or distributed via the tertiary industry to end users and consumers (usually through wholesalers, who in turn sell to retailers, who then sell them to individual customers).


title: Manufacturing

text: Manufacturing engineering is the field of engineering that designs and optimizes the manufacturing process, or the steps through which raw materials are transformed into a final product. The manufacturing process begins with the product design, and materials specification. These materials are then modified through manufacturing to become the desired product.


title: Manufacturing

text: Modern manufacturing includes all intermediate processes involved in the production and integration of a product's components. Some industries, such as semiconductor and steel manufacturers, use the term fabrication instead.


title: Manufacturing

text: The Modern English word "manufacture" is likely derived from the Middle French "manufacture" ("process of making") which itself originates from the Classical Latin "manū" ("hand") and Middle French "facture" ("making"). Alternatively, the English word may have been independently formed from the earlier English "manufact" ("made by human hands") and "facture". Its earliest usage in the English language was recorded in the mid-16th century to refer to the making of products by hand.


title: Manufacturing

text: Human ancestors have manufactured objects using stone and other tools since long before the emergence of "Homo sapiens" approximately 200,000 years ago. The earliest methods of stone tool making, known as the Oldowan "industry", date back to at least 2.3 million years ago, with the earliest direct evidence of tool usage found in Ethiopia within the Great Rift Valley, dating back to 2.5 million years ago. To manufacture a stone tool, a "core" of hard stone with specific flaking properties (such as flint) was struck with a hammerstone. This flaking produced sharp edges which could be used as tools, primarily in the form of choppers or scrapers. These tools greatly aided the early humans in their hunter-gatherer lifestyle to form other tools out of softer materials such as bone and wood. The Middle Paleolithic, approximately 300,000 years ago, saw the introduction of the prepared-core technique, where multiple blades could be rapidly formed from a single core stone. Pressure flaking, in which a wood, bone, or antler punch could be used to shape a stone very finely was developed during the Upper Paleolithic, beginning approximately 40,000 years ago. During the Neolithic period, polished stone tools were manufactured from a variety of hard rocks such as flint, jade, jadeite, and greenstone. The polished axes were used alongside other stone tools including projectiles, knives, and scrapers, as well as tools manufactured from organic materials such as wood, bone, and antler.


title: Manufacturing

text: Copper smelting is believed to have originated when the technology of pottery kilns allowed sufficiently high temperatures. The concentration of various elements such as arsenic increase with depth in copper ore deposits and smelting of these ores yields arsenical bronze, which can be sufficiently work hardened to be suitable for manufacturing tools. Bronze is an alloy of copper with tin; the latter being found in relatively few deposits globally caused a long time to elapse before true tin bronze became widespread. During the Bronze Age, bronze was a major improvement over stone as a material for making tools, both because of its mechanical properties like strength and ductility and because it could be cast in molds to make intricately shaped objects. Bronze significantly advanced shipbuilding technology with better tools and bronze nails, which replaced the old method of attaching boards of the hull with cord woven through drilled holes. The Iron Age is conventionally defined by the widespread manufacturing of weapons and tools using iron and steel rather than bronze. Iron smelting is more difficult than tin and copper smelting because smelted iron requires hot-working and can be melted only in specially designed furnaces. The place and time for the discovery of iron smelting is not known, partly because of the difficulty of distinguishing metal extracted from nickel-containing ores from hot-worked meteoritic iron.


title: Manufacturing

text: During the growth of the ancient civilizations, many ancient technologies resulted from advances in manufacturing. Several of the six classic simple machines were invented in Mesopotamia. Mesopotamians have been credited with the invention of the wheel. The wheel and axle mechanism first appeared with the potter's wheel, invented in Mesopotamia (modern Iraq) during the 5th millennium BC. Egyptian paper made from papyrus, as well as pottery, were mass-produced and exported throughout the Mediterranean basin. Early construction techniques used by the Ancient Egyptians made use of bricks composed mainly of clay, sand, silt, and other minerals.


title: Manufacturing

text: The Middle Ages witnessed new inventions, innovations in the ways of managing traditional means of production, and economic growth. Papermaking, a 2nd-century Chinese technology, was carried to the Middle East when a group of Chinese papermakers were captured in the 8th century. Papermaking technology was spread to Europe by the Umayyad conquest of Hispania. A paper mill was established in Sicily in the 12th century. In Europe the fiber to make pulp for making paper was obtained from linen and cotton rags. Lynn Townsend White Jr. credited the spinning wheel with increasing the supply of rags, which led to cheap paper, which was a factor in the development of printing. Due to the casting of cannon, the blast furnace came into widespread use in France in the mid 15th century. The blast furnace had been used in China since the 4th century BC. The stocking frame, which was invented in 1598, increased a knitter's number of knots per minute from 100 to 1000.


title: Manufacturing

text: The Industrial Revolution was the transition to new manufacturing processes in Europe and the United States from 1760 to the 1830s. This transition included going from hand production methods to machines, new chemical manufacturing and iron production processes, the increasing use of steam power and water power, the development of machine tools and the rise of the mechanized factory system. The Industrial Revolution also led to an unprecedented rise in the rate of population growth. Textiles were the dominant industry of the Industrial Revolution in terms of employment, value of output and capital invested. The textile industry was also the first to use modern production methods. Rapid industrialization first began in Britain, starting with mechanized spinning in the 1780s, with high rates of growth in steam power and iron production occurring after 1800. Mechanized textile production spread from Great Britain to continental Europe and the United States in the early 19th century, with important centres of textiles, iron and coal emerging in Belgium and the United States and later textiles in France.


title: Manufacturing

text: An economic recession occurred from the late 1830s to the early 1840s when the adoption of the Industrial Revolution's early innovations, such as mechanized spinning and weaving, slowed down and their markets matured. Innovations developed late in the period, such as the increasing adoption of locomotives, steamboats and steamships, hot blast iron smelting and new technologies, such as the electrical telegraph, were widely introduced in the 1840s and 1850s, were not powerful enough to drive high rates of growth. Rapid economic growth began to occur after 1870, springing from a new group of innovations in what has been called the Second Industrial Revolution. These innovations included new steel making processes, mass-production, assembly lines, electrical grid systems, the large-scale manufacture of machine tools and the use of increasingly advanced machinery in steam-powered factories.


title: Manufacturing

text: Building on improvements in vacuum pumps and materials research, incandescent light bulbs became practical for general use in the late 1870s. This invention had a profound effect on the workplace because factories could now have second and third shift workers. Shoe production was mechanized during the mid 19th century. Mass production of sewing machines and agricultural machinery such as reapers occurred in the mid to late 19th century. The mass production of bicycles started in the 1880s. Steam-powered factories became widespread, although the conversion from water power to steam occurred in England earlier than in the U.S.


title: Manufacturing

text: Electrification of factories, which had begun gradually in the 1890s after the introduction of the practical DC motor and the AC motor, was fastest between 1900 and 1930. This was aided by the establishment of electric utilities with central stations and the lowering of electricity prices from 1914 to 1917. Electric motors allowed more flexibility in manufacturing and required less maintenance than line shafts and belts. Many factories witnessed a 30% increase in output owing to the increasing shift to electric motors. Electrification enabled modern mass production, and the biggest impact of early mass production was in the manufacturing of everyday items, such as at the Ball Brothers Glass Manufacturing Company, which electrified its mason jar plant in Muncie, Indiana, U.S. around 1900. The new automated process used glass blowing machines to replace 210 craftsman glass blowers and helpers. A small electric truck was now used to handle 150 dozen bottles at a time whereas previously used hand trucks could only carry 6 dozen bottles at a time. Electric mixers replaced men with shovels handling sand and other ingredients that were fed into the glass furnace. An electric overhead crane replaced 36 day laborers for moving heavy loads across the factory.


title: Manufacturing

text: Mass production was popularized in the late 1910s and 1920s by Henry Ford's Ford Motor Company, which introduced electric motors to the then-well-known technique of chain or sequential production. Ford also bought or designed and built special purpose machine tools and fixtures such as multiple spindle drill presses that could drill every hole on one side of an engine block in one operation and a multiple head milling machine that could simultaneously machine 15 engine blocks held on a single fixture. All of these machine tools were arranged systematically in the production flow and some had special carriages for rolling heavy items into machining positions. Production of the Ford Model T used 32,000 machine tools.


title: Manufacturing

text: Lean manufacturing (also known as just-in-time manufacturing), was developed in Japan in the 1930s. It is a production method aimed primarily at reducing times within the production system as well as response times from suppliers and to customers. It was introduced in Australia in the 1950s by the British Motor Corporation (Australia) at its Victoria Park plant in Sydney, from where the idea later migrated to Toyota. News spread to western countries from Japan in 1977 in two English-language articles: one referred to the methodology as the "Ohno system", after Taiichi Ohno, who was instrumental in its development within Toyota. The other article, by Toyota authors in an international journal, provided additional details. Finally, those and other publicity were translated into implementations, beginning in 1980 and then quickly multiplying throughout the industry in the United States and other countries.


title: Manufacturing

text: Emerging technologies have offered new growth methods in advanced manufacturing employment opportunities, for example in the Manufacturing Belt in the United States. Manufacturing provides important material support for national infrastructure and also for national defense.


title: Manufacturing

text: On the other hand, most manufacturing processes may involve significant social and environmental costs. The clean-up costs of hazardous waste, for example, may outweigh the benefits of a product that creates it. Hazardous materials may expose workers to health risks. These costs are now well known and there is effort to address them by improving efficiency, reducing waste, using industrial symbiosis, and eliminating harmful chemicals.


title: Manufacturing

text: The negative costs of manufacturing can also be addressed legally. Developed countries regulate manufacturing activity with labor laws and environmental laws. Across the globe, manufacturers can be subject to regulations and pollution taxes to offset the environmental costs of manufacturing activities. Labor unions and craft guilds have played a historic role in the negotiation of worker rights and wages. Environment laws and labor protections that are available in developed nations may not be available in the third world. Tort law and product liability impose additional costs on manufacturing. These are significant dynamics in the ongoing process, occurring over the last few decades, of manufacture-based industries relocating operations to "developing-world" economies where the costs of production are significantly lower than in "developed-world" economies.


title: Manufacturing

text: From a financial perspective, the goal of the manufacturing industry is mainly to achieve cost benefits per unit produced, which in turn leads to cost reductions in product prices for the market towards end customers. This relative cost reduction towards the market, is how manufacturing firms secure their profit margins.


title: Manufacturing

text: Manufacturing has unique health and safety challenges and has been recognized by the National Institute for Occupational Safety and Health (NIOSH) as a priority industry sector in the National Occupational Research Agenda (NORA) to identify and provide intervention strategies regarding occupational health and safety issues.


title: Manufacturing

text: Surveys and analyses of trends and issues in manufacturing and investment around the world focus on such things as:


title: Manufacturing

text: In addition to general overviews, researchers have examined the features and factors affecting particular key aspects of manufacturing development. They have compared production and investment in a range of Western and non-Western countries and presented case studies of growth and performance in important individual industries and market-economic sectors.


title: Manufacturing

text: On June 26, 2009, Jeff Immelt, the CEO of General Electric, called for the United States to increase its manufacturing base employment to 20% of the workforce, commenting that the U.S. has outsourced too much in some areas and can no longer rely on the financial sector and consumer spending to drive demand. Further, while U.S. manufacturing performs well compared to the rest of the U.S. economy, research shows that it performs poorly compared to manufacturing in other high-wage countries. A total of 3.2 million – one in six U.S. manufacturing jobs – have disappeared between 2000 and 2007. In the UK, EEF the manufacturers organisation has led calls for the UK economy to be rebalanced to rely less on financial services and has actively promoted the manufacturing agenda.


title: Manufacturing

text: According to the United Nations Industrial Development Organization (UNIDO), China is the top manufacturer worldwide by 2019 output, producing 28.7% of the total global manufacturing output, followed by United States, Japan, Germany and India.


title: Manufacturing

text: UNIDO also publishes a Competitive Industrial Performance (CIP) Index, which measures the competitive manufacturing ability of different nations. The CIP Index combines a nation's gross manufacturing output with other factors like high-tech capability and the nation's impact on the world economy. Germany topped the 2020 CIP Index, followed by China, South Korea, the United States and Japan.


title: Manufacturing

text: These are the top 50 countries by total value of manufacturing output in US dollars for its noted year according to World Bank.


title: Certified Lover Boy

text: Certified Lover Boy is the sixth studio album by Canadian rapper and singer Drake, released on September 3, 2021, by OVO Sound and Republic Records. Its production was handled by frequent collaborators 40, Nineteen85, PartyNextDoor, OZ, and Vinylz, among others. Lil Baby, Lil Durk, Giveon, Jay-Z, Travis Scott, Future, Young Thug, Yebba, 21 Savage, Project Pat, Tems, Ty Dolla Sign, Lil Wayne, Rick Ross, and Kid Cudi appear as guest artists.


title: Certified Lover Boy

text: Similar to Drake's previous releases, the album predominantly deals with his views on fame and success, particularly his dominance within the music industry, alongside disloyalty, tainted romances, feuds, and loneliness. Primarily a hip hop record, a hazy atmosphere dominates the album's sound, which includes elements of crunk and trap. Several writers found aspects of the album to be reminiscent of "Thank Me Later" (2010), "Take Care" (2011) and "Nothing Was the Same" (2013). Designed by English artist Damien Hirst, the album's artwork, which features 12 emoji of pregnant women, was the subject of much controversy.


title: Certified Lover Boy

text: Highly anticipated, "Certified Lover Boy" was met with mixed reviews from music critics upon release, most of whom felt it was comparable to Drake's other releases and highlighted its structure, but criticized the level of lyrical insight and the production's lack of sonic variety. Nevertheless, it was nominated for Best Rap Album at the 2022 Grammy Awards, until Drake withdrew the album from consideration in December 2021, and won Top Rap Album at the 2022 "Billboard" Music Awards.


title: Certified Lover Boy

text: The album was a commercial success, debuting at number one on the "Billboard" 200 with 613,000 album-equivalent units. It became Drake's tenth US number-one album and achieved the largest opening week in the US for an album in 2021 at the time, breaking Apple Music and Spotify records for the biggest opening-day streams on those platforms. It achieved the all-time record for the most US top-ten singles from one album (9), with its lead single, "Way 2 Sexy", debuting atop the "Billboard" Hot 100 as Drake's ninth US number-one hit.


title: Certified Lover Boy

text: During one of his concerts, in April 2019, Drake announced that he had started to work on a new album. In June 2019, he teased the album via Instagram, where he captioned a post with "Album mode". On December 10, Drake made a guest appearance at DaBaby's concert in Toronto, where he revealed that he was working on the album: "I'ma go back to the crib and try to finish this album up so we can turn up in 2020". In March, on Instagram Live, Drake confirmed a finalized version of "Not Around", a leaked song later retitled to "TSU", would feature on "Certified Lover Boy". That same month, frequent collaborator Boi-1da previewed two snippets of songs with Drake during a "Verzuz" with Hit-Boy. The two snippets were dubbed "I Did" and another snippet with Roddy Ricch was dubbed "In the Cut". Drake officially announced his sixth studio album just hours before the release of "Dark Lane Demo Tapes", and scheduled for release in late 2020.


title: Certified Lover Boy

text: Drake later previewed two new songs, one an unreleased track titled "Lie to Me" and the other a demo version of his 2020 DJ Khaled collaboration "Greece", on Instagram Live. On July 29, 2020, Drake's recording engineer Noel Cadastre revealed the album was "90% done". On August 14, 2020, Drake announced the title of the album. In October, Drake announced that the album would be released in January 2021, but it was postponed once again due to Drake suffering an anterior cruciate ligament injury.


title: Certified Lover Boy

text: "Certified Lover Boy" was dedicated to the late models Nadia Ntuli and Miss Mercedes Morr. Ntuli, who was a close friend of Drake's, was killed in a motor vehicle accident in Dubai in early 2021. Morr, born Janae Gagnier, was found dead in her Texas apartment on August 29, 2021. She was believed to be the victim of a murder–suicide.


title: Certified Lover Boy

text: Several writers found aspects of "Certified Lover Boy" to be reminiscent of "Thank Me Later" (2010), "Take Care" (2011) and "Nothing Was the Same" (2013). The album generally surrounds individualism; similar to Drake's previous records it predominantly deals with his views on fame and success, particularly his dominance within the music industry. Further themes concern disloyalty and tainted romance, feuds and loneliness. The album is noted for its hazy atmosphere. Genres featured on the album include chipmunk soul, crunk, and trap.


title: Certified Lover Boy

text: Craig Jenkins of "Vulture" called "Certified Lover Boy" a "patient trickle of Drake lore and fan service that could have come out as is at almost any point along the last decade in his career". "We worry not about the shaky present and the unknowable future but about the recent past, the objects of our scorn and the ones who got away", Jenkins notes.


title: Certified Lover Boy

text: On May 1, 2020, Drake surprise-released his mixtape "Dark Lane Demo Tapes", which was announced mere hours before its release. In the mixtape announcement shared on Instagram, Drake revealed that his sixth studio album, then untitled, would be released sometime in the third quarter of 2020. Although the album was not released that summer, the non-album single "Laugh Now Cry Later" featuring Lil Durk was released in August. On October 24, a teaser trailer for the album was released, revealing that the album was to be released in January 2021. American football player Odell Beckham Jr. later said it would be released on January 1, 2021, which later went unreleased. The teaser referenced covers of Drake's previous albums and mixtapes: "So Far Gone" (2009), "Take Care" (2011), "Nothing Was the Same" (2013) and "Dark Lane Demo Tapes" (2020). Drake announced in January 2021 that the album would no longer be released that month, due to a leg injury he sustained that required surgery.


title: Certified Lover Boy

text: On March 5, 2021, Drake released an extended play titled "Scary Hours 2", a sequel to the 2018 EP, to generate further anticipation for the upcoming album. The EP included three songs, and includes guest appearances from Lil Baby and Rick Ross. The music video for the EP's lead single, "What's Next", premiered on the same day. All three songs from the EP respectively debuted at number one, two and three on the " Billboard" Hot 100. In April, Drake appeared on the YSL Records song "Solid" with Gunna and Young Thug. The song was originally intended for "Certified Lover Boy", but because the album was postponed, Drake gave the song to Gunna.


title: Certified Lover Boy

text: On June 13, 2021, Drake revealed on "Caffeine.TV" that he would be releasing the album before the end of summer. Making an appearance on "Fri Yiy Friday" on July 30, a radio show on Sirius XM channel Sound 42, Drake revealed that "Certified Lover Boy" "is ready. [I'm] looking forward to delivering it". On August 27, the album's release date of September 3 was revealed during a teaser aired on ESPN's "SportsCenter". Drake later confirmed the date and revealing the album artwork on August 30. That same day, billboards featuring lyrics from the album were plastered around Drake's hometown of Toronto.


title: Certified Lover Boy

text: On September 1, two days before the album's release, billboards were placed throughout the United States, Canada, and Nigeria revealing the album's featured artists according to their hometown. An Atlanta billboard announced 21 Savage, Future, Lil Baby, and Young Thug, a Chicago billboard announced Lil Durk, and a New York City billboard announced "the GOAT", which was assumed, and later confirmed, to be Jay-Z. A Memphis billboard announced Yebba and Project Pat, while Tems was announced on a Lagos billboard. Both Giveon and Ty Dolla Sign were announced on a California billboard. As the reveal continued, a Cleveland billboard announced Kid Cudi, a Miami billboard announced Rick Ross, cited as "the biggest boss", a Houston billboard announced Travis Scott, referred to as "the hometown hero", and another Toronto billboard announced Lil Wayne, who Drake coined as the "best rapper alive".


title: Certified Lover Boy

text: "Way 2 Sexy" was released as the album's lead single on September 3, 2021, as well an accompanying music video. The song peaked at number one on the "Billboard" Hot 100. "Girls Want Girls" featuring Lil Baby, was released to rhythmic contemporary radio on September 28, 2021, as the album's second single, the song peaked at number two on the "Billboard" Hot 100.


title: Certified Lover Boy

text: The music video for "Knife Talk" featuring 21 Savage and Project Pat, was released on November 4, 2021, The song peaked at number four on the "Billboard" Hot 100.


title: Certified Lover Boy

text: The album's artwork features 12 emoji of pregnant women in varying clothing colors, hair colors and skin tones. It was designed by English artist Damien Hirst. The artwork was met with a negative reception from fans and critics alike, who called the image "lazy" and "ridiculous". It was named the worst album artwork of the year by "Exclaim!" on their "30 Worst Album Covers of 2021" list.


title: Certified Lover Boy

text: "Certified Lover Boy" was met with mixed reviews. At Metacritic, which assigns a normalized rating out of 100 to reviews from professional publications, the album received an average score of 60 based on 20 reviews, indicating "mixed or average reviews". Aggregator AnyDecentMusic? gave it 5.5 out of 10, based on their assessment of the critical consensus.


title: Certified Lover Boy

text: Reviewing the album for "Pitchfork", Matthew Strauss stated, "With much of "Certified Lover Boy", Drake seems to be doing what he thinks Drake would do, and ticking the box is taking its toll". Brandon Yu of "Variety" praised the album, stating, ""Certified Lover Boy" is a perfectly fine record – it's expensively well-produced, like all of Drake's albums, and easily likable with a decent batting average for a nearly hour-and-a-half record". Okla Jones of "Consequence" said, "Drake's new release may lack some of the variety of his previous albums, but its concepts and musical structure make for a solid body of work". Mikael Wood of the "Los Angeles Times" wrote a glowing review of the album, defending Drake's usage of an R. Kelly credit as a "thoughtless error", and saying it "expertly displays his strengths" while showing a new tendency to understate his accomplishments by merely predicting in "You Only Live Twice" that the album would go platinum when previous albums have been certified platinum several times. Wood described the album as being "enjoyment even at its bleakest".


title: Certified Lover Boy

text: In a lukewarm review, "The Guardian"s Alim Kheraj wrote, "Personally, sonically and thematically, Drake seems resistant to change. It's frustrating: the songs aren't bad, and in some cases they're excellent, a reminder of the unflattering emotional honesty that initially set him apart from his peers. However, they also hew to a formula that works for him". Nathan Evans of "Clash" said, "Aubrey Graham hands over his fifth project to cross 80 minutes, an hour and a half smorgasbord of all-new tracks. In his defence, the Drake cuisine is far too extensive and varied at this point, but this dilemma has been around for a number of years now and some sort of sacrifice for a better, more cohesive project has to be made if he wants to release another classic".


title: Certified Lover Boy

text: Writing for "The Independent", Sam Moore stated, ""Certified Lover Boy"s greatest crime is just how bland and boring it is. There's very little here that Drake has not done better or more emphatically elsewhere; his album is deprived of any kind of experimentation or insight. He rose to the top baring his soul. Now it feels like there's no soul to bare". In a mixed review, "The Arts Desk"s Harry Thorfinn-George stated, "A lot of "CLB" feels rehashed, but the way it captures Drake at an awkward junction in his life is intriguing". Gary Suarez of "Entertainment Weekly" said, "The new album is like watching the eighth season of a sitcom and growing hyper-aware of all the recycled jokes and actors' laugh lines".


title: Certified Lover Boy

text: "Certified Lover Boy" was nominated for Best Rap Album at the 2022 Grammy Awards until Drake withdrew the nomination on December 6, 2021.


title: Certified Lover Boy

text: "Certified Lover Boy" was highly anticipated. It broke Apple Music and Spotify 2021 records for largest streaming debut within a single day, beating Drake's own previous album "Scorpion" (2018). The album set the record for most US top-ten singles from one album, with lead single "Way 2 Sexy" becoming his ninth number one, surpassing albums by Michael Jackson, Janet Jackson and Bruce Springsteen.


title: Certified Lover Boy

text: In the United States, "Certified Lover Boy" debuted at number one on the "Billboard" 200 chart as Drake's tenth consecutive chart-topping album in the country. It opened with 613,000 album-equivalent units, which consists of 46,000 album sales, and 562,000 streaming units calculated from the 743.7 million on-demand streams of the album's tracks. The 613,000 tally marked the biggest debut-week units of 2021, surpassing Kanye West's "Donda" (309,000), and the biggest opening week since Taylor Swift's "Folklore" (2020) debuted with 846,000 units. Drake became the eighth artist in the "Billboard" 200 history to accumulate ten number-one albums. "Certified Lover Boy" also marked the biggest week for an R&B/hip-hop album, a rap album, and an album by a male artist, since "Scorpion".


title: Certified Lover Boy

text: In the United Kingdom, "Certified Lover Boy" debuted at number one on the UK Albums Chart with 46,000 units sold in its first week while the tracks were streamed 70.4 million times, accounting for 96% of his first-week sales, becoming Drake's fourth album to reach the top spot in the country.


title: Certified Lover Boy

text: In February 2022, the International Federation of the Phonographic Industry (IFPI) reported that Drake was the world's fourth best selling artist of 2021, behind BTS, Taylor Swift and Adele.


title: Polyethylene

text: Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging (plastic bags, plastic films, geomembranes and containers including bottles, etc.). , over 100 million tonnes of polyethylene resins are being produced annually, accounting for 34% of the total plastics market.


title: Polyethylene

text: Many kinds of polyethylene are known, with most having the chemical formula (CH). PE is usually a mixture of similar polymers of ethylene, with various values of "n". It can be "low-density" or "high-density": low-density polyethylene is extruded using high pressure () and high temperature (), while high-density polyethylene is extruded using low pressure () and low temperature (). Polyethylene is usually thermoplastic, but it can be modified to become thermosetting instead, for example, in cross-linked polyethylene.


title: Polyethylene

text: Polyethylene was first synthesized by the German chemist Hans von Pechmann, who prepared it by accident in 1898 while investigating diazomethane. When his colleagues Eugen Bamberger and Friedrich Tschirner characterized the white, waxy substance that he had created, they recognized that it contained long −CH− chains and termed it "polymethylene".


title: Polyethylene

text: The first industrially practical polyethylene synthesis (diazomethane is a notoriously unstable substance that is generally avoided in industrial application) was again accidentally discovered in 1933 by Eric Fawcett and Reginald Gibson at the Imperial Chemical Industries (ICI) works in Northwich, England. Upon applying extremely high pressure (several hundred atmospheres) to a mixture of ethylene and benzaldehyde they again produced a white, waxy material. Because the reaction had been initiated by trace oxygen contamination in their apparatus, the experiment was difficult to reproduce at first. It was not until 1935 that another ICI chemist, Michael Perrin, developed this accident into a reproducible high-pressure synthesis for polyethylene that became the basis for industrial low-density polyethylene (LDPE) production beginning in 1939. Because polyethylene was found to have very low-loss properties at very high frequency radio waves, commercial distribution in Britain was suspended on the outbreak of World War II, secrecy imposed, and the new process was used to produce insulation for UHF and SHF coaxial cables of radar sets. During World War II, further research was done on the ICI process and in 1944, Du Pont at Sabine River, Texas, and Bakelite Corporation at Charleston, West Virginia, began large-scale commercial production under license from ICI.


title: Polyethylene

text: The landmark breakthrough in the commercial production of polyethylene began with the development of catalysts that promoted the polymerization at mild temperatures and pressures. The first of these was a catalyst based on chromium trioxide discovered in 1951 by Robert Banks and J. Paul Hogan at Phillips Petroleum. In 1953 the German chemist Karl Ziegler developed a catalytic system based on titanium halides and organoaluminium compounds that worked at even milder conditions than the Phillips catalyst. The Phillips catalyst is less expensive and easier to work with, however, and both methods are heavily used industrially. By the end of the 1950s both the Phillips- and Ziegler-type catalysts were being used for high-density polyethylene (HDPE) production. In the 1970s, the Ziegler system was improved by the incorporation of magnesium chloride. Catalytic systems based on soluble catalysts, the metallocenes, were reported in 1976 by Walter Kaminsky and Hansjörg Sinn. The Ziegler- and metallocene-based catalysts families have proven to be very flexible at copolymerizing ethylene with other olefins and have become the basis for the wide range of polyethylene resins available today, including very-low-density polyethylene and linear low-density polyethylene. Such resins, in the form of UHMWPE fibers, have (as of 2005) begun to replace aramids in many high-strength applications.


title: Polyethylene

text: The properties of polyethylene can be divided into mechanical, chemical, electrical, optical, and thermal properties.


title: Polyethylene

text: Polyethylene is of low strength, hardness and rigidity, but has a high ductility and impact strength as well as low friction. It shows strong creep under persistent force, which can be reduced by addition of short fibers. It feels waxy when touched.


title: Polyethylene

text: The commercial applicability of polyethylene is limited by its low melting point compared to other thermoplastics. For common commercial grades of medium- and high-density polyethylene the melting point is typically in the range . The melting point for average commercial low-density polyethylene is typically . These temperatures vary strongly with the type of polyethylene, but the theoretical upper limit of melting of polyethylene is reported to be . Combustion typically occurs above .


title: Polyethylene

text: Polyethylene consists of nonpolar, saturated, high-molecular-weight hydrocarbons. Therefore, its chemical behavior is similar to paraffin. The individual macromolecules are not covalently linked. Because of their symmetric molecular structure, they tend to crystallize; overall polyethylene is partially crystalline. Higher crystallinity increases density and mechanical and chemical stability.


title: Polyethylene

text: The standard method to test plastic density is ISO 1183 part 2 (gradient columns), alternatively ISO 1183 part 1 (MVS2PRO density analyzer).


title: Polyethylene

text: Most LDPE, MDPE, and HDPE grades have excellent chemical resistance, meaning that they are not attacked by strong acids or strong bases and are resistant to gentle oxidants and reducing agents. Crystalline samples do not dissolve at room temperature. Polyethylene (other than cross-linked polyethylene) usually can be dissolved at elevated temperatures in aromatic hydrocarbons such as toluene or xylene, or in chlorinated solvents such as trichloroethane or trichlorobenzene.


title: Polyethylene

text: Polyethylene absorbs almost no water; the gas and water vapour permeability (only polar gases) is lower than for most plastics. Oxygen, carbon dioxide and flavorings, on the other hand, can pass it easily.


title: Polyethylene

text: Polyethylene burns slowly with a blue flame having a yellow tip and gives off an odour of paraffin (similar to candle flame). The material continues burning on removal of the flame source and produces a drip.


title: Polyethylene

text: Polyethylene cannot be imprinted or bonded with adhesives without pretreatment. High-strength joints are readily achieved with plastic welding.


title: Polyethylene

text: Polyethylene is a good electrical insulator. It offers good electrical treeing resistance; however, it becomes easily electrostatically charged (which can be reduced by additions of graphite, carbon black or antistatic agents).


title: Polyethylene

text: When pure, the dielectric constant is in the range 2.2 to 2.4 depending on the density and the loss tangent is very low, making it a good dielectric for a capacitor


title: Polyethylene

text: Depending on thermal history and film thickness, PE can vary between almost clear (transparent), milky-opaque (translucent) and opaque. LDPE has the greatest, LLDPE slightly less, and HDPE the least transparency. Transparency is reduced by crystallites if they are larger than the wavelength of visible light.


title: Polyethylene

text: The ingredient or monomer is ethylene (IUPAC name ethene), a gaseous hydrocarbon with the formula CH, which can be viewed as a pair of methylene groups (−−) connected to each other. Typical specifications for PE purity are <5 ppm for water, oxygen, and other alkenes contents. Acceptable contaminants include N, ethane (common precursor to ethylene), and methane. Ethylene is usually produced from petrochemical sources, but also is generated by dehydration of ethanol.


title: Polyethylene

text: Ethylene is a stable molecule that polymerizes only upon contact with catalysts. The conversion is highly exothermic. Coordination polymerization is the most pervasive technology, which means that metal chlorides or metal oxides are used. The most common catalysts consist of titanium(III) chloride, the so-called Ziegler–Natta catalysts. Another common catalyst is the Phillips catalyst, prepared by depositing chromium(VI) oxide on silica. Polyethylene can be produced through radical polymerization, but this route has only limited utility and typically requires high-pressure apparatus.


title: Polyethylene

text: Pressure-sensitive adhesives (PSA) are feasible if the surface chemistry or charge is modified with plasma activation, flame treatment, or corona treatment.


title: Polyethylene

text: Polyethylene is classified by its density and branching. Its mechanical properties depend significantly on variables such as the extent and type of branching, the crystal structure, and the molecular weight. There are several types of polyethylene:


title: Polyethylene

text: UHMWPE is polyethylene with a molecular weight numbering in the millions, usually between 3.5 and 7.5 million amu. The high molecular weight makes it a very tough material, but results in less efficient packing of the chains into the crystal structure as evidenced by densities of less than high-density polyethylene (for example, 0.930–0.935 g/cm). UHMWPE can be made through any catalyst technology, although Ziegler catalysts are most common. Because of its outstanding toughness and its cut, wear, and excellent chemical resistance, UHMWPE is used in a diverse range of applications. These include can- and bottle-handling machine parts, moving parts on weaving machines, bearings, gears, artificial joints, edge protection on ice rinks, steel cable replacements on ships, and butchers' chopping boards. It is commonly used for the construction of articular portions of implants used for hip and knee replacements. As fiber, it competes with aramid in bulletproof vests.


title: Polyethylene

text: HDPE is defined by a density of greater or equal to 0.941 g/cm. HDPE has a low degree of branching. The mostly linear molecules pack together well, so intermolecular forces are stronger than in highly branched polymers. HDPE can be produced by chromium/silica catalysts, Ziegler–Natta catalysts or metallocene catalysts; by choosing catalysts and reaction conditions, the small amount of branching that does occur can be controlled. These catalysts prefer the formation of free radicals at the ends of the growing polyethylene molecules. They cause new ethylene monomers to add to the ends of the molecules, rather than along the middle, causing the growth of a linear chain.


title: Polyethylene

text: HDPE has high tensile strength. It is used in products and packaging such as milk jugs, detergent bottles, butter tubs, garbage containers, and water pipes. One-third of all toys are manufactured from HDPE. In 2007, the global HDPE consumption reached a volume of more than 30 million tons.


title: Polyethylene

text: PEX is a medium- to high-density polyethylene containing cross-link bonds introduced into the polymer structure, changing the thermoplastic into a thermoset. The high-temperature properties of the polymer are improved, its flow is reduced, and its chemical resistance is enhanced. PEX is used in some potable-water plumbing systems because tubes made of the material can be expanded to fit over a metal nipple and it will slowly return to its original shape, forming a permanent, water-tight connection.


title: Polyethylene

text: MDPE is defined by a density range of 0.926–0.940 g/cm. MDPE can be produced by chromium/silica catalysts, Ziegler–Natta catalysts, or metallocene catalysts. MDPE has good shock and drop resistance properties. It also is less notch-sensitive than HDPE; stress-cracking resistance is better than HDPE. MDPE is typically used in gas pipes and fittings, sacks, shrink film, packaging film, carrier bags, and screw closures.


title: Polyethylene

text: LLDPE is defined by a density range of 0.915–0.925 g/cm. LLDPE is a substantially linear polymer with significant numbers of short branches, commonly made by copolymerization of ethylene with short-chain alpha-olefins (for example, 1-butene, 1-hexene, and 1-octene). LLDPE has higher tensile strength than LDPE, and it exhibits higher impact and puncture resistance than LDPE. Lower-thickness (gauge) films can be blown, compared with LDPE, with better environmental stress cracking resistance, but they are not as easy to process. LLDPE is used in packaging, particularly film for bags and sheets. Lower thickness may be used compared to LDPE. It is used for cable coverings, toys, lids, buckets, containers, and pipe. While other applications are available, LLDPE is used predominantly in film applications due to its toughness, flexibility, and relative transparency. Product examples range from agricultural films, Saran wrap, and bubble wrap to multilayer and composite films. In 2013, the world LLDPE market reached a volume of US$40 billion.


title: Polyethylene

text: LDPE is defined by a density range of 0.910–0.940 g/cm. LDPE has a high degree of short- and long-chain branching, which means that the chains do not pack into the crystal structure as well. It has, therefore, less strong intermolecular forces as the instantaneous-dipole induced-dipole attraction is less. This results in a lower tensile strength and increased ductility. LDPE is created by free-radical polymerization. The high degree of branching with long chains gives molten LDPE unique and desirable flow properties. LDPE is used for both rigid containers and plastic film applications such as plastic bags and film wrap. In 2013, the global LDPE market had a volume of almost US$33 billion.


title: Polyethylene

text: The radical polymerization process used to make LDPE does not include a catalyst that "supervises" the radical sites on the growing PE chains. (In HDPE synthesis, the radical sites are at the ends of the PE chains, because the catalyst stabilizes their formation at the ends.) Secondary radicals (in the middle of a chain) are more stable than primary radicals (at the end of the chain), and tertiary radicals (at a branch point) are more stable yet. Each time an ethylene monomer is added, it creates a primary radical, but often these will rearrange to form more stable secondary or tertiary radicals. Addition of ethylene monomers to the secondary or tertiary sites creates branching.


title: Polyethylene

text: VLDPE is defined by a density range of 0.880–0.915 g/cm. VLDPE is a substantially linear polymer with high levels of short-chain branches, commonly made by copolymerization of ethylene with short-chain alpha-olefins (for example, 1-butene, 1-hexene and 1-octene). VLDPE is most commonly produced using metallocene catalysts due to the greater co-monomer incorporation exhibited by these catalysts. VLDPEs are used for hose and tubing, ice and frozen food bags, food packaging and stretch wrap as well as impact modifiers when blended with other polymers.


title: Polyethylene

text: Recently, much research activity has focused on the nature and distribution of long chain branches in polyethylene. In HDPE, a relatively small number of these branches, perhaps one in 100 or 1,000 branches per backbone carbon, can significantly affect the rheological properties of the polymer.


title: Polyethylene

text: In addition to copolymerization with alpha-olefins, ethylene can be copolymerized with a wide range of other monomers and ionic composition that creates ionized free radicals. Common examples include vinyl acetate (the resulting product is ethylene-vinyl acetate copolymer, or EVA, widely used in athletic-shoe sole foams) and a variety of acrylates. Applications of acrylic copolymer include packaging and sporting goods, and superplasticizer, used in cement production.


title: Polyethylene

text: The particular material properties of "polyethylene" depend on its molecular structure. Molecular weight and crystallinity are the most significant factors; crystallinity in turn depends on molecular weight and degree of branching. The less the polymer chains are branched, and the lower the molecular weight, the higher the crystallinity of polyethylene. Crystallinity ranges from 35% (PE-LD/PE-LLD) to 80% (PE-HD). Polyethylene has a density of 1.0 g/cm in crystalline regions and 0.86 g/cm in amorphous regions. An almost linear relationship exists between density and crystallinity.


title: Polyethylene

text: The degree of branching of the different types of polyethylene can be schematically represented as follows:


title: Polyethylene

text: The figure shows polyethylene backbones, short-chain branches and side-chain branches. The polymer chains are represented linearly.


title: Polyethylene

text: The properties of polyethylene are highly dependent on type and number of chain branches. The chain branches in turn depend on the process used: either the high-pressure process (only PE-LD) or the low-pressure process (all other PE grades). Low-density polyethylene is produced by the high-pressure process by radical polymerization, thereby numerous short chain branches as well as long chain branches are formed. Short chain branches are formed by intramolecular chain transfer reactions, they are always butyl or ethyl chain branches because the reaction proceeds after the following mechanism:


title: Polyethylene

text: Polyethylene is produced from ethylene, and although ethylene can be produced from renewable resources, it is mainly obtained from petroleum or natural gas.


title: Polyethylene

text: Moreover, the widespread usage of polyethylene poses difficulties for waste management if it is not recycled. Polyethylene, like other synthetic plastics, is not readily biodegradable, and thus accumulates in landfills. Recycling is made easier if marked with a recycling code or resin identification code. This can read "PE" or "02" ("plastic number 2") for PE-HD and "04" ("plastic number 4") for PE-LD.


title: Polyethylene

text: In Japan, getting rid of plastics in an environmentally friendly way was the major problem discussed until the Fukushima nuclear disaster in 2011 became a larger issue. It was listed as a US$90 billion market for solutions. Since 2008, Japan has rapidly increased the recycling of plastics, but still has a large amount of plastic wrapping which goes to waste.


title: Polyethylene

text: In 2010, a Japanese researcher, Akinori Ito, released the prototype of a machine which creates oil from polyethylene using a small, self-contained vapor distillation process.


title: Polyethylene

text: Polyethylene, like other synthetic plastics, is not readily biodegradable, and thus accumulates in landfills. However, there are a number of species of bacteria and animals that are able to degrade polyethylene.


title: Polyethylene

text: In May 2008, Daniel Burd, a 16-year-old Canadian, won the Canada-Wide Science Fair in Ottawa after discovering that "Pseudomonas fluorescens", with the help of "Sphingomonas", can degrade over 40% of the weight of plastic bags within six weeks. He later guessed that it would be gone after six more weeks.


title: Polyethylene

text: The thermophilic bacterium "Brevibacillus borstelensis" (strain 707) was isolated from a soil sample and found to use low-density polyethylene as a sole carbon source when incubated together at 50 °C. Biodegradation increased with time exposed to ultraviolet radiation.


title: Polyethylene

text: "Acinetobacter" sp. 351 can degrade lower molecular-weight PE oligomers. When PE is subjected to thermo- and photo-oxidization, products including alkanes, alkenes, ketones, aldehydes, alcohols, carboxylic acid, keto-acids, dicarboxylic acids, lactones, and esters are released.


title: Polyethylene

text: In 2014, a Chinese researcher named Jun Yang discovered that Indian mealmoth larvae could metabolize polyethylene from observing that plastic bags at his home had small holes in them. Deducing that the hungry larvae must have digested the plastic somehow, he and his team analyzed their gut bacteria and found a few that could use plastic as their only carbon source. Not only could the bacteria from the guts of the "Plodia interpunctella" moth larvae metabolize polyethylene, they degraded it significantly, dropping its tensile strength by 50%, its mass by 10% and the molecular weights of its polymeric chains by 13%.


title: Polyethylene

text: In 2017, researchers reported that the caterpillar of "Galleria mellonella" eats plastic garbage such as polyethylene.


title: Polyethylene

text: When exposed to ambient solar radiation the plastic produces two greenhouse gases, methane and ethylene. Of particular concern is the plastic type which releases gases at the highest rate: low-density polyethylene (or LDPE). Due to its low density properties it breaks down more easily over time, leading to higher surface areas. The production of these trace gases from virgin LDPE increase with surface area/time, with rates at the end of a 212-day incubation of 5.8 nmol g-1 d-1 of methane, 14.5 nmol g-1 d-1 of ethylene, 3.9 nmol g-1 d-1 of ethane and 9.7 nmol g-1 d-1 of propylene. When incubated in air, LDPE emits gases at rates ~2 times and ~76 times higher in comparison to water for methane and ethylene, respectively.


title: Polyethylene

text: Polyethylene may either be modified in the polymerization by polar or non-polar comonomers or after polymerization through polymer-analogous reactions. Common polymer-analogous reactions are in case of polyethylene crosslinking, chlorination and sulfochlorination.


title: Polyethylene

text: In the low pressure process α-olefins (e.g. 1-butene or 1-hexene) may be added, which are incorporated in the polymer chain during polymerization. These copolymers introduce short side chains, thus crystallinity and density are reduced. As explained above, mechanical and thermal properties are changed thereby. In particular, PE-LLD is produced this way.


title: Polyethylene

text: Metallocene polyethylene (PE-M) is prepared by means of metallocene catalysts, usually including copolymers (z. B. ethene / hexene). Metallocene polyethylene has a relatively narrow molecular weight distribution, exceptionally high toughness, excellent optical properties and a uniform comonomer content. Because of the narrow molecular weight distribution it behaves less pseudoplastic (especially under larger shear rates). Metallocene polyethylene has a low proportion of low molecular weight (extractable) components and a low welding and sealing temperature. Thus, it is particularly suitable for the food industry.


title: Polyethylene

text: Polyethylene with multimodal molecular weight distribution consists of several polymer fractions, which are homogeneously mixed. Such polyethylene types offer extremely high stiffness, toughness, strength, stress crack resistance and an increased crack propagation resistance. They consist of equal proportions higher and lower molecular polymer fractions. The lower molecular weight units crystallize easier and relax faster. The higher molecular weight fractions form linking molecules between crystallites, thereby increasing toughness and stress crack resistance. Polyethylene with multimodal molecular weight distribution can be prepared either in two-stage reactors, by catalysts with two active centers on a carrier or by blending in extruders.


title: Polyethylene

text: Cyclic olefin copolymers are prepared by copolymerization of ethene and cycloolefins (usually norbornene) produced by using metallocene catalysts. The resulting polymers are amorphous polymers and particularly transparent and heat resistant.


title: Polyethylene

text: The basic compounds used as polar comonomers are vinyl alcohol (Ethenol, an unsaturated alcohol), acrylic acid (propenoic acid, an unsaturated acid) and esters containing one of the two compounds.


title: Polyethylene

text: Ethylene/vinyl alcohol copolymer (EVOH) is (formally) a copolymer of PE and vinyl alcohol (ethenol), which is prepared by (partial) hydrolysis of ethylene-vinyl acetate copolymer (as vinyl alcohol itself is not stable). However, typically EVOH has a higher comonomer content than the VAC commonly used.


title: Polyethylene

text: EVOH is used in multilayer films for packaging as a barrier layer (barrier plastic). As EVOH is hygroscopic (water-attracting), it absorbs water from the environment, whereby it loses its barrier effect. Therefore, it must be used as a core layer surrounded by other plastics (like LDPE, PP, PA or PET). EVOH is also used as a coating agent against corrosion at street lights, traffic light poles and noise protection walls.


title: Polyethylene

text: Copolymer of ethylene and unsaturated carboxylic acids (such as acrylic acid) are characterized by good adhesion to diverse materials, by resistance to stress cracking and high flexibility. However, they are more sensitive to heat and oxidation than ethylene homopolymers. Ethylene/acrylic acid copolymers are used as adhesion promoters.


title: Polyethylene

text: If salts of an unsaturated carboxylic acid are present in the polymer, thermo-reversible ion networks are formed, they are called ionomers. Ionomers are highly transparent thermoplastics which are characterized by high adhesion to metals, high abrasion resistance and high water absorption.


title: Polyethylene

text: If unsaturated esters are copolymerized with ethylene, either the alcohol moiety may be in the polymer backbone (as it is the case in ethylene-vinyl acetate copolymer) or of the acid moiety (e. g. in ethylene-ethyl acrylate copolymer). Ethylene-vinyl acetate copolymers are prepared similarly to LD-PE by high pressure polymerization. The proportion of comonomer has a decisive influence on the behaviour of the polymer.


title: Polyethylene

text: The density decreases up to a comonomer share of 10% because of the disturbed crystal formation. With higher proportions it approaches to the one of polyvinyl acetate (1.17 g/cm). Due to decreasing crystallinity ethylene vinyl acetate copolymers are getting softer with increasing comonomer content. The polar side groups change the chemical properties significantly (compared to polyethylene): weather resistance, adhesiveness and weldability rise with comonomer content, while the chemical resistance decreases. Also mechanical properties are changed: stress cracking resistance and toughness in the cold rise, whereas yield stress and heat resistance decrease. With a very high proportion of comonomers (about 50%) rubbery thermoplastics are produced (thermoplastic elastomers).


title: Polyethylene

text: A basic distinction is made between peroxide crosslinking (PE-Xa), silane crosslinking (PE-Xb), electron beam crosslinking (PE-Xc) and azo crosslinking (PE-Xd).


title: Polyethylene

text: Chlorinated Polyethylene (PE-C) is an inexpensive material having a chlorine content from 34 to 44%. It is used in blends with PVC because the soft, rubbery chloropolyethylene is embedded in the PVC matrix, thereby increasing the impact resistance. It also increases the weather resistance. Furthermore, it is used for softening PVC foils, without risking the migrate of plasticizers. Chlorinated polyethylene can be crosslinked peroxidically to form an elastomer which is used in cable and rubber industry. When chlorinated polyethylene is added to other polyolefins, it reduces the flammability.


title: Polyethylene

text: Braskem and Toyota Tsusho Corporation started joint marketing activities to produce polyethylene from sugarcane. Braskem will build a new facility at their existing industrial unit in Triunfo, Rio Grande do Sul, Brazil with an annual production capacity of , and will produce high-density and low-density polyethylene from bioethanol derived from sugarcane.


title: Polyethylene

text: Polyethylene can also be made from other feedstocks, including wheat grain and sugar beet. These developments are using renewable resources rather than fossil fuel, although the issue of plastic source is currently negligible in the wake of plastic waste and in particular polyethylene waste as shown above.


title: Polyethylene

text: The name polyethylene comes from the ingredient and not the resulting chemical compound, which contains no double bonds. The scientific name "polyethene" is systematically derived from the scientific name of the monomer. The alkene monomer converts to a long, sometimes "very" long, alkane in the polymerization process. In certain circumstances it is useful to use a structure-based nomenclature; in such cases IUPAC recommends poly(methylene) (poly(methanediyl) is a non-preferred alternative). The difference in names between the two systems is due to the "opening up" of the monomer's double bond upon polymerization. The name is abbreviated to "PE". In a similar manner polypropylene and polystyrene are shortened to PP and PS, respectively. In the United Kingdom and India the polymer is commonly called "polythene", from the ICI trade name, although this is not recognized scientifically.


title: White dwarf

text: A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes from the emission of residual thermal energy; no fusion takes place in a white dwarf. The nearest known white dwarf is at 8.6 light years, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun. The unusual faintness of white dwarfs was first recognized in 1910. The name "white dwarf" was coined by Willem Luyten in 1922.


title: White dwarf

text: White dwarfs are thought to be the final evolutionary state of stars whose mass is not high enough to become a neutron star or black hole. This includes over 97% of the other stars in the Milky Way. After the hydrogen-fusing period of a main-sequence star of low or medium mass ends, such a star will expand to a red giant during which it fuses helium to carbon and oxygen in its core by the triple-alpha process. If a red giant has insufficient mass to generate the core temperatures required to fuse carbon (around 1 billion K), an inert mass of carbon and oxygen will build up at its center. After such a star sheds its outer layers and forms a planetary nebula, it will leave behind a core, which is the remnant white dwarf. Usually, white dwarfs are composed of carbon and oxygen (CO white dwarf). If the mass of the progenitor is between 8 and 10.5 solar masses (), the core temperature will be sufficient to fuse carbon but not neon, in which case an oxygen–neon–magnesium (ONeMg or ONe) white dwarf may form. Stars of very low mass will be unable to fuse helium; hence, a helium white dwarf may form by mass loss in binary systems.


title: White dwarf

text: The material in a white dwarf no longer undergoes fusion reactions, so the star has no source of energy. As a result, it cannot support itself by the heat generated by fusion against gravitational collapse, but is supported only by electron degeneracy pressure, causing it to be extremely dense. The physics of degeneracy yields a maximum mass for a non-rotating white dwarf, the Chandrasekhar limit — approximately 1.44 times — beyond which it cannot be supported by electron degeneracy pressure. A carbon–oxygen white dwarf that approaches this mass limit, typically by mass transfer from a companion star, may explode as a type Ia supernova via a process known as carbon detonation; SN 1006 is thought to be a famous example.


title: White dwarf

text: A white dwarf is very hot when it forms, but because it has no source of energy, it will gradually cool as it radiates its energy away. This means that its radiation, which initially has a high color temperature, will lessen and redden with time. Over a very long time, a white dwarf will cool and its material will begin to crystallize, starting with the core. The star's low temperature means it will no longer emit significant heat or light, and it will become a cold black dwarf. Because the length of time it takes for a white dwarf to reach this state is calculated to be longer than the current age of the known universe (approximately 13.8 billion years), it is thought that no black dwarfs yet exist. The oldest known white dwarfs still radiate at temperatures of a few thousand kelvins, which establishes an observational limit on the maximum possible age of the universe.


title: White dwarf

text: The first white dwarf discovered was in the triple star system of 40 Eridani, which contains the relatively bright main sequence star 40 Eridani A, orbited at a distance by the closer binary system of the white dwarf 40 Eridani B and the main sequence red dwarf 40 Eridani C. The pair 40 Eridani B/C was discovered by William Herschel on 31 January 1783. In 1910, Henry Norris Russell, Edward Charles Pickering and Williamina Fleming discovered that, despite being a dim star, 40 Eridani B was of spectral type A, or white. In 1939, Russell looked back on the discovery:


title: White dwarf

text: I was visiting my friend and generous benefactor, Prof. Edward C. Pickering. With characteristic kindness, he had volunteered to have the spectra observed for all the stars – including comparison stars – which had been observed in the observations for stellar parallax which Hinks and I made at Cambridge, and I discussed. This piece of apparently routine work proved very fruitful – it led to the discovery that all the stars of very faint absolute magnitude were of spectral class M. In conversation on this subject (as I recall it), I asked Pickering about certain other faint stars, not on my list, mentioning in particular 40 Eridani B. Characteristically, he sent a note to the Observatory office and before long the answer came (I think from Mrs. Fleming) that the spectrum of this star was A. I knew enough about it, even in these paleozoic days, to realize at once that there was an extreme inconsistency between what we would then have called "possible" values of the surface brightness and density. I must have shown that I was not only puzzled but crestfallen, at this exception to what looked like a very pretty rule of stellar characteristics; but Pickering smiled upon me, and said: "It is just these exceptions that lead to an advance in our knowledge", and so the white dwarfs entered the realm of study!


title: White dwarf

text: The white dwarf companion of Sirius, Sirius B, was next to be discovered. During the nineteenth century, positional measurements of some stars became precise enough to measure small changes in their location. Friedrich Bessel used position measurements to determine that the stars Sirius (α Canis Majoris) and Procyon (α Canis Minoris) were changing their positions periodically. In 1844 he predicted that both stars had unseen companions:


title: White dwarf

text: If we were to regard "Sirius" and "Procyon" as double stars, the change of their motions would not surprise us; we should acknowledge them as necessary, and have only to investigate their amount by observation. But light is no real property of mass. The existence of numberless visible stars can prove nothing against the existence of numberless invisible ones.


title: White dwarf

text: Bessel roughly estimated the period of the companion of Sirius to be about half a century; C.A.F. Peters computed an orbit for it in 1851. It was not until 31 January 1862 that Alvan Graham Clark observed a previously unseen star close to Sirius, later identified as the predicted companion. Walter Adams announced in 1915 that he had found the spectrum of Sirius B to be similar to that of Sirius.


title: White dwarf

text: In 1917, Adriaan van Maanen discovered Van Maanen's Star, an isolated white dwarf. These three white dwarfs, the first discovered, are the so-called "classical white dwarfs". Eventually, many faint white stars were found which had high proper motion, indicating that they could be suspected to be low-luminosity stars close to the Earth, and hence white dwarfs. Willem Luyten appears to have been the first to use the term "white dwarf" when he examined this class of stars in 1922; the term was later popularized by Arthur Stanley Eddington. Despite these suspicions, the first non-classical white dwarf was not definitely identified until the 1930s. 18 white dwarfs had been discovered by 1939. Luyten and others continued to search for white dwarfs in the 1940s. By 1950, over a hundred were known, and by 1999, over 2,000 were known. Since then the Sloan Digital Sky Survey has found over 9,000 white dwarfs, mostly new.


title: White dwarf

text: Although white dwarfs are known with estimated masses as low as 0.17  and as high as 1.33 , the mass distribution is strongly peaked at 0.6 , and the majority lie between 0.5 and 0.7 . The estimated radii of observed white dwarfs are typically 0.8–2% the radius of the Sun; this is comparable to the Earth's radius of approximately 0.9% solar radius. A white dwarf, then, packs mass comparable to the Sun's into a volume that is typically a million times smaller than the Sun's; the average density of matter in a white dwarf must therefore be, very roughly, 1,000,000 times greater than the average density of the Sun, or approximately 10 g/cm, or 1 tonne per cubic centimetre. A typical white dwarf has a density of between 10 and 10 g/cm. White dwarfs are composed of one of the densest forms of matter known, surpassed only by other compact stars such as neutron stars, quark stars (hypothetical), and black holes.


title: White dwarf

text: White dwarfs were found to be extremely dense soon after their discovery. If a star is in a binary system, as is the case for Sirius B or 40 Eridani B, it is possible to estimate its mass from observations of the binary orbit. This was done for Sirius B by 1910, yielding a mass estimate of , which compares well with a more modern estimate of . Since hotter bodies radiate more energy than colder ones, a star's surface brightness can be estimated from its effective surface temperature, and that from its spectrum. If the star's distance is known, its absolute luminosity can also be estimated. From the absolute luminosity and distance, the star's surface area and its radius can be calculated. Reasoning of this sort led to the realization, puzzling to astronomers at the time, that due to their relatively high temperature and relatively low absolute luminosity, Sirius B and 40 Eridani B must be very dense. When Ernst Öpik estimated the density of a number of visual binary stars in 1916, he found that 40 Eridani B had a density of over 25,000 times the Sun's, which was so high that he called it "impossible". As A.S. Eddington put it later, in 1927:


title: White dwarf

text: We learn about the stars by receiving and interpreting the messages which their light brings to us. The message of the companion of Sirius when it was decoded ran: "I am composed of material 3,000 times denser than anything you have ever come across; a ton of my material would be a little nugget that you could put in a matchbox." What reply can one make to such a message? The reply which most of us made in 1914 was — "Shut up. Don't talk nonsense."


title: White dwarf

text: As Eddington pointed out in 1924, densities of this order implied that, according to the theory of general relativity, the light from Sirius B should be gravitationally redshifted. This was confirmed when Adams measured this redshift in 1925.


title: White dwarf

text: Such densities are possible because white dwarf material is not composed of atoms joined by chemical bonds, but rather consists of a plasma of unbound nuclei and electrons. There is therefore no obstacle to placing nuclei closer than normally allowed by electron orbitals limited by normal matter. Eddington wondered what would happen when this plasma cooled and the energy to keep the atoms ionized was no longer sufficient. This paradox was resolved by R. H. Fowler in 1926 by an application of the newly devised quantum mechanics. Since electrons obey the Pauli exclusion principle, no two electrons can occupy the same state, and they must obey Fermi–Dirac statistics, also introduced in 1926 to determine the statistical distribution of particles which satisfy the Pauli exclusion principle. At zero temperature, therefore, electrons can not all occupy the lowest-energy, or "ground", state; some of them would have to occupy higher-energy states, forming a band of lowest-available energy states, the "Fermi sea". This state of the electrons, called "degenerate", meant that a white dwarf could cool to zero temperature and still possess high energy.


title: White dwarf

text: Compression of a white dwarf will increase the number of electrons in a given volume. Applying the Pauli exclusion principle, this will increase the kinetic energy of the electrons, thereby increasing the pressure. This "electron degeneracy pressure" supports a white dwarf against gravitational collapse. The pressure depends only on density and not on temperature. Degenerate matter is relatively compressible; this means that the density of a high-mass white dwarf is much greater than that of a low-mass white dwarf and that the radius of a white dwarf decreases as its mass increases.


title: White dwarf

text: The existence of a limiting mass that no white dwarf can exceed without collapsing to a neutron star is another consequence of being supported by electron degeneracy pressure. Such limiting masses were calculated for cases of an idealized, constant density star in 1929 by Wilhelm Anderson and in 1930 by Edmund C. Stoner. This value was corrected by considering hydrostatic equilibrium for the density profile, and the presently known value of the limit was first published in 1931 by Subrahmanyan Chandrasekhar in his paper "The Maximum Mass of Ideal White Dwarfs". For a non-rotating white dwarf, it is equal to approximately , where is the average molecular weight per electron of the star. As the carbon-12 and oxygen-16 which predominantly compose a carbon–oxygen white dwarf both have atomic number equal to half their atomic weight, one should take equal to 2 for such a star, leading to the commonly quoted value of 1.4 . (Near the beginning of the 20th century, there was reason to believe that stars were composed chiefly of heavy elements, so, in his 1931 paper, Chandrasekhar set the average molecular weight per electron, , equal to 2.5, giving a limit of 0.91 .) Together with William Alfred Fowler, Chandrasekhar received the Nobel prize for this and other work in 1983. The limiting mass is now called the "Chandrasekhar limit".


title: White dwarf

text: If a white dwarf were to exceed the Chandrasekhar limit, and nuclear reactions did not take place, the pressure exerted by electrons would no longer be able to balance the force of gravity, and it would collapse into a denser object called a neutron star. Carbon–oxygen white dwarfs accreting mass from a neighboring star undergo a runaway nuclear fusion reaction, which leads to a Type Ia supernova explosion in which the white dwarf may be destroyed, before it reaches the limiting mass.


title: White dwarf

text: New research indicates that many white dwarfs – at least in certain types of galaxies – may not approach that limit by way of accretion. It has been postulated that at least some of the white dwarfs that become supernovae attain the necessary mass by colliding with one another. It may be that in elliptical galaxies such collisions are the major source of supernovae. This hypothesis is based on the fact that the X-rays produced by those galaxies are 30 to 50 times less than what is expected to be produced by type Ia supernovas of that galaxy as matter accretes on the white dwarf from its encircling companion. It has been concluded that no more than 5 percent of the supernovae in such galaxies could be created by the process of accretion onto white dwarfs. The significance of this finding is that there could be two types of supernovae, which could mean that the Chandrasekhar limit might not always apply in determining when a white dwarf goes supernova, given that two colliding white dwarfs could have a range of masses. This in turn would confuse efforts to use exploding white dwarfs as standard candles in determining distances.