bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of an engineering tool to quantify the explosion hazard of flammable liquid spills
Authors: Tamanini Francesco
Published: April 2004

Flammable liquid spills, or slow heavy vapor releases, produce flammable layers which, if ignited, can cause damage to the enclosure containing the release. The question of pressure development in the ensuing explosion has been addressed in a previous paper. This paper describes a model to predict the fuel distribution in the flammable layer as a function of the parameters that define the spill (or fuel release) scenario. Since the model is intended for use in engineering predictions, it is designed to be easy to use and compatible with widely available computer resources. Accordingly, the flow field is treated as one‐dimensional taking only variations in the vertical direction into account.

This simplifying assumption is supplemented by special adjustments for effects not accurately addressed without the horizontal gradients. This includes sub‐models to deal with forced ventilation and cases where the vaporizing pool occupies only a fraction of the floor area of the enclosure.

The model has been validated by comparison with available data from vaporizing pools, and for diffusing heavy vapors. Overall agreement with the experiment is satisfactory, and generally on the conservative side. On the basis of these results, the formulation has been judged suitable for use in combination with the method to predict the pressure increase from combustion of the flammable layer. These two elements are part of an integrated tool developed for use by FM Global Loss Prevention Consultants. The paper discusses the implications of this modeling approach in terms of protection design.
Evaluating vent manifold inerting requirements: Flash point modeling for organic acid‐water mixtures
Authors: Garland R. Wayne , Malcolm Michael O.
Published: April 2004

We wanted to reduce risk to very low levels in our manufacturing operations. We also needed to predict the effect on risk of potential future process changes. A survey was done on all processes to determine where flammable and combustible materials may be used. Process vessels were screened to determine which may be operating above the flash point without inert blanketing and with sufficient vapor space to generate a significant fire or explosion. This work was needed to ascertain whether or not to inert the process vessel, as well as its potential effect on the vent manifold system. An accurate assessment requires data on chemical flash points, but available data was limited primarily to pure components, not the mixtures—organic acids with water or anhydrides—with which we were dealing. Assessments using pure component data would have been very conservative, but also would have resulted in process modifications requiring large capital expenditures. To generate more accurate data we ran a four‐component experiment designed for organic acid: water mixtures. Two different models were required to describe the results due to boundary issues. Excellent correlations were achieved. Results from this study helped us achieve our safety objectives with minimal capital expenditures.
Runaway reactions in aluminum, aluminum chloride, HCl, and steam: An investigation of the 1998 CONDEA Vista explosion in Maryland
Authors: Reza Ali , Kemal Abid , Markey Peter E.
Published: April 2004

On October 13, 1998, an explosion and fire occurred at a 3,000 gallon reactor in the linear alkyl benzene (LAB) process at the CONDEA Vista plant in Maryland. Process materials released from the various vessels and piping fueled a subsequent fire that took approximately two hours to extinguish. The accident investigation revealed that, prior to the explosion, the bottom of the reactor was plugged with approximately 180 gallons of a sludge‐like mixture of coarse aluminum powder, aluminum chloride, and various hydrocarbons. The explosion occurred approximately 10 minutes after steam was introduced at the bottom of the reactor in an effort to break up the sludge accumulation.

A series of reduced‐scale chemical reactivity tests were completed to investigate the potential reactions between steam and manufactured sludge similar to what had accumulated inside the reactor. Rapid runaway chemical reactions were observed after steam was injected into this mixture, and pressures in excess of 45 barg (660 psig), and temperatures in excess of 700° F were recorded before the test vessels ruptured. A review of possible chemical reactions between steam, aluminum, and aluminum chloride confirms that the predominant reaction mechanism is the exothermic hydrolysis of aluminum chloride to produce HCl vapor. Significant amounts of hydrogen gas can also be generated as the aluminum reacts with the acid/steam mixture after it is stripped of its protective oxide coating. The investigators concluded that the root cause of this accident was direct and sustained contact between the steam and accumulated sludge at the bottom of the reactor.
Further uses of the heat of oxidation in chemical hazard assessment
Authors: Britton Laurence G. , Frurip David J.
Published: April 2004

Flammability: The “net heat of oxidation” technique described in an earlier publication is extended to predicting the lower flammable limits, lower limit flame temperatures, and limiting oxygen concentrations of chlorinated organic fuels having H:Cl ratios greater than unity. A new Rule is derived for predicting the effect of initial temperature on the lower flammable limits and limiting oxygen concentrations of organic fuels. It is suggested that this Rule be used in preference to the modified “Burgess‐Wheeler” Rule. The effect of initial pressure is discussed.

Instability: Net heats of oxidation (kcal/mol oxygen) for a series of disparate fuel groups are compared with “ΔHD,” the maximum heat of decomposition (cal/g) calculated using CHETAH methodology. Given the reasonable assumption that CHETAH's “maximum heat of decomposition” cannot exceed the net heat of combustion “ΔHC,” examination is made as to whether the ratio of these parameters (each expressed in units of kcal/mol), coined the “Reaction Heat Ratio” (RH), provides a useful new indicator for instability assessment.

Of these parameters, the net heat of oxidation (ΔHC/S) is the best indicator to help assign NFPA Instability Ratings. However, ΔHC/S cannot generally be used to assign ratings for organo‐peroxides. Also, its performance as an indicator for hazardous polymerization depends on the ΔHC/S difference between the reacting monomer and the polymer product, so it should become increasingly unreliable as the monomer ΔHC/S approaches ‐100 kcal/mol oxygen. The ranking method tacitly assumes organic polymers to have a constant heat of oxidation of about ‐100 kcal/mol oxygen. Errors in this assumption must invalidate the ranking approach where ΔHC/S differences are small. Finally, separate “cut‐offs” must be used at each NFPA Instability Rating for organo‐nitrates versus other organics containing combinations of CHON atoms. Additional materials need to be examined to extend this preliminary analysis. The net heat of oxidation would be a useful additional output parameter of the CHETAH program, if only for its application in flammability assessment. No conclusions are drawn regarding the usefulness of net heat of oxidation or RH in conducting CHETAH hazard assessments, since this procedure requires consideration of several variables. However, the analysis may be helpful to the ASTM E 27.07 subcommittee responsible for developing the program. For example, the ‐ΔHD ⩾ 700 cal/g cut‐off used to assign a “high” CHETAH hazard rating typically corresponds to organic materials rated NFPA 1, the second to lowest hazard rating.
Fire exposure of liquid‐filled vessels
Authors: Simpson Larry L.
Published: April 2004

Pressure vessels in the chemical industry generally have top‐mounted pressure relief valves (PRVs) sized to handle fire exposure and other possible scenarios. Designers usually assume that the fire scenario causes liquid to boil and vapor to vent, regardless of the initial liquid level. Under some circumstances, however, a high liquid level, together with thermal expansion, can result in a vessel being full of liquid when the PRV opens. If so, the initial fluid discharged through the PRV would be a two‐phase gas‐liquid stream.

This paper analyzes non‐reactive phenomena occurring during the heat‐up and venting process in non‐agitated liquid‐filled pressure vessels. A new criterion is developed to determine if the vapor‐venting sizing assumption is justified. Results from several cases show that pressures in most liquid‐filled vessels sized for vapor‐only flow will be below the ASME Code‐allowable values during fire exposure. Hence, the common industry practice of ignoring two‐phase flow when sizing fire cases is usually justified.
Lessons learned from an explosion in a large fractionator
Authors: Woodward John L. , Thomas J. Kelly , Kelly Brian D.
Published: April 2004

During plant start‐up, a critical interface exists at block valves located at battery limits of process units. A relatively small leak at a battery‐limit isolation point was established as the source of gas that caused an explosion in a 26‐foot diameter fractionator on a Fluid Coker nearing the end of a maintenance turn a round. This incident could easily have occurred in any modern oil refinery or chemical plant. This paper shares the technology and learning associated with small release scenarios that are often overlooked in large‐scale plant operations.

The explosion event did not damage the fractionator shell, but displaced all but two of the sieve trays in the column, and produced minor damage in the overhead condensers and receiver drum. Importantly, the consequent down‐time resulted in a major production loss. Damage analysis supports the proposition that a deflagration occurred in the top portion of the fractionator involving under 50 lbs. of fuel. It is believed that relatively small leaks, persisting over a period of a few hours, supplied the required amount of fuel. The accident investigation identified multiple potential pathways whereby natural gas leaking past battery limit block valves could have reached the fractionator.

This incident highlights the importance of securing leak tight connections between active and inactive sections of process systems. As a result of this experience, several procedural and organizational reforms have been instituted.
IEC 61508/61511—Pain or gain?
Authors: Timms Clive Roger
Published: April 2004

The introduction of IEC 61508 provided safety system practitioners with the first internationally accepted generic benchmark policy for safety‐related systems. However, many practitioners find the way in which the standard is often presented and promoted quite intimidating. But, there is no need to be intimidated. The grassroots rationale of the standard is fundamental common sense, and there have been significant developments in practical software aids that remove the pain.

An optimal design can lead to considerable capital cost savings from focused Safety Integrity Level (SIL) assessment, component selection, and logic simplification. Experience shows that up to 40% savings can be achieved with the aid of software tools at the design stage.

Full life cycle considerations also require alignment of a design with appropriate maintenance and testing strategies. This can afford significant opportunities to reduce maintenance and testing costs, production deferment, and the avoidance of nuisance trips. These opportunities become very achievable with the aid of software tools.

Software tools can help to achieve these not insignificant benefits by aiding design, and setting optimal testing and maintenance calculations to meet SIL requirements.
Investigation of catastrophic vessel overpressurization
Authors: Long Lisa A.
Published: April 2004

This paper summarizes the U.S. Chemical Safety and Hazard Investigation Board's investigation of a 1998 catastrophic vessel overpressurization incident at a petroleum separation facility near Pitkin, Louisiana. Sonat Exploration Company (now El Paso Production Company) owned the site. Two separation trains were set up to produce crude oil and natural gas from a high‐pressure, three‐phase mixture of crude oil, natural gas, and water. Employees were in the process of purging a pipeline when a separation vessel was overpressurized and catastrophically failed. It ruptured and released natural gas, which ignited and produced a large fireball. Four workers were instantly killed, and nearby tanks and piping were damaged. The lack of formal engineering design reviews and hazard analyses, adequate pressure relief devices, and written operating procedures for each phase of facility operations were identified as root and contributing causes of the incident.
The survivability of steel and aluminum 33.5 pound propane cylinders in fire
Authors: Birk A. M. , Vandersteen Jonathan D. J.
Published: April 2004

All pressure cylinders in North America used for liquefied petroleum gases (LPG) must meet the standards set by the Compressed Gas Association (CGA), regardless of whether they are made of steel or aluminum. However, there is anecdotal evidence from accidents that suggests that an aluminum propane cylinder is much more likely to fail than a steel one when exposed to fire in an accident. In order to test and quantify this, a series of fire tests were performed on standard 33.5 lb (DOT 4E240) propane cylinders. Three aluminum cylinders and three steel cylinders were tested under three different fire conditions, covering a range of fire engulfment severity. In all cases, the cylinders were horizontal and the fire was directed onto the side and top of the cylinders. In matching tests, all 3 aluminum cylinders failed in less than 10 minutes, including one boiling liquid expanding vapor explosion (BLEVE), while all 3 steel cylinders did not fail even after more than 40 minutes in the fire. This paper presents the results and an analysis of the fire test data.
Mitigation of backdraft with water mist: A reduced‐scale experimental study
Authors: Weng W. G. , Fan W. C.
Published: April 2004

Backdraft is a special fire behavior in a limited‐ventilation building. It can develop from fires of either ordinary combustibles, or ignitable liquids that become oxygen‐starved, yet continue to generate a fuel‐rich environment. If abundant fresh air is abruptly supplied by opening a door or breaking a window, the hot gas in this vitiated building will rapidly combust and a fireball and blast wave will take place. Backdraft can occur abruptly with powerful destruction, which may cause fatalities and the collapse of buildings. In this paper, the results of a reduced‐scale experimental test series using water mist to mitigate backdraft are presented. This reduced‐scale compartment (length x width x height with 1.2 m x 0.6 m x 0.6 m) was fitted with a door end opening geometry (width x height with 0.2 m x 0.4 m). Water mist was generated by a downward‐directed pressure nozzle operated at pressure of 0.2 MPa. The experimental results show that water mist is an effective mitigating tactic able to suppress backdraft in a building fire, primarily by means of reducing unburned fuel mass fraction, rather than by a thermal mechanism of cooling.
Dynamic model‐based technique for detecting faults in a chemical reactor
Authors: Chetouani Yahya , Mouhab Nordine , Cosmao Jean‐Marie , Estel Lionel
Published: April 2004

In this paper, we present a method for detecting faults that can appear in some parts of a chemical plant. This method is based on statistical information generated by the Extended Kalman Filter (EKF) technique and is designed to reveal any drift from the normal behavior of the process. Originally developed for linear systems, our contribution to this method consists in extending it to unsteady state nonlinear systems, such as stirred reactors in the presence of exothermic chemical reactions. We examined the abnormal behavior of a chemical reactor due to one fault in its control parameters. An abrupt variation of cooling flow rate has been studied experimentally. The objective of this experimental study is to detect the presence of such faults online, and to pinpoint the moment one occurs.
On the ability of process hazard analysis to identify accidents
Authors: Baybutt Paul
Published: April 2004

Process hazard analysis (PHA) has become the standard way of identifying possible accidents in processes. However, despite the large number of studies that have been performed since OSHA's Process Safety Management standard was issued in 1992, accidents still occur. When this happens the effectiveness of PHA and the quality of the studies performed may be questioned. Litigation can arise, and attorneys may try to make the case that someone was negligent because the PHA did not identify the accident that occurred.

While it is possible that PHAs may miss accident scenarios owing to the quality of the study performed, there are other reasons why scenarios may not be identified. This paper identifies and describes such reasons.
Young children learning about living things: A case study of conceptual change from ontological and social perspectives
Authors: Venville Grady
Published: April 2004

Although research from a developmental/psychological perspective indicates that many children do not have a scientific understanding of living things, even by the age of 10 years, little research has been conducted about how students learn this science topic in the classroom. This exploratory research used a case‐study design and qualitative data‐collection methods to investigate the process of conceptual change from ontological and social perspectives when Year 1 (5‐ and 6‐year‐old) students were learning about living things. Most students were found to think about living things with either stable, nonscientific or stable, scientific framework theories. Transitional phases of understanding also were identified. Patterns of conceptual change observed over the 5‐week period of instruction included theory change and belief revision as well as reversals in beliefs. The predominant pattern of learning, however, was the assimilation of facts and information into the students' preferred framework theory. The social milieu of the classroom context exposed students' scientific and nonscientific beliefs that influenced other individuals in a piecemeal fashion. Children with nonscientific theories of living things were identified as being least able to benefit from socially constructed, scientific knowledge; hence, recommendations are made for teaching that focuses on conceptual change strategies rather than knowledge enrichment. © 2004 Wiley Periodicals, Inc. J Res Sci Teach 41: 449–480, 2004
Study of additive compatibility with poly(vinyl chloride) (PVC). 2: Dynamic mechanical analysis of PVC lubrication by stearic acid and its derivatives
Authors: Fisch Michael , Bacaloglu Radu
Published: April 2004

The glass transition temperatures of PVC containing stearic acid derivatives as lubricants have been used to define two new parameters of lubrication: the saturation concentration and the efficiency constant. The saturation concentration represents the maximum amount of lubricant compatible with PVC in a specific formulation. The lubricant molecules are associated with the surface molecules of the PVC primary particles or are in the interstitial space between them. The use of lubricants at significantly lower concentration than the saturation concentration ensures their permanence in the polymer. They then act as internal lubricants reducing the viscosity of the melt. The use of lubricants at much higher concentrations than saturation concentration leads to formation of lubricant pools between PVC primary particles. Increased temperature or longer time ensures the release of lubricants from these pools at the surface of the polymer giving the lubricants an external character. At a normal usage of 0.5 to 1.5 phr (approximately 1.6–5 meq stearate) to 100 g PVC, methyl, barium and calcium stearates may be considered internal, aluminum and sodium internal/external, zinc, lithium, magnesium stearates and stearic acid itself external lubricants.
Materials and testing for extrusion of RPVC construction products
Authors: Rapacki Steven R.
Published: April 2004

Rigid PVC extruded construction products take many forms. Typical are house siding, window profiles, storm doors, pipe, fencing, and various accessory items generrally used for installation. In addition to these solid products, foam or cellular rigid PVC materials are entering the marketplace as substitutes for the traditional solid materials, or allowing PVC to capture other maintenance free applications; typical forms now in use include interior molding profiles and foam core pipe. This article focuses on the formulation ingredients constituting the articles mentioned above, how they are put together and influence the manufacturing process and final product, and how they can be tested to determine fit to the application requirements.
FR characteristics of phosphate ester plasticizers with inorganic additives in PVC
Authors: Moy Paul Y.
Published: April 2004

Two common approachs to flame retard flexible PVC are phosphate ester plasticizers and antimony oxide. When used individually, each displays excellent flame suppressing characteristics. However, the combination of the two has been reported to show lower than expected flame resistance. Zinc borate plays a synergistic role with mixtures of phosphate ester plasticizers and antimony oxide, producing one of the most effective FR composite in this study. A review of this behavior in various PVC formulations is presented.
Vinyl foam: Effect of density on physical properties
Authors: Patterson John
Published: April 2004

The technology of extruding rigid viyl foam has grown substantially over the last 10 years. Formulation additives, tooling and processing expertise have made possible a variety of applications such as profile, sheet, and foam core pipe. Many PVC foam manufactures are interested in reducing the density of their products to reduce costs and achieve lighter weights. The properties, however, are very dependent on the density of the foam product. A fundamental understanding of the relationship of physical properties to foam density is the objective of this paper, along with looking at ways to improve them.
Scale effects upon morphology development during mix melting of multiphase polymer blends in ZSK extruders
Authors: Yu Dong‐Woo , Esseghir Mohammed , Curry John
Published: April 2004

Replicate experiments were performed on ZSK‐30 and ZSK‐40 split barrel extruders concerning structure developments from PS‐PE pellet blends during the melting process. PS is the minor phase. PE grades were choosen to accommodate viscous and thin matrix phase viscosities. The large extruder displays a more diverse cross channel structure and retarded phase development for some blends. Inferior dispersion is especially obvious in the larger extruder when processing low viscosity matrix blends. Similar phase development occurs in the extruders for high viscosity matrix blends.
Development of a mathematical model for the calculation of the pressure drop in extrusion dies
Authors: Lang U. , Michaeli W.
Published: April 2004

Analytical approaches for calculating the pressure drop in extrusion dies are limited because they are only applicable in ideal flow channel geometries. In finite element calculations the pressure drop in different flow channels was determined. Parallel the cross section of those geometries was calculated, transformed into the ideal form of a slit or circle, and analytical calculations were done. From the results a correction function was derived. This enables realistic pressure drop calculation by applying simple analytical equations.
Predicting maximum field service temperatures from solar reflectance measurements of vinyl
Authors: Hardcastle Henry K.
Published: April 2004

Vinyl products continue penetrating Western U. S. markets. Vinyl products may show unacceptable heat distribution when installed in Western environments even after demonstrating a long tradition of acceptable heat build performance in Eastern U. S. environments. This paper presents a methodology for predicting maximum field service temperatures from solar reflectance measurements. Solar reflectance data (ASTM E‐903 and E‐892), field measurement data and a predictive model for a variety of vinyl systems are shown. This methodology may be used in addition to ASTM D‐4803 and is not limited to vinyl materials.
New benzoate plasticizers for polyvinyl chloride: Introduction and performance example
Authors: Arendt William D. , Lang Jiamin
Published: April 2004

Two new unique benzoate ester plasticizers that will offer the vinyl formulator improved performance have been developed. One is an excellent solvator that will yield lower plastisol viscosities than existing plasticizers. The other will provide an excellent alternate with low volatility. The new products provide expanded performance utility over existing benzoates and phthalates on a global basis. Basic plastisol performance data and an example of use in a specific application, vinyl leathercloth, are presented. The data demonstrates that these blends are compatible, effective high solvating plasticizers and are performance alternates for plastisols and other polyvinyl chloride applications.
Extraction resistant polymer stabilizers
Authors: Gray Robert L. , Lee Robert E. , Neri Carlo
Published: April 2004

A new generation of polysiloxane based polymer stabilizers is examined. The flexibility and versatility of polysiloxane backbones have allowed the development of a family of products that provide outstanding radical trapping efficiency, an unexpected resistance to extraction, and a high degree of compatibility in certain polymeric systems. Functionalization with graftable moieties results in a product that can be chemically bound to the polymer itself. The key to success in this work was optimizing the balance of graft linkages and mobility of the stabilizer chain.
New trends in polymer stabilization
Authors: Solera Peter
Published: April 2004

Polymer stabilization has been an active area of research and development for several decades. In this review, advances in phosphite chemistry are discussed with regard to hydrolysis resistance and color retention. The use of lactones as carbon centered radical traps is reviewed with examples showing the increase in performance over traditional base stabilization systems. Discoloration issues arising from hindered phenolic antioxidants are outlined, and, N,N‐dialkylhydroxylamine chemistry is reviewed as a means of avoiding phenolic discoloration while providing polymer protection. Color fading in demanding fiber applications is explored as well as a new stabilizer designed for color retention. The elimination of acid‐base interaction with NOR hindered amines is considered especially as it pertains to acidic polymer applications such as flame retardant end uses and agricultural films. Hindered amine stabilization chemistry and NOR performance data are discussed.
Properties of a thermoplastic elastomer derived from polyacrylate/PVC
Authors: Rehm Torsten
Published: April 2004

The polymerization of vinyl chloride in the presence of suitable elastomer dispersions yields so‐called PVC graft polymers. These may be processed on standard PVC equipment into flexible articles having a high mechanical strength and good indentation recovery. The ultimate physical properties are governed largely by the separation during processing into PVC‐rich and elastomer‐rich phases. For a polymer of poly(butyl acrylate) and PVC, this separation is examined by means of dynamic mechanical analysis (DMA). A method is presented by which it is possible to quantitatively classify the PVC molecules on the basis of grafted and ungrafted fractions as well as their respective size of the domains. The method allows the influence of processing conditions on stiffness, hardness, tensile strength, and elongation at break to be explained. Furthermore, reversible and irreversible property changes are shown to occur during reprocessing of test specimens.
Accelerated degradation of highly loaded polypropylene
Authors: Benavides R. , González‐Hernandez R. , González‐Cantú M. C. , Reyes‐Vielma B. , Billingham N. C.
Published: April 2004

The accelerated aging of six formulations of polypropylene highly loaded with calcium carbonate and containing a surfactant additive (stearic acid) as well as an ultraviolet (UV) stabilizer was studied. Degradation was followed by measuring mechanical properties (elongation percentage and impact resistance), the dynamic mechanical behavior and some chemical changes such as molecular weight and carbonyl group formation along with oxidation temperatures, found by chemiluminescence. The addition of 30 phr of filler to the polymer reduced the stability of the mixture, and the stearic acid used to treat the filler enhanced this effect considerably. On the other hand, the addition of the photostabilizer controlled to some extent such negative effects, though not completely. The most stable formulation was the polypropylene containing only the UV stabilizer.
Low‐melting sulfate glasses as additives to semirigid PVC and their flame retardant and smoke suppressant properties
Authors: Tian Chunming , Wang Hai , Ma Zhiguang , Guo Huazhi , Xu Jianzhong
Published: April 2004

The role of low‐melting sulfate glasses (LMSG) as additives on the flame retardant and smoke suppressant properties of semirigid poly(vinyl chloride) (PVC), as well as the mechanism for flame retardancy and smoke suppression, were studied through the Limiting Oxygen Index (LOI) test. Smoke Density Rating (SDR) test, DTA‐TG, and SEM. The results show that the LMSG have good smoke suppressant properties. When the PVC compound contains 40 parts of LMSG, the SDR value will be reduced by about 45%. The Cu2+, Zn2+, Mn2+, and Ni2+ sulfates, as well as MoO3, cause PVC to crosslink and form char, and the melt can protect not only the char formed during combustion and thermal degradation, but also undecomposed polymer. That is the main mechanism for flame retardation and smoke suppression when the additives melt. The mechanical properties of the PVC compounds containing different levels of LMSG were also studied.
Fire and flame retardants for PVC
Authors: William Coaker A.
Published: April 2004

The flammability performance of PVC plays a significant role in its selection for many applications. Its relatively high chlorine content (56.8%) makes it more resistant to ignition and burning than most organic polymers. In the case of flexible PVC, the plasticizers that contribute flexibility in most instances detract from its resistance to fire. To meet specifications such as oxygen index, heat release, smoke evolution, or extent of burning in cable tests, flame‐retardant (FR) and smoke‐suppressant (SS) additives are often incorporated. Synergistic combinations of FR and SS additives help PVC formulations meet many stringent FR specifications cost effectively.
Acrylic process aids for PVC: From theoretical concepts to practical use
Authors: Disson Jean‐Pierre , Girois Stéphane
Published: April 2004

Acrylic process aids have been widely used for decades in the production of both rigid and flexible PVC materials. Their advantages are well‐known and are briefly reviewed in this paper. Excessive use of process aids or selection of the wrong molecular weights may, however, lead to undesirable behavior ultimately resulting in defects in PVC materials. These limitations are discussed in detail and explained on the basis of general polymer science considerations. Some criteria to optimize the proper selection of the level and nature of the process aids in PVC formulations are given in relation to the final applications, such as films, window and foam profiles, pipes, and so on.
Effects of process temperature on the weathering performance of rigid poly(vinyl chloride)
Authors: Zehner Burch E. , Hartley Jeff
Published: April 2004

Elevated process temperatures can accompany current high extrusion rates of rigid poly(vinyl chloride). Various colored weatherable siding compounds were studied in the processing temperature range of 193°C to 227°C. The extruded compounds showed only minor color shifts due to increased melt temperatures. Outdoor exposure through four years in Arizona, Florida, and Ohio demonstrated typical color change but did not exhibit significant color shift relating to the initial processing temperatures. The samples extruded at elevated melt temperatures did demonstrate reduced impact strengths prior to outdoor exposure. Florida‐exposed and Ohio‐exposed samples lost impact strength throughout five years of exposure, with the samples processed at higher temperatures continuing to show lower impacts over time.
The influence of flame retardant structure on UV stabilization approaches in polypropylene
Authors: Gray Robert L. , Lee Robert E. , Sanders Brent M.
Published: April 2004

UV stabilization of polypropylene fiber containing brominated flame retardants has been the focus of intense technical efforts with only limited success. Acid generated by the flame retardants deactivates HALS, thus severely reducing the HALS' effectiveness. Because of this interaction, flame retarded polypropylene fiber has been generally restricted to applications requiring little or no UV stability. Evaluation of structure‐performance characteristics of both flame retardants and stabilizers allow development of packages which optimize processability, flame retardancy, and UV stability. This paper reviews progress in the stabilization of flame retarded PP fiber and presents new advances in this field.
An introduction to toughened polyamide‐4,6
Authors: Harding Jeff A.
Published: April 2004

Impact modified polytetramethylene adipamide (polyamide‐4,6) has recently been introduced. The author compares this compound to a toughened polyamide‐6,6 and a toughened polyamide‐6 in selected impact resistance and elevated temperature tests. Based on the results, toughened polyamide‐4,6 promises similar impact strength; and, better retention of stiffness, creep modulus, and toughness at elevated temperatures. Apparent improvements in melt stability make it suitable for extrusion, as well as injection molding applications.
Impact‐modified poly(vinyl chloride) and methyl methacrylate copolymer blends. Part 2: Thermal‐mechanical properties
Authors: Burke Dennis Michael
Published: April 2004

The objectives of this study were to determine the compatibility of various blends of commercially available rigid, unplasticized, impact‐modified polyvinyl chloride (UPVC) and methyl methacrylate (MMA) copolymers. The effects of acrylic type and loading level on compatibility were investigated. The resultant alloys or blends were subsequently evaluated for compatibility through examination of the following properties: processability, rigidity, strength, impact resistance, heat resistance, clarity, and ultra‐violet aging. This report limits itself to the discussion of the thermal‐mechanical properties, specifically dynamic mechanical properties in torsion (ASTM D 5279).
The role of lubricants in rigid PVC foam processing
Authors: Decker Robert W.
Published: April 2004

This study is designed to evaluate the role that lubricants have in the processing and final cell morphology of extruded rigid PVC foam. By developing a standard formulation in which only the type of lubricant was varied, the direct effects of functionality of the lubricant could be observed. It was found that not only is lubricant type very important for ease of processing, but also it determines the effectiveness of the blowing agent and the final density of the foamed material.
New rigid vinyl compound molding technology
Authors: Summers James W. , Toyoda Paul , Weir Scott , Beal Chris , Toensing Carl
Published: April 2004

During injection molding, it is not uncommon for shear heating to cause localized temperatures exceeding 300°C. This heating, if not suppressed, can cause vinyl degradation. Three main factors influence shear heating. They are (a) mold design, especially restrictions such as small gates; (b) injection conditions, especially injection velocity; and (c) compound viscosity. To address the compound factor, two new vinyl compounds have been created for custom injection molding, which are especially designed to suppress the shear heating temperatures. Geon® M3700 has good impact at room temperature, and Geon® M3800 has outstanding impact at room temperature and at low temperatures. These compounds use a new technology that produces a balance of properties never before achievable. These innovative compounds show enhanced processability including improved static thermal stability, improved shear stability, tolerance of higher injection screw rpms, tolerance of higher injection speeds, the ability to mold at lower injection pressures, reduced molding cycles, and the ability to fill thin part walls. Also designed into the compounds are improved color fastness during exposure to light, improved appearance, and reduced corrosiveness. Other properties such as impact strength, tensile strength, modulus, heat deflection temperature, hardness, UL flammability rating, specific gravity, and mold shrinkage remain comparable to older technology.
Fatigue crack propagation and damage evolution in PBT‐GF and SAN‐GF
Authors: Pavšek Vojko , Ehrenstein Gottfried W.
Published: April 2004

Our earlier investigations of fatigue behavior in PBT‐GF and SAN‐GF with different fiber lengths have shown that fatigue crack propagation (FCP) can be described in terms of elastic‐plastic fracture mechanics. In this work it is shown that the influence of structural material parameters on the resistance to FCP correlates with the extent of energy dissipation at the crack tip. With increasing fiber length, the zone of energy dissipation is increased. By means of microscopic investigations, the prevailing damage in the zone of energy dissipation is identified as micro cracks in the matrix.
The determination of polymer additive effects in a spherilene process HDPE matrix upon water carry‐over in water quenched, cast film extrusion
Authors: Cowell Timothy J. , Brunner Clayton B.
Published: April 2004

A test method useful in determining the effects of polymer additives upon water carry‐over (WCO) in water quenched, cast film extrusion is presented. Data from this test is obtained on film specimens based in a Spherilene process HDPE resin individually doped with 250 and 500 ppm of six various primary and secondary antioxidants and acid scavengers. Water contact angles and film surface tension data is also presented. The WCO test is reproducible and data may be applied to commercial production. Different additives that carry out the same function in the polymer may have greatly varying WCO properties; these differences are not detected by equilibrium goniometry.
“Go with the flow!”: Advantages of high melt flow rate ignition resistant polycarbonate vs. IR PC/ABS blends
Authors: Ogoe Samuel A. , Grelle Peter F. , Watkins Thomas J. , Masloski Peter J. , Kallman Mark A.
Published: April 2004

Polycarbonate (PC) has some inherent ignition resistant (IR) characteristics with good physical and mechanical properties. However, polycarbonate resins are not as easily processed as some styrenic materials, because of the high viscosity of PC. Extensive studies have been performed to develop an easy flow (high MFR) ignition resistant polycarbonate (IR PC) resin rated UL‐94 of V‐O down to 1.6 mm (0.0625 in) thickness and 5V down to 3.2 mm (0.125 in) thickness. This unique high MFR polycarbonate resin contains reduced levels of IR additives, in comparison to standard IR polycarbonate resins, which help to maintain the physical and mechanical properties of the polycarbonate base resin, without sacrificing the flammability properties of the final product. Using a high MFR polycarbonate resin improves processability and minimizes possible thermal degradation, resulting in improvement of overall processing performance and cost.
The influence of plasticizer on extruded thermoplastic starch
Authors: Van Der Burgt M. C. , Van Der Woude M. E. , Janssen L. P. B. M.
Published: April 2004

This paper describes the use of an extruder for the plastification process of potato starch with glycerol and water as plasticizers. The influence of both plasticizers is expressed in the water absorption index (WAI) and water solubility index (WSI). The amount of water added prior to extrusion is a tool to protect the starch polymers from degradation and to improve the extruder performance.
Weathering performance of rigid PVC pigmented with iron‐containing pigments: The relationship between weathering and the chemical nature of the iron contained
Authors: Peake Geoffrey T.
Published: April 2004

Weathering performance of rigid PVC pigmented with iron oxide or some complex inorganic pigments (CIP) containing iron can be poor. Consideration of iron‐containing CIP's for use in exterior PVC leads to the common question: “How much ‘free iron’ is present in the pigment?” It has been unclear what “free iron” means and therefore difficult to know which iron‐containing pigments will weather well and which will not. Some formulators may avoid iron‐containing pigments altogether by electing not to formulate in a color space only achievable with those pigments. We compare the weathering performance of a series of iron‐containing CIP's to the amount of iron contained, the crystal phases, and the amount of acid‐extractable iron. We see a strong correlation between the weathering performance and the extractable iron content. Many iron‐containing pigments have good weathering performance in PVC, so one shouldn't exclude iron‐containing pigments from consideration based solely on the iron content. The acid‐extractable iron is an indicator of the expected weathering performance. Careful evaluation and selection of pigments may allow consideration of previously avoided pigment combinations.
Requirements for medical vinyl compounds
Authors: Rakus Julius P.
Published: April 2004

What makes a material suitable for applications in the medical device industry? It is a question often asked, but seldom answered in a definitive way. This paper examines vinyl compounds from various viewpoints and attempts to define the requirements for their medical use with respect to formulation, chemical and mechanical purity, and performance characteristics such as viscoelastic properties, appearance, sterilizability, shelf life, and biological safety. Primary consideration is given to the situation in the United States, with a brief review of the position of some other countries' regulatory agencies. An outline is presented of how material suppliers can assure their customers and the regulators about the suitability of the compounds in question for various applications.
Characterization and properties of polyphthalamide/polyamide blends and polyphthalamide/polyamide/polyolefin blends
Authors: Desio Glenn P.
Published: April 2004

Polyphthalamide(PPA)/polyamide(PA) blends were analyzed to determine the effect of PA addition to PPA on melting point, glass transition temperature, dynamic modulus, and heat distortion temperature. Results indicate that the choice of PPA and the choice of PA for the blend systems affects not only the above properties but also the miscibility of the blend systems. In general, PA addition to PPA lowers the melting point and glass transition, which potentially makes these blend materials easier to process. Also, the PPA/PA blends were observed to have dynamic modulus curves with transitions shifted to lower temperatures and crystalline plateaus shifted to lower modulus.

PPA/PA/polyolefin(PP) systems were investigated to determine if a useful balance of properties could be obtained, even though the blend components would have to be processed at unusually high processing temperatures (in excess of 320°C). Morphological characterization indicates that small dispersed domains of PP are obtained. The modifiers utilized in these systems were either found at the interface of the PP domain or dispersed within the PP domain. The properties of PPA/PA/PP blends indicates that these systems are ductile and have a good balance of strength, stiffness, impact, and thermal performance.
Processing‐morphology‐property relationships in polyethylene/acrylonitrile copolymer/compatibilizer blends
Authors: Shah M. , Jabarin S. A.
Published: April 2004

Effects of blend composition, compatibilizer, and processing conditions on the morphology, rheology, and mechanical properties of the ternary blends are investigated. Introduction of compatibilizer and increasing shear rate lead to a finer particle dispersion. A modification of Wu's equation is utilized to obtain an estimate of the interfacial tension. The results indicate a reduction in interfacial tension upon addition of compatibilizer. Morphological stability of these blends is studied by reprocessing them in an injection molding machine and a twin‐screw extruder. The nature of the reprocessing history was found to govern the morphology and the mechanical properties of the blends investigated.
Low volatility antioxidants for scorch protection of polyurethane foams
Authors: Gray Robert L. , Lee Robert E. , Sanders Brent M.
Published: April 2004

Work continues to be done to provide effective stabilization of flexible bun stock formulations required by the reduction of chlorofluorocarbon (CFC) blowing agents, the associated increase of water content, and increased exotherm. Butylated hydroxytoluene (BHT) has served well as an antioxidant. However, its high volatility and tendency to form highly colored by‐products have limited its versatility.
Recent advances in the stabilization of flexible and semirigid PVC
Authors: Burley Joseph W.
Published: April 2004

Both the European and USA markets for liquid mixed metal stabilizers have moved or are moving to cadmium‐free products. Self‐lubricating products now dominate demanding areas such as calendering and extrusion in the European marketplace while the USA market has produced higher efficiency products by other means. In both markets, the use of organic costabilizers has played a major role in the formulation of cadmium‐free products. The merits of self‐lubricating technology and a new class of patented pyrrolidines are discussed here.
Installing a color system: The people considerations
Authors: Becker Elaine F.
Published: April 2004

The introduction of low‐price color systems, both quality control and color formulation, has brought affordability and practicality to the medium and small plastics companies. While color systems today are faster, cheaper, more accurate, easier to use than ever before, they are not that much more successful at doing what they were designed to do than they were 25 years ago. The pitfalls of start‐up and implementation and the people problems have changed very little and are still a major factor in determining the degree of success. This paper discusses the ramifications of who is chosen to implement the system, what their charter is, and the resources that they are given. Factors to be considered and creating the right environment when implementing a color system are discussed. Some suggestions for planning a successful start‐up and installation are given.
Use of inert gases in extruded medium density polypropylene foams
Authors: Dey S. K. , Natarajan P. , Xanthos M. , Braathen M. D.
Published: April 2004

Carbon dioxide gas was used as a physical blowing agent to produce medium density polypropylene foam sheets using a single screw extruder. The mechanical properties of the foam were similar in the machine direction and in the transverse direction. A better surface finish and a lower density foam was produced by using a commercial wrapping film as a cap layer. The process conditions and die design data are presented in an attempt to relate to product characteristics.