bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficiency of flameless venting devices
Authors: Going John E. , Chatrathi Kris
Published: April 2004

Over the last 10 years, several flameless venting devices have been globally available to extinguish flames discharged from a deflagration vent. These devices have primarily been used on industrial equipment located indoors with the potential for explosions or deflagrations. Both NFPA 68 and VDI 3673 guidelines prohibit the discharge of deflagration vents inside of buildings, and prescribe the use of vent ducts to direct the discharge outdoors to a safe location. This, however, requires an increase in vent area to overcome inefficiencies due to the discharge restrictions of the vent duct. The use of devices to extinguish flame from deflagration vents also results in less efficient venting. The efficiency of these devices was evaluated via large‐scale deflagration testing. Volumes from 0.5 m3 to 4 m3 were utilized with vent area ratios (A/V⅔) in the range of 0.1 to 0.3. Tests were conducted with fuel dusts having Ksts of up to 300 bar.m/sec. The effect of vent static burst pressure was also evaluated. Several methods of validating flame extinguishment were utilized and external effects were measured, including pressure and sound measurements outside the flameless venting device, and temperature on the surface of the device.
Connections: How a pipe failure resulted in resizing vessel emergency relief systems
Authors: Hendershot Dennis C. , Keiter Alan G. , Kacmar Jim , Magee Joseph W. , Morton Paul C. , Duncan Warren
Published: April 2004

Early on a Saturday morning, a two‐inch pipe in an unoccupied building in a plant shut down for the weekend ruptured violently. There were no injuries because nobody was in the building at the time. Nearby piping was bent and ruptured by impact from the failed pipe, and there was other minor equipment damage. The released material did not ignite, and was contained by the building spill containment system. The initial investigation of the incident determined that the ruptured pipe had been liquid‐filled, blocked in by closed valves, and overheated. The investigation could have stopped at that point, blaming the rupture on thermal expansion of the trapped liquid. However, a more detailed root cause investigation that yielded significant new knowledge of the thermal stability of the material was performed. This knowledge also resulted in redesign of the plant piping and the emergency relief systems on a number of plant vessels.
Flammability potential of halogenated fire suppression agents and refrigerants
Authors: Ural Erdem A.
Published: April 2004

Halogenated hydrocarbons are often used as fire suppression agents or refrigerants due to their low‐ or no‐flammability potential at atmospheric pressure and room temperature. However, these substances can form highly flammable mixtures with air at sufficiently high pressures—even at room temperature, and in the absence of other flammable vapors.

General flammability behavior indicates that there is a critical pressure (also referred to in the literature as the pressure limit of flammability), below which all possible mixtures of the Agent and air are non‐flammable. Above the critical pressure, a range of mixtures are explosible at room temperature. While this behavior does not affect the intended use and performance of these agents, recognizing this property, and determining the critical pressure are vital to establishing safety procedures that can avoid accidental explosions.

This paper presents an analysis, supporting data, and a screening method to evaluate the explosibility potential that may arise from deliberate or unintentional elevated pressure handling of refrigerants and fire protection agents. The data and the accompanying analysis suggests that even a fire protection agent such as HFC‐227ea may form an explosible mixture with air at room temperature if the pressure is above approximately 60 psig.

There is a definite need for the systematic characterization of refrigerant and fire protection agent flammability at elevated pressures, using appropriate experimental techniques discussed in the text.
Evaluation of available indices for inherently safer design options
Authors: Khan Faisal I. , Sadiq Rehan , Amyotte Paul R.
Published: April 2004

Inherent safety is a proactive approach for loss prevention during process plant design. It has been proven that, considering the lifetime costs of a process and its operation, an inherent safety approach can lead to a cost‐optimal option. Application of inherent safety at the early stages of process design yields the best results with respect to process selection, conceptual design, and engineering design. However, in spite of being an attractive and cost‐effective approach to loss prevention, it is not widely used. Reasons have been suggested for this lack of widespread use, but the lack of systematic tools to apply inherent safety principles is perhaps the most important one.

A detailed study was conducted to analyze the performance of available hazard indices with reference to various inherent safety principles (guidewords). The performance of four main indices (Dow, Mond, Inherent Safety, and Safety Weighted Hazard [SweHI] indices) was studied for five inherent safety guidewords. None of the indexing procedures can capture all of the inherent safety guidewords, although the SWeHI and Dow Index were found to be robust on many accounts. It is recommended that a new specific index be developed for inherently safer design evaluation. The SWeHI and Dow indexing procedures may be a good basis on which to build.
CSB'S reactive chemical hazard investigation: Description and lessons learned
Authors: Joseph Giby , Long Lisa A. , Mitchell Kevin , Murphy John F.
Published: April 2004

The U.S. Chemical Safety and Hazard Investigation Board (CSB) began operations as an independent federal agency in 1998. Its primary mission is to prevent chemical‐related incidents (fires, explosions, or toxic releases) in commercial or industrial settings by conducting incident investigations, reporting on causes, and issuing safety recommendations. This paper discusses some findings of the reactive chemical hazard investigation that originated from CSB's investigation of a runaway reaction at Morton International in 1998. As a result of this investigation, the Board made recommendations to promote the safe handling of reactive chemicals. Incident data sources were surveyed to determine the number and impact of reactive chemical incidents. Through site visits and surveys, the Board gathered information about reactive chemical hazard management for select small, medium, and large companies within the chemical industry. OSHA and EPA were also surveyed to determine current regulatory approaches for managing reactive chemical hazards and to identify future agency plans. This paper focuses on evidence that supports the Board's findings and recommendations on improving reactive chemical process safety.
Analysis of an LPG explosion and fire
Authors: Rodante Thomas V.
Published: April 2004

In September 1997, an LPG release occurred at the Hindustan Petroleum Corporation, Ltd. refinery in Visakhapatnam, India. The resulting explosion and fire destroyed most of the facility's administrative buildings, numerous LPG storage vessels, processing units, and an adjacent petroleum liquid storage terminal. Fifty‐six people were declared dead, but the fatality number could have been as high as 3 times the official estimate. Property damage was estimated at US $15 million.

It is known that a leak occurred during receipt of LPG cargo from a pressurized ship. The subsequent vapor cloud spread throughout the refinery tank farm, administrative complex, utilities area, and at least one process unit before eventually finding an ignition source. The investigation team developed numerous release theories. However, none of these theories could be substantiated by first hand witnesses' testimonies since all personnel directly involved in the tank filling operation were killed. Vapor cloud dispersion computer modeling was used to evaluate the credibility of various release scenarios. This paper discusses the events leading up to the explosion, the damages sustained, and compares quantitative dispersion modeling results to the physical damage and witness testimony obtained during the investigation.
Effects of plate impingement on the flammable volume of fuel jet releases
Authors: Sposato Christina , Tamanini Francesco , Rogers William J. , Mannan M. Sam
Published: April 2004

The effects of plate impingement on the flammable mixture produced by a fuel jet release were modeled with a commercial computational fluid dynamics (CFD) code. First, the CFD code was used to simulate the release of a free turbulent jet to assure that the code agreed with established trends. Equations were derived to determine the volume of the free jet above the lower flammable limit. The code was then used to model a jet confined by a wall or a circular plate. Computer simulated concentration profiles of the source fluid and air mixtures were analyzed to determine mixture volumes above the lower flammable limit. The flammable mixture volume was normalized and determined as a function of plate radius and distance.
Methodology and software for assessing reactivity ratings of chemical systems
Authors: Kossoy Arcady , Hofelich T.
Published: April 2004

To resolve various problems in creating a process, or conducting stability analysis, and/or hazard assessments, one needs t o know the reactivity of a chemical system. The National Fire Protection Association (NFPA) requires use of a reactivity rating number to describe such reactivity potentials as thermal stability, interaction with water, and gas generation. For assessing thermal stability of a substance, NFPA has recently accepted a new quantitative approach based on the idea of “Instantaneous Power Density.” Though it has many advantages compared to the largely qualitative previous approach, the new method has one serious draw‐back—it doesn't take into account the peculiarities of such complex cases as self‐accelerating or multi‐stage reactions. This, in turn, can lead to a less‐than‐safe, or unsafe, design.

In this paper, we propose a method to generalize the concept of instantaneous power density by considering the maximal power density as the quantitative measure of the reactivity, allowing one to take proper account of kinetic complexity. We also briefly discuss the ReRank software which was developed to assess reactivity ratings in general, and specifically, to calculate reactivity rating numbers.
Method for estimating decomposition characteristics of energetic chemicals
Authors: Chervin Sima , Bodman Glenn T.
Published: April 2004

Experimental data on the decomposition characteristics of approximately400 chemicals, representing various classes of energetic materials, were summarized by chemical class and statistically analyzed. Average decomposition characteristics, such as energy of decomposition and decomposition onset temperature, were determined for chemical classes containing the following energetic groups: nitro, nitroso, N‐oxide, oxime, hydroxylamine, tetrazole, azide, triazene, triazole, diazo, azo, hydrazine, and perchlorate. Additional statistical information is presented for each chemical class, such as number of chemicals analyzed, ranges, and standard deviations for the decomposition parameters analyzed. For chemical classes containing an energetic group attached to an aromatic ring, the presence and position of another substituting group in the ring can significantly influence the decomposition onset temperature. The study summarizes the list of activating and deactivating functional groups, and the positions in the ring where the strongest activation or deactivation occurs. The authors also recommend a method for estimating decomposition parameters of new chemicals.
Folk theories of “inquiry:” How preservice teachers reproduce the discourse and practices of an atheoretical scientific method
Authors: Windschitl Mark
Published: April 2004

Despite the ubiquity of the term “inquiry” in science education literature, little is known about how teachers conceptualize inquiry, how these conceptions are formed and reinforced, how they relate to work done by scientists, and if these ideas about inquiry are translated into classroom practice. This is a multicase study in which 14 preservice secondary science teachers developed their own empirical investigations—from formulating questions to defending results in front of peers. Findings indicate that participants shared a tacit framework of what it means to “do science” which shaped their investigations and influenced reflections on their inquiries. Some facets of the participants' shared model were congruent with authentic inquiry; however, the most consistent assumptions were misrepresentations of fundamental aspects of science: for example, that a hypothesis functions as a guess about an outcome, but is not necessarily part of a larger explanatory system; that background knowledge may be used to provide ideas about what to study, but this knowledge is not in the form of a theory or other model; and that theory is an optional tool one might use at the end of a study to help explain results. These ideas appear consistent with a “folk theory” of doing science that is promoted subtly, but pervasively, in textbooks, through the media, and by members of the science education community themselves. Finally, although all participants held degrees in science, the participants who eventually used inquiry in their own classrooms were those who had significant research experiences in careers or postsecondary study and greater science‐content background. © 2004 Wiley Periodicals, Inc. J Res Sci Teach 41: 481–512, 2004
Super tough PVC alloy with high heat distortion temperature
Authors: Huynh‐Ba Gia
Published: April 2004

Poly(vinyl chloride) (PVC) is an inexpensive commodity polymer with many good properties such as flame retardancy and rigidity. Unfortunately, its heat distortion temperature is around 75°C. To increase its toughness, plasticizers or elastomers are added with a loss in both heat distortion temperature (HDT) and flame retardancy. Low molecular weight imidized acrylic having a Tg < 130°C when added to PVC shows a modest gain in HDT but at the expense of toughness. Inclusion of a rubber to improve the toughness of the acrylic modified composition lowers its HDT as well as its flame retardancy. The technology reported here details a method utilizing an “alloy” polymer added to PVC to increase both its toughness and HDT.
Poly (α‐methylstyrene‐styrene‐acrylonitrile) as a heat deflection additive for PVC: Physical and rheological properties
Authors: Zerafati Saeid
Published: April 2004

Poly(α‐methylstyrene‐styrene‐acrylonitrile) (AMSAN) is an additive used to improve the heat deflection temperature of PVC. The effect of its addition on the HDT of a typical injection molding formulation is studied. Other physical properties like impact strength, yield strength, modulus of elasticity, and viscosity are also reported. It is shown that HDT and impact strength are decoupleable based on the amount of AMSAN and impact modifier in the formulation. Calculation of the required percentage of heat distortion additive and impact modifier for a typical injection molding application are demonstrated.
Radiation sterilization compatibility of medical packaging materials
Authors: Shang Sherwin , Ling Michael T. K. , Westphal Stanley P. , Woo Lecon
Published: April 2004

We have examined gamma sterilization compatibility for many of medical packaging materials. Techniques used include thermal analysis, physical testing, optical property evaluations, and failure analysis. For a variety of PVC formulations, gamma radiation often leads to discoloration. This results from conjugated poly‐ene sequences formed through dehydrohalogenation degradation during ionizing radiation. In addition to unacceptable color formation, excessive pH shifts and high extractables are often observed. For most polylefins, radiations was found to deplete the antioxidant package and lead to discoloration and/or mechanical failures. For polypropylenes, the degradation can lead to the well‐publicized catastrophic failures during post radiation shelf life storage. These examples and methods to ensure radiation compatibility and shelf‐life stability are presented.
The impact of metallocenes on PVC
Authors: Wilson Robert B.
Published: April 2004

PVC has been under attack from environmental groups for some time. Whatever the merits of the environmentalists' arguments, PVC has resisted this attack in many applications because of a unique combination of performance and price. As a result, the PVC industry has been experiencing a period of good growth. Metallocene based polyolefin resins are the first materials that appear to be a threat to that position. Recent reports of the performance of metallocene resins have demonstrated an incredible performance boost when compared with conventional PE or PP. This talk will examine the threat from the development of metallocenes.
Recycling durable vinyl products
Authors: Wisner D'Lane
Published: April 2004

This is a description of the key aspects that have made a vinyl siding recycling project in Grand Rapids, Michigan, successful to date. Although Grand Rapids is hoped to be a template for other recycling projects there are some unique parts of the project that other regions of the country or even the city next door to Grand Rapids may not be able to duplicate. It would not be advisable at this point in time to advocate a nation‐wide vinyl siding recycling program based on the early results from Grand Rapids. On the other hand, the day may come when recycling the waste from residential construction sites (including the vinyl products) will be more widespread. At any rate, what Grand Rapids has proven is that vinyl as a material is ready for recycling.
The Dilemma of flexible PVC from an independent compounder's perspective
Authors: Lederer Bertram
Published: April 2004

Flexible PVC compounds produced by the Plastics Division of Teknor Apex are used in most major end‐use markets. Our materials are molded and extruded for applications in wire and cable, automotive, medical, building and construction, appliances, toys, food packaging, housewares, power tools, recreational products, and many other industries. This involvement with diverse markets gives us a wideranging perspective on attitudes towards flexible PVC among people involved in product design, material specification, purchasing, sales and marketing, processing, and other important functions at corporations large and small.

“The Dilemma of Flexible PVC” reflects what we see, from our conversations and business dealings with these customers, as a critical crossroads for the material. On the one hand, we see many new opportunities for greater market penetration by flexible PVC because of dynamic new product development in the industry and continuing cost/performance advantages compared to other thermoplastics.

On the other hand, we are hearing escalating concerns from the marketplace about the environmental friendliness and safety of flexible PVC that may threaten these opportunities.

These negative attitudes toward PVC are certainly not new, but we are hearing them with increasingly greater frequency. They are coming from design engineers and other material specifiers developing new applications, and from people involved in long‐standing flexible PVC applications.
Beyond color: Modifiers and additives that affect appearance
Authors: Burgess Alan
Published: April 2004

In today's globally competitive market, product distinction is a key to success. Therefore, the ability to produce unique and appealing special effects becomes a powerful marketing tool for savvy manufacturers of plastic and other parts. High shelf‐appeal not only positions a product to attract the eye of the consumer, but also supports the impression that a product is of higher quality, a more playful or elegant design, or represents the latest that technology has to offer. When it comes to special effects, the buying public is insatiable and market demand is hindered only by the imagination of manufacturers and consumers. The ability of current color technology to support this demand requires that additive suppliers, color formulators, and plastics processors work in close partnership. This paper surveys the development of traditional and newer special effects technologies and describes some of the challenges encountered in developing them.
The structure of lead stabilizers. 2: Basic salts of inorganic acids
Authors: Grossman Richard F. , Krausnick Dale
Published: April 2004

FTIR and NMR measurements were used to infer structural formulas for the heat stabilizers dibasic lead phosphite, tribasic and tetrabasic lead sulfates, and basic lead carbonate. These compounds are not the customarily written double salts of lead oxide or hydroxide, but distinct species capable of rapid HCI neutralization.
Phosphate ester additives as melt flow modifiers in ABS
Authors: Moy Paul Y.
Published: April 2004

Melt flow modification of plastic composites is becoming increasingly important in the design of thin wall moldings. One approach to enhancing melt flow properties is by using phosphate esters. While phosphate ester plasticizers have been used for many years in flexible vinyl applications, the recent development of oligomeric phosphate esters offers high stability, low fugitive characteristics and melt flow enhancement to these demanding situations at a modest level. This paper discusses the influence of these additives to mechanical and melt flow properties in different process regimes for ABS.
Effect of physical aging on the impact retention and heat distortion temperature of vinyl products
Authors: Zerafati Saeid , Black Janine
Published: April 2004

Physical properties of polymers change with time. Exposure of amorphous polymers to high temperature will reduce their free volume, which in turn increases their heat distortion temperature and decreases their impact strength. Heat distortion additives, such as poly(α‐methylstyrene‐styrene‐acrylonitrile) (AMSAN), enhance the glass transition temperature of PVC and help in the impact retention of the polymer by slowing down the aging process. In this paper, physical aging of PVC is explored, effect of annealing time and temperature on the impact strength and HDT is reported, and conclusions regarding the retention of impact resistance upon aging are drawn.
Mechanical properties of extrusion‐foamed rigid PVC/wood‐flour composites
Authors: Mengeloglu Fatih , Matuana Laurent M.
Published: April 2004

This study was conducted to characterize the mechanical properties of extrusion‐foamed neat rigid PVC and rigid PVC/wood‐flour composites by using endothermic and exothermic chemical foaming agents (CFAs). The specific elongation at break (ductility) of the samples was improved by foaming, while the opposite trend was observed for the tensile strength and modulus of the samples, regardless of the chemical foaming agent type. In addition, experimental results indicated that foaming reduced the Izod impact resistance of both neat rigid PVC and rigid PVC/wood‐flour composites but that this reduction was not statistically significant for the composites. A comparison between batch microcellular processing and extrusion foam processing was made, which demonstrated that foams with very fine cells (microcellular processed) exhibit better impact strength than foams with larger cells (extrusion processed with CFAs).
Confirming the pinking mechanism of PVC profiles in mild climatic conditions
Authors: Lemaire Jacques , Siampiringue Narcisse , Girod Nicolas , Delprat Patrick , Parmeland Georges , Macdonald Neil , Spriet Christine
Published: April 2004

Pinking of TiO2‐pigmented PVC can be observed for profiles exposed to the mild environmental conditions of northern European countries. In a previous paper, the pinking phenomenon was accounted for at the molecular level by the formation of polyene sequences, which are not completely photooxidatively bleached in conditions of oxygen starvation. This causation has been confirmed by exposing to visible light in a SEPAP 12.24 apparatus profiles in which pinking was produced during 4 year‐weathering in N.W. France. The fast phototransformations in visible light of chloropolyenes in trans‐configurations leading to α‐chloropolyenes in cis‐configurations accounts for the conversion of pinking into limited graying. It appears that the first and more intense graying observed after the initial exposure to UV and visible light of profiles in the SEPAP 12.24 can be essentially attributed to the photoreduction products of lead stabilizers. Graying could be bleached through thermooxidation at 65°C, could not be converted into pinking, and has no environmental relevance.
Coprecipitates of dibasic lead phthalate and tribasic lead sulfate
Authors: Grossman Richard F.
Published: April 2004

Coprecipitates of dibasic lead phthalate and tribasic lead sulfate tend to crystallize with the latter forming the core of a core/shell structure. The reactivity of this structure towards hydrolysis of ester plasticizers is considerably lower than that of physical blends of the basic lead salts.
Effect of processing parameters on fusion and mechanical properties of a twin‐screw extruded rigid PVC pipe
Authors: Moghri M. , Garmabi H. , Akbarian M.
Published: April 2004

The effect of varying mass temperature and screw speed on the fusion level and mechanical properties of a rigid PVC pipe produced by a twin‐screw extruder has been investigated. Differential Scanning Calorimetry (DSC) and capillary rheometry have been used to determine pipe fusion levels. While yield stress was shown to be completely insensitive to fusion level, a very distinct maximum of falling weight and notched Charpy impact strengths and elongation at break was observed at moderate fusion level. Short‐term burst strength values increased with degree of fusion while hydrostatic internal pressure tests revealed optimum resistance for pipes of varying fusion level. The effect of processing temperature on fusion in the Brabender Plasticorder was also examined.
Impact modification of polypropylene
Authors: Rabinovitch Elvira B. , Summers James W. , Smith Greg
Published: April 2004

This paper compares the modification mechanism provided by ethylene‐octene (EO) copolymer to that of ethylene‐propylene‐diene terpolymer (EPDM) rubber. Within the limits of this study, the highest impact strength was achieved at 30–40% rubber content, regardless of the rubber type. An increase in rubber melt viscosity resulted in overall greater impact strength. At the optimum concentration, the high‐viscosity (MFI = 1 to 5) EO rubber provided modification mainly via a crazing mechanism, while the EPDM rubber functioned by energy dissipation through the three‐dimensional network structure formed with the polypropylene matrix. This paper also discusses the effects of the processing conditions on the physical properties of PP/EPR copolymer. An increase in processing temperature and screw speed resulted in a reduced number of discrete rubber particles and nearly no or very slight increase in impact strength, but a very significant reduction in tensile strength and tensile modulus.
How about alternatives to phthalate plasticizers?
Authors: Krauskopf Leonard G.
Published: April 2004

Phthalate plasticizers have historically served as the preferred plasticizers to impart flexibility to PVC and several other polar polymers. They provide a desirable balance of cost and performance properties. Their acceptable and safe use is unmatched in medical appliances, food processing, and packaging applications, as well as in many other end uses. Potential alternatives do not have the historical record of acceptable performance found with phthalate plasticizers. Nevertheless, the “Precautionary Principle” has caused certain segments of society to clamor for alternates to phthalate plasticizers. This paper reviews known “non‐phthalate” plasticizers and provides comparisons to the traditional “General Purpose” (GP) phthalate plasticizers; “General Purpose” plasticizers are those that impart optimum overall performance properties in PVC at lowest cost.
Evaluation of novel derivatives of 2,2‐dimethyl‐1,3‐diaminopropane as thermal and UV stabilizers in medium‐density polyethylene films
Authors: Berlanga Duarte M. L. , Rosales Jasso A. , Allen N. S.
Published: April 2004

Novel oligoalkylenamines (Additive A2) were obtained by the reaction between 2,2‐dichloropropane and 1,3‐diamino‐2,2‐dimethylpropane. The presence of partially hindered amine groups in the product was confirmed by NMR. The amines were evaluated as thermal and UV stabilizers in medium‐density polyethylene (MDPE) films containing Irganox 1330 (PEA2Ir), Chimassorb 944 (PEA2CH), or a mixture of Irganox 1330 and Chimassorb 944 (PEA2M) by following changes in the concentration of carbonyl groups in the IR region of 1718 cm−1. Under UV aging, the amine mixture A2 interacts with Chimassorb 944 in a synergistic way that is explained by the quenching of charge transfer complexes. Under thermal aging, a synergistic effect was observed in formulations containing Irganox 1330. It is still not clear if alkyl ethers of hydroxylamines from A2 are more stable at 100°C or if their nitroxyl radicals are more reactive than the corresponding species from Chimassorb 944.
Effects of processing and degree of fusion on the rheology of PVC
Authors: Hinrichsen Einar L. , Thorsteinsen Pål
Published: April 2004

PVC foils made from polymer grades having K‐values of 58 and 68 have been milled at different temperatures and shear conditions on a two‐roll mill. Compression molded foils were also made from the softest grade. The resulting samples have been studied using DSC and rotational dynamic rheometry at temperatures below and above the processing temperatures. DSC confirmed the correlation between the processing temperature and the temperature Tb separating endotherm A and B. However, this correlation is only valid for high processing temperatures (≥150°C). Also, if the processing temperature is lowered at the end of the processing, Tb will be lower than the maximum processing temperature. In most cases the area of endotherm A increased with increasing processing temperature and shear. From measurements of tan(δ) we find that when measuring at a temperature below the lowest processing temperature, the higher the degree of fusion, the larger is the relative amount of the elastic energy stored. Measuring at a temperature above the highest processing temperatures yields the opposite result. In between there is a transition zone where polymer grades having different M̄w respond differently to changes in thermomechanical processing history. These and other observations are discussed in terms of the gel‐destruction temperature introduced by Lyngaae‐Jørgensen, the breakdown of the particulate structure, and the creation of a three‐dimensional fusion network held together by ordered and crystalline regions.
An example of rigid PVC foam formulating using a statistical experimental design approach
Authors: Dunkelberger D. L. , Herman H. R.
Published: April 2004

A study was undertaken to understand the effect of PVC molecular weight, modifier molecular weight, and modifier loading on die swell and foam density in a rigid PVC formulation. We used a statistical experimental design to separate the effects from the noise of normal experimentation. Die swell and foam density of extruded pieces were measured and analyzed in a commercially available software package. Analysis of the experimental data shows that the die swell response is linear over the experimental range, while the foam density response is curved. The mathematical model developed in the data analysis is then used to predict the performance responses when the experimental factors are changed.
Inert‐gas extrusion of rigid PVC foam
Authors: Dey S. K. , Jacob C. , Xanthos M.
Published: April 2004

A novel approach to the extrusion of high‐density, rigid PVC foam uses commercial RPVC compounds with inert‐gas physical blowing agents (carbon dioxide and argon). The process was developed on a segmented single‐screw extruder with L/D of 40. On‐line monitoring of process variables was also carried out. This technique provides an alternative to conventional processing methods using chemical blowing agents.
The effect of test variables and extrusion conditions on heat deflection temperature of PVC
Authors: Rabinovitch Elvira B.
Published: April 2004

It is commonly expected that the heat deflection temperature of finished plastic products will match the values, reported by the material supplier. However, in practice, a significant deviation from the published data is frequently observed. This paper gives insight into the reasons for such a discrepancy. It presents information on the effect of the test variables, such as load, sample conditioning, sample flatness and extrusion conditions, such as: melt temperature and draw‐down (internal stresses), on heat deflection temperature of rigid PVC.
The additive/antistat interaction in polypropylene
Authors: Dieckmann Dale , Nyberg Wayne , Lopez Dan , Barnes Paul
Published: April 2004

Analytical and performance data demonstrate chemical interactions between glycerol esters and various other additives, primarily acid neutralizers. This phenomenon is pronounced when the additive is a strong base, like synthetic hydrotalcite, or a metal carboxylate. The performance of lactate neutralizers is compared to stearates and metal bases. Chemical reactions are proposed based on the analytical tests performed.
Long fiber reinforced polyamide and polycarbonate composites. II: Fatigue behavior and morphological property
Authors: Lin S. H. , Ma C. C. M. , Tai N. H.
Published: April 2004

Fatigue behavior and morphology of long glass fiber reinforced semicrystalline polyamide (nylon 6,6) and amorphous polycarbonate (PC) composites were investigated. The fiber length distribution in the molded samples was calculated by image analyzer. The tension‐tension fatigue loading tests at various levels of stress amplitudes were studied. The two‐parameter Weibull distribution function were applied to obtain the statistical probability distribution of experimental data. A good correlation existed between the experimental data and the Weibull distribution curves. Straight line SN curves of long glass fiber reinforced semicrystalline polyamide and amorphous polycarbonate composites at various probabilities were established. The stiffness of the composite under tension‐tension fatigue loading was measured. The thermal stress history was also investigated by thermo‐imaging techniques during fatigue life testing. Further, failure morphology was examined by scanning electron microscopy (SEM). The results showed that the fracture behavior of the ductile damage in polyamide is different from the brittle damage in polycarbonate.
CPE domain breakup in CPE/PVC blends
Authors: Berard Mark T. , Williams Suzanne M.
Published: April 2004

The proper morphology of the impact modifier in a polymer blend is important for the modifier to function properly. Well‐dispersed particles of less than 1.0 micron in size are needed. For chlorinated polyethylene (CPE) in rigid PVC, this morphology is developed during normal extrusion conditions. The CPE coats the unmelted PVC primary particles, creating a network‐like structure. Then, since CPE is at a low concentration (<5%), when the PVC melts, phase inversion occurs, giving discrete CPE particles in a continuous matrix of PVC. Further CPE domain breakup then occurs in the blend melt state, resulting in the desired morphology for impact modification.
Studies of possible chemical emissions from PVC articles used in indoor applications and the effect on indoor air quality
Authors: Howick Christopher J. , McCarthy Sally A.
Published: April 2004

Owing to their widespread use in interior applications, PVC products are frequently discussed in studies of indoor air quality. This paper reports results from the study of products in use and also products based on laboratory formulations that incorporate both unnaturally high and low levels of ingredients that could volatilize into the indoor air, thus giving a worst and best case scenario in terms of indoor emissions. Both PVC wallcovering and PVC flooring formulations have been studied, and laboratory produced samples have been subjected to gas chromatographic analysis to determine both the chemical species and the concentrations at which these can be emitted in typical interior applications. In all cases, including the worst ones, the level of these species in the indoor air is well below the permitted interior levels for the species concerned. These results, plus some outline of the concern over indoor health, are presented.
Microcellular foaming of polypropylene containing low glass transition rubber particles in an injection molding process
Authors: Wang Chicheng , Cox Karen , Campbell Gregory A.
Published: April 2004

Microcellular foams in polypropylene containing rubber particles were produced in an injection molding process. The foams are generated because of the thermodynamic instability and are controlled by formation process. The effect of processing parameters on microcellular foaming was investigated in the injection molding process. Injection speed and pressure are less important factors but packing pressure plays an important role in controlling the foam density. A critical packing pressure, about 5 × 106 Pa, was found to generate microcellular foams in our polypropylene material system. Rubber particles inside the polypropylene seem to stabilize the microcellular foams.
Improving gamma radiation resistance: Medical grade, flexible clear PVC compounds
Authors: Luther Douglas W. , Linsky Leonard A.
Published: April 2004

Flexible clear PVC compounds tend to yellow and darken during and after exposure to gamma radiation. This has been an obstacle to their use in the medical market. The purpose of this investigation was to improve the gamma stability of flexible PVC. The variables of interest were resin molecular weight, plasticizer loading, stabilizer type, and choice of antioxidant. By screening resins, plasticizers, stabilizers, lubricants, and antioxidants, a promising candidate formulation was identified and optimized by statistically designed experiment, with hardness added as an additional variable. The criterion for improvement was color change after gamma irradiation, compared with an identical unexposed specimen. Thus, a series of gamma stable formulations were created exhibiting improved post irradiation color stability.
Dynamic mechanical thermal analysis—an effective testing tool for a recyclability study of glass reinforced plastics
Authors: Song Jim H.
Published: April 2004

Glass fiber reinforcement usually gives substantial improvement in some key physical properties of plastics materials, such as heat resistance and stiffness (modulus), but at the expense of impact and flow (processability) properties. Upon recycling, however, we observe the reverse phenomenon. The key consideration of the recyclability of glass reinforced plastics is usually based on how much the key properties of glass reinforced materials are changed during a given recycling period. The assessment of the key physical properties of materials—heat resistance, impact, and stiffness—before and after recycling involves time‐consuming and expensive molding testing processes. This paper demonstrates how those three properties of glass reinforced plastics materials before and after recycling can be determined by a single dynamic mechanical thermal analysis (DMTA) test, thus greatly simplifying the key property assessment work in a recyclability study of glass reinforced plastics.
Performance‐property of novel glass fiber reinforced polypropylene compounds and their applications
Authors: Davé P. , Chundury D. , Baumer G. , Overley L.
Published: April 2004

The objective of this work was to investigate the property enhancement of polypropylene compounds due to glass fiber reinforcement at various levels. General trends in properties, performance and application were carefully established and surveyed. Second generation metallocene‐based glass fiber reinforced polypropylene compounds were also studied in terms of their “property‐performance” characteristic and compared to the original series. Addition of nylon to glass fiber reinforced polypropylene compounds was investigated as a further possible avenue for creating a new family of polymer alloys. Comparisons of properties, advantages, and applications were made.
Kinetic modeling of commercial scale mass polymerization of vinyl chloride
Authors: Chung S. T. , Jung S. H.
Published: April 2004

The kinetic model for the mass polymerization has been developed for a commercial scale mass polymerizer, which shows an anomalous polymerization rate behavior. Non‐equilibrium of the refluxed monomer between monomer and polymer phase was proposed to account for this anomaly. Monomer conversion and polymer average molecular weights can be predicted with this mathematical model. The developed model has been successful in simulating a commercial mass polymerizer of 60 m3 size for the optimization of production recipe with respect to the productivity and quality of polyvinyl chloride (PVC).
Reprocessing of medical vinyl compounds
Authors: Rakus Julius P.
Published: April 2004

There is increasing public concern over the disposal of plastic waste. The escalating cost of vinyl compounds would also make it desirable to reuse unavoidable process waste and surplus devices, not only in lower value markets, but also for medical device end users. This study examines the mechanical properties, radiolytic stability, and biological safety of vinyl compounds reprocessed after long‐term storage, and concludes that under certain conditions, reprocessing for use in the medical device market may be an option safely considered.
Analysis of stabilizers in polymer substrates
Authors: Thomas Mark P.
Published: April 2004

A general overview of the analytical techniques available to qualitate and quantitate the additive stabilizers in polyolefins is presented. A review of several sample preparation techniques, including polymer dissolution, supercritical fluid extraction and microwave dissolution is presented. This is followed by a general overview of the various chromatographic techniques, ranging from thin layer chromatography to supercritical fluid chromatography, which may be used for stabilizer analysis. Several spectroscopic analytical techniques that are used in the research environment are discussed, as well as techniques that may be used in the production environment for process control. Some of the practical considerations faced by analytical chemists are also described.
Advanced recycling technology for unsorted plastic waste
Authors: Khait Klementina
Published: April 2004

The object of this paper is to present results of our continuous effort to develop an advanced recycling technology for unsorted (mixed) plastic waste. The pulverization of plastics occur when pressure and high shear are coupled with extensive cooling of the extruder. Under certain processing parameters, plastic chips or flakes (used as feedstock) are converted into a controlled particle size powder. Melt flow rate data has been generated for post‐consumer polyolefins previously made via the new Solid‐State Shear Extrusion (SSSE) pulverization process. A first‐of‐a‐kind laboratory scale, modified co‐rotating twin‐screw extruder ZE‐25 was built by H. Berstorff Maschinenbau, GmbH, Germany, and is now operational at BIRL's Polymer Reclamation Center. Although the post‐consumer polyolefins include a variety of colors, the products from this process are homogeneous, and unusually light in color. The pastel color of the pulverized material demonstrates another advantage of this process as a step in plastics recycling. Several parts of different geometry have been injection molded using coarse powder as a feedstock without pelletization. Mixes of post‐consumer, muliticolor flakes of high density polyethylene (HDPE) and green/clear flakes of polyethylene terphthalte (PET) have been successfully pulverzed and tested. Currently, HDPE and PET are being sorted due to their incompatibility in order to be recycled. This novel extrsion‐pulverization process offers new opportunities for developing value‐added products from commingled plastic waste.
The structure of lead stabilizers. I: Basic lead carboxylates
Authors: Grossman Richard F. , Krausnick Dale
Published: April 2004

Infrared and nuclear magnetic resonance spectra of basic lead carboxylates used as heat stabilizers for halogenated polymers indicate that these salts are not complexes or double compounds of lead oxide, as suggested in most textbooks, but rather unique compounds of interesting structure. Lead stabilizers probably function in these polymers by converting hydrogen chloride to water, interfering with acid catalysis of the elimination reaction.
Total quality: Out of reach or within reach?
Authors: Prasad Sharad
Published: April 2004

In the recent past, Quality has increasingly gained in importance in the manufacturing sector on a global scale. Quality Standards like ISO‐9000 series, QS‐9000 series and Malcolm Baldrige National Quality Award have brought on a movement that seems to be gaining momentum by the day. Development of a Total Quality Program for any manufacturing facility must take some key factors into consideration for the program to work. The key factors that need to be considered in a PVC Compounding or a Bottle Blow Molding setup are presented in a generic format to show the merit and applicability to other manufacturing industries. Introductions to some major concepts and tools in Quality Control including Variables. Attributes, Sampling Plans, Cause–Effect Diagrams, Quality Function Deployment, Statistical Process Control and Quality Auditing are presented to measure the efficacy of the Quality Program to achieve Total Quality.
Vinyl molding compounds: Formulation and performance evaluation
Authors: Stevenson Janis C. , Fazey Antony C.
Published: April 2004

Today's vinyl molding compounds are successfully meeting the combined challenges of physical properties, appearance, processability, and cost requirements in a variety of specialty injection molding applications such as appliance parts, business equipment, and electrical enclosures. One of the major reasons why vinyl materials are so versatile is that the poly(vinyl chloride) resins on which they are based can be easily modified with a wide variety of additives to tailor the particular performance features of the compounds to their intended applications. Determination of an appropriate combination of PVC resin and additives to produce an effective and cost‐competitive compound, however, is not a simple process. Important considerations in formulating a vinyl molding compound and evaluating its performance are discussed here.
Tricks of the trade
Authors: Marx Fred
Published: April 2004

This paper provides a valuable collection of observations, ideas, and experiences useful to “old timers” and especially to “newcomers” involved in vinyl technology. It is noted that the information may frequently be applied to other plastics. It compiles a list of troubleshooting recommendations based upon many years of practical experience.