bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical thickening of low profile polyester resin systems
Authors: Volgstadt F. R. , Sieglaff C. L. 
Published: December 2004

AbstractLow profile polyesters and sheet molding compounds, SMC, are two of many resin‐glass composites that have been commercialized in the past few years. They have evolved through application of earlier technologies and have opened up possibilities for fiber‐reinforced plastics. Because of rapid growth, insufficient time has been spent documenting the technical aspects of making SMC. Techniques are thus described that we have used to characterize the rheological properties of the resin mix during its transition from liquid‐like (viscous) behavior of the initial formulation through the solid‐like (elastic) behavior of the resultant SMC.
Prediction and evaluation of the susceptibilities of glassy thermoplastics to environmental stress cracking
Authors: Henry L. F. 
Published: December 2004

AbstractGlassy, amorphous thermoplastics experience a nearly universal susceptibility to crack and craze formation in the combined presence of stress and a chemical environment. This susceptibility has been evaluated for styrene‐acrylonitrile copolymers according to the factors which effect craze initiation and those which limit the rates of flaw propagation. Molecular weight, styrene‐acrylonitrile ratio, rubber content, and rubber phase morphology are variables which were found to affect flaw initiation and propagation. Fundamental characterization of the chemical parameters which control the initiation of craze formation in polysulfone and polycarbonate is also presented. In particular, “3‐dimensional” solubility parameters have been observed to be a reasonable means of characterizing susceptibility to environmental stress cracking.
Prediction of diallyl phthalate molding performance from laboratory tests I. Characterization and quality control of diallyl phthalate compounds
Authors: Slysh Roman , Hettinger Arthur C. , Guyler Karl E. 
Published: December 2004

AbstractThe purpose of this study was two‐fold:

To determine the relationship between the composition and curing characteristics of glass‐reinforced diallyl phthalate (DAP) compounds and their molding performance.
To develop quality control tests in order to assure their satisfactory processing.
DAP compounds were analyzed with regard to composition, flow, curing characteristics, and heat stability. Tests involving “Spiral of Archimedes” and differential scanning calorimetry (DSC) were used to determine the flow and curing characteristics, respectively. A Brabender torque rheometer was employed to measure both flow and curing properties of DAP. The results obtained indicate that curing properties are of major importance in controlling the DAP processing. Good correlation was observed between the Brabender processing time, the onset curing temperature as measured by DSC, and the molding performance. A computer program was developed capable of calculating the kinetic parameters from the dynamic DSC scan of uncured DAP compounds. The curing data obtained from this method agree with those determined by isothermal DSC. A method based on the penetration of a hot metallic cone has been developed to measure rapidly the percent cure of molded DAP parts. The above mentioned techniques are recommended for the quality control of DAP molding compounds.
Phenylation of PVC with triphenylaluminum and related model reactions
Authors: Kennedy Joseph P. , Ichikawa M. 
Published: December 2004

AbstractIt was theorized that the heat stability of PVC may be improved by exchanging the “weak” (allylic and tertiary) chlorines by groups of higher bond strength, e.g., phenyl. Thus PVC was phenylated by ϕ3Al in carbon disulfide slurry for various times (1 to 5 hrs) and temperatures (from −30 to +45°C). The ϕ3Al concentration, temperature and time of ϕ3Al treatment greatly affect the ultimate heat stability of PVC. Significant improvement in the heat stability was obtained by treating PVC in carbon disulfide at 25°C for 1 hr. The mechanism of phenylation was studied by model experiments in which the possible structural irregularities in PVC were simulated by small molecule chlorine compounds, i.e., 3‐chloro‐1‐butene, 1,3‐dichloro‐1‐butene, 4‐choro‐2‐pentene were models for terminal and inchain allylic chlorines, t‐butyl chloride was the model for tertiary chlorine at branch site, and isopropyl chloride simulated regular secondary chlorines. The reactions between ϕ3Al and these chlorides were carried out at 35°C for various times and the NMR spectra were analyzed. The ϕ3Al + tBuCl reaction in carbon disulfide gives t‐butylbenzene (Wurtz coupling) and isobutylene oligomers. Evidently ϕ3Al (or the ϕ2AlCl formed) dehydrochlorinates tBuCl to isobutylene which rapidly oligomerizes in the presence of Lewis acids. In aromatic diluents, i.e., benzene, chlorobenzene, and o‐chlorotoluene, Friedel‐Crafts t‐butylation of the diluent occurs; in mesitylene t‐butylation is absent presumably because of steric hindrance and small amounts of t‐butylbenzene are formed by Wurtz coupling. All the allyl chlorides examined are rapidly phenylated by ϕ3Al in carbon disulfide at 35°C and yield the expected products: 3‐chloro‐1‐butene → 1‐phenyl‐2‐butene; 1,3‐dichloro‐1‐butene → 1‐chloro‐3‐phenyl‐1‐butene; 4‐chloro‐2‐pentene → 4‐phenyl‐2‐pentene. The kinetics of phenylation by ϕ3Al of model compounds have been studied and the following rate constants were obtained: kallyl = too fast to measure, ktBuCl = 1.0, and kiPrCl = 9 × 10−4 l/mole min. Evidently the rate of the ϕ3Al + RCl reaction is mainly determined by the stability of the R⊕ intermediate: substituted allylic⊕ ≫ tertiary⊕ ≫ secondary⊕.
The influence of stabilizers on the fusion of rigid poly(vinyl chloride)
Authors: Kulås Finn Ragnar , Thorshaug Niels Peter 
Published: December 2004

AbstractIt is known that the fusion rate of rigid PVC in an extruder partly depends upon the lubricants that are used. In the present study it is shown that different stabilizers have a great influence upon the rate of fusion of rigid PVC. Results from extrusion experiments and the Brabender Plastograph strongly indicate that a correlation exists between rapid melting in the extruder and the melt viscosity‐temperature relation of the polymer blend. The reason why certain stabilizers cause a more rapid fusion of the PVC is attributed to the chemical structure of the stabilizers.
Strain history of the melt in film blowing
Authors: Farber Robert , Dealy John 
Published: December 2004

AbstractTechniques have been developed for measuring the strain and thermal histories of fluid elements as they move from the die lips to the freeze line. Motion pictures were analyzed to determine the rates of extension in the machine and transverse directions. A radiation pyrometer was used to measure the temperature of the film. These techniques were used to study the film blowing of polyethylene; a 2.5‐in. diameter die was used, and blow‐up ratios in the range of 1.8 to 3.4 were employed. Film thickness ranged from 2 to 4 mils. The maximum measured extensional strain rates in both the transverse and machine direction were in the range of 0.15 to 0.6 sec−1. Standard shrinkage and impact tests were performed on the finished films, and an attempt was made to correlate the results with several simple empirical norms of the strain history. No correlation could be discerned. The results of this study are inconsistent with some popular ideas about the origin of orientation in blow films, but they are consistent with some recently published data on the influence of deformation on orientation in melt‐drawn capillary extrudate.
Superdrawn crystalline polymers: A new class of high‐strength fiber
Authors: Clark E. S. , Scott L. S. 
Published: December 2004

AbstractA new kind of acetal fiber has been discovered which has a tensile strength of 1.7 GPa (250,000 psi) and an elastic modulus of 35 GPa (5 × 106psi). This fiber is produced by a special two‐stage drawing process in the solid state which requires careful control of deformation rate and temperature. Previously known drawn fibers are reported to consist of folded‐chain blocks joined by a limited number of tie‐molecules. It is hypothesized that the second stage of the novel drawing process eliminates the lamella (block) surfaces which act as strength‐limiting stress concentrators. A new type of fiber is created in which any remaining chain‐folds are distributed as defects in a continuous crystal matrix. It is the continuity of the crystal matrix which is believed responsible for the remarkable properties of the fiber.
The effect of sudden strain‐rate change on the yield behavior of bisphenol‐A polycarbonate
Authors: Yee Albert F. , Detorres Pablo D. 
Published: December 2004

AbstractWe wish to investigate the path dependence of yield processes in glassy polymers and to understand this dependence, if any, in terms of molecular mechanisms. To this end the effect of sudden strain‐rate change on the yield behavior of bisphenol‐A polycarbonate has been investigated. In the experiment, a specimen was initially deformed at a constant elongation rate R1; at an elongation Δlc the rate was suddenly changed to another constant elongation rate R2. R1 was either lower or higher than R2. The yield stress subsequent to the rate change was found to be lower than if the entire deformation was at R1. These results can be satisfactorily explained in terms of Robertson's theory of the yielding of glassy polymers if it is assumed that the “bond flexing” in his theory manifests itself in anelastic deformation.
The significance of capillary rheology testing temperature for predicting PVC extrudability
Authors: Shah Pravin L. 
Published: December 2004

AbstractA rheological investigation of the saturated fatty acids as lubricants for PVC was made in a Sieglaff‐McKelvey rheometer over a wide temperature range. Results reveal that with an increase in carbon chain, fatty acids became more effective in reducing the melt viscosity of PVC. It was also discovered that the maximum viscosity variation due to these materials was observed at 350°F. At test temperatures of 400°F and above, no major viscosity differences were observed. Furthermore, the changes in the melt viscosity were more pronounced at shear rates less than 200 sec−1. The usefulness of the measured viscosity variations at the critical test temperature of 350°F was shown by extrusion. An excellent correlation between the apparent melt viscosity and extrusion melt temperature was found. The criticalness of the test temperature in assessing the effect of lubricants on PVC flow is discussed.
Viscometric behavior of high‐density polyethylene solutions at high temperatures
Authors: Brockmeier N. F. , Westphal S. P. 
Published: December 2004

AbstractThe steady shear viscosities of high density polyethylene disolved in highly branched isoparaffin solvents have been measured with a high‐pressure autoclave viscometer at temperatures ranging from 150 to 250°C and over a range of shear rates from 0.02 to 170 sec−1. Laboratory measurements on solutions ranging from 15 to 67 wt percent polymer were used to develop and calibrate a mathematical model for solution viscosity intended for a range of from 10 to 100 wt percent polymer. The foundation for the model consists fo two equations: the modified Martin equation is used to describe the effect of concentration, and the Sabia equation is used to describe pseudoplastic behavior. The model correlates viscosities that can range over nine orders of magnitude with sufficient accuracy for most process design work, averaging less than 10 percent error. Both the data and the model indicate that at constant stress the activation energies (EA) for the effect of temperature on viscosity are higher for solutions in the midrange of composition than for either of the pure components. This peak in EA is related to the density difference between polymer and solvent.
Blade‐coating of a viscoelastic fluid
Authors: Greener Yehuda , Middleman Stanley 
Published: December 2004

AbstractA theory is presented which describes the dynamics of blade‐coating of a viscoelstic fluid onto a moving sheet. The method begins with the usual “lubrication” approximation, and develops the solution as a perturbation about the Newtonian case. Viscoelasticity is described by an empirical constitutive equation which shows non‐Newtonian viscosity and finite normal stress behavior consistent with typical observations of polymeric fluids. Theoretical results indicate a small increase in coating thickness due to departure from Newtonian behavior, and a significant decrease in the magnitude of the pressure developed under the blade. Consequently, the blade loading can be reduced significantly by viscoelastic effects. The results for the loading may be an artifact of the specific constitutive model, since it can be shown that some viscoelastic fluids, specifically an “elastic Newtonian” fluid, would exhibit increased loading relative to the inelastic Newtonian case.
Packing and discharge in injection molding
Authors: Koita Y. T. 
Published: December 2004

AbstractIn a reciprocating‐screw injection‐molding machine, the screw or plunger forces the plastic into the mold. It remains in the forward position under pressure for a fixed time during which plastic flow into the mold or ‘packing’ takes place. After the timer runs out, the screw moves back while rotating thus releasing the pressure on the plastic in the mold. At this time, if the gate has not frozen, flow of plastic out of the mold or ‘discharge’ takes place. In this study, clear rigid PVC, poly (vinyl chloride), was molded with varying amounts of packing and discharge. Photoelastic stress patterns for parts observed between cross‐polaroids suggested that packing and discharge give rise to high frozen stresses due to molecular orientation in the gate area. Mechanical strength tests on the molded parts show that these high stresses are a source of weakness. Short forward times for the plunger significantly improve the mechanical properties of the parts in the gate area and at the same time have a significant influence on part dimensions, especially in the gate vicinity. Laminations observed at the gate interface can also be reduced by controlling the extent of molecular orientation introduced by packing and discharge.
A theory of roll coating of viscous and viscoelastic fluids
Authors: Greener Yehuda , Middleman Stanley 
Published: December 2004

AbstractA theory for roll coating of a fluid onto a moving sheet is developed utilizing the usual “lubrication approximations.” The effects of fluid and operating parameters on coating thickness and pressure distribution are determined for a Newtonian fluid, and for a purely viscous non‐Newtonian fluid obeying the Power Law. The results for these cases are obtained analytically, and are rather straightforward.A viscoelastic fluid is considered, of a type which shows typical non‐Newtonian shear behavior observed in polymer melts and solutions and which also exhibits normal stress behavior. Analytical solutions are not possible, but a perturbation method, using a viscoelastic perturbation parameter related to a Deborah number, yields an approximate solution. Only terms to first order in the perturbation parameter are given. Subject to that degree of approximation, the following conclusions are drawn:

Non‐Newtonian shear behavior reduces the pressure distribution, and increases the coating thickness.
Elasticity of the type usually observed in polymer solutions makes only a minor contribution to the roll‐separating (load‐carrying) force. The contribution is positive, but smaller than the corresponding negative contribution due to the non‐Newtonian shear effects.
An increase in load‐carrying capacity would require a different viscoelastic fluid than the type considered here—one that is essentially Newtonian in shear but, independently, capable of developing significant normal stresses.
Role of singlet oxygen in photo‐oxidative degradation and photostabilization of polymers
Authors: Rabek J. F. , R̊anby B. 
Published: December 2004

AbstractEvidence is presented that singlet oxygen may have an important role in the photo‐oxidation of polymers. Increased attention is being paid to singlet oxygen as a possible reactive intermediate in the initiation step of the photodegradation of polymers. Singlet oxygen may be produced by energy transfer either from impurities or internal groups after excitation, e.g. carbonyl groups, which are present in commercial polymers. As a consequence, reactions of singlet oxygen may also be important in the stabilization of polymers, e.g. leading to search for new and more effective antioxidants.
Ultra‐high molecular weight high‐density polyethylene as a gear material
Authors: Yelle Henri , Poupard Maurice 
Published: December 2004

AbstractTests have been made for use of a high‐density polyethylene of ultra‐high molecular weight as a gear material. The gears had a diametral pitch of 10 and 30 teeth. They were tested in mesh with a steel gear of the same size in two operating conditions: (1) in still air without lubrication, and (2) in oil with generous lubrication.The effects of speed, temperature, and initial lubrication on the load capacity of the gears were tested and an equation was developed to express the limits of these gears operating without lubrication. In the lubricated conditions, the influence of oil flow and its temperature on the gear teeth temperature were evaluated. The wear of the plastic gear was measured in both operating conditions and wear rate was calculated as a function of the load and gear life. Curves are presented suggesting design limits of the gears in the two operating conditions. There are also recommendations on the center distance setting and the backlash to use.
The flow behavior and impact strength of poly(butylene‐terephthalate) as a function of several processing variables
Authors: Van Der Wielen Michael P. 
Published: December 2004

AbstractThe flow behavior of poly (butylene‐terephthalate) (PBT) has been investigated using a capillary extrusion rheometer. The behavior was measured as a function of temperature, moisture content, and residence time of the molten polymer in the rheometer barrel. The temperature and moisture dependence of PBT are compared with polycarbonate. The notched Izod impact strength of injection‐molded PBT is also reported as a function of moisture content and residence time at processing temperatures.
The detection of structure in amorphous polymers by electron microscopy: Particle flow
Authors: Chapoy L. L. , Sørensen A. 
Published: December 2004

AbstractDuring the last several years there has been considerable interest in the occurrence of structure in certain bulk polymers normally thought to be structurally homogeneous. Specifically, it has been proposed that polymers produced by emulsion polymerization may retain a particle structure in the bulk state. This has been demonstrated by both rheological measurements and by electron microscopy. In this work we show conclusively that at least part of the particle structure observed by electron microscopy for polystyrene is an intrinsic feature of the fracture surface and is in no way related to the history of the sample.
Characterization of advanced composite materials for structural design
Authors: Waddoups M. E. 
Published: December 2004

AbstractOur preliminary characterization of advanced composite materials has been conducted simultaneously with the development of large‐scale primary and secondary aircraft structures. We have demonstrated significant advantages over metal structure on a one‐to‐one basis. Our efficiency levels gained to date demonstrate that we have extracted about fifty percent of the maximum potential advantage. Recovery of the remaining efficiency will result from understanding material characteristics and development of advanced design concepts. We will develop and demonstrate a summary format for viewing the structural response of monolithic metals and polymers and then document the observed responses of advanced composites within the format. Our data show that the addition of high‐modulus fibers into a polymeric matrix produces a physically distinct material with substantial advantage over unreinforced polymers. The unique properties of composite materials yield a significant advantage in physical properties and in design. Full advantage of material orientation has yet to be developed in a practical design but through examples we can illustrate the potential. We develop two examples: (1) stress concentration control through buffer stripping and (2) fracture control through buffer stripping. The impact of composite material characteristics as aircraft materials and design methods is also reviewed.
Sorption kinetics and equilibria in annealed glassy polyblends
Authors: Hopfenberg H. B. , Stannett V. T. , Folk G. M. 
Published: December 2004

AbstractThe sorption kinetics and equilibria of n‐hexane in glassy polyblends of polystyrene and poly(2,6 dimethyl‐1,4 phenylene oxide) were studied as a function of annealing conditions. Cast film samples were annealed 20°C above their respective glass transition temperatures for two hours and twenty‐four hours. The rate of relaxation‐controlled (Case II) sorption of n‐hexane in these films was reduced markedly consequent to annealing. The effect of annealing on the sorption kinetics and the independently determined film densities was more pronounced for the poly(phenylene oxide)‐rich samples. Although sorption rates were reduced by as much as a factor of 100, the sorption equilibrium was insignificantly affected by annealing. Super Case II transport was observed for the slow absorbing annealed samples whereas the more rapid sorption in the unannealed samples followed ideal Case II kinetics. The more pronounced effects of annealing for the poly(phenylene oxide)‐rich samples on sorption rates and film densities were explained by considering the increasing difference between the film Tg and the drying temperature used in the original film preparation for the poly(phenylene oxide)‐rich samples. These results suggest that glassy polymers, cast and dried well below their glass transition temperatures, will be subject to large long‐term reductions in absorption rates and specific volume. Moreover, residual, excess free volume significantly affects relaxation‐controlled absorption of vapors in partially annealed glassy polymers.
World‐wide weathering of poly(vinyl chloride)
Authors: Szabo Emery , Lally Robert E. 
Published: December 2004

AbstractIn order to determine the effect of outdoor aging in various areas of the world, poly(vinyl chloride), PVC, compositions were exposed at test sites in Australia, Canada, England, Germany, South Africa, and in Piscataway, New Jersey. These results are related to the climatological data from the different test sites. The data obtained show the effects of a three‐year period of exposure on clear and filled, flexible and rigid PVC compositions. The merits of various types of additives are shown in respect to the outdoor aging properties of PVC compounds. It was observed that the exposure conditions vary from severe for Australia and South Africa to mild for England. However, the general results obtained throughout the world correlate well with those from the exposure site in New Jersey.