bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal degradation of polystyrene: Changes in molecular composition
Authors: Daoust D. , Bormann S. , Legras R. , Mercier J. P. 
Published: December 2004

AbstractThe changes in the molecular composition of purified commercial polystyrene following thermal degradation were analyzed by gel permeation, reverse phase liquid and gas chromatography. Three major low molecular weight compounds were identified: styrene monomer, a dimer, and a trimer. The composition, the molecular weight, and the structure of the two oligomers were determined by elementary analysis, mass spectroscopy, nuclear magnetic resonance, and infrared spectroscopy. A linear structure with an ethylene end group is proposed for the two oligomers. The appearance of these degradation compounds is explained on the basis of an intramolecular mechanism involving chain‐end folding and transfer of a labile tertiary hydrogen.
Long‐time stress relaxation of a filled elastomer in vacuum environments
Authors: Ward Thomas Carl 
Published: December 2004

AbstractSamples of a filled elastomeric ablative material were stored at 45°C and ca. 10−6 torr for 7 months. Their tensile stressrelaxation modulus at constant strain was measured throughout the 7 months. Results of the testing are discussed primarily by comparisons of the data to atmospheric‐pressure moduli (determined in this work for shorter periods of time) and with moduli predicted from short‐time testing. Confirmation of the strengthening effects of vacuum on this composite were obtained. The use of time‐temperature superposition techniques as an approximate accelerated testing procedure for this material under these conditions was also verified.
Environmental craze growth in polycarbonate
Authors: Parvin M. , Williams J. G. 
Published: December 2004

AbstractEnvironmental craze growth in polycarbonate was studied under plane stress and plane strain conditions. In plane stress, the craze growth rate could not be described in terms of either initial stress intensity factor, Ko, net or gross stress. In plane strain, Ko was found to be the governing factor for craze growth, as has been previously reported for poly(methyl methacrylate) (PMMA). For shallow cracks (<1 mm), there is evidence of an inherent flaw effect.
Physical aging of linear and network epoxy resins
Authors: Kong Eric Siu‐Wai , Wilkes Garth L. , McGrath James E. , Banthia A. K. , Mohajer Y. , Tant M. R. 
Published: December 2004

AbstractNetwork and linear epoxy resins principally based on the diglycidyl ether of bisphenol‐A and its oligomers have been prepared and studied. Both diamine and anhydride crosslinking agents were utilized. In addition, some rubber modified epoxies and a carbon fiber reinforced composite was investigated. All of these materials display time‐dependent changes in many of their properties when they are stored (following quenching) at temperatures below their glass transition temperature (sub‐Tg annealing). For example, the degree of stress relaxation for a given time period is observed to decrease in a linear fashion with the logarithm of time during sub‐Tg annealing. Young's modulus and yield stress were also found to increase ire physical aging. Solvent sorption experiments initiated after different sub‐Tg annealing times have demonstrated that the rate of solvent uptake can be indirectly related to the free volume of the epoxy resins. The effect of water on the physical aging of these epoxy resins was not found to be a significant variable. Residual thermal stresses were also found to have little effect on the physical aging process, although this variable was not studied in detail. Finally, the physical aging process also affected the sub‐Tg properties of uniaxial carbon fiber reinforced epoxy material and the effects were as expected. The importance of the recovery or physical aging phenomenon, which affects the durability of epoxy glasses, is considered in view of the widespread applications for these resins as structural materials.
Extrudate swell and extrusion pressure loss of polymer melts flowing through rectangular and trapezoidal dies
Authors: White James L. , Huang David 
Published: December 2004

AbstractA theoretical and experimental study of pressure losses and extrudate swell of flow through dies with complex crosssections is presented. The range of utility of models based on one‐dimensional shearing on pressure loss‐extrusion rate behavior is indicated. A procedure to predict extrudate profiles emerging from complex dies is developed. This is based on consideration of the idea of unconstrained elastic recovery from long dies. The theoretical predictions are contrasted with experiments on polystyrene and polypropylene.
Significance of deformation rate softening of memory in viscoelastic fluid mechanics and polymer processing
Authors: White James L. , Minoshima Wataru 
Published: December 2004

AbstractIt is pointed out that in viscoelastic fluid constitutive equations, non‐linear response to deformation rate and strain beyond the second order is usually interpreted in terms of the deformation rate or strain dependence of the memory function. These non‐linearities act to decrease the extent of the memory. The dependence may be characterized by one or more dimensionless material parameters. A new dimensionless group based on the primary material parameters describing the intensity of the deformation rate dependence of the memory function is introduced and its significance is discussed. This is called the Yamamoto number. The solutions of viscoelastic fluid mechanics problems are considered to depend upon both the Weissenberg and Yamamoto numbers. Such problems include topics of interest in polymer melt processing such as uniaxial elouigatioiial flow, fiber spinning and vortex development in extrusion through a die entry.
Effects of residual stress and orientation on the fatigue of injection molded polysulfone
Authors: Mandell J. F. , Smith K. L. , Huang D. D. 
Published: December 2004

AbstractThe tensile fatigue behavior of unnotched injection molded polysulfone specimens has been investigated. The effects of orientation and residual stress were studied by comparing asmolded specimens with annealed or annealed and quenched specimens with a known residual stress pattern. The treatments are shown to have differing effects at high stresses, where failure is by shear yielding and necking, and at intermediate stresses, where failure is by fatigue crack propagation. The geometries of fatigue cracks are described for each case. An attempt is made to separate the effects of crack and craze initiation from crack propagation, and cyclic loading from cumulative time under load.
Simulation of cavity filling and curing in reaction injection molding
Authors: Manzione Louis T. 
Published: December 2004

AbstractThis report describes a procedure to stimulate the reaction injection molding process. The analysis considers the conversion that occurs during cavity filling with reactive fluids and the subsequent cure in the mold based on initial conditions derived from the filling analysis. Extensive conversion can occur during cavity filling when highly reactive resins are used. High conversion material with attendant high viscosity can be found in the cavity during filling without flow seizure because the conversion is non‐uniform. The overall cycle time can be decreased by promoting conversion during cavity filling as long as flow seizure is avoided. Temperature and conversion profiles during cure in the mold elucidate thermal runaway and its importance in reaction injection molding. The simulation can be used to explore material and process parameter sensitivity, predict the cycle time and the maximum exotherm temperature, and evaluate moldability.
Batch polymerization of styrene‐optimal temperature histories
Authors: Wu G. Z. A. , Denton L. A. , Laurence R. L. 
Published: December 2004

AbstractOptimal temperature histories for the batch thermal polymerization of styrene are determined using Pontryagin's maximum principle. The theoretical predictions are compared with experimental measurements of conversion and molecular weight distribution. The excellent agreement suggests policy improvements in batch radical chain growth polymerizations.
Miscibility of poly(α‐methyl siyrene‐co‐acrylonitrile) with polyacrylates and polymethacrylates
Authors: Goh S. H. , Paul D. R. , Barlow J. W. 
Published: December 2004

AbstractA copolymer formed from 30 percent acrylonitrile and 70 percent α methyl styrene by weight, or αMSAN, has been examined for miscibility in blends with various polyacrylates and polymethacrylates. None of the polyacrylates or poly(vinyl acetate) were miscible with α‐MSAN at room temperature or above. The methyl and ethyl esters of the polymethacrylate series (PMMA, PEMA) proved to be miscible with α MSAN, but none of the higher homologues were miscible under these conditions. Blends of both PMMA and PEMA with α MSAN exhibited lower critical solution temperatures. The observed cloud points decreased as PMMA molecular weight increased up to 105 where kinetic effects caused an apparent reversal of this trend. Atactic PMMA interacts more strongly with αMSAN than does either isotactic PMMA or atactic PEMA. These structural effects are compared with similar trends found in other systems.
The lower critical solution temperature (LCST) of non‐polar polymer solutions: An introduction
Authors: Somcynsky Thomas 
Published: December 2004

AbstractThe phase behavior at high temperatures of non‐polar polymer solutions is discussed in a qualitative way in terms of the free volume theory of liquids developed by Prigogine, Patterson and Flory. This theory is necessary to explain the existence of a Lower Critical Solution Temperature (LCST) in non‐polar polymer solutions and the related exothermic heats of mixing. The classical theory of polymer solutions and its limits is first reviewed.
Electrical conductivity changes associated with thermal decomposition of phenolic‐ and silicone‐based materials
Authors: Johnson R. T. , Biefeld R. M. 
Published: December 2004

AbstractElectrical conductivity changes during thermal decomposition of several phenolic and silicone materials have been measured while increasing temperature from 25 to ∼ 700°C at a rate of 10°C per minute in a nitrogen atmosphere, The materials are based on phenolic and silicone resins and are reinforced with glass chopped fabric or cloth. The electrical results are correlated with mass loss and thermal decomposition product data obtained using mass spectroscopy and thermal gravimetric analysis. Peaks in the conductivity temperature dependence and deviations from ohmic behavior are found to be associated with material decomposition and/or outgassing. An excellent correlation is obtained between thermal stability and temperature‐dependent electrical properties. Results suggest that electrical conductivity can be used as a thermal analytical tool in characterizing these materials.
Rotational molding of thermosetting three‐phase syntactic foams
Authors: Narkis M. , Puterman M. , Boneh H. , Kenig S. 
Published: December 2004

AbstractThermosetting three‐phase syntactic foams consisting of glass micro balloons, resin, and air voids dispersed in the resin were studied and are reported in the present work. Specimens for measurements of density and compressive properties were cut from the syntactic foam walls of hollow products prepared in rotational molding. These walls are characterized by loose‐packed structures, densities from 0.12 to 0.24 g/cm3, and compressive strength from 3 to 20 kg/cm2. The free void fraction of these loose‐packed structures is compared with close‐packed structures as a function of resin weight fraction, and semi‐quantitative relationships are derived. Potential applications of such hollow articles are as core materials for large products of complex geometries where light weight combined with a good balance of mechanical properties, low dielectric loss, and good thermal resistance are desired.
Environmental effects of silicone oil on tensile and fatigue properties of polystyrene
Authors: Chen C. C. , Morrow D. R. , Sauer J. A. 
Published: December 2004

AbstractA series of polished polystyrene specimens, coated with silicone oil, were tested in tension and in tension‐compression fatigue cycling at 21 Hz. Oils of four different viscosities, ranging from 5 cSt to 1000 cSt, were utilized. The craze initiation stress and the tensile fracture stress both increased with the increase of oil viscosity. For the 1000 cSt oil, the stress‐strain curve was essentially the same as that of an uncoated sample. The average lifetime to fracture in the fatigue tests depends upon the stress amplitude and on the oil viscosity. For the 1000 cSt oil, the fatigue behavior is similar to that of uncoated samples, except at high imposed stresses, where lifetime is somewhat lower. For the low viscosity oil, the average lifetime is from one to two decades less than for uncoated samples. Discussion is given of the influence of stress amplitude and oil viscosity on the test results and on the morphology of the fracture surfaces.
The elastic change of volume in pressurized bottles made from polymeric materials
Authors: Wu Ru‐Yu , Stachurski Z. H. 
Published: December 2004

AbstractThe relations describing the elastic change of volume of thermoplastic cylindrical pressurized containers are presented. Discussions have been made on various cases including isotropic (i.e., un‐oriented), uniaxially, and biaxially oriented materials. These relations are expected to be helpful for selecting the optimum processing conditions (i.e., draw ratio) in order to achieve the desired properties of polymeric pressurized containers.
The weathering of engineering thermoplastics
Authors: Cooney J. D. 
Published: December 2004

AbstractThe photostability of four engineering thermoplastics, ARDEL, CYCOLOY, NORYL, and HOVEL, have been examined by mandrel bend tests on extruded channel as well as infrared and ultraviolet‐visible spectroscopy on thin films. ARDEL D‐100 and ROVEL 501 resins were found to have excellent stability to simulated sunlight, while CYCOLOY HHI and NORYL PX 1278 were found to have poor light stability. ARDEL is a polyarylate composed of bisphenol A. terephthalic acid, and isophthalic acid condensation units. CYCOLOY is an alloy of acrylonitrile‐butadiene‐styrene and polycarbonate. NORYL is a blend of poly(phenylene oxide) and polystyrene. ROVEL is an olefin‐modified styrene‐acrylonitrile.
The relationship of carbon black dispersion to electrical resistivity and vulcanizate physical properties
Authors: Cembrola R. J. 
Published: December 2004

AbstractThe degree of dispersion of carbon black in rubber is known to be a determining factor in the physical properties of the composite. It is important, therefore, to have a reliable, quantitative technique for assessing carbon black dispersion. It has been known for some time that the degree of dispersion of carbon black is reflected in its electrical resistivity. A resistivity instrument, developed by B. Boonstra, has been redesigned and constructed for use in this study. Factors that influence resistivity (i.e., black type, volume loading, and mixing time) are examined. Physical property and dynamic mechanical measurements are made, and their relationship to black dispersion is investigated. Light microscopy is also used to evaluate dispersion, and these data are compared to the resistivity results.
Modeling of poly(ethylene terephthalate) reactors: 5. A continuous prepolymerization process
Authors: Ravindranath K. , Mashelkar R. A. 
Published: December 2004

AbstractA mathematical model for the continuous prepolymerization of BHET to PET, carried out in a series of stirred tank reactors, has been developed. The influence of process and operational variables on productivity, as well as the side‐product formation (which controls the product quality), have been studied in a range as close to industrial practice as possible. The overall conclusions concerning the productivity profile, as well as some side products, appear to be substantiated from the available data in the open literature. The results of the mathematical model have been used to highlight the key process and operational variables that are likely to give the best productivity and product quality in industrial practice.
Studies on polyurethane protective surface material resistance to cavitation erosion
Authors: Xiong Xiao Han , Min Gao Xue , Tao Zhou Qi , Li Xie Shan , Zhi Chen Rui 
Published: December 2004

AbstractThe polyurethane protective surface material, which were made from four different types of polyester and polyether polyol, have been studied with respect to their ultimate properties. The PTMG (polyoxytetramethylene glycol)‐ and PPG (polyoxypropylene giyco)‐based polyurethane protective surface materials exhibited the best results. Use of JIPNs (joint interpenetrating polymer networks), prepared from combinations of polyurethnes with an epoxy adduct with coupling agents and talc, could clearly improve the adhesive strength resistance to water in negative pressure cavitation erosion (by determination with a rotating dish apparatus) and the adhesive strength resistance toward boiling water. The polyurethane protective surface material, which was composed of three separated layers, showed better resistance to cavitation erosion than an epoxy system, poly(methyl methacrylate), aluminum, steel, and different alloys in tests using the venturi tube and the rotating dish apparatus for simulated cavitation erosion, as well as in some power stations in actual field trials.
Fracture analysis of acrylonitrile‐butadiene‐styrene resins
Authors: Sridharan N. S. , Broutman L. J. 
Published: December 2004

AbstractThe fracture properties of three grades of acrylonitrile‐buta‐diene‐styrene(ABS) were evaluated and compared. In preliminary studies, J1c (J integral) results obtained using the Begley and Landes procedure for single‐edge‐notched tension specimens and compact tension specimens were compared to establish the validity of the J1c criterion. It is shown that the Rice single‐specimen approximation can be applied for this material, resulting in considerable simplification of the testing procedure. The J1c values for two of the grades were evaluated at two or more rates using the compact tension geometry and the single‐specimen procedure over a temperature range of–60° to + 75°C. The results are analyzed in terms of a modified Eyring model, and the activation energies for the two grades of ABS were found to be 13.7 and 36.7 Kcals/mole, respectively.
Time and temperature effects on the fracture toughness of rigid poly(vinylchloride) pipe materials
Authors: Mandell J. F. , Darwish A. Y. , McGarry F. J. 
Published: December 2004

AbstractThe fracture toughness of rigid poly(vinylchloride) pipe materials has been investigated over a range of temperatures and rates. Conditions are described for valid fracture toughness (KIC) tests and notch insensitive (ductile) behavior; time‐temperature effects on transitions in KIC are defined. The modes of crack extension are characterized over a range of temperatures, and the mechanisms of crack resistance are discussed, including some quantitative data for the yielded zone at the crack tip.
Multiphase polymer processing: Controlled‐ingredient‐distribution mixing and its effect on some properties of styrene‐butadiene (SBR)/butadiene‐acrylonitrile copolymer rubber blend compounds
Authors: Lee Bung‐Lin 
Published: December 2004

AbstractThe flex‐crack‐growth resistance and oil‐swelling resistance of a styrene‐butadiene (SBR)/butadiene‐acrylonitrile co‐polymer (NBR) rubber blend are studied as a function of the distribution of ingredients in the individual rubber phases. The blends consist of 70:30 weight ratio of SBR:NBR with incorporation of 82.5 phr carbon black and other ingredients via the controlled‐ingredient‐distribution mixing procedure. The results show that flex crack growth is affected by the distribution of carbon black. Better flex crack growth resistance could be achieved by adding 10 percent of carbon black to the NBR rubber phase and 90 percent to the SBR phase. The swelling of these rubber blends in ASTM #2 oil is also affected by the location of carbon black and by the mixing history. The blends with more black initially preloaded in the SBR phase have lower swelling, as have blends with shorter cross‐mixing time or the mill. A simple equation based on the permeation/moduli of composite materials is proposed to describe the swelling of this rubber blend in terms of the swelling of the constituent rubber phases, the distribution of ingredient in the individual rubber phases, and the blend morphology. One of the key assumptions is to consider the individual black preloaded rubber as a continuum. The quantitative correlation with the observed swelling data is reasonably good.
Photo‐Oxidation and photo‐stabilization of blends of low‐density polyethylene and styrene‐butadiene‐styrene copolymers
Authors: David C. , Zabeau F. , Jacobs R. A. 
Published: December 2004

AbstractThe photo‐oxidation of blends of low‐density polyethylene and styrene‐butadiene‐styrene block copolymers has, been shown to result mainly from the degradation of the pollybutadiene part of the material. The solution infra‐red and fluorescence spectra, and mechanical properties have been studied as a function of the irradiation time. Evidence of some interaction between the components of the blend could be obtained.
The microstructure of injection‐molded semicrystalline polymers: A review
Authors: Katti S. S. , Schultz M. 
Published: December 2004

AbstractThe microstructure of semicrystalline polymers solidified with and without concurrent applied strain is reviewed. Fluid flow in the filling and packing stages of injection‐molding are discussed. Observations of the microstructures of a number of polymers under various conditions are described. In general, the microstructure is extremely inhomogeneous and anisotropic; a skin layer is highly oriented (or, in some cases, finely granular), whereas the core is composed of larger, isotropic spherulites. The principles governing the formation of such microstructures are given. Relations between microstructure and macroscopic properties are briefly described.
Numerical simulation of a single‐screw plasticating extruder
Authors: Acur E. E. , Vlachopoulos J. 
Published: December 2004

AbstractA fully‐predictive steady‐state computer model has been developed for a single‐screw plasticating extruder. Included in the model are a model for solids flow in the feed hopper; a variation of the Darnell and Mol model for the solids conveying zone; a variation of Tadmor's melting model for the melting zone; an implicit finite difference solution of the mass, momentum, and energy conservation equations for the melt‐conveying zone of the extruder and die; and a predictive correlation for the extrudate swell at the die exit. A temperature‐ and shear‐rate‐dependent viscosity equation is used to describe the melt‐flow behavior in the model. The parameters in the viscosity equation are obtained by applying regression analysis to Instron capillary rheometer data. Given the material and rheological properties of the polymer, the screw geometry and dimensions, and the extruder operating conditions, the following are predicted: flow rate of the polymer, pressure and temperature profiles along the extruder screw channel and in the die, and extrudate swell at the die exit. The predictions have been confirmed with experimental results from a 11/2 in. (38 mm) diameter, 24:1 L/D single‐screw extruder with a 3/16 in. (4.76 mm) diameter cylindrical red die. High‐ and low‐density polyethylene resins were used.