bluuebunny/crossref_metadata_2025 huggingface dataset:
Shape changes during drawing of non‐circular extruded profiles
Authors: Griffith R. M. , Tsai J. T.
Published: December 2004

Deformation during cooling and take‐up of rectangular, triangular and T‐shaped profiles were investigated. Experimental results show that there is an excellent agreement between changes in a cross‐section dimension and prediction from the theory for various take‐up speeds. The correlations decrease in the case where other process variables such as different melt temperatures and output rates are involved. Based on undrawn sample measurements, it has been concluded that to a high degree of approximation only a scaled‐down change in shape occurs along the drawing path after die swell is completed. Industrial practices in handling profiles during cooling and take‐up which may cause deviations from geometrically similar deformation were examined. Metal guides and local cooling by small water streams along the drawing path were used to impose shear forces on the profile. It was found that the effects of such shear forces has been small in comparison with the effects of elongational stress as indicated by only slight, if any, deviation from geometrically similar changes in cross‐sections. Based on the data obtained, it is concluded that feedback control during profile drawing to give correct size is feasible based on monitoring a single dimension. The correct shape can, however, be obtained only by choice of the proper die geometry and other extrusion conditions.
Hygrothermal history dependence of moisture sorption kinetics in epoxy resins
Authors: Apicella A. , Nicolais L. , Astarita G. , Drioli E.
Published: December 2004

A history dependent solubility model is generalized in accordance with the Dual Mode Sorption Theory to take into account a history dependency of effective water diffusion coefficients in epoxy resins, based on hypothesized microcavitational damage due to the combined effects of temperature and sorbed moisture. Sorption data presented in a different paper are analyzed in the light of a transport model in which part of diffusing molecules are completely immobilized in the formed microcavities. The nature of the hypothesized damaging process is in agreement with the diffusion coefficient depressions and solubility increases experimentally found and theoretically predicted by the model.
Bending and breaking fibers in sheared suspensions
Authors: Salinas A. , Pittman J. F. T.
Published: December 2004

An experimental study was made of single fibers rotating and bending in Couette flow of a Newtonian liquid. A previous result for critical fiber buckling was re‐tested and found satisfactory, and the transition between ‘springy’ and ‘snake’ rotation was delineated. The minimum radius, of curvature achieved during rotation in the “snake orbit” regime was measured as a function of fiber aspect ratio, Young's modulus, and fluid shear stress. Two correlations are presented which are constrained to satisfy limiting conditions for very stiff and very flexible fibers. Together with a result from thin rod theory, these correlations may be used to predict breaking conditions for fibers of known Young's modulus and ultimate tensile strength. Predictions are tested in experiments where two types of glass fiber are broken in suspension and found satisfactory. Results show that several reinforcing materials will probably break within the range of conditions covered by our experiments, or in a region which can be treated by extrapolation from our results.
Thermoplastic interpenetrating polymer networks of a triblock copolymer elastomer and an lonomeric plastic. II. Mechanical behavior
Authors: Siegfried D. L. , Thomas D. A. , Sperling L. H.
Published: December 2004

Thermoplastic interpenetrating polymer networks, IPN's, are defined as combinations of two physically crosslinked polymers. A styrene‐b‐ethylene‐co‐butylene‐b‐styrene (SEBS) triblock elastomer was combined with an ionomer prepared from a random copolymer of styrene, methacrylic acid, and isoprene (90/10/1 by volume), and subsequently neutralized. Two subclasses of the thermoplastic IPN's were identified. A sequential polymerization method yielded the chemically blended thermoplastic IPN's (CBT IPN's). Melt blending of the separately synthesized polymers produced the mechanically blended thermoplastic IPN's (MBT IPN's). Stress‐strain and Rheovibron characterization revealed that the CBT IPN's exhibited greater tensile strength and higher elongation at break, but lower moduli than the MBT IPN materials of the same overall composition. Analysis of moduli data with the theories of Takayanagi, Davies, Budiansky, and Kerner disclosed more equal dual phase continuity for the MBT IPN's than the CBT IPN's at each composition. The low modulus of the more rubbery CBT IPN compositions was attributed to a decrease in the effective chain end‐to‐end distance between crosslinks in the elastomeric (EB) center block, brought about by the synthetic method.
The feasibility of electrical monitoring of resin cure with the charge‐flow transistor
Authors: Senturia Stephen D. , Sheppard Norman F. , Poh Soon Y. , Appelman Howard R.
Published: December 2004

A new technique for the electrical monitoring of polymerization reactions such as resin cure is described. The technique is based on the charge‐flow transistor, which resembles a conventional metal‐oxide‐semiconductor field‐effect transistor (MOSFET), but with a portion of the metal gate replaced by the resin under study. Electrical signals obtained from several resins undergoing cure are presented, along with an electrical circuit model that can account for the principal features of these signals. The dramatic change in signal shape during cure can be related to corresponding changes in both the real and imaginary parts of the dielectric constant.
A biaxial extensiometer for molten plastics
Authors: Rhi‐Sausi J. , Dealy J. M.
Published: December 2004

While biaxial stretching plays a central role in several polymer processes, there has been no technique suitable for laboratory study of controlled biaxial stretching of molten thermoplastics at typical melt processing temperatures. The sheet inflation technique, which has been used previously to study rubbers and very high viscosity melts, has been adapted for use with molten thermoplastics by the use of oil as an inflation medium. Problems encountered in the use of the first prototype were eliminated in a second model, which is thought to produce reliable results. Stress growth data are presented for a low density polyethylene and for a polystyrene. A basic limitation of the technique is that the maximum achievable strain is in the range of 1.3 to 1.7, and this is often insufficient to bring out the nonlinear viscoelastic behavior of the melt.
Mold release agents. I. Fatty acids and selected fluorinated compounds as releasants for polyurethane from cold rolled steel
Authors: Schneberger Gerald L. , Nakanishi Todd
Published: December 2004

The effect of saturated aliphatic fatty acids and a number of fluorinated polar organic compounds on the release of polyurethane foam from cold rolled steel has been investigated. Little release was observed with aliphatic acids of less than 10 carbons or with the organic compounds. Release behavior increased with aliphatic chain length from C12 to C18. Stearic acid release increased only marginally above 0.034 μ g/cm2. Infrared studies of demolded eluted surfaces indicated that stcaric acid at levels of up to 178 μ g/cm2 was apparently removed from the surface by foam.
Outgassing of high temperature‐resistant organic polymeric materials
Authors: Demaxss Peter
Published: December 2004

Four polymeric materials, polyphenylene oxide, polyquinoline, acetylene substituted polyimide, and polybenzimidazole, reported to possess high‐temperature resistance, were investigated in order. to determine their outgassing characteristics as related to their suitability for high temperature applications in confined structures. The materials were sequentially exposed to 150, 250 and 450°C for 3 h periods and the types and amounts of their outgassed products were determined. The amounts of outgassed‐ products were small from polyquinoline, acetylene substituted polyimide, and polybenzimidazole. It was concluded that those materials would be suitable for use in applications where high‐temperature resistance (up to 450°C) is required, providing that normal ventilation is available. The quantity of outgassed products from polyphenylene oxide was too great to consider that material suitable for shipboard or other confined structure applications requiring high‐temperature resistance.
Molecular weight distribution control in continuous “living” polymerizations through periodic operation of the monomer feed
Authors: Meira G. R. , Johnson A. F.
Published: December 2004

The main objective of the work is to explore the problem of producing polymers of any desired molecular weight distribution (MWD) in isothermal, solution, “living”, anionic polymerizations carried out in continuous tubular reactors. For this purpose, a novel control scheme was designed and implemented, which involves the periodic operation, of the monomer solution flow rate, with the flow profile automatically derived from the required MWD and other data. For experimental validation, a polymerization rig was especially built that included a process computer and an automatic gel permeation chromatograph. The chromatograph permitted the measurement of the MWD of the reactor effluent in a matter of minutes and the process computer was employed to implement the control policies and to perform the chromatograph data acquisition and reduction. In spite of the practical problems encountered, experiments showed at least a semi‐quantitative validity of the method.
Circular couette flow of a polymerizing fluid
Authors: Lindt J. T.
Published: December 2004

Flow of a polymerizing fluid between rotating concentric cylinders has been analyzed theoretically. A solution has been obtained employing a finite difference method. Using a RIMtype (reaction injection molding) urethane system as an example, the velocity, temperature, and NCO group concentration fields have been described as functions of time. A numerical example is given to demonstrate the applicability of the present analysis to reactive processing and viscometry. The mixing characteristics and the flow rate associated with circular drag flows involved, e.g., in reactive extrusion, have been shown to depend strongly on the operating conditions. It has also been demonstrated that the range of applicability of Couette viscometers to fast curing systems may be limited by the interfering time‐dependent temperature gradients involved. It has been concluded that analysis of the. present nature provides a useful design and evaluation tool applicable to Couette flow problems in reactive processing and viscometry.
Studies on structural foam processing. IV. Bubble growth during mold filling
Authors: Han Chang Dae , Yoo Hee Ju
Published: December 2004

An experimental and theoretical study was carried out to achieve a better understanding of bubble growth during the filling of gas‐charged molten polymers into a rectangular mold cavity. For the experimental study, a rectangular mold cavity (15.24 × 4.55 × 0.64 cm) was constructed, with glass windows on both sides to permit recording on a movie film of the growth of gas bubbles in the mold cavity as a molten polymer containing inert gas was injected into it. Sodium bicarbonate (generating carbon dioxide) was used as a chemical blowing agent, and the polymer used was a general purpose clear polystyrene. All experimental runs were made at isothermal molding conditions, and the injection rate was varied. It was found that, at and above a certain injection rate, little bubble formation was observed in the mold cavity during injection except at and near the moving melt front. For the theoretical study, the growth of a single gas bubble in a viscoelastic medium (represented by the DeWitt model), subjected to high injection rates, was considered by including the effects of diffusion from the liquid phase to the gas phase, interfacial tension between the liquid and the gas phases, and stress relaxation of the melt upon ejection. It was found that the level of stresses, built up in the met during injection, has a profound influence on the formation and growth of gas bubbles during the initial stage of mold filling. Also, a multichannel mold cavity was employed in order to observe the effect of processing variables on the cell size and its distribution in molded specimens. A uniform cell structure was obtained at higher injection pressures, at an optimum injection melt temperature, and with an optimum combination of blowing agent and nucleating agent concentrations.
Effect of thermal aging on impact strength acrylonitrile‐butadiene‐styrene (ABS) terpolymer
Authors: Wolkowicz Michael D. , Gaggar Satish K.
Published: December 2004

A high speed puncture impact apparatus was used to measure impact loss in thermally aged ABS (acrylonitrilebutadiene‐styrene) as a function of time and temperature. Impact energy values decreased to a low level and degraded surface layer thickness increased as a function of aging time at three aging temperatures. Systematic removal of surface layers from thermally aged samples progressively increased impact energy values to control levels. Infrared spectroscopy, differential scanning calorimetry and molecular weight data indicate that degradation occurs in the rubber, graft and rigid phases at different times during the thermal aging period. Microscopy results show a critical degraded layer thickness which causes brittle failure of the entire sample.
Viscoelastic dissipations in the fracture of glassy polymers near their glass transition temperature
Authors: Mascia L. , Bakar M.
Published: December 2004

The viscoelastic energy dissipations within the bulk of the test specimen are not taken into account by classical fracture mechanics. In this study it is shown that on approaching the glass transition temperature, the amount of energy dissipated in the bulk of the specimen relative to that required to create two new surfaces can be substantial, and it may be estimated from measurements carried out on specimens with different gauge lengths. Furthermore stress relaxations can take place at the crack tip, even in absence of yielding. These can be sufficiently pronounced to eliminate stress intensification and give rise to constant fracture stress conditions.
Dimensional variations of two spherical polymeric particles during sintering
Authors: Rosenzweig N, , Narkis M.
Published: December 2004

A quantitative “Round Neck” (RN) model based upon volume balances and considerations of surface tension phenomena is proposed for simulation of coalescence of two spherical polymeric particles; during sintering. This model and an early model developed by Frenkel are compared and evaluated against experimental data to show their suitability to simulate geometrical variations of a particle pair during sintering.
The fracture toughness of polypropylene containing poly(ethylene terephthalate) fibers
Authors: Hamer J. W. , Woodhams R. T.
Published: December 2004

The fracture toughness of polypropylene was increased tenfold by the addition of 30 volume percent of chopped poly(ethylene terephthalate) rovings without any appreciable sacrifice in strength or modulus. The resulting fracture toughness was independent of temperature to −40°C. For maximum effectiveness the rovings must be integrated so that the component filaments cannot disperse during the processing and injection molding stages. The three different methods employed to measure fracture toughness showed good correlation with each other and confirmed the general utility of the Izod test (with slight modification) as a measure of fracture energy. The increased toughness was attributed almost entirely to frictional energy losses during fiber pullout. Polyester fibers can be useful additives for increasing the fracture toughness of brittle resins where processing temperatures do not preclude their use.
Poly(n‐Butyl acrylate)/polystyrene interpenetrating polymer networks and related materials. II. Aspects of molecular mixing via modulus‐temperature studies
Authors: Yeo J. K. , Sperling L. H. , Thomas D. A.
Published: December 2004

The glass transition, rubbery modulus, and tensile behavior of poly(n‐butyl acrylate)/polystyrene interpenetrating polymer networks (IPN's), semi‐1 IPN's, and their corresponding random copolymer networks were studied as a function of both composition ratio and crosslink density. Two temperatures were selected for analysis: 25°C, halfway between the two transition temperatures, and at 160°C., in the rubbery plateau region. The modulus data at 25°C were compared with wellknown composite models. The moduli of the IPN's and semi‐1 IPN's lie close to the Davies model in the polymer II rich region but follow the Budiansky model in the polymer I rich region. In one interpretation of the Coran‐Patel model, a phase inversion takes place around ϕ2 = 0.8, which is higher than the composition at which the phase connectivity of polymer II begins to appear, ϕ = 0.5, via electron microscopy studies. The rubbery modulus behavior of the full and semi‐1 IPN's follow the equation of Siegfried, et al. reasonably well, which considers the deformation effect of polymer I in terms of the rubber elasticity front factor.

The stress‐strain behavior of both the full and semi‐1 IPN's was similar to that of toughened plastics at polymer II rich compositions, and to that of reinforced elastomers at polymer I rich compositions.
Thermal degradation of polystyrene: Changes in molecular composition
Authors: Daoust D. , Bormann S. , Legras R. , Mercier J. P.
Published: December 2004

The 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

Samples 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

Environmental 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

Network 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

A 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

It 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

The 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

This 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

Optimal 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

A 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

The 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

Electrical 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

Thermosetting 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

A 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

The 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

The 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 development of surface texture in blown polypropylene film
Authors: Hobbs S. Y. , Pratt C. F.
Published: December 2004

The reorganization processes that give rise to surface fibrillation in blown polypropylene film are described in some detail with the aid of numerous photomicrographs. A relationship between stalk surface morphology and degree of surface roughness is noted.
The relationship of carbon black dispersion to electrical resistivity and vulcanizate physical properties
Authors: Cembrola R. J.
Published: December 2004

The 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

A 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

The 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

The 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

The 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

The 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

The 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

The 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

A 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.
Recent advances in interpenetrating polymer networks
Authors: Frisch K. C. , Klempner D. , Frisch H. L.
Published: December 2004

We review the synthesis, morphology, and physical and mechanical properties of IFNs as well as the related pseudo‐IPNs, in which only one of the polymers is crossliriked. Recent studies have shown that the degree of phase separation achieved in these materials is strongly dependent on the compatibility of blends of the linear polymer constituents of the IPN components as well as the kinetics of chain extension and the presence of grafting between component polymers. We illustrate this by a series of IPNs consisting of a polyurethane and an acrylic copolymer. The acrylic is a typical automotive enamel. An enhancement in properties results, which is dependent on the amount of grafting and the kinetics of polymerization. Also discussed are IPNs of a polyurethane and an epoxy, which exhibit a synergism in adhesive properties, and IPNs of a RIM polyurethane with several epoxies and unsaturated polyesters. In addition, also reported are the preliminary studies on the first successful preparation of a three‐component IPN, consisting of a polyurethane, an epoxy, and an acrylic.
Pressure drop of polymeric melts in conical converging flow: Experiments and predictions
Authors: Kwon T. H. , Shen S. F. , Wang K. K.
Published: December 2004

It is of importance to estimate the pressure drop of polymeric materials in a converging die with an abrupt change in geometry for many polymer processes. In the present study, experiments have been conducted with an extruder and conical dies of four different converging angles for two different polymeric melts under various processing conditions. As part of the analysis, numerical calculations have been carried out using a finite element method (FEM) for a power‐law fluid model, A simple formula for estimating pressure drops has also been derived based on a power‐law fluid model with normal‐stress effects incorporated. In particular, the formula with the normal‐stress term excluded underpredicts pressure drops systematically at high flow rates, giving very similar results to those by the FEM calculation. When the normal‐stress term is included, the formula is in bettor agreement with the experimental data, confirming that the normal stress effect is important at high flow rates. Other formulae in the literature have been also compared with the present experimental data.
Multidimensional control of profile extrusion
Authors: Stevenson James F. , Lee L. James , Griffith Richard M.
Published: December 2004

Dimensional changes in complex profile extrusions are classified as overall size and local shape changes which can be related naturally and systematically to changes in operating conditions. The theoretical basis and supporting experimental data for simultaneous, independent control of certain classes of extrudate dimensions are presented for the following strategies: (1) size control by manipulating line speed relative to extruder output rate, (2) shape control by manipulating extrudate swell through adjustments in stock temperature, and (3) shape control by manipulating local die flow by adjusting the die temperature set point.
Solid state extrusion of polytetrafluoroethylene fibers
Authors: Mc Gee Robert L. , Collier John R.
Published: December 2004

Polytetrafluoroethylene (PTFE) was solid state extruded to fiber form at temperatures between 250 and 300°C and at pressures between 7000 and 15,000 psi. The PTFE fibers had a diameter of 0.0502 inches and the reduction ratio for extrusion was 55.8. The fibers were tested for mechanical strength, and examined with a scanning electron microscope, which revealed a fibrous structure at high magnifications. The melting point of the fibers was 342°C by differential scanning calorimetry. The tensile properties were enhanced with an increase in processing temperature and pressure, the highest properties resulting from an extrusion temperature of 300°C and pressures greater than 10,000 psi. A tensile strength of 5500 psi and a secant modulus of 250,000 psi were obtained.
The effect of flow on cavity surface temperatures in thermoset and thermoplastic injection molding
Authors: Frutiger R. L.
Published: December 2004

In the Injection molding process, nonuniform heat transfer between the polymer and the mold caused by flow during the cavity filling stage can lead to spatial variations in the cavity surface temperature. This can result in an increase in cycle time or poor part quality. An investigation of the flow‐induced, nonuniform, cavity surface temperature is reported here. A flow model for a thin, rectangular, end‐gated cavity and a model for the steady‐state temperature distribution in a simple mold are developed. These are applied to some thermosetting and thermoplastic systems. For both filled and unfilled thermosets, it is found that a simple plug flow model gives a good approximation for the heat transfer during flow. For thermoplastics, however, the full flow solution must be used. For the cases considered in this study, the steady‐state temperature variation along the cavity surface is less for the thermoplastics than for the thermosets.
Physical aging and biaxial creep in cellulose acetate butyrate
Authors: Questad D. L.
Published: December 2004

Torsional and tension‐torsion creep studies have been performed on cellulose acetate butyrate at 65°C. The aging shift factor, μ, at this temperature has been determined to be 0.85. This is somewhat higher than 0.75 which was suggested as a maximum value for cellulose acetate butyrate (5). Axial stresses cause the torsional retardation times to become shorter. The change in retardation time is mainly determined by the magnitude of the axial stress and not by the length of time during which the axial stress is applied. Torsional stresses cause the axial retardation times to shift in a similar manner. The shifting of retardation times follows a maximum shear stress criterion.