bluuebunny/crossref_metadata_2025_split huggingface dataset:
Press‐forming of continuous‐fiber‐reinforced thermoplastic composites
Authors: Manson Jan‐Anders E. , Schneider Terry L. , Seferis James C. 
Published: December 2004

AbstractProcess‐induced effects on thermoplastic‐based composites were investigated for laminates processed under high production rate conditions. Press‐formed carbon‐fiber‐reinforced poly(ether ether ketone) (PEEK) was used as a model system. The morphology and laminate quality were investigated on unidirectional laminates processed at cooling rates from 0.3 to 120°C/s and annealing of 177°C and 300°C. The laminate quality was examined for degree of consolidation, compaction, and fiber‐matrix uniformity. Combined calorimetric and density measurements, as well as micrographic techniques, were used for examination of the laminates. The fracture toughness for the laminate was measured as a function of the position over the thickness of a 40‐ply thick unidirectional laminate. This study clearly demonstrates the importance of uniform pressure distribution over the laminate to achieve a void free and homogeneous laminate.
Physical properties of some injection molded thermoplastics of various glass contents
Authors: Loveless H. S. , McWilliams D. E. 
Published: December 2004

AbstractThis paper discusses the influence of fiber‐glass reinforcement content on the physical properties of four theroplastic injection molded materials. In addition, the effects of binder difference (i.e., thermoplastic vs. thermosetting), associated with the reinforcement, are described.Several properties that were expected to show response to glass content and binder differences have been examined. Among these are short‐ and long‐term tensile strength, flexural properties, compressive resistance, impact strength, deflection temperature under load (DTL), and environmental stress cracking.This work has demonstrated that fiber‐glass reinforcement of the particular thermoplastics described in this paper has led to substantial improvements in both the stiffness and strength characteristics of the base resins. The responses to binder chemistry difference was found to be slight in many instances for the resins, as reflected by the tests described herein. However, the long‐term tensile, impact, DTL, and stress‐cracking tests have shown considerable sensitivity to binder change in some cases, especially with respect to the polypropylene, SAN and polyamide plastics. The particular response to a given binder system, however, appears to vary both with the material under test and the property used to detect such response.
Surface fracture in injection molding of filled polymers
Authors: Ballman R. L. , Kruse R. L. , Taggart W. P. 
Published: December 2004

AbstractIn injection molding certain polymers, fracture of the polymer stream sometimes occurs at the mold surface. This phenomenon has been found to be a tearing apart of the polymer surface layer accompanied by downstream slip of the flowing melt at the polymer/mold interface. Fracture occurs early in mold filling and is initiated usually at the gate to the mold cavity. Analysis of the fracture mechanism indicates that fracture is caused by: (1) high shearing stress in the melt as it fills the mold; (2) poor polymer/mold adhesion; and (3) low polymer surface cohesive strength.
Quantitative thermal analysis of polyblends
Authors: Bair H. E. 
Published: December 2004

AbstractA new quantitative thermal analysis technique was attempted on ABS and Noryl‐type polyblends. A particular component within a polyblend was identified by its glass transition temperature and the amount of the component was determined from the increase in specific heat at the glass transition temperature.Two commercial Noryl resins were determined to be blends of high impact polystyrene and polyphenylene oxide in 47‐47 and 69‐17 proportions by weight, respectively. Polystyrene appears to be cosoluble with polyphenylene oxide without the formation of any complex. The PS‐PPO polyblends yield single sharp glass transitions which are a function of concentration.
Fine structures and fracture processes in plastic‐rubber two‐phase polymer systems IV. Temperature and strain rate dependences of tensile properties
Authors: Imasawa Y. , Matsuo M. 
Published: December 2004

AbstractYield stress (σY) and elongation to break (εb) were measured over a wide range of temperature under three different strain rates (\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}) for a series of polyvinylchloride‐rubber blends, ABS polymer and high‐impact polystyrene. It was found that a temperature‐strain rate reduction was possible for σY and the composite curve obtained by the superposition was expressed by the following relation:

where K1 and K2 are the material constants, and AT is the shift factor.As for εb, a new maximum was found at around room temperature in addition to the known maximum at around the glass transition temperature of the matrix phase. The results are discussed in terms of the craze theory for rubber toughening of plastics.
Elastic properties of model two‐phase continuous composites
Authors: White P. L. , Van Vlack L. H. 
Published: December 2004

AbstractThe dynamic elastic moduli were measured on macroscopic models simulating two‐phase microstructures where the second phase was present as a continuous, isotropic network. Using open‐pore polymer foams with higher‐moduli, infiltrating matrices, the composite moduli were found to be linear with volume fraction of the network phase. Variations of network cell size or surface area indicated that the moduli increased with increasing interfacial area, but only when interphase wetting was present and matrix contraction upon solidification occurred. Metallic foams with a lower moduli matrix produced moduli that were compatible with existing bounding theories for composites.
Isothermal kinetic studies using a thermomechanical analyzer I. Rates of polymer swelling and dissolution
Authors: Machin D. , Rogers C. E. 
Published: December 2004

AbstractThe use of a commercially available thermomechanical analyzer (TMA) operated in its isothermal mode is illustrated for studies of polymer‐swelling and dissolution in liquids. Results for a variety of polymer‐swelling agent systems demonstrate that information usually requiring more sophisticated experimental techniques can be readily obtained with the TMA. In particular rates of swelling and penetrant diffusion coefficients can be determined for selected systems. Dissolution measurements, exemplified here for polystyrene in three different solvents, can be utilized to obtain steady state rates of solvent penetration and rough estimates of the interdiffusion coefficient for a system. The experimental limitations involved in both types of measurement are discussed.
Structure‐Property relationships in polyacrylate‐poly(urethane‐urea) interpenetrating polymer networks
Authors: Matsuo M. , Kwei T. K. , Klempner D. , Frisch H. L. 
Published: December 2004

AbstractInterpenetrating polymer networks of polyacrylate (A) and poly (urethane‐urea) (U) were prepared by mixing lattices of self‐curing polyacrylate and urethane‐urea prepolymer followed by subsequent curing of each network. The structures of the mixtures were analyzed by the dynamic viscoelasticity and the electron microscopy. It was found that a phase inversion occurred from the “U‐phase particles in A‐phase matrix” to the “A‐phase in U‐phase matrix” at A/U ≑ 30/70 as the U‐phase content increases.With increasing A‐phase content, tensile strength started to increase and elongation‐to‐break becomes almost constant after the A‐phase formed a continuous phase. This implies that the tensile properties are closely related to the morphological features.
High‐temperature molding of pyrrones
Authors: Johnson C. L. , Bagley E. B. , Tolbert T. L. 
Published: December 2004

AbstractThe cross‐linked, ladderlike structure of cured pyrrones is not susceptible to forming at ordinary temperatures and pressures. At unusually high processing temperatures, of the order of 500°C, these intractable materials are observed to undergo transient flow sufficient to allow molding of the material. This observation, supported by analytical information, suggests that the flow occurs because of the breakage of covalent organic bonds and subsequent structural rearrangement of the cross‐linked polymer network. This is in accord with a number of isolated reports of the pyrolytic behavior of several polymers.
Survey of a new concept—liquid resin molding
Authors: Uglione H. L. 
Published: December 2004

AbstractThe need for low‐pressure molding of electronic assemblies and devices has long been realized by customers and plastic processors throughout the military, space, and commercial industry. Probably the single, greatest advance in this area to date has been the introduction of liquid resin molding or, as sometimes called, liquid transfer molding and liquid injection molding. This paper briefly discusses the studies being conducted in the area of material developments, applications, and tooling considerations and cites several case histories comparing the advantages of liquid resin molding vs powder molding. This paper also includes the relatively new efforts being investigated for economical mass production of solid state light‐emitting diodes and solid state optical numerical readouts.
The effect of temperature on the elastic properties of polymer melts
Authors: Han C. D. 
Published: December 2004

AbstractA correlation is developed between the melt elasticity and temperature, the melt elasticity being defined by the normal stress difference. The correlation follows the form of the Arrhenius equation, for the temperature range tested, for high density polyethylene and polypropylene melts. Measurements were taken using the capillary rheometer which is described in detail in the author's earlier publications. The author further presents a correlation between the pressure drop at the entrance of a capillary and the residual pressure at the exit of the capillary (exit pressure). The correlations presented in the paper support the author's earlier contention that the exit pressure is indeed a manifestation of elastic behavior.
Capillary extrusion of composite materials
Authors: Lim Timothy T. S. 
Published: December 2004

AbstractInvestigations on the extrusion characteristics of composite systems were performed on the Sieglaff‐McKelvey capillary rheometer, with particular emphasis on the characterization of flow instability and “melt fracture” phenomena. The mechanisms of melt fracture appear to be identical for both the filled and unfilled polymers (1. Polyethylene with glass beads; 2. Ethylene‐propylene copolymer with graphitized carbon black). In all cases, the flow curves exhibit a plateau at some value of the shear stress. Above this shear stress plateau, melt fracture occurs. Although slip flow is the dominant mode of transport during melt fracture, the slippage in the tube may not be a necessary condition for the subsequent severe melt fracture.
Melt flow instabilities in capillary flow of two‐phase polymer systems
Authors: Han C. D. , Lamonte R. R. 
Published: December 2004

AbstractAn experimental study was made of melt flow instabilities in extrusion of two‐phase polymer systems. For the study, blends were prepared from two polymers: polystyrene (Dow Chemical STYRON 686) and high density polyethylene (Union Carbide DMDJ 4309). The experimental technique used in the present study was the same as that described in a previous paper by the authors. The study shows that there are abrupt increases both in exit pressure and in the recoverable shear strain (defined as the ratio of the exit pressure to shear stress) at the critical flow conditions. It has also been found that an addition of a small amount of high density polythylene (2.5 wt‐% and 5.0 wt‐%) increases the critical shear rate of polystyrene and hence results in a higher throughput rate before extrudate distortion is actually observed. This result is explained in terms of the independently determined melt elasticity of the two‐phase systems investigated.
Polybutadiene/polystyrene interpenetrating polymer networks
Authors: Curtius A. J. , Covitch M. J. , Thomas D. A. , Sperling L. H. 
Published: December 2004

AbstractInterpenetrating polymer networks (IPN's) of polybutadiene (PB) and polystyrene (PS) were prepared using both random (containing 36% cis, 55% trans, and 9% 1,2 vinyl) PB and high‐cis PB. For both series, a wide range of PB/PS compositions were synthesized. Using samples stained with osmium tetroxide, electron microscope studies revealed an irregular cellular structure of a few hundred Ångstrom diameter with the first component, PB, making up the cell walls. The size of the cells was found to depend on the PB crosslink density for the random materials. Modulus‐temperature data revealed two distinct glass transitions, confirming the microscopy finding of two phases. However, the transition temperature and transition slope varied with composition, and with the microstructure of the polybutadiene, giving evidence of significant molecular mixing. Stress‐strain data on the IPN's showed that materials rich in PB behave like self‐reinforced elastomers. Charpy impact resistance experiments on materials rich in PS indicated values of 5 ft‐lb/in. of notch, which compares well with graft‐type polyblends of similar PB/PS composition. The results were interpreted in the light of the recent theoretical work of Bragaw, who considered the importance of the distances between domain boundaries with respect to crack acceleration mechanics. Although the IPN's considered herein exhibited somewhat less than the predicted optimum phase dimensions, the arrangement of the domains is different from ordinary impact resistant plastics.
The optical properties of two‐phase polymer systems: Single scattering in monodisperse, non‐absorbing systems
Authors: Conaghan B. F. , Rosen S. L. 
Published: December 2004

AbstractTwo‐phase polymer systems have achieved commercial importance due mainly to the improvement in impact strength brought about by the addition of dispersed rubber particles to a normally brittle glassy polymer. Rubber‐reinforced polystyrene and ABS plastics are two familiar examples. An important drawback of this class of materials is their lack of transparency, caused by the scattering of light at the interface between the phases. The theory of light scattering by spherical particles indicates that the degree of scattering (turbidity) is a function of the amount of dispersed phase present, its particle size, the ratio of refractive indices of the phases, and the wavelength of light. Quantitative predictions of the effects of the above parameters on the transparency of two‐phase systems can be made, providing answers to the questions “How close must the refractive indices be?” and “What size must the dispersed‐phase particles be?” for a given level of transparency. Calculations for typical polymer pairs reveal that at a given dispersed‐phase level, a maximum in turbidity is obtained roughly in the range of particle sizes thought to be necessary for good impact strength. Also, if the refractive indices are matched at a particular temperature, small particle sizes greatly increase the temperature range over which scattering is minimized.
Deep drawability of biaxially rolled thermoplastic sheets
Authors: Broutman L. J. , Kalpakjian S. , Chawla J. 
Published: December 2004

AbstractThe deep drawability of biaxially cold‐rolled thermoplastic sheets has been studied using polycarbonate, polyvinyl chloride, and acrylonitrile‐butadiene‐styrene polymers. Each polymer was rolled to two different reductions in thickness. The deep drawability of these rolled sheets was measured by determining the limiting draw ratio using a Swift cup test. Strain ratios were measured in three directions for each of the rolled sheets in order to determine the normal and planar anisotropy of the sheets. It has been determined that the drawability of a sheet can be correlated with the normal anisotropy of the sheet and it is the increase in normal anisotropy of a sheet which increases the drawability of the sheet. It has also been shown that lubrication increases the drawability due to a reduction in punch force.
On the re‐equilibration of nylon 6
Authors: Reimschuessel H. K. , Nagasubramanian K. 
Published: December 2004

AbstractBased upon known polymerization kinetics, the extent and rate of re‐equilibration of nylon 6 have been analyzed. Relationships have been developed for the calculation of the rates of molecular weight change and monomer regeneration as functions of initial water concentration, degree of polymerization, and type and concentration of end groups. The results are in good agreement with published data.
Growth of fatigue cracks in polycarbonate
Authors: Arad S. , Radon J. C. , Culver L. E. 
Published: December 2004

AbstractThe rapid increase in the rate of application of thermoplastics in engineering design problems and the interest in the structural use of these materials have resulted in the requirement of comprehensive information about the behaviour of thermoplastics when subjected to cyclic loading conditions. In addition to the “total fatigue life” data already available for many materials, attempts have been made to analyse the crack initiation and steady crack growth processes and determine the effects of parameters such as mean load, frequency and crack geometry on the rate of crack propagation. The results of an investigation of these aspects of fatigue crack growth in a brittle thermoplastic, polymethylmethacrylate (PMMA), have already been reported. In this paper, the results of a test program devised to study the behaviour, at room temperature and in air, of a polycarbonate, (PC), under similar loading conditions, are presented. Fracture Mechanics concepts have been used to analyse the results. It was found that a relationship of the form ȧN = β λn already shown to predict the cyclic fatigue crack propagation rate in PMMA, is also applicable to polycarbonate. However, when the effects of frequency and loading rate were studied, it was found that after the magnitude of parameter K̇( = ΔK/half the periodic time) exceeded 4000 lbf in. −3/2 s−1, the influence of the mean level of stress intensity factor, Km, became negligible in comparison to the effect of ΔK.
Thermal conductivity of polyethylene: The effects of crystal size, density and orientation on the thermal conductivity
Authors: Hansen D. , Bernier G. A. 
Published: December 2004

AbstractThermal conductivity measurements were made on polyethylene samples which had been crystallized at different temperatures in order to vary density and lamellar crystal thickness. Tests were also made on polyethylenes which were oriented by mechanical shearing and by crystallization in a temperature gradient. The thermal conductivity increased linearly by 50% as the density went from 0.96 to 0.99 gm/cc. By orientation the conductivity was increased ten fold in the direction of molecular orientation and decreased two fold in the perpendicular direction. For samples oriented by deformation at different temperatures, the conductivity apparently correlates with birefringence.
Principles of rotational molding
Authors: Rao M. Anandha , Throne James L. 
Published: December 2004

AbstractRotational molding is a process by which powdered or liquid plastics are converted into hollow articles. This paper is devoted to the theoretical understanding of the process of rotational molding. There are seven sections:The Art, wherein we describe the process, discuss previous attempts at understanding the process, and mention processes that are similar in principle to rotational molding.Transient Heating of Mold Surface, wherein we show that the criterion for selection of mold materials is the ratio of the thermal diffusivity to the thermal conductivity, and present the heating curve for a mold in a rotational mold machine.Melting of Plastic Powder in a Rotating System, wherein we discuss in detail those physical powder characteristics that are necessary for good flow within the mold cavity.Fluid Flow During Rotational Molding, wherein we discuss the velocity profiles within the melt film, point out that there is very little bulk polymer flow possible within the mold cavity under normal processing conditions, and consider capillary flow forces and surface wetting.Sinter‐Melting, wherein we compare the Kuczynski‐Neuville empirical sintering model with the Lontz viscoelastic model, conclude that the latter is correct for the sintering of materials such as ABS, and apply the Frenkel glass densification theory to the prediction of void disappearance in sinter‐melt polymers.Degradation, wherein we compare our experimental tensile strengths of polystyrene, obtained at varying oven cycle times and oven set point temperatures, with values obtained from degradation models given in the literature.Laboratory Simulation of Rotational Molding, wherein we propose two series of experiments, the first series being carried out without using rotational molding equipment, and the second using rotational molding equipment with molds having relatively simple geometries.
The effectiveness of polymer additives as determined by torsional braid analysis
Authors: Williams Bernard L. 
Published: December 2004

AbstractTorsional braid analysis has been explored as a means of providing a quantitative measure for the effectiveness of polymer additives. Quantitative determinations have been made of antioxidant activity of selected compounds when formulated with certain elastomers prone to oxidative crosslinking on heat aging. The torsional braid technique has been used to determine the time dependence of the sharp torsional modulus increase which corresponds to a change from a rubbery to a highly crosslinked state. This time dependence is taken as a measure of the rate of oxidative crosslinking in heat‐aged elastomer films coated on a Fiberglas braid. In this manner an assessment of antioxidant activity can be made. The effect of concentration and aging temperature on antioxidant activity can be made also. It has been also possible to use this technique to study the effect of structural changes in an antioxidant on its resultant activity. Feasibility studies have also been made on antiozonants in natural rubber and cis‐polybutadience at three temperatures. A value of 10.9 Kcal/mole was calculated for the activation energy for the oxidative crosslinking reaction of cis‐polybutadiene.
The injection molding of thermoplastics part I: Theoretical model
Authors: Kamal M. R. , Kenig S. 
Published: December 2004

AbstractA mathematical model is proposed for the quantitative treatment of the injection molding of thermoplastics as it relates to the behavior of polymer in the cavity. The model is based on setting up the equations of continuity, motion, and energy for the system during each of the stages of the injection molding cycle (filling, packing and cooling) and the coupling of these equations with practical boundary conditions. The treatment takes into consideration the non‐Newtonian behavior of the melt, the effect of temperature on density and viscosity, the latent heat of solidification, and the differences in thermal properties between the solid and the melt. In employing the model, it is necessary to know the pressure‐time variation at the cavity entrance. Numerical solutions have been obtained for the case of spreading radial flow in a semi‐circular cavity. The numerical results yield significant data on the progression of the melt front, the flow rate, and the velocity profiles at different times and positions in the cavity. They also yield temperature and pressure profiles throughout the packing and cooling stages.