bluuebunny/crossref_metadata_2025_split huggingface dataset:
The injection molding of thermoplastics part II: Experimental test of the model
Authors: Kamal M. R. , Kenig S. 
Published: December 2004

AbstractExperimental studies have been conducted with a 2 1/3 oz reciprocating‐screw injection molding machine to check the validity of a proposed theoretical model for injection molding. A semi‐circular cavity has been employed in the study to achieve spreading radial flow during the filling stage. Both high speed photography and pressure transducer measurements have been employed to obtain data on polyethylene. The photographic studies confirm the existence of spreading radial flow throughout the filling stage, and are in very good agreement with data obtained with the transducer on the progression of the melt front in the cavity. The results show that the proposed theoretical model yields predictions which are in good agreement with experimental data for all stages of the injection molding cycle with polyethylene. The model also predicts a composite pressure‐time curve for the overall cycle which is similar to those reported in the literature and which satisfactorily represents the data obtained in this study. It is also possible to predict a short shot under selected molding conditions in agreement with observation. The main problems in the application of the model arise during the filling stage near the cavity entrance where viscoelastic and end effects are important and where some of the assumptions inherent in the model may not be valid.
Uniaxial extension of polyvinyl chloride in the high‐elastic state
Authors: Vinogradov G. V. , Fikhman V. D. , Alekseyeva V. M. 
Published: December 2004

AbstractThe dependence of true stress on the extension ratio of PVC threads has been determined for a wide range of extension rates. Since the polymer subjected to deformation was in the high‐elastic state (at temperatures from 90 to 160°), the deformations were predominantly high‐elastic. The dependence of true stress on the amount of high‐elastic deformation is described by the Mooney‐Rivlin equation.Relaxation moduli have been found on the basis of measurements of stress relaxation at constant deformation after various extension ratios were attained at different rates. Within the limits of deformation regimes at which the true stress is an increasing function of extension ratio the relaxation moduli do not depend on extension ratio and rate of extension. This enables one to arrive at a master curve of the relaxation modulus versus relaxation time with the reservation indicated above concerning the increasing character of the dependence of true stress on extension ratio. The relaxation spectrum represented by the high‐elasticity plateau has been determined from the relaxation moduli according to the first approximation.The experimental data for a very wide range of deformation regimes and temperatures are presented in the form of an invariant dependence of the ratio of true stress to the rate of deformation on the product of deformation time by extension ratio.The ultimate strength of the specimens frozen rapidly after the attainment of definite extension ratios is determined by the accumulated high‐elastic deformation.
Critical regimes of shear in linear polymers
Authors: Vinogradov G. V. , Insarova N. I. , Boiko B. B. , Borisenkova E. K. 
Published: December 2004

AbstractThe state of the problem of elastic turbulence is critically discussed. It is shown that the development of elastic turbulence is associated with the transition of polymer systems to the high elastic state.Model experiments with a narrow‐MWD polybutadiene have been carried out. The method of vizualization of the flow in a flat slit with the aid of circular‐polarized light has been used. The results of polarization‐optical investigation are compared with the results of capillary viscometry and dynamic measurements at small amplitudes. It is shown, in accordance with theoretical predictions, that when a polymer passes from the fluid to the high elastic state with an increase in the shear rate, it ceases to behave as a fluid under shear. This is accompanied by various forms of flow perturbation at the duct exit and entrance and inside the duct. Perturbations at the duct entrance and exit are due to stress concentration in these zones. The transition of a polymer to the high elastic state near the walls inside the duct gives rise to the “stick‐slip” process or to continuous slippage along the duct walls, depending on the velocity of polymer movement. This can be clearly traced by the changes in the interference band pattern. Still higher velocities result in an intensive process of continuity break (rupture) in the polymer and in its chaotic movement in the duct as an aggregate of irregularly shaped lumps, which, relaxing, may form a continuous body again. Attention is drawn to the significance of these observations for a quantitative description of the viscosity anomaly of polymer systems and of the relationship between the viscosity anomaly with various flow irregularities and perturbations in such systems.
Some factors influencing cooling rates of rotationally molded parts
Authors: Throne James L. 
Published: December 2004

AbstractRecently, rotational molding engineers, concerned with warpage and uneven cooling in parts, have been “pre‐cooling” the mold in forced draft air after removal from the oven and prior to water quenching to removal temperature. In this paper, we analyze some of the factors that influence the rate of heat removal from an amorphous plastic in a metal mold. We find that mold thickness and thermal diffusivity, convection heat transfer coefficient of the cooling fluid, the thermal properties of the plastic and the initial, final and “freezing” temperatures of the plastic influence this cooling rate and the corresponding rate of volumetric shrinkage. We illustrate our analysis with several examples and discuss some guidelines in detail.
Prediction of polymer processing characteristics using the C. W. Brabender plasti‐corder torque rheometer
Authors: Allen Edward O. , Williams Robert F. 
Published: December 2004

AbstractThe Brabender Plasti‐Corder is shown to be an effective tool for predicting the processing characteristics of thermoplastic polymers. Procedures for determining the molding temperature range, the relative melt viscosity over a continuous temperature range, and the stability of molding and experimental curtain coating materials are presented.Molding temperature ranges can be determined by first establishing the Brabender torque which corresponds to the maximum viscosity at which a material will just fill the cavity in a particular injection system under full injection pressure and maximum injection rate. This torque is constant for any material to be molded in this system. A Brabender torque‐temperature curve is then obtained on the pertinent resin and the temperature which corresponds to the torque associated with the maximum viscosity is the minimum molding temperature. Maximum molding temperature is the temperature at which the log of the torque deviates from a linear dependence on temperature.The stability of thermoplastic compositions can be shown by a Brabender torque‐time curve at constant temperature. An unstable polymer shows decreasing torque with time if the decomposition predominantly consists of chain scission.
Solids conveying in screw extruders part III: The delay zone
Authors: Kacir L. , Tadmor Z. 
Published: December 2004

AbstractA theoretical model was developed for the newly‐defined delay zone of the plasticating screw extruder. The delay zone starts at the end of the solids conveying zone, i.e. at the point where the solid plug surface contacting the barrel melts and forms a film of melt up to where the steady state melting mechanism starts to operate. The model permits the film thickness and pressure profiles in this zone to be calculated. Published results were used to support the validity of the model. The results indicate that the film thickness at the end of the delay zone is several times the flight clearance. Finally, a criteria, based on the final value of the film thickness, is suggested to calculate the length of the delay zone.
Energy transport to molten flowing polymer systems: I. Development of an apparatus to obtain temperature profiles
Authors: Saltuk Ismail , Siskovic Nandor , Griskey Richard G. 
Published: December 2004

AbstractAn improved apparatus for studying temperature profiles in molten, flowing polymers has been developed. The apparatus incorporates modifications and improvements of earlier temperature profile devices. In addition, this unit made it possible to study temperature profile development as a function of axial flow length. Data taken with the apparatus were found not only to be precise and highly reproducible but also to show the proper trends with respect to physical behavior.
The bending of polymers under tension as related to a deep drawing process
Authors: Buettner William B. , Marshall D. I. , Manson John A. 
Published: December 2004

AbstractTwo engineering plastics, an acrylonitrile‐butadiene‐styrene resin (ABS resin, Cycolac MS) and a rigid polyvinyl chloride resin (PVC resin, Dacovin 2082) were investigated to determine the effects of cold working. In particular, the “bending under tension” stress system of a deep drawing process was considered. The object was to determine the effect of the blank‐holder pressure, the ratio of the punch radius to the material thickness, the speed of deformation and the temperature of deformation. The stress‐strain characteristics of the deformed and undeformed material were markedly different. Upper yield points were lower in the deformed specimens, the tensile strengths were decreased by 10 to 15% and the %‐elongation at break was higher—up to double the values for underformed specimens. An analysis indicated that these effects can be attributed to non‐homogeneous yielding. The results also indicated that crazing plays an important role in permitting an ABS material to permanently conform to a radius with no geometric constraints.
The particle flow of polystyrene during capillary extrusion
Authors: Nielsen K. Strange 
Published: December 2004

AbstractThe melt flow of emulsion polymerized polystyrene has been investigated in accordance with the particle flow concepts developed by Berens and Folt. Particles were found to be present in the extrudate up to 210°C and resins with larger particles were found to have lower viscosities. The molecular weight appears to have no significant effect on the melt viscosity above a certain molecular weight. The energy of activation for viscous flow at 190°C and at shear stress of 5 × 105 dynes/cm2 was found to be 29–33 kcal/mol depending on type of resin.
The macroscopic volume changes of selected polymers subjected to uniform tensile deformation
Authors: Powers John M. , Caddell Robert M. 
Published: December 2004

AbstractHigh density polyethylene (PE), polycarbonate (PC), and polymethylmethacrylate (PMMA) were subjected to uniaxial tensile deformation up to the onset of instability or necking. Simultaneous readings of longitudinal extension and transverse contraction (width and thickness) were obtained continuously during the loading period. From these data, plots of longitudinal versus “average” transverse strain were produced and it was found that the trends were neither constant nor linear over the full strain range employed. Additional plots of per cent volume change versus longitudinal strain indicate that the PMMA and PC show a maximum volume increase of about 0.6% while PE shows a maximum volume decrease on the order of 2.5%. Similar volume decreases have been noted by others and it would appear that structural changes are the most likely cause of this behavior.
Evaluation of melt flow as a measure of low density polyethylene processability into blown films
Authors: Plochocki Andrew , Czarnecki Lech 
Published: December 2004

AbstractMelt capillary flow and extrudate swelling for low density polyethylenes (LDPE), differing in ease of heavy‐duty, blownfilm extrusion, have been employed as processability criteria. LDPE of good processability is characterized by a unique combination of melt fluidity, temperature, shear rate dependence and melt elasticity. These characteristics of flow are correlated with LDPE film blowing process variables such as maximum take‐up speed, film thickness scatter, and extruder temperatures profile. Intuitively, these melt flow criteria should be extended to Trouton's viscosity and the tensile strength of the melt. The limited development of the elongation viscometry techniques, however, has limited their application.
Effect of rubber particle size on deformation mechanisms in glassy epoxy
Authors: Sultan Jacques N. , McGarry Frederick J. 
Published: December 2004

AbstractWhen tested in tension, a cross‐linked epoxy resin can be made to exhibit shear yielding. A modified von Mises criterion, τ = τ0 − μP describes the yielding behavior of the same resin under a biaxial stress system, indicating that the flow of the material is pressure sensitive.Butadien‐acrylonitrile elastomer particles suspended in the cross‐linked epoxy matrix induce large local deformations when the composite material is stressed. Particles a few hundred Angstroms in diameter cause the glassy matrix to exhibit shear banding, and the macroscopic failure envelope of such a system follows a modified von Mises criterion similar to that of the matrix resin. It was found that the coefficient of internal friction, τ, and the activation energy for yielding are approximately the same for the two cases. With larger particles (5‐15,000 Å diam) the failure mode changes as shown by the macroscopic yield envelope and the associated activation energy. Electron micrographs of the fracture surfaces show microcavitation, similar to crazing around each particle; the deformed glassy polymer around each particle retracts upon heating the matrix above its Tg. The fracture surface work value of the unmodified matrix is 1.75 × 105 ergs/cm2. With 10 pph small particles, the value increases to 3.32 × 105 and with 10 pph of large particles, to 15.48 × 105 ergs/cm2.
Synergism in thermal stabilization of polyvinyl chloride
Authors: Deanin Rudolph D. , Landers James F. , Byczko Richard W. , Linzer Ira 
Published: December 2004

AbstractPlasticized polyvinyl chloride was thermally stabilized by barium, cadmium, and zinc laurates, epoxidized soybean oil, and monoalkyl diaryl phosphite, and by combinations of these stabilizers. Of 26 possible combinations, 18 showed some improvement, 8 showed useful improvement, 7 showed marked improvement, and 3 systems were outstanding. Of the 26 combinations, 10 showed distinct synergism, based mainly upon combinations of Group II‐B metals with Group II‐A metals, “secondary” stabilizers, or both. Combinations of Group II‐B metals with “secondary” stabilizers were particularly interesting and promising.
The mechanical behavior of thermoplastic materials in the deep drawing process
Authors: Evans Robert E. 
Published: December 2004

AbstractThis study presents a mechanical analysis of the deep drawing of thermoplastics in the glassy state. A theoretical stress analysis is conducted by applying principles of classical plasticity together with several assumptions. A simple model is presented relating drawing performance with the mechanical properties of the plastic measured under the conditions of the fabrication operation. An experimental procedure is described for evaluating the drawability of a plastic. Data on thirteen thermoplastics are used to demonstrate the applicability of the theory developed.
Low temperature transitions in a crosslinked urethane
Authors: Wischmann Kenneth B. , Brassell Gilbert W. 
Published: December 2004

AbstractWe have investigated the low temperature transitions in a urethane prepolymer crosslinked with various amines and triols by measuring their dynamic mechanical properties over a temperature range of 25°C to approximately − 190°C. In the formulations studied, a low temperature transition was observed near − 140°C and the transition was shown to be related to the electronic and steric influences of the curing agent structure at the crosslink site. A quantitative relationship was demonstrated between the low temperature transition peak intensity and the polymer's crosslink density. The above relationships were derived from torsion pendulum and solvent swell experimentation.
The effect of flake aspect ratio on the flexural properties of mica reinforced plastics
Authors: Lusis J. , Woodhams R. T. , Xanthos M. 
Published: December 2004

AbstractTwo naturally occurring micas, phlogopite and muscovite, were ground and classified according to their average aspect ratios (flake equivalent diameter to thickness ratio). These flakes were then used to reinforce a polystyrene copolymer and a polyester resin. The compression molded test pieces were tested in flexure and the flexural strengths and flexural moduli determined for each aspect ratio. The experimental results indicate a strong dependence of strength and modulus on the flake aspect ratio up to a value of 100–200 for these systems. At high volume fractions, 0.6 to 0.7, high aspect ratio mica composites yielded flexural strengths of 35–45,000 psi with flexural moduli of 10–14 million psi. Notched Izod values were in the range of 0.5–1.4 ft lb per inch of notch. These results were compared with the theoretical treatments of Padawer and Beecher, and Riley.
Model filler reinforcement studies by small angle X‐ray scattering
Authors: Myers M. E. , McIntyre D. 
Published: December 2004

AbstractPolybutadiene rubbers, filled with polydichlorostyrene or polystyrene latices having spherical diameters of approximately 500Å, were examined by small angle x‐ray scattering. The filler latices were examined by x‐ray scattering as a function of strain. The sample elongations ranged up to 400 percent. An analysis of the scattering of the polydichlorostyrene filler latices showed that there was deformation of the filler particles up to 25 percent. Such a deformation is not expected on the basis of the mechanical properties of bulk glassy polydichlorostyrene. However, deformation into ellipsoids of revolution is consistent with the x‐ray evidence. The deformation of the latices is reasonable.
Viscoelastic properties of heterophase blends of homopolymers and block copolymers
Authors: Choi G. , Kaya A. , Shen M. 
Published: December 2004

AbstractStress relaxation and dynamic mechanical measurements were carried out for two types of heterophase polyblends. One is obtained by blending homopolymers of butadiene and styrene (high impact polystyrene or HIPS); the other by blending homopolymer of butadiene with a triblock copolymer of styrene‐butadiene‐styrene (SBS/B). It was found that for HIPS, time temperature superposition is difficult, and the shift factors cannot be adequately interpreted by a reasonable model. For SBS/B it is impossible to carry out superposition. Modulus‐temperature and loss tangent curves determined by dynamic mechanical experiments indicate the presence of new transition near −40°C. Possible mechanisms giving rise to this new transition are discussed.
Flow behavior of well characterized polyethylene melts
Authors: Miltz Joseph , Ram Arie 
Published: December 2004

AbstractA careful characterization and rheological study of low density polyethylene (LDPE) reveals that long‐chain branching (LCB) plays a decisive role. At constant molecular weight (M̄w) higher LCB reduces the Newtonian viscosity ηo and the shear sensitivity, increases the activation energy Eo, and finally delays transition to pseudoplastic flow to higher shear rates and the onset of melt fracture to higher shear stresses (τd). The flow parameters ηo, \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma _{cr} $\end{document}cr, τd, and the derived flow relaxation times are uniquely correlatable by means of a modified molecular weight (gM̄w) incorporating the LCB effect. High density polyethylene are less shear sensitive than their low‐density counterparts, have a lower activation energy, fracture at higher shear stress levels and cannot be regarded as branchless LDPE's.
Effect of an epoxidized novolac resin anhydride structure on the properties of resin
Authors: Johnson Ronald E. , Fricke A. L. 
Published: December 2004

AbstractThe properties of an epoxidized novolac resin cured with two homologous series of substituted succinic anhydrides (alkenyl and alkyl) have been determined and the effects of anhydride structure on properties have been evaluated. Substituted succinic anhydrides yield cured resins with lower strengths, lower heat distortion temperatures, and lower moduli. Use of substituted succinic anhydrides could broaden the range of application of alicyclic anhydrides to include those requiring a more flexible resin. Effects of specific elements of anhydride structure have been consistently interpreted from properties measurements and from aging and solvent resistance studies.
The mechanical properties of high‐density rigid polyurethane foams in compression: I. Modulus
Authors: Phillips P. J. , Waterman N. R. 
Published: December 2004

AbstractA series of rigid polyurethane foams of densities varying from 65 kg/m−3 to 400 kg/m−3 have been tested in compression as a function of rate and temperature. It has been found that a linear relation exists between density and modulus if the data is referred to a constant thermodynamic temperature.
Morphology of a polyurethane‐polyacrylate interpenetrating polymer network
Authors: Frisch K. C. , Klempner D. , Migdal S. , Frisch H. L. , Ghiradella H. 
Published: December 2004

AbstractInterpenetrating polymer networks of the SIN type (simultaneous interpenetrating networks) composed of a polyacrylate and a polyurethane were prepared. They were made by mixing several concentrations of the linear polymer and prepolymer in solution, together with their respective chain extending and crosslinking agents and catalysts, casting films and curing them in situ. The morphology was studied by differential scanning calorimetry and electron microscopy in order to determine the extent of chain entanglement of the two networks (interpenetration). It was found that little or no phase separation occurred, thus implying extensive interpenetration.
The plasticating process in injection molding
Authors: Donovan R. C. 
Published: December 2004

AbstractA mathematical representation of the plasticating process in a reciprocating‐screw injection‐molding machine has been formulated as a design tool for simulating the effect of processing parameters on the melting performance, the melt temperature, and the pressure profile. Comparisons with experimental data on low density polyethylene (LDPE), acrylonitrile butadiene styrene (ABS), and polyvinyl chloride (PVC) under a wide variety of processing conditions are described.
The surface area of bulk poly(vinyl chloride)
Authors: Salovey R. , Cortellucci R. , Roaldi A. 
Published: December 2004

AbstractThe porosity of poly (vinyl chloride) (PVC) resin particles produced in bulk polymerization is sensitive to polymerization conditions. Using scanning electron microscopy, 60μ spherical beads of PVC are shown to be composed of loosely packed 1μ spherical subparticles. This complex morphology is characterized by a variability in surface area. The surface area of bulk PVC materials can be measured by a chromatographic technique. The elution time of n‐octane as a probe molecule on PVC packed columns is simply related to PVC surface area. At approximately constant particle size (measured by Coulter counter and optical microscopy), surface areas measured by argon adsorption are correlated to chromatographic elution times. The bulk density, plastisol viscosity and pore volume (from mercury penetration porosimetry) are determined and related to specific surface area.