bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of the chemical structure of low‐profile additives on the curing behavior and chemorheology of unsaturated polyester resin
Authors: Lee Dai‐Soo , Dae Han Chang 
Published: December 2004

AbstractAn experimental study was conducted to investigate the effect of the chemical structure of low‐profile additives on the curing behavior and chemorheology of unsaturated polyester resin during isothermal cure. For the study a general‐purpose unsaturated polyester resin was cured in the presence of t‐butyl perbenzoate as Initiator. The curing behavior of the resin was investigated using differential scanning calorimetry (DSC). Three different thermoplastic low‐profile additives were used, namely poly(vinyl acetate) (PVAc), poly(styrene‐co‐butadiene), which is also known as KRATON DX‐1300, and dehydrochlorinated Isobutylene/isoprene copolymer, often referred to as conjugated diene butyl (CDB) rubber. Each of the these additives, about 30 weight percent, was first dissolved in styrene. The solution was then mixed with unsaturated polyester resin and CaCO3. The CaCO3 particles helped stabilize the emulsions consisting of resin and KRATCN, and of resin and CDB. For each resin formulation, a series of isothermal DSC runs were made at various levels of cure pressure. It was found that for all three low‐profile resins investigated, the final degree of cure went through a maximum as cure pressure was increased from atmospheric to 6.21 MPa (900 psi). We have observed evidence that in the presence of an initiator generating free radicals, the unsaturated double bonds in the KRATON and CDB undergo grafting reactions with the styrene monomers and unsaturated polyester resin, increasing the glass transition temperature of KRATON and CDB, to an extent which varies with the cure conditions employed. Both steady and oscillatory shearing flow properties were determined using a cone‐and‐plate rheometer. The rheological measurements indicate that the resin/CaCO3/KRATON and resin/CaCO3/CDB systems give rise to gel times shorter than the resin/CaCO3/PVAc system. It is concluded that both KRATON and CDB are more effective, both for enhancing the rate of cure of unsaturated polyester resin and imparting impact properties to the cured composites, than those thermoplastic low‐profile additives that contain neither unsaturated double bonds nor a chemical structure that has rubber‐like properties in the solid state.
Shear yielding of biaxially oriented styrene‐acrylonitrile copolymer films
Authors: Chau C. C. , Rubens L. C. 
Published: December 2004

AbstractThe shear yielding processes in the deformation of biaxially oriented styrene‐acrylonitrile (SAN) copolymer films (machine oriented with draw ratio = 6.9 in the machine direction and 2.9 in the transverse direction) were studied. In the transverse direction, two sets of shear bands with an intersection angle of about 123.6 degrees (61.8 degrees with the tensile axis) were developed. When necking occurred, the bands in the necked region were thin and discontinuous with an intersection angle of about 81 degrees. In the machine direction, shear bands appeared to be short and diffused with an intersection angle of about 119.2 degrees. Only a slight necking effect was observed. The Luders strain in the transverse direction was about 0.56 and in the machine direction, about 0.16. The shearstrain‐volume of activation obtained from the strain rate dependence of shear stress was about 3440 ± 400 Å3 in the machine direction and 2700 ± 500 Å3 in the transverse direction. The work hardening behavior in both directions seemed to follow a linear relationship between 1n (tensile stress) and tensile strain at large strains. From a consideration of localized shearing toward tensile axis, the fraction of deformed materials was calculated. These observations indicated that (1) a strong orientation hardening effect existed in unbalanced biaxially oriented films, resulting from the difference of the amount of deformable materials between individual directions; and (2) deformation proceeded by shear banding with the high orientation direction involved more correlated molecular segments than the low orientation direction during the activation process.
Prediction of polymer‐filler redistribution in injection molding
Authors: Emerman Steven H. 
Published: December 2004

AbstractPolymer‐filler redistribution is the process whereby a polymer melt with an initially homogeneous distribution of filler obtains an inhomogeneous distribution upon injection molding. The purpose of this paper is to develop a set of rules for predicting polymer‐filler redistribution. The predictions are based upon experiments on lateral particle migration in pseudoplastic fluids and theoretical calculations on lateral particle migration in second‐order fluids. Predictions are made concerning the existence of a “surface of accumulation,” the dependence of filler concentration on distance from the gate, and the effects of injection time and barrel temperature. The predictions compare favorably with experiments in a dumbbell specimen using polymers Luran 378P and Ultraniid B3, both containing glass beads.
Characterization of polyethylene cable insulation by chemiluminescence measurements. I. Method development
Authors: Cooper Anthony R. 
Published: December 2004

AbstractChemiluminescence (CL) measurements have been performed on polyethylene electrical cable insulation. Matched pairs of unaged and aged materials were used where possible. The polyethylene materials investigated included crosslinked polyethylene, low density polyethylene, and ethylene‐propylene rubber. Various experimental techniques were examined to see if any distinctions could be made between unaged and aged samples. Chemiluminescence spectra were obtained for the first time for these materials. The spectra show differences between materials and also between unaged and aged samples.
Polymerization of ε‐caprolactam in an extruder: Process analysis and aspects of industrial application
Authors: Menges G. , Bartilla T. 
Published: December 2004

AbstractThe polymerization of caprolactam into polyamide 6 on corotating twin‐screw extruders provides the processor with technically and economically interesting aspects of application. Using the extruder as a small reactor, it is possible, on the one hand, for small batches of polyamide to be optimized for specific applications, and, on the other hand, for large quantities of polymerized polyamide melts to be fed into different processes. Apart from the extrusion of filaments, films, and profiles, the continuous polymerization process also can be coupled up to discontinuous processes. This so‐called rapid polymerization in the extruder not only brings price advantages as compared with standard polyamides, but also gives higher molecular weights and, hence, improved properties.
Transesterification reactions in molten polymers
Authors: Lambla M. , Druz J. , Bouilloux A. 
Published: December 2004

AbstractThe transesterification reaction of molten ethylene and vinyl alcohol copolymers (EVA), in presence of paraffinic alcohols and basic catalysts, leads to high conversion of the ester groups to secondary alcohol in both discontinuous and continuous processing equipment. Various kinds of alcohols and two different catalysts were used. Sodium methoxide is a powerful catalyst for the equilibrated transesterification reaction, but we also observed side reactions, such as cross‐linking with low‐molecular‐weight alcohols and hydrolysis of the catalyst followed by partial saponification of the EVA. Kinetic studies were performed in the presence of dibutyltin dilaurate, an efficient catalyst without any side reactions. The solubility of the main alcohol reagents was verified by diffusion measurements. The general reaction scheme and the related kinetics, corresponding to a homogeneous system, lead to a fair evaluation of the rate constants.
Solvent‐induced crystallization of a compatible polymer blend
Authors: Waywood W. J. , Durning C. J. 
Published: December 2004

AbstractWe studied solvent‐induced crystallization (SINC) in a compatible blend of poly (butylene terephthalate) (PBT) and a polyarylate (PAr) over a range of blend compositions and temperatures; liquid acetone was the crystallizing agent. Acetone transport kinetics were followed by mass uptake measurements in thin films and by optical microscopy. Crystallization kinetics were followed by density measurements. For the 0.2 mm thick films used, those with higher weight fractions of PST (50 to 60 percent by weight) exhibit diffusion controlled transport and crystallization over the entire range of temperatures studied (0 to 55°C). Those with lower weight fractions of PBT (∼30 percent by weight) display Case II sorption and crystal growth controlled crystallization at 0°C. The latter is rare for SINC in homopolymers and results from a sharp reduction in the PBT crystallization rate in the presence of the noncrystallizable PAr.
Application of rigid polyurethane integral‐skin foams to thermal insulating unit cases for car air conditioners
Authors: Gotoh Masao , Iida Makoto , Waragai Kenichi , Iijima Kazumi 
Published: December 2004

AbstractIntegral‐skin foams of rigid polyurethane are sandwich structures consisting of a core layer of closed cells enclosed in rigid surface layers on both sides. We examined the layer composition of integral‐skin foam with the objective of maximum flexural strength, and then studied possibilities of reconciling the strength and thermal insulating properties in housings for evaporators in car air conditioners; i.e., unit cases. This examination showed that the most practical density range (250 ≦ ρpall ≦ 500 kg/m3) provides vibratile resistance and thermal insulating properties. In actual car‐running tests, a maximum 0.1 MPa stress was generated on unit cases with overall densities of 350 kg/m3, We found this to be 0.4% of the flexural strength of an integral‐skin foam and 2% of the fatigue strength. In the forcible vibratile test, a stress of 0.5 to 1.0 MPa was generated at the resonance point of a unit case with 250 to 500 kg/m3 overall density. We found that these values are 2 to 5% of integral‐skin foam's flexural strength and 10 to 25% of its fatigue strength. These values are of the same level as the conventional unit case made of polypropylene blended with talc. An integral‐skin foam with an overall density of 250 kg/m3, nearly equal to half the weight of polypropylene, has the same level of resistance to vibration.
The effect of orientation on the CO2 sorption of polystyrene
Authors: Carfagna C. , Nicodemo L. , Nicolais L. 
Published: December 2004

AbstractThe chain orientation, induced by hot drawing, decreases the sorption capacity of polystyrene due to the tighter packing of macromolecules in the oriented material. Density measurements and decay of birefringence indicate that the loss of orientation Is a much more rapid phenomenon than the thermal shrinkage of the polymer.
Internal mixing: A practical investigation of the influence of intermeshing rotor configuration and operating variables on mixing characteristics and flow dynamics
Authors: Freakley P. K. , Patel S. R. 
Published: December 2004

AbstractThis paper deals with the measurement and interpretation of pressures and temperatures produced by the mixing of a rubber compound in the chamber of an internal mixer equipped with interlocking rotors. Pressure transducers and infrared/fiber optic temperature sensors were sited flush with the inner surface of the mixing chamber of a Francis Shaw KO Intermix of 2 L chamber volume. The variation of pressure with transducer position In the chamber wall and with rotor position was measured for selected fill factors and rotor speeds at “equilibrium” conditions (quasi‐static power requirement for the mixer) and at intervals during a complete mixing cycle. Two rotor designs were studied. Interpretation of the results was carried out with reference to biconical rotor rheometer measurements on the mixed rubber compounds and by reference to four regimes of viscoelastic behavior identified for two‐roll mill mixing. A basic flow analysis was carried out by use of the lubrication approximation in conjunction with an isothermal power‐law model.
Simulation of planar welding flows: Part 2. Strain history, stress calculation, and experimental comparison
Authors: Wei K. H. , Nordberg M. E. , Winter H. H. 
Published: December 2004

AbstractA numerical method is described for calculating the stress a viscoelastic melt exhibits in a flow, based on approximate kinematics. The method assumes that the kinematics are reasonably close to those of a shear‐thinning fluid such as the Carreau model. The strain history of a given flow and the resulting stress are calculated via a tracking method from finite element kinematics. Fullfield flow birefringence experiments were done for lowdensity polyethylene and polystyrene flowing past a thin plate divider in a 1.254‐mm planar slit die. By digitally analyzing birefringence photographs of the flow field, the birefringence was measured over two dimensions. These birefringence results are in good agreement with birefringence fields calculated from the numerical simulations and the stress‐optical law. The flow fields were most highly oriented in a region surrounding the weld interface just downstream of the plate divider. This orientation relaxed farther downstream, with polystyrene relaxing faster than low‐density polyethylene.
Thermal effects in the necking of polymers
Authors: Liu Tuo‐Min , Harrison I. R. 
Published: December 2004

AbstractA certain fraction of the mechanical work performed on a specimen is converted into heat during necking of plastic material. A method for measuring this fraction is proposed when specimens are drawn in two different surroundings, air and water. Differences in the heat transfer coefficients of these two media influence the temperature rise during necking. The fraction (α) of mechanical work converted into heat can be calculated using data determined at only one draw rate. The value of α calculated for polypropylene is 0.55 and for polyethylene it is 0.48.
The effects of residual stress on the mechanical properties of glassy polymers
Authors: Hornberger L. E. , Devries K. L. 
Published: December 2004

AbstractResidual stresses can have either beneficial or detrimental effects on the mechanical properties of plastics. Manufacturing processes frequently impose residual stresses on plastics. In this study, controlled thermal processes were used to impose surface compressive stresses on polycarbonate beam samples (6.4 by 12.5 by 80 mm). Resistance strain gage and photoelastic techniques were developed to measure the magnitude of these stored stresses. The compressive surface stresses were found to be between 14 MPa (2000 psi) and 31 MPa (4500 psi) and to vary with process method and cooling rate. The mean fatigue life (in bending) of the treated beam samples was found to improve by a factor of 10 over that of untreated samples. The increase in the fatigue life of the treated samples appears to be directly related to the magnitude of the surface compressive residual stress in the samples. The imposed residual stress, as determined by photoelastic measurements, has not appreciably relaxed after 1 year of storage at room temperature.
Phase behavior of ternary polymer blends
Authors: Su A. C. , Fried J. R. 
Published: December 2004

AbstractThe effect of varying interaction parameters on the phase diagrams of ternary polymer blends was explored by simulating spinodals through use of the Flory‐Huggins lattice theory. Results indicate that miscibility is favored for the case of ternary mixtures of marginally miscible or marginally immiscible pairs where all pair interactions are nearly athermal. Miscibility is restricted for asymmetric ternary blends when one of the polymer pairs is either strongly miscible or strongly immiscible. For symmetric blends of partially immiscible pairs, both two‐phase and three‐phase miscibility gaps are predicted.
Failure modes for polycarbonate under clearance‐fit pin‐loading
Authors: Naik R. A. , Prabhakaran R. 
Published: December 2004

AbstractThe failure modes and failure sequences for polycarbonate specimens loaded by a clearance‐fit pin were investigated. Specimens were tested in various configurations to produce failures by different engineering failure modes. Photographs of the isochromatic fringe patterns were taken at different levels of damage development to examine the failure modes. A finite element stress analysis was used to explain the observed failure onset modes. Damage onset predictions were made based on a modified von Mises criterion. Failures involving net‐tension damage initiated in the net‐tension mode and failed ultimately in the same mode. Cleavage failures were observed for specimens with very small end‐distances. Bearing failures were preceded by damage onset in a net‐tension mode. Certain large‐hole specimens failed in a buckling failure mode.
Microstructural diagnosis of block copolymer nonlinear mechanical properties I. Uniaxial stress/strain
Authors: Diamant Joram , Williams Michael C. , Soane David S. 
Published: December 2004

AbstractAn earlier study on the linear dynamic properties of triblock copolymers was continued into the nonlinear property regime. Uniaxial tensile tests were performed on styrene‐butadiene‐styrene block copolymers. The three polymers, having polystyrene (PS) fractions 0.27, 0.29, and 0.48, also represented three molecular weights (0.49, 0.58, and 1.0 × 105). Specimens were prepared by casting from three solvents (methyl ethyl ketone, MEK; cyclohexane; and a 9:1 mixture of tetrahydrofuran and MEK). This wide range of variables led to a correspondingly wide spectrum of properties, including the “plastic‐to‐rubber” transition in some cases. Stress‐strain curves were characterized by modulus, yield stress, general elevation, and fracture stress and elongation. Results were interpreted in terms of microstructural parameters obtained from the earlier linear tests, including interphase properties, and molecular features as well. Special insight emerged from comparison of first‐cycle (to 300 percent elongation) and second‐cycle tests, including changes in modulus, yielding, level, and the appearance of set. Additional data on sample preparation influences and PS continuity effects on sample properties were also obtained.
The modeling of batch and continuous emulsion polymerization reactors. Part I: Model formulation and sensitivity to parameters
Authors: Rawlings J. B. , Ray W. H. 
Published: December 2004

AbstractA detailed model for the prediction of the behavior of batch or continuous emulsion polymerization reactors has been formulated, and an efficient numerical scheme for simulation developed. The model makes use of population balance equations and detailed mechanisms for chemical and physical rate processes. The numerical procedure chosen for its solution is orthogonal collocation on finite elements. In this paper, a few comparisons with experimental data are presented to demonstrate the model validity. Finally, a parametric sensitivity study is carried out to identify the most important kinetic and physical parameters. In the sequel, a comprehensive comparison of model predictions with a wide variety of experimental data will be presented.
Numerical simulation of wire‐coating low‐density polyethylene: Theory and experiments
Authors: Mitsoulis E. , Wagner R. , Heng F. L. 
Published: December 2004

AbstractThe wire‐coating process was analyzed numerically making use of a particular die design employed in highspeed industrial operations. Both the lubrication approximation theory and a fully two‐dimensional finite element analysis were applied under isothermal and nonisothermal conditions, respectively. Particular emphasis has been given to the heat transfer effects between the melt arid the solid and free boundaries. A variety of thermal boundary conditions was studied, ranging from adiabatic to constant temperature walls. The influence of dimension less groups such as Peclet, Nahme, and Biot numbers is examined. Oscillation‐free solutions are obtained for the temperature field by using a standard finite element Streamline‐Upwind/Petrov‐Galerkin technique. Rheological data for a wire‐coating low‐density polyethylene (LDPE) resin (Alathon‐3535) were used in the analysis. The predictions include pressure and temperature distributions, shear stresses and shear rates both at the die wall and the wire, and wire tension for different wire speeds. The numerical results are compared with a set of experimental data for LDPE in a typical die used by Du Pont Co. It is found that the isothermal lubrication approximation for power‐law fluids overestimates pressure distributions when applied at die operating temperature. The nonisothermal finite element analysis gives better predictions, especially when realistic thermal boundary conditions are imposed, with the experimental results lying between those found from simulations assuming isothermal walls (upper limit) and adiabatic walls (lower limit).
Performance study of barrier screws in the transition zone
Authors: Amellal K. , Elbirli B. 
Published: December 2004

AbstractThis paper defines through a mathematical model the advantages and disadvantages of barrier screws as far as their melting and mixing performances in the transition zone are concerned. The melting analysis is based on the Tadmor's original model, and the flow in the melt channel is considered to be non‐Newtonian and nonisothermal. The performance of these barrier screws is investigated for the solids channel in terms of melting rate/interface a I contact area; melting efficiency; melting length; solid bed velocity profile; and power consumption in the melt film at barrel surface. For the melt channel, their performance is investigated in terms of pressure buildup; average bulk temperature; power consumption in the melt channel and in the main flight clearance at barrel surface; and average bulk mixing. The present study confirms that the increased‐pitch multichannel screw (Ingen Housz screw) outperforms clearly the other barrier screws investigated, since it gives the highest melting rate with reasonable pressure buildup in the melt channel. When compared with conventional screws, all the barrier screws examined give better melting performance.
Deep drawing of polypropylene sheets under differential heating conditions
Authors: Machida T. , Lee D. 
Published: December 2004

AbstractMeans of improving the deep drawability of thermoplastic sheets were explored by introducing temperature gradients in the deforming material during deep drawing of initially flat sheets. The specific experimental procedure consisted of either limiting the heating to the flange section of the deforming sheet or exposing the entire material to higher temperatures. At the same time, the initial blank size and the clamping force at the flange section were varied systematically. Both polypropylene and polypropylene with 40 percent calcium carbonate in the form of sheet were tested up to 130°C. It is demonstrated that the draw‐ability increases markedly with increasing temperature gradient between the flange and punch sections. The results of measured strain distribution in the deformed part indicate that the magnitude of temperature difference between the flange and punch sections determines the relative amount of deep drawing and stretching in the wall of the formed part, which in turn dictates the drawability of the material.
A method for estimation of polymer melt temperature fluctuation in a single screw extrusion process
Authors: Wilczyński Krzysztof 
Published: December 2004

AbstractA method for estimating the polymer melt extrudate temperature fluctuation in the single screw extrusion process is proposed. Predictions of the melt temperature fluctuation is feasible if the extrusion process parameters are known. The method is superior to these in the literature because it incorporates effects of the melting process on the temperature fluctuation. The method has been verified experimentally.