bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase inversion during compounding with a low melting major component: Polycaprolactone/polyethylene blends
Authors: Ratnagiri Ram , Scott Chris E. 
Published: April 2004

AbstractMost of the morphology development in compounding of immiscible blends is known to occur at short mixing times. In this investigation, the effect of rheology of the minor component on its tendency to form a continuous phase at short mixing times is studied. it was shown that phase inversion during compounding can occur even with a low‐melting major component. Four different blends with polyethylene as the high‐melting‐point minor component and polycaprolactone as the low‐melting‐point major component were chosen. Rheological measurements on the individual components were made both in the solid and melt states. Softening temperatures from these measurements were more representative of the observed processing behavior than the peak values as calculated from differential scanning calorimetry data. Compounding runs in a batch intensive mixer indicated that the minor component formed the continuous phase at short mixing times, in the blends with the low viscosity polyethylene. This was shown to correlate with its low modulus in the solid state and its low viscosity in the melt. A ramped temperature protocol during compounding delayed the melting of polyethylene thus preventing phase inversion from occurring. The blends with the higher viscosity polyethylene did not show phase inversion during compounding.
The effects of particle bulk modulus on toughening mechanisms in rubber‐modified polymers
Authors: Chen Xiao‐Hong , Mai Yiu‐Wing 
Published: April 2004

AbstractThe interaction of a blunting mode I plane‐strain crack tip with a periodic array of initially spherical rubber particles directly ahead of and parallel to the crack front in the effective medium is studied by the crack tip‐particle interaction model. The local stress concentrations responsible for rubber cavitation, matrix crazing and shear yielding are obtained by three‐dimensional large deformation elastic‐plastic finite element analysis with a sub‐modeling technique to explore the relationship between these toughening mechanisms. It is shown that rubber particles can act as stress concentrators to initiate matrix crazing or shear yielding but they behave differently from voids at high triaxiality because of their high bulk modulus. Particle bulk modulus affects significantly the hydrostatic stress inside rubber particles as well as the plastic deformation in the ligament between the crack tip and particles. Rubber cavitation or interface debonding relieves the triaxial stress planestrain condition so that extensive plastic deformation can be developed in the toughening process.
A global computer software for polymer flows in corotating twin screw extruders
Authors: Vergnes B. , Valle G. Della , Delamare L. 
Published: April 2004

AbstractA global computation model for self‐wiping corotating twin screw extruders is proposed. Based on a ID approximated approach, it has been validated by comparison with experimentation and more sophisticated numerical models. It allows one to obtain, for any screw profile including left‐and right‐handed screw elements and kneading discs, the profile along the screws of the main flow variables, such as pressure, mean temperature, residence time, and filling ratio. Owing to the approximations made, this model can be easily and rapidly run on a personal computer or a workstation. Important applications may be found in screw profile design, scaleup, compounding or reactive extrusion.
Dielectric properties of bisphenol‐A novolac type epoxide oligomer as a parameter for cure monitoring
Authors: Koike Tsuneo , Ishizaki Noritoshi 
Published: April 2004

AbstractDielectric properties above the glass transition temperature (Tg) have been investigated for three bisphenol‐A novolac type epoxide oligomers (PGEBANs) that have some branching in each molecule in comparison with the diglycidyl ether of bisphenol‐A (DGEBA) oligomer without branching. The relationship between the dielectric relaxation time (τ) and Tg for the branched PGEBAN oligomers is expressed by a modified Williams‐Landel‐Ferry (WLF) equation taking Tg as a variable at fixed temperatures from 70 to 100°C. The WLF‐type relationships between τ and Tg for the two types of uncured epoxide oligomers, the branched PGEBAN and the nonbranched DGEBA, were found to be useful for predicting the Tg of a branched DGEBA‐alicyclic amine system during the middle stage of curing.
Scratch and mar resistance of filled polypropylene materials
Authors: Chu J. , Rumao L. , Coleman B. 
Published: April 2004

AbstractPigmented mineral‐filled polypropylene (PP‐PMF) is marketed as a potential alternative to ABS (acrylonitrile‐butyldiene‐styrene) for interior automotive components. However, PP‐PMF is easily damaged by surface scratch and mar, thus limiting its acceptance for interior applications. This study investigates the test methods used to quantify the extent of scratch and mar damage and the effect of different mineral fillers on the scratch and mar resistance of PP‐PMF. Correlation was found between scratch visibility and scratch hardness, which can be measured by laser profilometer. The PP‐PMF specimen with 13 wt% talc is the worst in terms of scratch visibility. Wollastonite filler provided higher scratch and mar resistance, while the addition of 0.5 wt% lubricant showed some beneficial effect.
The effect of PTFE on the friction and wear behavior of polymers in rolling‐sliding contact
Authors: Rao M. , Hooke C. J. , Kukureka S. N. , Liao P. , Chen Y. K. 
Published: April 2004

AbstractThe effect of PTFE on the tribological behavior of polymers in rolling sliding contact has been investigated. The two most widely used polymers — nylon 66 and polyacetal—were used as the base material. Tests were conducted over a wide range of running conditions using a twin disc rolling‐sliding test rig for both the unfilled materials and for the base materials filled with 20 wt% PTFE. The experimental results showed that the friction and wear performance of the PTFE filled polymers was superior to that of the unfilled polymers. In addition the surface cracking that was found in unfilled PA66 and was thought to be responsible for premature fracture of components such as gear teeth was suppressed by the PTFE. It is suggested that a combination of high surface temperature and high surface tensile stress, produced by friction, is required to initiate these cracks and that PTFE, by reducing friction, inhibits crack formation.
Rheological and mechanical properties in polyethylene blends
Authors: Cho Kyucheol , Lee Byung H. , Hwang Kyu‐Myun , Lee Hoseok , Choe Soonja 
Published: April 2004

AbstractMelt rheology and mechanical properties in linear low density polyethylene (LLDPE)/low density polyethylene (LDPE), LLDPE/high density polyethylene (HDPE), and HDPE/LDPE blends were investigated. All three blends were miscible in the melt, but the LLDPE/LDPE and HDPE/LDPE blends exibiled two crystallization and melting temperatures, indicating that those blends phase separated upon cooling from the melt. The melt strength of the blends increased with increasing molecular weight of the LDPE that was used. The mechanical properties of the LLDPE/LDPE blend were higher than claculated from a simple rule of mixtures, whiele those of the LLDPE/HDPE blend conformed to the rule of mixtures, but the properties of HDPE/LDPE were less than the rule of mixtures prediction.
Numerical simulation of thermoplastic wheat starch injection molding process
Authors: Abbégs B. , Ayad R. , Prudhomme J.‐C. , Onteniente J.‐P. 
Published: April 2004

AbstractA numerical study is carried out on the thermoplastic wheat starch injection molding process. The simulation is performed using currently available molding software to determine optimal molding parameters. The molding of a standardized sample for tensile test is considered. It is shown that the conventional continuum mechanics equations can be used for modeling the injection molding of thermoplastic starch. These equations are solved using the finite element method. Comparisons with some experimental results are presented, indicating good agreement. Data on the processing of thermoplastic starch and several other basic aspects are also provided.
Characterization of the fracture toughness of rubber‐toughened polypropylene thin plates
Authors: Marchal Y. , Oldenhove B. , Daoust D. , Legras R. , Delannay F. 
Published: April 2004

AbstractThe fracture toughness of PP‐EP (Polypropylene‐Ethylene‐Propylene) blends is studied at room temperature using the “essential work of fracture” (EWF) method. The results obtained by applying this method are compared with those of puncture and tensile tests. Whereas the classical puncture tests do not allow classifying the rubber‐toughened PP‐EP blends, the EWF method proves to be a sensitive technique to monitor the effect of composition and morphology of the blend on fracture toughness. Moreover, the application of the EWF method allows monitoring how the fracture toughness of a material depends on its ability to deform extensively before fracturing and on its capacity to bear some load. A good combination of these two properties thus yields materials presenting an optimal fracture toughness.
Additive group contributions to density and glass transition temperature in polyurethanes
Authors: Fedderly Jeffry , Compton Eric , Hartmann Bruce 
Published: April 2004

AbstractThe method of additive properties was applied to the density and glass transition temperature, Tg, of linear amorphous polyurethanes. This method assumes that certain polymer properties result from the additive effects of unique constituent group properties and that these group properties are independent of their environment. To determine the component properties, 14 model polyurethanes were synthesized. The polymers contained only the following four groups: urethane, phenylene, methylene, and ether oxygen. The densities and Tg's of these polymers were measured. Using these measured values, the known composition of each polymer, and an appropriate additive from, the molar component properties were calculated using a matrix least‐squares simultaneous fit algorithm. An error analysis confirmed that the component values were determined with greater accuracy than literature results. The densities ranged from 1.0 to 1.2 g/cm3 and measured versus predicted densities agreed to within 0.3% on the average. Tg's ranged from −70°C to 70°C and measured versus predicted Tg's agreed to within 1.3% on the average.
Chemical recycling of reinforced polyurethane from the automotive industry
Authors: Modesti M. , Simioni F. 
Published: April 2004

AbstractR‐RIM PU (reinforced‐reaction injection molding polyurethanes) from the automotive industry (production scrap and parts at the end of their life cycle) can be recycled for the production of new RIM PU by a chemical process. Among the various possible chemical processes (hydrolysis, alcoholysis, aminolysis, and pyrolysis), we have examined glycolysis, a particular form of alcoholysis, for the purpose of obtaining a mixture of oligomers sufficiently similar to a polyol to be used in the production of new R‐RIM PU. Glycolysis with dipropylene glycol (DPG) of R‐RIM PU forms a monophasic product that could be used in the preparation of new, highly crosslinked polymers, similar to those used in the preparation of rigid thermal insulation foams. The same product, because of its high hydroxyl number, cannot be directly re‐used in the production of new RIM PU. Partial substitution of free DPG in the glycolysis product with a triol having high molecular weight forms a homogeneous mixture suitable for production of new RIM PU. This final product has been used in the original R‐RIM application introducing an appropriate optimization of formulation. In comparison with RIM PU obtained from only virgin materials, the loss in properties of molded parts based on even high amounts of regenerated polyol was only marginal.
An experimental study and model assessment of polymer sintering
Authors: Bellehumeur C. T. , Bisaria M. K. , Vlachopoulos J. 
Published: April 2004

AbstractExperiments were conducted using pairs of particles inside a hot stage microscopy setup with the ultimate objective to study the coalescence, which is a crucial stage in the rotational molding process. It was found that the geometry of the particles had no significant effect on the sintering rate. The sintering rate increases as the viscosity of the resin decreases. However, this effect became less important as the particle size decreased. The experimental results of this study have been compared with the available mathematical models based on balance of viscous and surface tension forces. The model developed by Frenkel and a corrected version by Eshelby predict a faster coalescence than observed experimentally. However, Hopper's model is in relatively good agreement with the present experimental data. Yet there is evidence that mechanisms other than Newtonian viscous flow may play a role in polymer sintering.
Free radical grafting of diethylmaleate on linear low‐density polyethylenes
Authors: Rosales C. , Márquez L. , González J. , Perera R. , Rojas B. , Vivas M. 
Published: April 2004

AbstractGrafting of preformed polymers is an important method for preparing polymers with functional groups. Lately, the use of extruders as polymerization reactors has increased considerably in industry. However, the knowledge of the total reaction process is still limited. Grafting of diethylmaleate on linear low‐density polyethylenes (LLDPEs) was carried out in solution and in a corotating twin screw extruder. The effects of initiator and diethylmaleate concentrations, temperature, and reaction time on graft content and on crosslinking were investigated. The functionalization reaction was also conducted in the presence of an electron donor material to minimize the amount of crosslinked products in the extruder. The grafted products were characterized by means of FTIR and the thermal behavior of LLDPEs and that of its grafted products was determined.
Interaction of process variables with the fracture behavior of amorphous polystyrene during attrition
Authors: Kubisiak Michael P. , Quesnel David J. 
Published: April 2004

AbstractThis study investigates the fracture of oriented general‐purpose polystyrene. Specimen microstructure was controlled using an extrusion‐sheeting technique where draw ratio, polymer melt temperature, cooling roll temperature, and nip roll pressure changed according to a designed experiment. Sharp‐notched tension results display a 4X difference in longitudinal vs. transverse specimen values. Shrinkage measurements show contraction in the machine direction amplifies with increasing draw ratio. Craze formation is visible only in those specimens tested in the longitudinal direction. Fracture mechanisms have strong orientation dependence and the extrusion‐sheeting process produces an ideal system to study the effect on attrition. Comminution studies illustrate draw ratio has an effect on the final median particle size and width distribution of the powder. Increasing the draw ratio reduces the volume median particle size and minimizes the formation of fine particles. A monotonic fracture mechanism was initially considered but rejected in favor of a low cycle fatigue model based on estimates of fracture strength.
The essential fracture work concept for toughness measurement of ductile polymers
Authors: Wu Jingshen , Mai Yiu‐Wing 
Published: April 2004

AbstractThe essential work of fracture method is explored. The method was used to determine the fracture toughness of a series of toughened polymer blends and the crack resistance of a thin ductile polymer film, which could not be tested using the J‐integral method. A comparison between J‐integral and the specific essential work of fracture was carried out to test the equivalence of the two methods. The effects of geometry on the essential work of fracture and the plane‐stress/plane‐strain transition were studied. It has been shown that the specific essential work of fracture is a material constant, independent of sample geometry, and equivalent to the critical J‐integral. The plane‐stress/plane‐strain transition is found to depend on the nature of the material tested. The sample thickness requirement for valid plane‐strain specific essential work of fracture is discussed, and it is proposed that the size requirement for the plane‐strain specific essential work of fracture may be less rigorous than that for plane‐strain JIC measurement.
Impact and dynamic fracture resistance of crystalline thermoplastics: Prediction from bulk properties
Authors: Leevers Patrick S. 
Published: April 2004

AbstractThe behavior of tough, crystalline thermoplastics in notched impact tests leads to the definition of crack initiation resistance and propagation resistance as two distinct properties, Gc and GD. It is shown here that a single criterion—adiabatic thermal failure of a crack‐tip cohesive zone—can be applied to predict both. Dynamic fracture resistance GD emerges as a geometry independent, though crack speed and temperature dependent, material property, whose minimum value GD,min depends only on temperature and bulk physical properties. GD,min can be measured using a simple pressurized‐tube test. Crack initiation resistance Gc, however, is inherently influenced by geometry and impact speed, although its lower bound is also GD,min. Craze extension and failure of a notched impact specimen, and hence Gc, can be predicted for a specific temperature, given bulk thermal property data and a dynamic stress/strain curve measured by impact bending of an unnotched beam. For materials that comply with the model, sharp‐notched Charpy type impact tests will not arrive at a unique Gc value, while Izod type tests, for which a revised compliance calibration is presented, may fail to establish any Gc value at all.
Photography and microscopy of the instrumented n‐Izod test
Authors: Havriliak S. , Cruz C. A. , Slavin S. E. 
Published: April 2004

AbstractThe ubiquitous n‐Izod test is universal in its use yet condemned by its critics. Rather than criticize the test we have undertaken a course of study to understand it. In this work we report the photographic results taken at short exposure times with various delays after contact is made by the hammer. The photographic studies were made on polycarbonate and on modified and unmodified poly(vinyl chloride) with the notch radius as a variable. These results show that the damage is always contained within the notch. This permits an estimate of the strain rate, which depends on notch diameter. Instrumented n‐Izod measurements show that most of the energy is absorbed before little bending takes place, meaning that the sample is primarily in tension. These observations lead to the conclusion that the test is a high speed tensile test whose strain rate can be varied by changing the notch radius. Microscopic measurements show that, when toughening nylon 6, with small (<200 nm) core//shell particles, the matrix suffers large local ductile deformations without particle cavitation. Rubber cavitation does not occur until after the particles have been deformed by the fracture process.
The effect of the secondary relaxations on the fracture toughness of nylon 6/amorphous nylon 6IcoT blends
Authors: Liu Yun , Donovan James A. 
Published: April 2004

AbstractThe fracture toughness of semicrystalline nylon 6, amorphous nylon 6IcoT, and their blends can be represented as the inherent toughness plus the toughness due to the formation of the crack tip plastic zone. The inherent toughness originates mostly from the molecular alignment near the crack tip plus a small contribution from chain scission. The plastic zone contribution is determined by its size and the energy dissipated by irreversible plastic deformation. The inherent toughness and the energy dissipated in the process zone are temperature dependent and primarily determined by the stress‐induced molecular movement, which is related to the operative secondary β or γ relaxation.
Effective volume changes during fatigue and fracture of polyacetal
Authors: Lesser Alan J. 
Published: April 2004

AbstractConventional tensile dilatometry techniques are extended to cyclic fatigue applications to study volume changes that occur during controlled‐load cyclic fatigue of polyacetal. During fatigue, in‐situ measures of the irreversible and elastic volume change are monitored together with dynamic viscoelastic parameters (E′, E″, and Tan δ), and changes in the energy densities (strain energy, potential energy, and irreversible work). The results show that the effective irreversible volume of the polyacetal gradually increases over a wide range of applied cyclic stress. However, at high stress levels and/or frequencies (i.e., low‐cycle, thermally dominated regime), the effective Poisson's ratio of the polyacetal increases as it softens (evidenced by the dynamic viscoelastic data). Conversely, at lower stress levels, the Poisson's ratio continually decreases coincident with decreases in the loss modulus (E″) and the irreversible work density. These results are indicative of entirely different mechanisms governing the low‐cycle (high stress level) and high‐cycle (low stress) regimes. Also, comparisons between tensile and fatigue dilatometry studies show that the dilational‐strain response of samples fatigued at high stress levels are similar to data obtained from monotonic tensile dilatometry. However, the dilationstrain response of samples fatigued at lower stress levels are distinctly different from low‐cycle fatigue and tensile dilatometry.
Designing reliable polymer coatings
Authors: Shaffer E. O. , McGarry F. J. , Hoang Lan 
Published: April 2004

AbstractA method to predict the ultimate adhesion performance of coatings subjected to biaxial, tensile stress is presented. A set of equations is developed to predict the onset of failure when the locus of failure is cohesive in the coating. The equations also have been extended to predict fatigue lifetime when a coating is cycled from a low temperature to room temperature. To test these equations, the Edge Liftoff Test (ELT) was developed. It consists of fabricating coatings of various heights on a rigid substrate and dicing the latter, so that the edges are 90° to the interface. The parts are cooled and the temperature of debonding is recorded. For thermal fatigue validation, cycles at which the first debond is observed are recorded. ELT results have been collected for a typical epoxy for both monotonic and cyclic cooling. The predictions are in agreement with results.
Cyclic fatigue—crack growth along polymer/glass interfaces
Authors: Ritter J. E. , Grayeski W. , Lardner T. J. 
Published: April 2004

AbstractDelamination of polymer/glass interfaces was studied under cyclic and monotonic loading using an interfacial, four‐point flexure sandwich specimen. Specifically, crack growth rates along epoxy acrylate/glass interfaces were characterized over a range of velocities from 10−9 to 10−6 m/s as a function of low (10–20% RH) and high (75–80% RH) humidities. For low humidities, interfacial crack growth rates under cyclic loading are almost two orders of magnitude greater than those under monotonic loading with energy release rates G = Gmax of the cyclic loading. At high humidities, interfacial crack growth rates under monotonic loading are approximately equal to cyclic fatigue crack growth rates at low humidity.