bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elastic moduli of highly oriented polyoxymethylene
Authors: Choy C. L. , Leung W. P. , Huang C. W. 
Published: May 2005

AbstractThe five independent elastic moduli C11, C12, C13, C33, and C44 for uniaxially drawn polyoxymethylene with draw ratio λ = 1‐16 have been measured from −60 to 120°C by an ultrasonic method at 10 MHz. Wide angle x‐ray diffraction and birefringence measurements indicate that the chains in the crystalline regions are fully aligned at λ = 5 but the degree of amorphous orientation increases steadily up to the highest draw ratio. Below the major amorphous γ relaxation (∼0°C at 10 MHz), only the axial longitudinal and tensile modulus, C33 and E0, show large increases. At 120°C, however, all the moduli increase with λ, with E0, E90 (transverse tensile modulus), C44 (axial shear modulus) and C66 (transverse shear modulus) increasing 10, 2.5, 3, and 2.5 times, respectively, as λ rises from 1 to 16. This improvement in mechanical properties may be attributed largely to the effect of taut tie‐molecules and crystalline bridges. Whereas the two‐parameter model of Seferis seems to be valid only below the γ relaxation, the Halpin‐Tsai equation can give a reasonable description of the mechanical behavior for the highly oriented samples (λ>5) over the entire temperature range.
Contrast enhanced photoresists—processing and modeling
Authors: Griffing B. F. , West P. R. 
Published: May 2005

AbstractThis paper will describe a new concept for the production of high contrast photopatterns. The method is designed to produce good quality patterns with very low contrast illumination through the use of photobleachable materials in conjunction with standard photoresists. A very thin bleachable layer is first applied to the photoresist surface. Following conventional exposure, the layer is removed and the resist developed in the ordinary way. As a result of the presence of the bleachable material, the contrast of the illumination that reaches the photoresist is increased. It is for this reason that the technique is called contrast enhancement. The degree to which the contrast is enhanced depends on both the photochemical properties of the bleachable material and the dose required to expose the underlying resist. The paper will discuss properties required of the bleachable material in order to make the technique feasible, such as the magnitudes of the extinction coefficient and the quantum yield. Bleaching experiments on candidate materials for the characterization of these parameters will be described. Also to be discussed is a model of the bleaching dynamics, which was used to calculate the improvements in contrast that are achieved as a function of base resist sensitivity. The extra processing steps required by the presence of the bleachable layer will be covered. Submicron resist patterns that demonstrate the resulting improvement in contrast will also be shown.
Effect of varying the composition of copolymers of glycidyl methacrylate and 3‐chlorostyrene (GMC) on electron lithographic performance
Authors: Novembre A. E. , Bowden M. J. 
Published: May 2005

AbstractThe polymerization kinetics, molecular parameters, and electron lithographic response of a series of copolymers of glycidyl methacrylate (GMA) and 3‐chlorostyrene (CLS) have been determined. The polymerization rate, molecular weight, and polydispersity decrease with increasing mole fraction of 3‐chlorostyrene (XCLS). Similarly, the sensitivity of this system decreases as the percentage of CLS in the copolymer increases. The value of D for the copolymer containing 14.3 mole percent CLS is 0.45 μC/cm2 increasing to 3.2 μC/cm2 for the 54 percent CLS copolymer of equivalent molecular weight. On the contrary the wet air and O2 plasma etch rates decrease as XCLS increases. For example, the etch rate using wet air for PGMA is ∼ 30 percent greater than GMC (XCLS = 0.54). The post exposure polymerization rate decreases as the CLS content increases. The extent of the post cure reaction is dose dependent being a maximum at D = 0.64 μC/cm2 for the copolymer containing 14.3 mole percent CLS.
Stress and displacement fields at the tip of a craze containing a crack
Authors: Warren William E. 
Published: May 2005

AbstractPlane elasticity theory is utilized to obtain expressions for the stress and displacement fields at the tip of a craze containing a crack. The craze is modeled as a very thin elliptical inclusion with different elastic properties from hat of the surrounding bulk polymer. Problem is solved by superimposing the solution of a crack problem onto the solution for a uniformly loaded homogeneous craze. Invoking stress free boundary conditions on the crack surface provides a singular integral equation of Hilbert type with a unique solution. Contour lines of constant hydrostatic stress and constant maximum shear stress around the craze tip are shown graphically. These two stress combinations have played prominent roles in a number of proposed craze growth criteria. Results show that even for relatively long cracks within the craze, very little stress enhancement at the craze tip occurs. Only as the crack tip approaches the craze tip does the enhancement become significant, tending to drive the craze region ahead of the crack.
Relaxation induced changes in electrical behavior of glassy chalcogenide semiconductors
Authors: Abkowitz M. 
Published: May 2005

AbstractEffects of structural relaxation and the glass‐transition process are clearly manifested in the electrical behavior of glassy‐chalcogenide films. Analysis of the transport and trapping of photoinjected carriers and of the thermal generation of free carriers in the bulk reveal that in chalcogenides each of these processes is mediated by a specific manifold of localized electronic states residing in the mobility (forbidden) gap. It is demonstrated that in the vicinity of Tg the population of these states varies systematically with the structural state of the glassy film always tending toward a temperature‐dependent quasi‐equilibrium. The present‐observations thus clearly establish the structural origin of key electronic‐gap states and simultaneously reveal the mechanism by which relaxation impacts electrical behavior.
Dynamic and steady‐state rheological properties of linear‐low‐density polyethylene melt
Authors: Saini D. R. , Shenoy A. V. 
Published: May 2005

AbstractLinear‐low‐density polyethylene (LLDPE) is steadily gaining importance in a wide variety of applications due to its excellent performance characteristics in the final product. The rheological properties of LLDPE in the dynamic and steady state are of great pragmatic importance and these have been studied in the present work. A correlation between the dynamic and steady‐state rheological properties has been attempted and good agreement has been found.
Volumetric effects in the injection molding of polymers
Authors: Isayev A. I. , Hariharan T. 
Published: May 2005

AbstractDensity and shrinkage measurements have been performed in quenched and molded slabs from polystyrene (PS) and poly (methylmethacrylate) (PMMA). Various processing conditions have been employed and their effect on density and shrinkage variation in the final parts, as well as volumetric aging vs. Elapsed time at room temperature, have been elucidated. A numerical simulation of the density variation in quenched parts and their aging has been performed by using first‐order rate theory for volumetric changes in conjunction with solving the transient one‐dimensional heat‐conduction equation with a convective heat‐transfer boundary condition at surface. A numerical simulation of the shrinkage in molded parts has been carried out by using the equation of state with a simultaneous solving of the governing equations for one‐dimensional mold filling during the cavity filling stage followed by transient one‐dimensional conduction during packing and cooling stages. Predicted results for density and shrinkage are compared with experimental data.
Measurement of thermal conductivity of polymer melts by the line‐source method
Authors: Lobo Hubert , Cohen Claude 
Published: May 2005

AbstractAn apparatus has been developed for the measurement of thermal conductivity of polymer melts. Based on the transient “line source method,” it is ideally suited to these materials because measurements can be made quickly, before the onset of thermal degradation. Also, little or no sample preparation is required. A number of commercial polymers have been tested, including some glass‐fiber filled composites.
Blends of cellulose with nylon 6 and poly(ε‐caprolactone) prepared by a solution‐coagulation method
Authors: Nishio Yoshtyuki , Manley R. St. John 
Published: May 2005

AbstractConditions are described for preparing blends of cellulose with nylon 6 (Ny6) and poly(ε‐caprolactone) (PCL) from solutions in N,N‐dimethylacetamide (DMAc)– lithium chloride (LiCl) by coagulation in a non‐solvent. The binary blend films of both series, obtained over a wide composition range (10/90–90/10) from mixed polymer solutions, were characterized by wide‐angle x‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and dynamic mechanical measurements. In the two series of cellulose blends the other component (Ny6 or PCL) was crystalline at every composition, but there was some degree of disproportional reduction of the crystallinity with an increase in cellulose content. From the dynamic Mechanical testing, the cellulose/Ny6 blends were found to be almost immiscible, although the possibility of a certain level of partial miscibility in the non‐crystalline regions was admitted at high cellulose concentrations (>80 wt%). For the cellulose/PCL blends, it was found that there was evidently an amorphous phase where a limited amount of cellulose could be well mixed with PCL. A relatively large shift of the midpoint in the PCL glass transition region to the higher temperature side was noted at the compositions containing 20 and 30 wt% cellulose. This effect is discussed in relation to the requirement of an optimum balance in the density of the interacting hydroxyl and ester groups, for obtaining true miscibility of cellulosics with PCL at the molecular level.
Gelation in thermosets formed by chain addition polymerization
Authors: Heise M. S. , Martin G. C. , Gotro J. T. 
Published: May 2005

AbstractThe physical behavior of the diglycidyl ether of bisphenol A, cured with different concentrations of 2‐ethyl‐4‐methylimidazole, was examined with dynamic mechanical and dielectric analyses, differential scanning calorimetry, and solvent extraction studies, ‘The network formation process was shown to depend strongly on the imidazole concentration’. At high imidazole concentrations, the gel point was characterized by a decrease in sol fraction, the crossover of the dynamic moduli and a rapid increase in viscosity. At low imidazole concentrations, the viscosity remained low until the sol fraction approached zero. For this system, the gel point, which occurred prior to the dynamic moduli crossover, was characterized by comparing the thermal properties of the network with the viscosity and dielectric behavior of the resin system during cure.
Some properties of polyethylene compounds with surface‐modified fillers
Authors: Schreiber H. P. , Viau J.‐M. , Fetoui A. , Deng Zhuo 
Published: May 2005

AbstractThe dispersion of variously surface‐treated CaCo3 fillers in linear low density polyethylene has been studied, along with mechanical properties of the filled compounds. Microwave plasma discharges were used to modify the filler surfaces. Inverse gas chromatographic analyses showed that plasma treatments could change the dispersive and non‐dispersive components of filler surface characteristics. A reduction in these surface energies facilitated the dispersion of the filler in the non‐polar polyethylene. Mechanical properties, particularly those at high deformation of the filled plastic, also responded to filler surface treatments, the ductility at failure increasing with a decrease in the filler's surface polarity. For any given elongation at failure, it was found that the amount of filler accommodated by the host polymer was raised by the appropriate surface modification procedure. The work illustrates the important contribution made by interfacial phenomena to various performance aspects of complex polymer systems.
Detergent assisted stress cracking in low density polyethylene
Authors: Chang P. , Donovan J. A. 
Published: May 2005

AbstractIgepal assisted environmental stress cracking (ESC) of LDPE has shown three characteristic regions with increasing crack driving force: Region I‐crack speed and craze length increased. Region II‐crack speed and duplex plastic zone length were constant, and Region Ill‐crack speed decreased while the deformation zone length increased. The activation energies for the three regions were 100, 23, 20 kJ/mole, respectively. The proposed rate controlling processes of ESC for the LDPE/Igepal system are: Region 1 is controlled by a;‐relaxation, and Region II and III are controlled by lamellar orientation. The Igepal plasticizes the amorphous phase and facilitates the stress induced orientation of the lamellar.
High temperature crystallization of poly(ethylene terephthalate)
Authors: Roland C. M. 
Published: May 2005

AbstractAnnealing poly(ethylene terephthalate) (PET) at high temperature results in a crystalline phase stable to 10°C higher than the temperature previously regarded as the equilibrium melting point. Melting temperatures as high as 289°C can be attained, which is equivalent to the equilibrium melting point determined herein for PET. The high melting point and tendency to superheat suggest that the crystals possess a substantial extended chain structure, notwithstanding the magnitude of the infrared fold band.
Injection molding of long fiber‐reinforced thermoplastics: A comparison of extruded and pultruded materials with direct addition of roving strands
Authors: Truckenmüller F. , Fritz H.‐G. 
Published: May 2005

AbstractAn injection molding process is proposed whereby roving strands are directly incorporated into the polymer melt by using a reciprocating‐screw‐plasticating unit. The direct incorporation of continuous fibers (DIF) offers the possibility to substitute the relatively expensive and limited pultrusion process currently used to produce long fiber pellets. In this preliminary study experimental investigations on glass fiber‐reinforced polyamide‐6,6 are carried out, starting with short and long fiber pellets in comparison to the direct incorporation of roving strands into the polymer melt. Some special aspects of the processing of long fiber‐reinforced thermoplastics are discussed. The results of fundamental mechanical and physical property investigations are presented, including fiber length distribution, fiber concentration, fiber bundling/clustering and fiber orientation. The influence of fiber diameter and fineness of strands (tex) on the feed‐in behavior and the resulting property profile is also discussed.
Studies on polyblends of poly(vinyl chloride) and acrylonitrile‐butadiene‐styrene terpolymer
Authors: Maiti S. N. , Saroop U. K. , Misra Ashok 
Published: May 2005

AbstractBlends of poly (vinyl chloride) (PVC) and acrylonitrile‐butadiene styrene (ABS) terpolymer were prepared in different ratios by a melt blending technique. ABS containing three different levels of rubber content were used. A quantitative assessment of ABS in PVC/ABS blends has been shown by infrared studies. ABS content has been shown as the presence of the characteristic acrylonitrile peak. Differential scanning calorimetry (DSC) studies have been carried out to study the glass transition (Tg) behavior of the blends. Two Tg values corresponding to PVC and styrene‐acrylonitrile (SAN) copolymer have been observed. Thermogravimetric analysis (TGA) reveals a significant improvement in thermal stability of these blends as compared to PVC. Mechanical properties show a significant increase in the impact strength which is related to rubber content of the ABS used. Morphological studies have been carried out by scanning electron microscopy which support the observation that an increase in rubber content results in greater ductility.
Chemorheology of unfilled and filled epoxy resins
Authors: Ng Hendra , Manas‐Zloczower Ica 
Published: May 2005

AbstractFilled thermosetting resins used for adhesives, sealants, and coatings are two‐phase systems whose rheological behavior is determined by the properties of both phases as well as by the interactions between the matrix and the filler. The chemorheological changes during the crosslinking of an epoxy system (EPON 828 with curing agent Y from Shell Chemical Co.) were investigated. The influence of an untreated silica filler on the reaction kinetics and the Rheological behavior of the system were also analyzed. The concentration of the filler was varied between 0 and 17.25 vol%. The influence of the filler on the gel point was explained in terms of the accelerating effect of the filler on the reaction kinetics.
The influence of knit‐lines on the tensile properties of fiberglass reinforced thermoplastics
Authors: Nadkarni V. M. , Ayodhya S. R. 
Published: May 2005

AbstractThe adverse effect of knit‐line formation on the mechanical properties of thermoplastics has been well documented for unfilled materials. A majority of these investigations concern amorphous polymers, whereas a number of engineering polymers are semicrystalline and also contain reinforcing fillers and fibers. The present investigation deals with the effect of knit‐lines on the mechanical behavior of unfilled and glass fiber‐reinforced semicrystalline polymers, such as polypropylene, poly(butylene terephthalate), poly(ethylene terephthalate), and poly(phenylene sulfide). Unfilled and fiber‐reinforced polystyrene was also investigated for reference. Tensile specimens with knit‐lines were produced by impinging melt fronts from two gates located at opposite ends of the dumbbell‐shaped mold. The effect of process conditions on the knit‐line strength was studied by varying primarily the melt and mold temperatures. The presence of glass fibers significantly reduced the knit‐line factor based on strength and strain to failure for the reinforced grades of all polymers relative to their respective unfilled grades. This is attributed to the lack of fiber flow across the knit‐line, which makes the material in the knit‐line region act as if it is not reinforced. The knit‐line strength could be changed through process modifications. For the unfilled grades of semicrystalline polymers, the presence of knit‐lines did not affect the yield strength but reduced the elongation at onset of necking, indicating that little spherulitic growth takes place across the knit‐line.
On the thermal behavior and mechanism of residual microstress buildup at the matrix interface in filled epoxy resins
Authors: Wang Hong‐Bing , Li Shan‐Jun , Yu Tong‐Yin 
Published: May 2005

AbstractWe have detailed the effects of annealing and temperature on the residual microstress at the matrix interface in rubber‐filled and glass bead‐filled epoxy resin systems. We found that annealing renders changes in residual microstress. The closer the annealing temperature to the glass transition temperature of the sample, the more pronounced the annealing effect on the stress. Also, we examined the interfacial residual microstress and found a linear relationship with annealing temperature. A description of the mechanism of the interfacial microstress buildup is proposed.
Morphology and permeability in extruded polypropylene/ethylene vinyl‐alcohol copolymer blends
Authors: Lohfink G. W. , Kamal M. R. 
Published: May 2005

AbstractStudies of the morphology of extruded polymer blend systems have shown that it is feasible to produce a laminar structure of an ethylene vinyl‐alcohol copolymer (EVOH) dispersed phase in a polypropylene (PP) matrix phase. The laminar structure forms in the core of the extrudate when a slit die is incorporated into the extrusion process. Morphological studies, including a study of morphology development inside the die and studies of the effect of processing conditions on the morphology of the final product, revealed that the laminar structure is a result of die design. Processing conditions influence mainly the shape and dimensions of the laminar core region of the extrudate. Oxygen permeation tests have shown that the blend exhibits lower oxygen permeability than pure PP, when EVOH is incorporated as a dispersed phase into the system. Oxygen transmission rates obtained with a blend system approach those obtained with a multilayer coextrusion product, although only at high EVOH concentrations. Comparison of experimental data with theoretical permeation predictions shows that, up to 20 wt% EVOH, the reduction in oxygen transmission rate follows the prediction for a homogeneous system. At 25 wt%, a considerable decrease in oxygen transmission rate is noticeable, and the trend for higher EVOH contents is towards the behavior of a multilayer system.
Impact properties of short carbon fiber reinforced nylon 6.6
Authors: Ishak Z. A. Mohd. , Berry J. P. 
Published: May 2005

AbstractThe impact properties of injection‐molded nylon 6.6 composites containing different loadings of short carbon fibers have been studied using an instrumented falling weight impact tester (IFWIT). Analysis of the impact data using linear elastic fracture mechanics (LEFM) has enabled the evaluation of the critical strain energy release rate, Gc. Instrumentation of the impact machine has facilitated the determination of another fracture mechanic parameter, the fracture toughness, Kc. Both parameters are observed to increase with increasing volume fraction of fibers. Examination of fracture surfaces using scanning electron microscopy (SEM) has revealed that the main energy dissipative processes responsible for toughening the composites is the fiber pull‐out mechanism.
Thermal properties of poly(pivalolactone)
Authors: Beshouri Sharon M. , Grebowicz Janusz S. , Chuah Hoe H. 
Published: May 2005

AbstractPolypivalolactone (PPVL) is a highly crystalline polyester formed either by nucleophilic or electrophilic ring‐opening polymerization of 2,2‐dimethyl‐β‐propiolactone, commonly known as pivalolactone (PVL). The thermal properties and crystallization kinetics of the polymer formed under reaction injection molding (RIM) conditions were studied. The crystallization kinetics of PPVL were measured using differential scanning calorimetry (DSC), and Avrami theory was used to interpret the bulk crystallization kinetics. A comparison was made with commercially prepared PPVL. The kinetics data indicate laboratory prepared PPVL, which is of lower molecular weight, has similar crystallization rates compared to the higher molecular weight commercial material. The kinetics data also indicate the rate of crystallization is relatively rapid overall for PPVL, with low activation energies of crystallization. The calorimetric studies also utilized DSC and simultaneous ther‐mogravimetric analysis/differential scanning calorimetry (TGA/DSC). Thermal analysis showed a clear difference in melting behavior between high and low molecular weight material, possibly a reflection of the presence of the α and γ‐crystal forms of the polymer.