bluuebunny/crossref_metadata_2025_split huggingface dataset:
Submicron lithography in Japan
Authors: Shibayama Kyoichi , Kato Tadao 
Published: December 2004

Abstract1Mbit D‐RAM. the most advanced VLSI device, is realized by a high performance stepper with the conventional optical techniques. However, as the optical lithography has an inherent limit of resolution, new technologies are being developed rapidly for the development of new generation VLSI devices (4M‐16Mbit D‐RAM) using shorter wavelength photons of i‐line. Electron beam (EB) lithography is already in practical mask making products, but the resolution limit is about 0.5 μm because of proximity effects. In order to make higher resolution and higher precision masks, high voltage EB technique is being developed to minimize the proximity effect, and fabricated 0.25 μm line and space by a single scan at 50kV. X‐ray technology 1; becoming practical after a long laboratory‐level study, using high performance X‐ray resists (CPMS: chlorinated polymetylstylene). Focused Ion Beam (FIB) technology has been anticipated for its capability of submicron lithography due to a reduced proximity effect. High speed submicron Si MOSFET and GaAs MESFET with 0.25 μm gate have been fabricated using FIB technology. Activities of submicron lithography technology in Japan (optical stepper, EB, X‐ray, and FIB) are described.
The reduction of reflective notches using “dyed” resist
Authors: Watts Michael P. C. , Debruin David , Arnold William H. 
Published: December 2004

AbstractVariation in line width caused by light scattered from the substrate (reflective notching) is a major problem in VLSI lithography. This paper demonstrates the reduction of reflective notches using a resist with increased absorptivity (a dyed resist). The optimal set of process conditions which minimize line width variations is explored.
Performance prediction of weldline structure in amorphous polymers
Authors: Kim Sang‐Gook , Suh Nam P. 
Published: December 2004

AbstractThe presence of a weldline generally reduces the mechanical strength of injection molded parts. A typical remedy to eliminate the problem of weak weldline structure has been to increase the melt temperature. This, however, is not an acceptable solution in some situations. A general solution to the weak weldline problem requires an in‐depth understanding of the thermomechanical history of the injection molding process. A theoretical model for the strength of weldlines is presented that provides a comprehensive physical insight of the bonding process at the weldline interface. The model is based on the self‐diffusion of molecular chains across the polymer‐polymer interface and the frozen‐in orientation that remains parallel to the interface. Both factors are analyzed separately and then superimposed to predict the strength of weldlines from known processing conditions and geometry. Experimental results show good correlation with predictions.
Stress development in supported polymer films during thermal cycling
Authors: Tong H. M. , Hu C.‐K. , Feger C. , Ho P. S. 
Published: December 2004

AbstractA simple and in‐situ bending‐beam technique has been used to investigate the stress‐temperature relationships for three different polymer coatings (viz, poly(methyl methacrylate), FR‐4 epoxy resin, and an amide‐imide polymer) during thermal cycling. With this technique, we were able to detect stress relaxation near the polymer's glass transition or caused by cracking of the polymer. Knowing the Poisson's ratio and Young's modulus for the polymer, this technique also allows calculation of the polymer's thermal expansion coefficient from measured thermal stress data. The calculated thermal expansion coefficient of poly(methyl methacrylate) (7 × 10−5/°C) is in good agreement with literature values (5 to 9 × 10−5/°C).
A study on polymer blending microrheology part 3: Deformation of newtonian drops submerged in another newtonian fluid flowing through a converging cone
Authors: van der Reijden‐Stolk C. , Sára A. 
Published: December 2004

AbstractThe theory of drop deformation in steady elongational flow is extended to the non‐steady elongational flow in a converging cone, Experiments with different fluid viscosities were carried out and compared with the theory, which is valid only for low deformations. The theory describes the drop deformation satisfactorily and under certain conditions even for higher deformations than expected.
Effect of intramolecular reactions in multifunctional step growth polymerizations in cascades of continuous‐flow, stirred‐tank reactors
Authors: Gupta Santosh K. 
Published: December 2004

AbstractA simple kinetic model describing intramolecular reactions in multifunctional step growth polymerizations of RAj monomers is presented. The model is far simpler than more detailed kinetic or Monte Carlo models which pose severe numerical difficulties close to gelation. The formulation presented is quite general, but it requires a relationship for the ensemble‐cum‐time average number of rings, rn, per molecule having n RAj units. A very simple yet intuitively correct equation has been chosen for rn, which involves an empirical parameter 𝒜 Results on cascades of homogeneous continuous‐flow stirred‐tank reactors (HCSTRs) show trends which are physically expected. The present formulation could possibly be used for scale‐up of HCSTRs, with 𝒜 obtained experimentally. It is hoped that future studies using rigorous models would lead to more fundamental and improved relationships for rn.
Structural studies on ethylene‐tetrafluoroethylene copolymer: III. Deformation mechanism of row‐crystallized film
Authors: Tanigami Tetsuya , Yamaura Kazuo , Matsuzawa Shuji , Ishikawa Masazumi , Miyasaka Keizo 
Published: December 2004

AbstractWide‐angle X‐ray diffraction, small‐angle X‐ray scattering, density, stress‐strain, and dynamic viscoelastic measurements have been applied to a row‐crystallized ethylene‐tetrafluoroethylene copolymer film prepared by extrusion from the melt under extension to investigate the deformation mechanism upon stretching. It is shown that the deformation below the temperature of the phase transition (the order‐disorder transition from the crystal phase to the mesophase) (Th) is somewhat like that of “hard” elastic materials which is associated with micro‐void formation, and that the deformation above Th is rubber‐like, associated with bending of the lamellae. Gas permeability measurements have also been used for the stretched films to investigate the supermolecular structure, and the results support the above description.
Molecular weight and molecular weight distribution from dynamic measurements of polymer melts
Authors: Tuminello W. H. 
Published: December 2004

AbstractA method for determining the molecular weight distribution (MWD) of a polymer melt has been developed using the dynamic elastic modulus (G'), plateau modulus (G), and zero shear complex viscosity (η). The cumulative MWD was found to be proportional to a plot of (G'/G)0.5 vs. measurement frequency (ω). Frequency (ω) was found to be inversely proportional to (MW)3.4, as expected. Results were scaled to absolute values using the empirical relationship η ∝ (M̄w)3.4, where M̄w is the weight‐average MW. M̄w, M̄n (number‐average MW) and M̄w/M̄n calculated from melt measurements were found to agree with size exclusion chromatography usually well within 10 percent for broad and bimodal distribution samples. M̄w/M̄n tended to be approximately 20 percent higher for narrow distribution samples (M̄w/M̄n < 1.2) because we did not account for a finite distribution of relaxation times from a collection of monodisperse polymer chains. We also did not account for the plasticizing effect of short chains mixed with long ones which caused peak positions to be closer together for Theological vs, size exclusive chromatography (SEC) determinations of MW for bimodal distribution blends.
The application of melt elasticity measurements to polymer processing
Authors: Maxwell Bryce 
Published: December 2004

AbstractIn recent years there has been increasing recognition of the importance of melt elasticity in polymer processing. A new instrument has been developed that determines the elastic properties of polymers in the melt state by measuring both the stress relaxation and strain recovery characteristics as a function of applied rate of strain, temperature, and magnitude of applied strain. Data on several different polymers will be presented together with examples of the significance of melt elasticity in such processing operations as thermoforming, blow molding, and film forming. A material parameter that is very important in the processing of polymers such as polystyrene and poly(methylmethacrylate) is the transition above the glass transition, Tg, referred to as the liquid‐liquid transition, TII. At this transition there is an abrupt change in the elasticity of the melt. Processing above or below this transition produces products with very different end use properties.
The determination of polymer interfacial tension by drop image processing: Comparison of theory and experiment for the pair, poly(dimethyl siloxane)/polybutndiene
Authors: Anastasiadis S. H. , Chen J. K. , Koberstein J. T. , Sohn J. E. , Emerson J. A. 
Published: December 2004

AbstractThe interfacial tensions of immiscible binary blends of poly(dimethyl siloxane) (PDMS) and polybutadiene (PBD) have been determined as a function of molecular weight and temperature. The technique employed for these measurements takes advantage of recent advances in the determination and analysis of pendant fluid drop profiles. The experimental data are compared to the predictions of square gradient theories and theories based on the diffusion equation approach as developed by Helfand and co‐workers. Qualitative agreement is obtained with both types of theory when the Flory‐Huggins interaction parameter is taken to be comprised of two terms: a temperature independent term of entropic origin; and an enthalpic term that is inversely dependent upon the temperature.
Synthesis and characterization of radiation curable polyurethanes containing pendant acrylate groups
Authors: Li C. , Nagarajan R. M. , Chiang C. C. , Cooper S. L. 
Published: December 2004

AbstractA series of radiation sensitive and relatively high molecular weight poly(tetramethylene adipate) polyurethanes containing pendant acryfate functionality was synthesized. These radiation curable materials possess good mechanical properties and behave like common thermoplastic elastomers prior to chemical crosslinking which further enhances their strength and insolublizes them. Both the precursor and the cured materials were characterized by stress‐strain, differential scanning calorimetry. and dynamic mechanical testing. It was found that the poly‐(tetramethylene adipate) soft segments with molecular weight of 2000 or higher were crystallizable in the cross‐linked network. The soft segment molecular weight and the diisocyanate type were found to be important in determining the tensile and thermal properties of these male‐rials. The crosslinking process was found to depress crystallization of the soft segments and to improve tensile properties. Increasing the soft segment molecular weight resulted in an Increased elongation al break bill a decreased ultimate stress for both the precursor linear polymers and the crosslinked materials.
Nonlinear viscoelasticity and yield: Application of a coupling model
Authors: Rendell R. W. , Ngai K. L. , Fong G. R. , Yee A. F. , Bankert R. J. 
Published: December 2004

AbstractAn approach to nonlinear viscoelasticity is described which is based on the “coupling model” of relaxation. A brief review of nonlinear viscoelasticity models is given to put the present approach into historical perspective. The physical basis of the coupling model is then described, and the quantitative predictions that the model has made in linear viscoelasticity and other areas of relaxation are discussed. The relaxation function predicted by the coupling model is used as a time‐dependent kernal in a constitutive equation for a description of nonlinear viscoelasticity. The model incorporates the strain history dependence and allows for the evolution of material structure. Simulations are presented showing how the model reproduces the essential features of constant strain‐rate, strain‐rate change, and strain‐step experiments. Experiments are described that can partially characterize the coupling model parameters and lead to quantitative tests of the model.
A comparison of the crack tip damage zone for fracture of Hexcel F185 neat resin and T6T145/F185 composite
Authors: Chakachery E. A. , Bradley W. L. 
Published: December 2004

AbstractHexcel F185 neat resin and T6T145/F185 graphite fiber‐reinforced composite were subjected to Mode I loading in the compact tension (CT) geometry (fibers parallel to the crack) and the energy per unit area of crack extension, JIC, determined to be 8100 and 1600 J/m2 respectively. In‐situ fracture studies using scanning electron microscopy on a CT‐type specimen of F185 showed extensive microcracking in a damage zone ahead of the crack tip, which was similar to the microcracking observed in the whitened area ahead of the crack tip in the macroscopic CT specimens. A simple calculation using a rule of mixtures approach suggests that the diminished size of the damage zone and the presence of rigid fibers in the damage zone in the composite are not a sufficient explanation for the significantly lower delamination toughness of the composite compared to the neat resin. From this it may be inferred that the strain to failure locally in the damage zone ahead of the crack in the composite may also be lower than that which can be tolerated in the neat resin. Evidence for this idea comes from the observation that microcrack coalescence seems to occur preferentially at the fiber/resin interface.
Stress‐Cracking of high density polyethylene in detergents
Authors: Tonyali Koksal , Rogers Charles E. , Brown Hugh R. 
Published: December 2004

AbstractCorrelations of the stress intensity factor, KI, with crack speed, ċ, have been obtained in a number of detergent solutions each having different detergent concentration. A constant crack speed region was observed in high density polyethylene. The KI independent constant crack speed was found to vary linearly with detergent concentration. The viscosity of the detergent solution increases with concentration and hence this region is not controlled by the hydrodynamic properties of the environment in contrast with Williams' model. The KI‐ċ data were compared with existing models of crack propagation.
Effects of loading history on fatigue crack growth in high density polyethylene and toughened poly(methyl methacrylate)
Authors: Bucknall C. B. , Dumpleton P. 
Published: December 2004

AbstractFatigue crack growth measurements are made on two grades of high density polyethylene (HDPE), of density 940 and 958 kg/m3, and on one transparent grade of toughened poly(methyl methacrylate) (PMMA). In both grades of HDPE, prolonged cycling is necessary to initiate a crack from a razor notch. Relationships between crack growth and stress intensity factorKare studied in all three materials. The results show that Paris plots of log (da/dn) against log ΔKare linear provided that: (a) the loading pattern applied to the specimen remains constant; and (b) growth has taken place for a sufficient period to eliminate the effects of previous loading history. However,da/dnis strongly dependent upon the ratio of minimum to maximum stress and upon the stress amplitude during previous cycles. Overloads cause accelerated growth which is followed by crack arrest when the stress amplitude is restored to its original level. The use of a transparent polymer enables a more detailed study of crack growth phenomena to be made during fatigue testing.
On the nonlinear characterization of the long term behavior of polymeric materials
Authors: Brueller O. S. 
Published: December 2004

AbstractIn the linear viscoelastic range the long term behavior of viscoelastic materials—such as polymers—can be described by using exponential series with a limited number of terms for the approximation of the relaxation modulus or of the creep compliance. This procedure can be extended to the nonlinear viscoelastic range by multiplying the linear parameters of the material by certain nonlinearity factors, which depend upon the level of the applied loading. Application of this method to stress relaxation data of several polymers has shown that nonlinearity factors can be approximated as linear functions of the applied constant strain. From creep tests, on the other hand, one can observe that the immediate strain response to the suddenly applied stress is linear elastic even in the nonlinear viscoelastic range of the investigated polymer. The computation of the linear viscoelastic material parameters as well as of the nonlinearity factors is conducted numerically by using least squares techniques. Good agreement between computed results and experimental data can be observed in the presented examples.
Fatigue failure mechanisms in polymers
Authors: Dao Kim C. , Dicken Dennis J. 
Published: December 2004

AbstractFatigue testing of polymers has revealed significant differences between the fatigue response of polymers and metals. Generally, fatigue failure in metals is a process of crack initiation, propagation, and failure. Also, fatigue damage in metals is cumulative and cycle dependent, but remains essentially independent of test frequency. Unlike that of metals, the fatigue behavior of polymers is influenced by viscoelastic effects. At high frequencies, softening and melting occur, and fatigue failure depends largely on the test frequency. At lower frequencies, fatigue failure becomes less sensitive to test frequency and results from crack initiation and propagation. These polymer characteristics arise from the production of hysteresis energy during fatigue. A portion of this energy is released as heat, some of which is dissipated, but most is absorbed in the sample, raising its temperature. This temperature rise leads to degradation of the material and a short fatigue life. Experiments were conducted to measure hysteresis energy and temperature rise for a talc‐filled polypropylene. A mathematical model was developed to calculate the energy and temperature distribution during fatigue. Correlation of the temperature rise predicted by the model with that observed experimentally provided values for the various energy terms that quantitatively defined the thermomechanical fatigue response of this polymer.
A rheometer for concentrated polymer solutions containing volatile solvents
Authors: Richards W. D. , Prud'Homme Robert K. 
Published: December 2004

AbstractA new rheometer cell and integrated transducer, which is capable of performing both steady state and dynamic measurements in a controlled environment and at elevated temperatures and pressures, is described here. This cell mounts onto either the Rheometrics Mechanical Spectrometer or the Rheometrics System Four rheometer and utilizes the wide range of shear rates and frequencies available on these instruments. The unique capabilities of the rheometer and cell permit measurement of the rheological properties of concentrated polymer, solutions containing volatile solvents at temperatures above the normal boiling point of the solvent. The steady shear and dynamic properties of several polystyrene/ethylbenzene solutions having polymer concentrations greater than 50 wt percent are presented to demonstrate the performance of the rheometer.
In situ composites: Blends of isotropic polymers and thermotropic liquid crystalline polymers
Authors: Kiss Gabor 
Published: December 2004

AbstractMelt blending of a variety of conventional isotropic polymers (both crystalline and amorphous) has shown that considerable reinforcement is obtained from the inclusion of thermotropic liquid crystalline polymers (LCP). When the LCP is a minor component it forms highly elongated domains parallel to the flow direction. The intrinsically high strength and stiffness of the LCP improve the mechanical properties of the resulting blend. This approach is distinguished from the common practice of filling polymers with chopped glass and carbon fibers by the fact that the reinforcing component comes into existence during processing (molding or extrusion). Many of the problems associated with fibrous fillers are avoided. For example, viscosity of the “in situ composite” is actually lower than that of the base polymer and wear on the compounding and processing equipment is reduced.
On the deformation of poly(methyl methacrylate) poly(ethylene oxide) blends: A molecular characterization by small‐angle neutron scattering
Authors: Lefebvre J‐M. R. , Porter Roger S. , Wignall G. D. 
Published: December 2004

AbstractThe deformation behavior of miscible amorphous/amorphous PMMA/PEO poly(methyl methacrylate)/poly(ethylene oxide) blends was compared with that of pure PMMA. Small‐angle neutron scattering experiments were performed on labeled systems made of PEO + D‐PMMA + HPMMA. Characteristic molecular parameters such as radius of gyration, Rg, molecular weight, Mw, and interaction parameter, X, were extracted from the coherent scattering cross sections, Molecular anisotropy was measured on the solid state coextruded samples, and the observed drawing efficiency is compared with, the results of shrinkage tests. In the case of PMMA/PEO blends, anomalous scattering behavior precludes any quantitative Interpretation of the scattering patterns, but revealed important structural changes upon drawing, namely a deformation‐induced phase separation.
The nucleation of microcellular thermoplastic foam with additives: Part I: Theoretical considerations
Authors: Colton J. S. , Suh N. P. 
Published: December 2004

AbstractMicrocellular foam is a polymeric foam with bubble sizes of 10 microns or less that is produced by saturating a polymer with gas and then utilizing the thermodynamic instabilities that result when the polymer is heated and the pressure is reduced to nucleate the cells. A model for the nucleation of microcellular foam in amorphous polymers with additives has been developed. The nucleation process depends on the solubility, concentration, and interfacial energy of any additives present. At very low levels, additives in solution act to increase the free volume of the polymer, resulting in homogeneous nucleation within the free volume Well above the solubility limit, heterogeneous nucleation dominates, as it lowers the activation energy for nucleation to levels below that for homogeneous nucleation. In the vicinity of the solubility limit of the additive, these two nucleation mechanisms compete. The polystyrene‐zinc stearate system has been chosen for experimental evaluation.