bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rubber‐filler interaction effects on the solid state dynamic mechanical properties of polyethylene/EPDM/calcium carbonate composites
Authors: Scott C. , Ishida H. , Maurer F. H. J. 
Published: December 2004

AbstractComposites of polyethylene, ethylene propylene diene rubber (EPDM), and calcium carbonate are milled and analyzed by solid state dynamic mechanical spectroscopy. The torsion pendulum measurements show that the multicomponent composites exhibit complex viscoelastic behavior. In composites of polyethylene and calcium carbonate, the experimentally observed modulus enhancement is greater than that expected from the properties of the constituent materials, assuming well‐dispersed inclusions. In composites of polyethylene, rubber, and calcium carbonate, interactions of the rubber with the filler surface are significant. Specifically, maleic anhydride modification of the EPDM results in rubber‐filler interactions that drastically influence the properties of the composite. The maleic anhydride modification results in a morphology with more rubber around the filler particles and thus an enhanced rubber glass transition peak. The rubber‐filler interaction has been attributed to salt formation at the filler surface. The interaction was also detected by solid state proton nuclear magnetic resonance (NMR) relaxation experiments. Treatment of the filler surface with gamma‐aminopropyltriethoxysilane (γ‐APS) or gamma‐methacryloxypropyltrimethoxysilane (γ‐MPS) has significant influence on the dynamic mechanical properties.
Melt‐spinning of in‐situ composites of a thermotropic liquid crystalline polyester in a miscible matrix of poly(ether ether ketone) and poly(ether imide)
Authors: Crevecoeur G. , Groeninckx G. 
Published: December 2004

AbstractBlends of a thermotropic liquid crystalline polyester (TLCP) and a thermoplastic matrix of 75 wt% poly(ether ether ketone) and 25 wt% poly(ether imide) were melt‐spun into fibers. The fibers were evaluated in terms of morphology and mechanical properties. Composite fibers containing more than 25 wt% TLCP exhibited a morphology in which the TLCP was dispersed as very long fibrils with good alignment of the molecules in the spinning direction; correspondingly the fibers followed the rule of mixtures behavior for stiffness versus composition. For fibers containing 5 and 10 wt% TLCP, both fibril aspect ratio and molecular orientation were lower, and the stiffness was below the rule of mixtures. This difference can be explained by interfacial tension effects, which are of paramount importance in the deformation of TLCP particles into fibrils.
Fatigue fracture of long fiber reinforced nylon 66
Authors: Wyzgoski M. G. , Novak G. E. 
Published: December 2004

AbstractThe fatigue behavior of long fiber reinforced nylon 66 has been investigated by measuring fatigue crack propagation rates of injection molded samples. Plaques varying in thickness from 3 to 10 mm were employed for nylong 66 containing either glass, carbon or aramid fibers. Both conventional chopped, short fiber reinforcements and pultruded long fiber filled nylon 66 were examined. Long fiber reinforced nylon 66 exhibits improved fatigue resistance as shown by decreases in fatigue crack propagation rates compared to short fiber filled composites. Using a fracture mechanics analysis, it is shown that the improvements are due primarily to the higher moduli of the long fiber reinforced nylon 66, with only a slight increase in the calculated strain energy release rate associated with fatigue crack growth. For short or long glass fibers, and for short carbon fibers, the effects of fiber orientation on fatigue crack growth rates can be predicted from the fracture mechanics model. More significant effects of fiber length on fatigue fracture energies are noted for long aramid and long carbon reinforced nylon 66. It is also shown that thicker plaques can exhibit poorer fatigue fracture behavior owing to their inferior core sections.
Rheology of short fiber filled thermoplastics
Authors: Ghosh Tamal , Grmela Miroslav , Carreau Pierre J. 
Published: December 2004

AbstractWe examine the applicability of the conformation tensor to describe the fiber orientation and rheology of moderately concentrated fiber‐filled thermoplastics subjected to large deformation flow. To retain computational simplicity, we assume a Newtonian matrix. We present a model that can account for orientation effects, Brownian motion, semiflexibility, and interactions through excluded volume effect, of the fibers. The model predicts a wide variety of rheological effects. We present predictions of steady shear viscosity, primary normal stress and the creep functions, as well as uniaxial elongational viscosity, due to the fibers. We have compared rheological data for 9.54 wt% carbon fibers in polyethylene and 30 wt% glass fibers in polypropylene, with the model predictions. By defining an “effective fiber concentration,” we have been able to correlate the model well with data. With fitting parameters from the steady state viscosity vs. shear rate data, we have been able to predict the steady state primary stress coefficient data as well as the creep data.
Application of artificial neural networks for the optimal design of sheet molding compound (SMC) compression molding
Authors: Twu Jun‐Tien , Lee L. James 
Published: December 2004

AbstractA sequential design optimization scheme based on artificial neural networks (ANN) is proposed. It is a combination of an ANN model and a nonlinear programming algorithm. The proposed scheme is implemented with network training, optimization, and sheet molding compound (SMC) process simulation in a closed loop. A “cyclic coordinate search” technique is employed to initiate the optimization process, to collect training data for the neural network model, and to perform a preliminary design sensitivity analysis. Emphasis is placed on the development of an integrated, automatic optimization‐simulation design tool that does not rely on the designer's experience and interpretation. Testing results based on the design of heating channels in an SMC compression molding tool show that the optimal design can be achieved with fewer data points than other methods, such as factorial design. The efficiency of the ANN method would be greater as the number of design variables grows.
DSC and TBA studies of the curing behavior of two dicy‐containing epoxy resins
Authors: Schneider N. S. , Sprouse J. F. , Hagnauer G. L. , Gillham J. K. 
Published: December 2004

AbstractThe curing behavior of two commercial dicy‐containing resins (I & II), both with recommended cures of 127°C/2 h, has been studied by differential scanning calorimetry (DSC), torsional braid analysis (TBA) and Fourier Transform infrared spectroscopy. Compositional analysis reveals that the two resins differ primarily in the amine/epoxy ratio and the nature of the main epoxy components. Factors contributing to the complex curing behavior observed with II are identified. Isothermal kinetic runs by DSC and TBA lead to estimates for the conversion at the gel point, and to results which suggest that the reactions of epoxy with amine and hydroxyl occur with similar activation energies and similar heats of reaction.
The isothermal crystallization of crosslinked polyethylene under uniaxial extension
Authors: Remec Thomas M. , Gaylord Richard J. 
Published: December 2004

AbstractAn experimental study of the crystallization of chemically crosslinked polyethylene at constant strain under isothermal conditions was carried out. Changes in the stress and birefringence were measured simultaneously as a function of time. Both the stress and the birefringence behavior are consistent with previous work carried out under constant rate of cooling conditions. This indicates that the cooling conditions do not affect the structural features of the crystallization process. A comparison of the stress and birefringence curves shows that there are periods off time during which both stress and birefringence increase; stress increases and birefringence decreases; stress decreases and birefringence increases; and both stress and birefringence decrease. None of the crystal morphological models proposed to date for the strain‐induced crystallization of crosslinked polyethylene appear to be able to account fully for this behavior.
The effect of strain‐induced crystallization on the ultimate properties of an elastomeric polymer network
Authors: Mark James E. 
Published: December 2004

AbstractElastomeric networks made up of chain molecules of sufficient structural regularity generally exhibit strain‐induced crystallization. Crystallites thus formed have a pronounced reinforcing effect within the network, and thus increase its ultimate properties (ultimate strength and maximum extensibility), Increase in temperature or addition of diluent (plasticizer) suppresses the strain‐induced crystallization and thus diminishes the ultimate properties. These effects are demonstrated using stress‐strain isotherms obtained in elongation for crystallizable networks of cis‐1, 4‐polybutadiene and of polyisobutylene. The magnitude of the effects of strain‐induced crystallization are determintud by comparisons of the ultimate properties of these two crystallizable networks with the corresponding ultimate properties of noncrysrallizable networks of polydimethylsiloxane.
Factors affecting the formation of hard elastic fibers
Authors: Noether H. D. 
Published: December 2004

AbstractFactors affecting the formation of hard elastic polypropylene and nylon 6,6 are described. In the case of polypropylene, it is shown that the morphology of the stress spin‐oriented fibers depends on the molecular weight, the molecular weight distribution, and the cooling rate. Narrow molecular weight distribution and/or fast cooling rate can lead to a smectic, essentially fibrillar morphology in contrast to the normally observed crystalline, essentially lamellar structure. Hard elastic nylon 6,6 fibers are produced by drawing regularly spun nylon 6,6 yarn to draw ratios in the range of 1.6‐3 and annealing the resulting fibers in phenol solutions (cone. 1‐5 percent). By this method, a highly increased crystalline order is created, simultaneously transforming the original morphology to a lamellare one or superimposing a lamellar morphology on the poorly organized fibrillar base. Some tensile and elastic characteristics of polypropylene and nylon 6,6 yarns as. functions of spinning and annealing variables are presented.
Monodisperse polyethylenes: Crystallization kinetics
Authors: Hser J.‐C. , Carr S. H. 
Published: December 2004

AbstractCrystallization kinetics of hydrogenated monodisperse polybutadienes have been measured using hot‐stage microscopy, and the data have been analyzed in terms of crystallization half‐time and Avrami exponent. Results obtained from hydrogenated polybutadienes having M̄w's in the range 5,100 to 340,000 were compared with what was obtained from several commercial polyethylenes. A four‐branch star hydrogenated polybutadiene was also included in this study. Crystallization half‐time at constant undercooling was found to go through a minimum when expressed as a function of M̄w; such behavior is consistent with polyethylene data already reported in the literature. It was found that crystallization half‐times for all polyethylene homopolymers studied (hydrogenated polybutadienes as well as commercial polyethylenes with their broad molecular weight distributions) exhibit similar exponential dependences on undercooling.
On the conformational behavior and solid‐state extrudability of crystalline polymers
Authors: Aharoni S. M. , Sibilia J. P. 
Published: December 2004

AbstractExtrusion experiments on thirteen polymers in our laboratory and extrusion and forging studies on nine polymers in other laboratories reveal that solid‐state extrusion and malleability occur in semi‐crystalline polymers that have a crystalline relaxation, αc at the temperature Tαc, and do not occur in semicrystalline polymers devoid of αc. The solid‐state extrusion takes place in the temperature range of Tαc ≤ T < Tm with Tm being the melting point. In this temperature, range, the polymeric crystals show a measure of disorder, observed by several techniques and by small heats and entropies of fusion. A survey of the literature indicates that, in general, polymers which have a αc and are solid‐state extrudable have shallow and broad bottoms to the energy‐wells describing their most stable crystalline conformations, and polymers showing no αc have steep‐walled energy‐wells for the same conformations.
Sorption and diffusion of hydrocarbon vapors in glassy polymers
Authors: Barrie James A. , Williams M. J. L. , Munday Keith 
Published: December 2004

AbstractSorption isotherms in the region of low relative pressures have been determined at several temperatures for methane, propane, and chlorodifluoromethane in polystyrene and for propane in bisphenol‐A polycarbonate and poly(vinylacetate). The results are well represented by the isotherm equation of Dual Sorption Theory as applied to glassy polymers. The temperature dependence of the isotherm parameters is examined and discussed; the Langmuir component to sorption decreases as the glass transition temperature is approached and measurements with poly(vinylacetate) confirm that this component is absent above the transition. Average diffusion coefficients were obtained from sorption (desorption) rate curves at constant pressure for propane in polystyrene and polycarbonate and a procedure developed for their analysis to yield the diffusion coefficients of the two sorbed species of penetrant. For the polycarbonate there is evidence of mobility in that fraction of the penetrant: population exhibiting Langmuir‐type sorption.
Solvent interactions with polysulfone
Authors: Dangayach K. C. B. , Bonner D. C. 
Published: December 2004

AbstractWe have used gas chromatography to study solvent interactions with polysulfone at temperatures below the glass transition. A previously published procedure has been employed to decompose the Gibbs energy of sorption of various solvents in polysulfone into its component contributions from dispersion forces, polar forces, and forces of specific interactions such as hydrogen bonding. The gas chromatographic results and the analysis of Gibbs energy of sorption has been used to establish general criteria for solubility of nonpolar, polar, and specifically interacting solvents in polysulfone.
Effect of sub‐Tg annealing on CO2 sorption in polycarbonate
Authors: Chan A. H. , Paul D. R. 
Published: December 2004

AbstractHigh pressure CO2 sorption data in polycarbonate (PC) are reported as a function of temperature and thermal history. The bulk physical structural changes produced by annealing at 125 and 135°C were monitored by density and thermal property changes. The sorption data are analyzed by the dual sorption model which assumes the sorption isotherm to consist of Henry's law and Langmuir sorption terms; The Langmuir capacity term C of PC can be grossly correlated with the reported volumetric parameters of the polymer. This excess volume interpretation of C has found support in the good correlation between C and the corresponding enthalpy relaxation from parallel Differential Thermal Analysis of the samples. Density measurements provide gross evidence of the free volume interpretation of C. The experimental uncertainties in the data compromise a more critical test of the relationship between C and the density of annealed samples.
Gravimetric and volumetric study of the sorption of gases and vapors in poly(vinyl chloride) powders
Authors: Berens A. R. 
Published: December 2004

AbstractThe sorption of a variety of gases and organic vapors in poly(vinyl chloride) (PVC) powders has been studied gravimetrically with a recording microbalance and volumetrically with a gas pycnometer and an automatic surface area analyzer. For nitrogen, carbondioxide, vinyl chloride, methanol, acetone, n‐butane, and benzene at low penetrant activities and temperatures below Tg, sorption isotherms exhibit the downward curvature characteristic of dual‐mode sorption. The solubility of each of these penetrants is lower in heat‐treated PVC samples than in samples recovered from the polymerization without additional heating. It has been possible to estimate the parameters of the dual‐mode sorption model for carbondioxide, vinyl chloride, and methanol. The results indicate that the history‐dependence of gas or vapor solubility is associated only with the “hole‐filling” term of the dual‐mode model; the normal dissolution or Henry's Law term is essentially unaffected by the prior heat treatment of the PVC.
Experimental deep‐channel velocity profiles and operating characteristics for a single‐screw extruder
Authors: Choo K. P. , Neelakantan N. R. , Pittman J. F. T. 
Published: December 2004

AbstractData have been obtained on the operation of a deep‐channel single‐screw extruder, pumping a Newtonian liquid under isothermal, developed flow conditions. Flow rate, screw speed, and pressure gradient characteristics were measured, and a tracer particle technique was employed to determine channel velocity profiles. The data were required for the testing and development of a computer model for flow in the extruder, which takes into consideration channel curvature. Results confirm the correctness of the computer solutions previously reported.
The influence of the axial pressure gradient on flow rate for Newtonian liquids in a self wiping, co‐rotating twin screw extruder
Authors: Denson C. D. , Hwang B. K. 
Published: December 2004

AbstractThe isothermal flow of a Newtonian liquid in a co‐rotating twin screw extruder having screw elements with three tips has been analyzed when the effect of the intermeshing zone on flow can be neglected. It was found that values for four dimensionless parameters must be specified in order to obtain a unique relationship between the dimensionless axial pressure gradient and the dimensionless volumetric flow rate. These parameters included the number of screw tips, the helix angle, the ratio of the clearance to the screw radius, and the ratio of the distance between screw centers‐to the screw radius Values for the dimensionless throughput and pressure gradient were computed for a range of helix angles at fixed values for all other dimensionless parameters. Shape factors were also computed and it was found that the shape‐factor for pressure How is substantially less than that for drag flow. Asymptotic values for both these factors at large values of the channel width (large helix angles) were found to be less than unity.
Iodinated polystyrene: An ion‐millable negative resist
Authors: Shiraishi H. , Taniguchi Y. , Horigome S. , Nonogaki S. 
Published: December 2004

AbstractIodinated polystyrene (IPS) is obtained by direct iodination of polystyrene and its lithographic characteristics are investigated. The sensitivity of the polymer to electron beams is increased as the result of iodination by a factor of about 10 and reaches 1 μC/cm2. Coated IPS films are very stable and no changes in exposure characteristics are observed even after pre‐baking at 220°C for 10 min. It is found that crosslinking does not proceed in a vacuum after electron beam exposure. The milling rate of IPS under Ar+ bombardment is measured to be 0.25 nm/s. This is lower than that of poly(glycidyl methacrylate‐co‐ethyl acrylate) (0.67 nm/s) and that of permalloy (0.42 nm/s), both obtained under the same conditions. The mechanism of sensitization by iodination is discussed.
Measurement and calculation of parison dimensions and bottle thickness distribution during blow molding
Authors: Kamal Musa R. , Tan Victor , Kalyon Dilhan 
Published: December 2004

AbstractExperimental data are reported regarding the dynamics of the blow molding process, including parison formation, growth, and inflation. These data have been obtained with the aid of high speed cinematography and pinch mold experiments, in conjunction with two commercial blow molding polyethylene resins. It is shown that pinch mold experiments alone do not yield accurate data regarding thickness and diameter swell. Furthermore, the inflation process involves decreasing rates of inflation with time, as a result of the rise in viscosity due to the cooling of the parison during inflation. Mathematical procedures are proposed for a first‐order estimation of parison length and swell as a function of time and the inflation behavior after clamping. In the absence of more dependable basic procedures, the proposed treatment is employed to estimate the effective transient swell functions for the parison using experimental data obtained under the specified conditions. The mathematical treatment is extended to determine the thickness distribution of the bottle. Good agreement is obtained between experimental and calculated results.
The melting performance of single screw extruders
Authors: Housz J. F. Ingen , Meijer H. E. H. 
Published: December 2004

AbstractA number of recent screw designs is analyzed for melting performance, using a simple analytical approach based on Tadmor's original work. The melting length for a screw with constant depth channel is used as reference. An ideal compression screw will have a melting length of one‐half the melting length of the reference screw. The Maillefer melt separation principle is discussed. The Maillefer screw melts in 2/3 of the length of the reference screw. Screws by Barr, by Dray and Lawrence and by Kim are shown to approach the ideal compression screw. A new design screw, using ideal compression and multiple channels and having a very large screw pitch, is shown to be a considerably more efficient melting device than any of the other, screws discussed.
The viscosity effect on autoacceleration of the rate of free radical polymerization
Authors: Dvornić Petar R. , Jaćović Mihailo S. 
Published: December 2004

AbstractThe reaction kinetics at 70°C were investigated for the suspension polymerization of methyl methacrylate initiated by benzoyl peroxide in the presence of variable amounts of dodecyl mercaptan. A dilatometric method designed to follow a suspension polymerization was used. It showed that the autoacceleration of the rate of polymerization begins at higher conversions and becomes less pronounced as the concentration of chain transfer agent is increased. The investigations focused on the determination of the viscosities of the reaction mixtures at the onset of autoacceleration. It was concluded from the flow curves obtained for different reaction mixtures that there exists a critical solution viscosity at which the autoacceleration begins, which supports the accepted theory about the nature of this phenomenon. Measured at a shear rate of 10,000 s−1 and at 25°C this viscosity was found to equal 0.6 poise regardless of the molecular weight of the growing polymer.
Effect of carriers on the performance of aluminum alloy joints bonded with a structural film adhesive
Authors: Brewis D. M. , Comyn J. , Cope B. C. , Moloney A. C. 
Published: December 2004

AbstractThe effect of polyester and nylon carriers on the durability of metal joints bonded with the modified epoxide adhesive BSL 312 has been examined. Joints have been exposed to air at 50°C and 100 percent RH for periods of up to 10,000 h. Some joints were under tensile stress and this seems to have no effect on durability. Carriers cause a slight lowering of the strength of dry joints, but they appear to have negligible effect on joint durability. An analysis of water distribution in exposed joints implies that the rate of strength loss is dependent upon the rate at which water enters joints by diffusion.