bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of concentration on apparent viscosity of a globular protein solution
Authors: Pradipasena Pasawadee , Rha Chokyun 
Published: December 2004

AbstractThe viscosity of a globular protein solution as a function of concentration was studied with a cone and plate viscometef (Ferranti‐Shirley Viscometer System) using, β‐lactoglobulin as a model. An aqueous buffer solution (pH 7, ionic strength 0.04) containing up to 40 percent protein was subjected to rates of shear between 800 and 17,000 sec−1. Specific viscosity of β‐lactoglobulin up to 10 weight percent was proportional to the weight concentration of protein in solution such that: ηs = η0 [ 1+0.8 (weight percent concentration)] where η0 and ηs are viscosity coefficients for the pure solvent and the solution, respectively. For 3‐40 weight percent, a linear relation of shear rate and shear stress was observed at high shear rates. Linearity began at 3500, 4300, 6800, and 7000 see−1 for 10, 20, 30 and 40 weight percent concentrations respectively. The apparent viscosity was lower below these critical shear rates.
The mechanisms of elevated temperature property losses in high performance structural epoxy resin matrix materials after exposures to high humidity environments
Authors: Browning Charles E. 
Published: December 2004

AbstractAbsorbed moisture was found to plasticize the type of cross‐linked epoxy resin system investigated, causing a lowering of the Ta and in turn affecting mechanical response, such as by shifting the relaxation moduli to shorter times. The phenomenon is described and quantified in terms of an existing free volume theory relationship. Weight gains greater than equilibrium amounts were observed without accompanyingTgchanges which is attributed to moisture entrapment during microcracking in the resin. Creep studies performed under water at 300° F established an additional mechanism for loss of elevated temperature properties which is characterized by the appearance and growth of cracks in the material. The observed failure processes are described in terms of an existing theory for rupture of cross‐linked rubbers. The process is governed by the synergistic effects of moisture, temperature, and stress. Moisture changes the viscoelastic response of the material so that stress‐induced crack formation and growth is facilitated.
On the damage energy of polymers in creep
Authors: Brüller O. S. 
Published: December 2004

AbstractCreep experiments carried out on transparent and translucent polymers permit the observation of irreversible material damage in the form of crazes or microcracks. The formation of such damage is strongly dependent on the applied stress, temperature and environmental conditions. The first appearance of observable material damage seems to be explicable by an energy criterion. The energy supplied by the external load can be divided into conserved and dissipated parts, each of them causing volume (isotropic) and shape (deviatoric) changes. The different parts of the energy can be computed if the creep‐compliance is approximated by a Prony‐Dirichlet series with a finite number of terms. Computations carried out for experiments with air as the environmental medium under isothermal conditions show the dependence between the appearance of first visible material damage (crazes or microcracks) and the conserved energy.
Oriented short glass‐fiber composites. IV. Dependence of mechanical properties on the distribution of fiber orientations
Authors: Kacir L. , Ishai O. , Narkis M. 
Published: December 2004

AbstractShort glass fiber‐epoxy laminates of controlled fiber orientation and distribution were loaded to failure under uniaxial tension. The mechanical characteristics of specimens with different orientation patterns, which were determined experimentally, were compared with analytical predictions based on “Laminate Analogy” methods. Results show good agreement between empirical data and prediction in the case of stiffness, stress‐strain relationship and strength based on ultimate strain criteria. A methodology is proposed according to which a well‐defined, orthotropic, short fiber reinforced plastic system can be prepared, analyzed, and optimized by tailoring it according to the loading pattern in a similar manner to that of the well‐established, continuous fiber reinforced laminates.
The use of urethane rubber/epoxide resin blends as matrix materials for glass and carbon fiber composites
Authors: Wells H. , Hancox N. L. 
Published: December 2004

AbstractWe consider the effects of using urethane rubber/epoxide resin blends as matrices for unidirectional glass and carbon fiber and for balanced‐weave glass fiber cloth composites. The mechanical properties of the unreinforced resin and various composites were measured for specimens with matrices containing up to 35 percent of urethane. The properties of the unreinforced resin show very marked changes between 30 and 35 percent of urethane due, it is believed, to the existence of discrete regions of urethane polymer throughout the matrix. The transverse properties of the unidirectional carbon fiber composites are significantly enhanced by the presence of 20 percent of urethane in the matrix without, apart from a decrease in the shear modulus, any marked change in other properties. This could prove useful in the applications of carbon fiber composites. Results for glass fiber materials are less dramatic, possibly because of poorer adhesion between the glass fiber and the urethane. If this is indeed the cause of the results, it should be possible to bring about an improvement for glass fiber composites by using fibers coated with a suitable coupling agent.
Prediction of transport properties of composites from equations of elasticity
Authors: Mehta B. S. , Dibenedetto A. T. , Kardos J. L. 
Published: December 2004

AbstractThe mathematically‐analogous equations of elasticity were used to predict the transport properties of anisotropic composite films. Composite films of controlled structural and physical characteristics were prepared by embedding impermeable glass ribbons in a cellulose acetate matrix. Simple but approximately‐precise equations of composite moduli developed by Halpin and Tsai were used to predict the composite permeability in terms of the permeabilities of the constituent phases and a structure factor which is a measure of the filler reinforcement and signifies the resistance of the filler phase to the diffusive flow in the composite medium. The discrepancy between the theoretical predictions and experimental composite permeabilities has been explained in terms of diffusive flux lines not staying in a single direction. In the case of glass ribbons the diffusive1 flow lines tend to bend away from the ribbons (regions of lower permeabilities). The extent of influence of the filler phase to impede the overall composite permeation is a function of the geometry, orientation and volume fraction of the filler.
The effect of accelerated weathering on the degradation of polymeric films
Authors: Kimball W. H. , Munir Z. A. 
Published: December 2004

AbstractThe influence of artificial weathering on three general properties of films of high‐impact polystyrene (HIP), poly(ethylene terephthalate) (PET), and poly(vinyl chloride) (PVC) was investigated, Degradation resulting from weathering was investigated in terms of changes in the water vapor permeation, mechanical properties, and optical transmission. The diffusivities and permeabilities of these three materials were significantly altered by weathering at two levels of exposure. Films of HIP were embrittled at both levels of exposure, whereas the PET films were embrittled only at the high level of exposure. Films of PVC showed embrittlement at the highest level of exposure and the lowest test temperature. Changes in the optical properties were less significant, amounting to a relatively small decrease in the transmission of the films in the visible range.
Measurement of the PVT behavior of cis‐1,4‐polybutadiene
Authors: Barlow J. W. 
Published: December 2004

AbstractThe volume of cis‐1,4‐polybutadiene between 5 and 55°C and 1 and 3000 atmospheres was measured to within a relative error of 0.1 percent with an especially developed, bellows‐type dilatometer. The presence of a small transition near 55°C was indicated by analysis of the data and confirmed by differential thermal analysis.
High speed wire coating by withdrawal from a bath of viscoelastic liquid
Authors: Middleman Stanley 
Published: December 2004

AbstractData are presented for the thickness H∞ of liquid coating entrained by continuous withdrawal at speed U of a wire of radius R from the free surface of a large bath. For Newtonian fluids of viscosity μ, density ρ and surface tension σ, the data are carried out to coating speeds beyond the applicability of current theories, to Capillary numbers of nearly one hundred. In the high speed range the data, which cover several orders of magnitude in viscosity, can be well represented by the equation

for Uμ/σ = Nca > 3. All data presented are at an essentially constant Goucher number of 0.08, where NGo ≡ R(ρg/2σ)1/2. Data for viscoelastic fluids show phenomena quite distinct, qualitatively and quantitatively, from Newtonian observations. In particular, strongly elastic fluids show a markedly reduced ability to be entrained onto the wire. Further, the coating thickness appears to become independent of Capillary number at high speed.
A class of mathematical models for sorption of swelling solvents in glassy polymers
Authors: Astaluta G. , Sarti G. C. 
Published: December 2004

AbstractA class of mathematical models for sorption of swelling solvents in glassy polymers is analyzed. The essential features of these models are the explicit consideration of the kinetics of swelling and of the driving force for swelling. It is shown that, even when all other elementary phenomena are modeled in the simplest possible way, all the experimentally observed features of the processes considered are correctly predicted.
Design and operation of screen packs
Authors: Carley James F. , Smith Wayne C. 
Published: December 2004

AbstractA method is presented for calculating the pressure drop in a polymer melt flowing through single or packed screens from orifice‐rheometer data, screen dimensions and flow rate. A design plot encompassing standard square‐woven and twilled‐dutch screens greatly simplifies the calculation. The design relationships are based on the assumption that, for the narrow range of shear usually encountered in a screen pack, the flow behavior is adequately represented by the power law. These relationships were developed from theoretical arguments and wide‐ranging experimental evidence reported elsewhere (1). Several examples involving screen packs in extrusion service are worked out in detail, The quantitative implications of the screen‐pack equations for extruder scale‐up are discussed.
The effect of molecular weight in the crystallization kinetics of glassy nylon 6
Authors: Engler Philip , Carr Stephen H. 
Published: December 2004

AbstractCrystallization of glassy nylon 6 has been investigated with differential scanning calorimetry and wide angle X‐ray diffraction in order to determine the effect of average molecular weight. Samples were prepared by quenching molten films between platens: chilled with liquid nitrogen. These films had number average molecular weights ranging from 10,000 to 42,000 and had polydispersity indices ranging from 2.0 to 3.1. Crystallization kinetics at large undercoolings were measured in terms of the systematic dependence of conversion half time, Avrami exponent and heat of crystallization. Number average molecular weight was observed to influence crystallization rate at large undercoolings through its effect on glass transition temperature. At intermediate undercoolings, molecular weight affected crystallization rate through terms other than the glass transition temperature. In addition, a dependence on the degree of order of the macromolecules, both prior to and after crystallization, was observed.
Annealing of drawn crystalline polymers
Authors: Peterlin A. 
Published: December 2004

AbstractThe annealing of drawn samples mobilizes the almost fully extended amorphous tie molecules which try to assume the thermodynamically required random conformations. The sample shrinks if annealed with free ends which permits the crystal blocks on different microfibrils and connected by almost fully extended taut tie molecules to move towards the position they had before plastic deformation. Hence the annealed sample has irretrievably lost most of its high axial elastic modulus which in the sample as drawn was caused by the high fraction of taut tie molecules. With fixed ends no shrinkage is possible so that the partial relaxation of interfibrillar taut tie molecules still lets them connect far away blocks. If their fraction is large enough so that in spite of the high surface to volume ratio which drastically depresses the crystallization temperature they can crystallize they do so after cooling to room temperature. The new axial crystalline bridges restore the high elastic modulus of the material before annealing, partially stabilize the sample against shrinkage during a new annealing, but also cause the dead bend effect which is the consequence of the replacement of flexible taut tie molecules in still amorphous conformation by rigid crystalline bridges. The drawing or extrusion at high temperature produces some annealing effects comparable with those of cold drawn material annealed with fixed ends.
Strength of discontinuous reinforced composites: I. Fiber reinforced composites
Authors: Halpin J. C. , Karoos J. L. 
Published: December 2004

AbstractThe strength of randomly oriented short fiber composites has been modeled by a quasi‐isotropic laminate. Lamination theory and a failure criterion will be used to approximate the stress‐strain response of a composite as it is loaded to failure. Experimental data are presented and compared with the maximum‐strain failure criterion.
Superdrawn filaments of polypropylene
Authors: Taylor W. N. , Clark E. S. 
Published: December 2004

AbstractFilaments of polypropylene having remarkably high strength and modulus have been prepared by the two‐stage drawing process of Clark and Scott (4). In the first stage, un‐oriented extruded billet is rapidly drawn to the natural draw ratio of ca 7X in hot silicone oil. The second stage of draw, a post neck draw process termed superdrawing, requires a slow rate of draw at carefully controlled temperatures to achieve maximum property values; the optimum conditions appear to be close to 4 percent/min at 130°C, The highest mechanical properties obtained were a Young's modulus of 22 GPa (240 gdtex, 3 × 106 psi) and a tensile strength of 0.93 GPa (10 gdtex, 1.3 = 105 psi) with an elongation to break of 7 percent. The filaments show a distinctive dead bend lack of recovery, WAXS data indicate high orientation of the molecules. SAXS data show no scattering to a resolution of 40 nm which is interpreted in terms of a continuous crystal matrix in the superdrawn filament. SEM micrographs of fractured filaments reveal a morphology of large fibrils of lath like habit with a thickness of ca. 0.1 μm. A series of experiments relating mechanical properties to the rate and temperature of superdrawing is interpreted in terms of two competing mechanisms; shearing displacement of microfibrils and unfolding of chain‐fold blocks. Models are offered to explain the observed mechanical and physical property changes on superdrawing.
Effect of gamma radiation and annealing on ultra‐oriented polyethylene
Authors: Perkins W. G. , Stannett V. T. , Porter Roger S. 
Published: December 2004

AbstractFilaments of ultra‐oriented high density polyethylene were solid‐state extruded at an extrusion (draw) ratio of 26 and subsequently irradiated under vacuum by a cobalt‐60 source at doses of 10,15, 20, 40 and 60 megarads (MRad). Several identically prepared but unirradiated strands were also tested. One set of samples at each dose was immersed in a silicone oil bath for one half hour at 128°C and one set was given no post‐irradiation thermal treatment. Characterization of the resultant morphologies included differential scanning calorimetry (DSC), birefringence, thermomechanical analysis (TMA), and tensile testing. Results from DSC measurements indicate that initial radiation crosslinking only slightly disrupts the crystal lattice, but on subsequent melting and re crystallization, the chains are unable to recrystallize effectively in their former habit. In all cases, melting point and crystallinity decrease with increasing radiation dose. Birefringence and TMA results indicate that orientation is not disrupted by irradiation. For unannealed samples, Young's modulus increases slightly then levels off while tensile strength and elongation at break increase initially, then drop, For annealed irradiated samples, Young's modulus rises at first, then levels off at higher doses. Tensile strength and elongation at break increase significantly with increasing radiation treatment, then essentially reach constant values at highest doses.
The thermal conductivity of several plastics determined by an improved line‐source apparatus
Authors: Underwood W. M. , Taylor J. R. 
Published: December 2004

AbstractThe line‐source method, previously used for measuring thermal conductivity of plastics, was increased in sensitivity so that automatic recording of data and data reduction by computer could be used, The correspondence between the underlying mathematics and the experiment is examined. The apparatus is described. The effect of experimental variables such as heating rate is determined‐ Measured values of thermal conductivity are reported for several commercial plastics, from room temperature, or lower, to processing temperatures. The precision of the results is excellent.
A critical analysis of the use of sample‐supportive techniques in the measurement of dynamic mechanical relaxation processes
Authors: Neumann R. M. , Senich G. A. , Macknight W. J. 
Published: December 2004

AbstractIt is shown that the technique of dynamic spring analysis (DSA) gives rise to a dynamic mechanical loss dispersion well above the glass transition temperature, Tg, analogous to the Tu process observed in torsional braid analysis. A mechanical model is proposed which explains why any composite sample consisting of an elastic support coupled to a viscous liquid must necessarily produce such a relaxation regardless of whether the liquid is monomeric or polymeric in nature. Loss tangent measurements performed on a series of polystyrenes of varying molecular weight and on glycerol using both DSA and a Rheometrics mechanical spectrometer show that the relaxation observed in DSA is not of molecular origin.
Some qualitative and quantitative features of die swell
Authors: Huilgol R. R. 
Published: December 2004

AbstractUpper and lower bounds for the die swell ratio are derived for all simple fluids in the presence of surface tension and under the assumptions that the flow remains viscometric up to a finite distance from the exit and that bounds on the shear stress distribution in this length exist. Both circular and plane jets are considered and the bounds so derived depend on the normal stress on the wall in the viscometric region. For Newtonian and power law fluids, this stress can be determined, a priori, from existing theories. However, for viscoelastic liquids, it is an open question at present.
Thermal and swelling properties of polystyrene‐polyolefin blends
Authors: Greco R. , Hopfenberg H. B. , Martusgelli E. , Ragosta G. , Demma G. 
Published: December 2004

AbstractModel blends of glassy amorphous polystyrene and each of four different crystallizable and rubbery polyolefins of varying side‐chain molecular weight (polyethylene, polypropylene, poly(1‐butene), poly (4‐methyl‐1‐pentene)) have been prepared by melt extrusion of the polymeric components. Density measurements, differential scanning calorimetry (DSC), swelling measurements, and X‐ray diffraction have been performed on the extruded fibers. In all cases, over the entire range of blend composition, the polymeric blends are immiscible and incompatible. The DSC measurements indicated that the polystyrene Tg was not decreased after blending and that the small reductions in the crystallinity and melting point of the respective polyolefins was best explained by thermal and kinetic interference with homo‐crystallization of the respective polyolefins in the blends. The volumetric swelling and gravimetric sorption of n‐hexane in the various blends increased monotonically with polystyrene content. The companion experiments, relating axial swelling with polystyrene content, indicated that this particular mode of distension actually decreased with increasing polystyrene content. The composite results, including DSC, X‐ray, density, volumetric swelling and axial swelling suggest that the polystyrene phase is essentially microfibrillar and oriented in the direction of extrusion.
Studies on structural foam processing II. Bubble dynamics in foam injection molding
Authors: Villamizar C. A. , Han Chang Dae 
Published: December 2004

AbstractAn experimental study was carried out to gain a better understanding of the dynamic behavior of gas bubbles during the structural foam injection molding operation. For the study, a rectangular mold cavity with glass windows on both sides was constructed, which permitted us to record on a movie film the dynamic behavior of gas bubbles in the mold cavity as a molten polymer containing inert gas was injected into it. The mold was designed so that either isothermal or nonisothermal injection molding could be carried out. Materials used were polystyrene, high‐density polyethylene, and polycarbonate. As chemical blowing agents, sodium bicarbonate (which generates carbon dioxide), a proprietary hydrazide and 5‐phenyl tetrazole, both generating nitrogen, were used. Injection pressure, injection melt temperature, and mold temperature were varied to investigate the kinetics of bubble growth (and collapse) during the foam injection molding operation. It was found that the processing variables (e.g., the mold temperature, the injection pressure, the concentration of blowing agent) have a profound influence on the nucleation and growth rates of gas bubbles during mold filling. Some specific observations made from the present study are as follows: an increase in melt temperature, blowing agent concentration, and mold temperature brings about an increase in bubble growth but more non‐uniform cell size and its distribution, whereas an increase in injection pressure (and hence injection speed) brings about a decrease in bubble growth but more uniform cell size and its distribution. Whereas almost all the theoretical studies published in the literature deal with the growth (or collapse) of a stationary single spherical gas bubble under isothermal conditions, in structural foam injection molding the shape of the bubble is not spherical because the fluid is in motion during mold filling. Moreover, a temperature gradient exists in the mold cavity and the cooling subsequent to mold filling influences bubble growth significantly. It is suggested that theoretical study be carried out on bubble growth in an imposed shear field under nonisothermal conditions.
On the limit of linear viscoelastic response in the flow between eccentric rotating disks
Authors: Jongschaap R. J. J. , Knapper K. H. , Lopulissa J. S. 
Published: December 2004

AbstractThe dependence on frequency of the limiting value of strain, ψL, for which linear Viscoelastic response occurs in eccentric rotating disks (ERD) flow is studied theoretically and experimentally. The theoretical investigations are based upon the general simple‐fluid theory of Coleman and Noll. It is shown that according to this theory ψL becomes independent of angular velocity, ω, at relatively high frequencies, whereas ψL becomes inversely proportional to ω at sufficiently low frequencies. The results of previous investigations, based upon some special rheological models, are discussed. The behavior predicted by the simple‐fluid theory is confirmed by experiments on polyisobutylene solutions.