bluuebunny/crossref_metadata_2025_split huggingface dataset:
Viscous flow and degradation of molten polypropylene
Authors: Schott Hans , Kaghan W. S. 
Published: May 2005

AbstractThe melt extrusion of a commercial polypropylene resin was studied with a screw extruder and a series of capillary dies of length:radius ratios varying from 0 to 65. Three temperatures and the range of shear rates encountered in industrial processing were covered. The temperature dependence of the apparent melt viscosity of polypropylene was intermediate between linear and branched polyethylene. Extrapolated zero shear activation energy for viscous flow was 9 ± 1 Kcal/mole. Shear dependence of the apparent viscosity of polypropylene melt was greater than for branched polyethylene in turn, greater for linear.
The anisotropy of creep behavior in oriented thermoplastics
Authors: Darlington M. W. , Saunders D. W. 
Published: May 2005

AbstractDetailed studies have been carried out on the anisotropy of creep and creep rupture behavior of thermoplastics oriented by the imposition of a large permanent deformation. This deformation is usually such as to produce simple fiber symmetry within the specimen. Experimental techniques have been devised for the accurate measurement of all three principal strains during tensile creep on small samples which are cut from the oriented specimens at various angles to the symmetry axis. In this way a full characterization of the creep behavior up to strains of 5 percent has been obtained at room temperature.Results are presented for work on rigid poly (vinyl chloride), poly(methyl methacrylate), and low density polyethylene. The results are discussed in terms of the time dependence and nonlinearity of the anisotropy. Creep rupture results on similar specimens are also presented and discussed. Anisotropy due to orientation is shown to be important in determining engineering properties and in understanding structure‐properties relationships.
Plastic deformation and structure of extruded polymer solids
Authors: Peterlin A. 
Published: May 2005

AbstractDuring extrusion the main deformation and orientation of macromolecules is achieved by the flow component with longitudinal gradient. The orientation increases drastically if some solidification occurs during flow, yielding row‐nucleated cylindrites and even fully oriented hard elastomers. In all cases the basic elements are stacks of very thin (∼100Å) folded‐chain lamellae connected by very few tie molecules. The plastic deformation of the solid transforms the original lamellar material into the extremely well oriented fibrous structure with high anisotropy of physical properties. The basic element are the highly aligned, very long and thin microfibrils bundled into fibrils. The axial strength of microfibrils is caused by the great many taut tie molecules connecting as almost crystalline bridges the crystalline blocks across the interposed amorphous layers. In plastic deformation of fibrous material the fibrils are sheared and longitudinally displaced. The latter mode is responsible for almost all the observed elongation. It smooths the structural defects on the surface of fibrils caused by the ends of microfibrils and thus produces a better lateral fit of fibrils resulting in rapidly increasing resistance to plastic deformation. The former mode extends the interfibrillar tie molecules and hence drastically increases their fraction per amorphous layer.
Hydrostatic extrusion of solid polyethylene
Authors: Davis L. A. 
Published: May 2005

AbstractSolid state processing of polyethylene (SS60‐050) by hydrostatic extrusion is investigated. Measurements are also reported for the tensile properties of polyethylene 60–050 under superposed hydrostatic pressure. With the latter data an estimate is made of the pressure required for extrusion of polyethylene in the absence of losses due to friction and redundant work. The limiting conditions for successful extrusion are discussed.
An approach for the processing engineer: Rheotechnics
Authors: Casale A. , Moroni A. , Ronzoni I. 
Published: May 2005

AbstractProcessing involves complex polymer flow problems, either in the melt or in solution. Rheologists have developed many studies with the aim of correlating polymer structure with flow properties and polymer processing. Most of these studies, however, have had relatively little impact on practical processing because of the difficulty in solving the mathematical equations involved. Recently, a relatively few papers have been published with the aim of bridging the gap between theoretical rheology and technology. The first part of the paper presents an account of works which have dealt with the process of filling a mold cavity. The second part discusses briefly some experimental results which provide a correlation between moldability and rheological properties. By analogy with the terms “electrology” and “electrotechnics,” the term “rheotechnics” is suggested for this new area of study.
Transport properties of polyvinylpyridinium anion‐exchange membranes
Authors: Wallace Richard A. , Vijayaraghavan N. V. 
Published: May 2005

AbstractMeasurements have been made of the electrical conductivity of water‐saturated heterogeneous anion‐exchange pyridinium membranes in their carbonate and hydroxyl ionic forms as a function of temperature. The pyridinium membranes were prepared from quaternized poly‐4‐vinylmethyl‐pyridinium resin electrolyte incorporated in a polyvinylidene fluoride matrix; the ratio of the pyridinium electrolyte to polyvinylidene fluoride was 4 to 1 by weight.The ion‐exchange capacity and water content of these anion‐exchange pyridinium membranes were measured. Corresponding Arrhenius activation energies of ion transport of carbonate and hydroxyl counter‐ions have been calculated. Self‐diffusion coefficients and the equivalent conductances of these pyridinium membranes in their carbonate and hydroxyl counter‐ion forms have also been determined over a wide temperature range and compared to the reported values for present quaternary ammonium anion‐exchange membranes.
A dry‐etch resistant positive‐working electron resist
Authors: Roberts E. D. 
Published: May 2005

AbstractThis paper describes two types of cross‐linked positive‐working electron resists. The first is based upon phenol‐formaldehyde resins crosslinked to poly‐(methyl methacrylate) by phenolic ester groups. The second type is based upon polystyrene, crosslinked by carboxylic acid anhydride groups. The resist properties can be varied by changing the proportion of crosslinks. A version of the second type which contains about 95 percent styrene units is described. This material shows very good resistance to degradation in a plasma‐etching process for preparing chromium on glass masks, even when it is used as a very thin film.
Proximity printing of chrome masks
Authors: Meyerhofer Dietrich , Mitchell Joe 
Published: May 2005

AbstractWe have investigated the application of proximity printing to the copying of chrome masks used for integrated circuit fabrication. The mask blanks were coated with various positive and negative photoresists. When plotting the difference in width between etched lines on the print and the corresponding feature on the mask as a function of the separation, one observes fluctuations due to the movement of the diffraction peaks in the optical image. For the negative resist, the averaged difference in width is approximately constant to separations of 25 micrometer (μm), while for positive resists it changes monotonically with increasing gap spacing. The measured results are compared with calculations using a model of the resist exposure and development and good agreement is obtained. On the basis of these results we conclude that proximity printing would be difficult to apply to mask replication, but that it has considerable promise for replicating 10X step‐and‐repeat reticles.
Craze fibril formation and breakdown
Authors: Kramer Edward J. 
Published: May 2005

AbstractAs crazes grow in areal extent they also increase in width. The areal growth involves craze tip advance which has been shown to occur by the Taylor meniscus instability. Craze widening, at least for air crazes, occurs by drawing more fibrillar material from the craze‐bulk polymer interfaces at essentially constant extension ratio. Simple arguments will be given to predict the scale of the fibrillation in terms of the stress S at the craze tip and interfaces and an effective polymer surface energy (Γ) where:

which assumes that all entangled chain crossing the surface are broken [γ represents the van‐der‐Waals (intermolecular) surface energy, d is the entanglement mesh size, vE is the entanglement density, and Ub is the energy required to break a single backbone bond]. These arguments also give the rate of fibrillation as a function of S, a nominal plastic resistance σy and Γ and can explain the fact that the stress for crazing increases relative to that for shear deformation as the entanglement density of the polymer is increased. The geometrically necessary entanglement loss (either by scission as assumed above or by disentanglement‐ at temperatures just below Tg) that accompanies fibril formation has important consequences for fibril stability. The probability p that a given entangled chain is lost can be computed from simple geometrical considerations knowing the fibril diameter D, its extension ratio λ and the mesh size d; p increases rapidly as Dλ½ becomes comparable to or less than d. These concepts can be tested in blends of high molecular weight polymer with chains of the same polymer that are too short to entangle.
Microstructural aspects of failure in semicrystalline polymers
Authors: Schultz J. M. 
Published: May 2005

AbstractMicrostructural features of semicrystalline polymers are reviewed, as are the roles of chain properties and thermal history in their development. Experimental results relating failure properties to microstructural detail are described. General models to explain inter‐ and intra‐spherulitic failure behavior are proposed. Important are (a) the role of spherulite size in boundary incompatibility, (b) competition between spherulite boundary cracking and intraspherulitic yielding, (c) competition between localized (interspherulitic) fracture and dispersed (intraspherulitic) fracture.
Craze failure by midrib creep
Authors: Verheulpen‐Heymans Nicole 
Published: May 2005

AbstractIt has been known for some time that crazes thicken during growth mainly by drawing in fresh material from the craze‐bulk interface, keeping the average craze fibril draw ratio approximately constant. Since Creep effects contribute only negligibly to craze growth rates these effects have generally been considered unimportant regarding craze breakdown. However, it is also known that the first stage of fracture is failure of the craze midrib, which is a highly drawn, very thin region down the middle of a craze. Because of the very low thickness of the midrib it has little influence on craze behavior, and information on midrib behavior is difficult to obtain. It is the purpose of this paper to attempt to rationalize what information is available.
Stress relaxation of glass‐fiber‐reinforced rigid polyurethane foam
Authors: Morimoto Kiyotake , Suzuki Toshio , Yosomiya Ryutoku 
Published: May 2005

AbstractFlexural stress relaxations were measured for rigid polyurethane foams (PUF) and glass‐fiber‐reinforced rigid polyurethane foams (FRU). The results were successfully analyzed in terms of the five element Maxwell model: (1) Samples reinforced with longer fibers exhibit reduced stress relaxation and reduced temperature dependency of stress relaxation; (2) The increased expansion ratio reduces the flexural modulus of both reinforced and non‐reinforced materials, but the stress relaxation tends to increase greatly at the higher temperature for PUF, while not so greatly for FRU; (3) The temperature dependency of E1 decreases as longer fibers are used to reinforce the polyurethane. The dependency is minimal for the polyurethane reinforced with continuous fibers, where the reinforcing effect is maximal; and (4) The activation energy calculated from τ2 according to the Arrhenius plot is smaller for the longer fiber reinforced polyurethane foams.
A study of the dynamics of foam growth: Analysis of the growth of closely spaced spherical bubbles
Authors: Amon Moris , Denson Costel D. 
Published: May 2005

AbstractA mathematical analysis of bubble growth in an expanding foam is presented. The analysis is based on a cell model whereby the foam is divided into spherical microscopic unit cells of equal and constant mass, each consisting of a liquid envelope (or shell) and a concentric spherical gas bubble. Expansion occurs by diffusion of a dissolved gas from the supersaturated envelope into the bubble. This cell model is capable of describing important qualitative features of a real system of numerous bubbles growing in close proximity to one another, and is intended as the building block of a global analysis of macroscopic foam expansion. The coupled algebraic and differential equations governing the growth of a cell are derived and solved numerically. Five dimensionless parameters are identified for the case of constant temperature and pressure outside the cell, and their effects are demonstrated through computer simulations of the system. Of these parameters, surface tension and initial radius prove to be of relatively little importance in the practical cases considered. The other parameters are the thermodynamic driving force, the cell mass (inversely proportional to the number density of bubbles), and the ratio of characteristic times for mass and momentum transport.
Molecular kinetic theory of the glass transition
Authors: Chow T. S. 
Published: May 2005

AbstractAn overview of a new molecular kinetic theory of glass‐transition phenomena is presented and experimental comparisons of its prediction for a variety of thermal and stress histories reviewed. The theory, which was developed in accordance with the balance of nonequilibrium statistical entropy, is shown to provide a unified interpretation of some recent models. The volume‐relaxation process in amorphous polymers over the glass‐transition region is regarded as the result of the collapse of a series of free volumes having different levels of energies of hole formation. An applied stress is shown to contribute to the variation of the entropy. An activation volume is introduced as a new tensorial extensive variable. The theory is applied to the phenomenon of physical aging in polymer glasses and shown to provide good quantitative agreement with the results of a well‐known experiment on volume recovery of poly(vinyl acetate). This supports the underlying postulate of a fundamental link between the apparent relaxation time and the mean energy of hole formation, the distribution of relaxation times and the free‐volume fractions. In contrast to the prevalent thinking toward free volume theories, an explicit expression between Tg and stress is presented and reveals that Tg does not continue to increase at all pressures but levels off to a semi universal asymptote at very high pressure. The calculated effect of stress rate is found to be in good agreement with dynamic viscoelastic measurements.
Physical aging of heavy metal fluoride glasses—sub‐Tg enthalpy relaxation in a ZrF4‐BaF2‐LaF3‐AlF3 glass
Authors: Moynihan C. T. , Bruce A. J. , Gavin D. L. , Loehr S. R. , Opalka S. M. , Drexhage M. G. 
Published: May 2005

AbstractThe enthalpy changes during structural relaxation or physical aging of a 58ZrF4‐33BaF2‐5LaF3‐4AlF3 (ZBLA) glass during annealing well below the glass‐transition temperature have been studied using differential‐scanning calorimetry at several sub‐Tg temperatures. Substantial relaxation within the course of several hours was detected at temperatures as low as sixty degrees below Tg (585K). The relaxation process is extremely nonlinear and self‐retarding. The time dependence of the enthalpy during the initial stages of annealing was modeled approximately using the Narayanaswamy‐Tool approach. The structural‐relaxation parameters obtained from this fit were used to predict rates of physical aging for rapidly cooled ZBLA glass at temperatures close to ambient.
Spectroscopic observations on nonequilibrium glassy poly(vinyl chloride) and polystyrene
Authors: Joss B. L. , Bretzlaff R. S. , Wool R. P. 
Published: May 2005

AbstractThe relationship of valence‐coordinate deformation to the temperature dependence of some infrared peak‐absorption frequencies in Poly(vinyl chloride) (PVC) and polystyrene (PS) is stated. A skeletal band and a CH2 rocking band in PVC and a ring‐mode band in PS were studied in two kinds of experiments: steady heating and cooling of a quenched (nonequilibrium, glassy) sample through its glass‐transition temperature, Tg, and long‐term annealing of quenched samples below Tg, followed by steady heating and cooling. The results, a slope discontinuity, ΔM, in the v(T) relation at Tg and a frequency shift, Δviso, during isothermal annealing below Tg, are analyzed in two theoretical approaches. Interchain and intrachain contributions to the observed frequency shifts are expected to occur with a differing relative significance in different kinds of molecular vibrations, leading to one possible method of distinguishing valence‐coordinate deformation (chain strain) from other effects.
Spherulite growth in isotactic polypropylene‐based blends: Energy and morphological considerations
Authors: Bartczak Z. , Gałȩski A. , Martuscelli E. 
Published: May 2005

AbstractThe kinetics of isothermal crystallization of polymer blends in which the matrix is a crystallizable polymer is considered. It is shown that depending on the difference in interfacial energies the inclusions are rejected or engulfed by the growing spherulite. Other factors influencing rejection, engulfing, and/or deformation of dispersed particles of the second polymer are the viscosity of the melt, the spherulite growth rate, and the size of dispersed particles. If the difference in interfacial energies is positive, then rejection or engulfing requires additional work to be done by the crystallization front. This dissipation of energy decreases the spherulite growth rate. It is estimated that the rejection of the second component is the most important phenomenon in the crystallization of blends. The spherulite growth rate of isotactic polypropylene in blends with low‐density polyethylene and several elastomers was studied as a function of crystallization temperature and concentration. The comparison of growth rate data with morphological changes occuring during crystallization of blends studied shows very good agreement with the theoretical predictions based on energetics considerations.
Tensile yield in nylon 6,6
Authors: Hartmann Bruce , Cole Richard F. 
Published: May 2005

AbstractUniaxial tension tests to, the yield point were performed on poly(hexamethylene adipamide) (nylon 6,6) as a function of temperature from 21 to 200°C at a strain rate of 2 min−1. At 21 and 60°C, measurements were also made at strain rates from 0.02 to 8 min−1. Using simple rate theory, reasonable values of activation volume were obtained, but the simple theory is inadequate to determine the activation energy. The yield‐strain temperature dependence changes at 160°C as a result of a reversible crystal‐crystal transition. Because of this behavior of the yield strain, the yield energy is not a linear function of temperature, as observed for several other polymers.
Tensile properties of polyarylate‐polycarbonate blends
Authors: Mondragon Iñaki , Nazabal Jon 
Published: May 2005

AbstractBlends of polyarylate (PA)‐a copolyester of bisphenol A with a mixture of terephthalic/isophthalic acids at 50/50 proportion–and polycarbonate of bisphenol A (PC) were melt mixed into films with a Brabender Plasticorder. The processing produced transreacted mixtures that exhibited a modulus and yield stress with a maximum that is above the linear (very similar to that observed for compatible polymer blends). The elongation at yield did not show any maximum but it is also above linearity.
Rheological and processing characteristics of polystyrene in the vicinity of Tll transition
Authors: Santamaría A. , Gallego F. , Muñoz M. E. 
Published: May 2005

AbstractRheological and processing parameters have been measured for a commercial polystyrene at temperatures from 155°C to 210°C resulting in no clear evidence for the existence of liquidliquid transition. Zero shear viscosities obtained from dynamic measurements and ends corrections and extrudate swell from capillary rheometry are analyzed, with the conclusion that the mechanism of flow is the same throughout the range of temperatures considered.
A new method of preparation of a rubber‐modified polyamide directly during caprolactam polymerization
Authors: Cimmino S. , D'Orazio L. , Greco R. , Maglio G. , Malinconico M. , Mancarella C. , Martuscelli E. , Musto P. , Palumbo R. , Ragosta G. 
Published: May 2005

AbstractA new method to obtain a rubber‐modified polyamide 6 (PA6) directly during the polymerization of the caprolactam (CL) is described. Binary and ternary blends containing ethylene‐propylene random copolymers (EPM) and/or a fictionalized EPM rubber (EPM‐g‐SA) were prepared and their morphology as well as their mechanical properties were investigated as function of composition and reaction conditions. It was found that the morphology of the blends is strongly dependent on the method of preparation. More complex structures are observed in blends obtained with the “Solution” preparation. For a better resolution of the morphology, the smooth ultramicrotomed surfaces were exposed to boiling xylene before SEM (scanning electron microscopy) examination. The rubbery phases are selectively dissolved whereas the PA6 matrix is left. The tensile mechanical properties and the Izod impact behavior are related to the mode and state of dispersion of the rubbery components. The impact properties of ternary PA6/EPM/EPMg‐SA (80/18/2) and (80/15/5) blends, prepared during the CL polymerization are comparable to those of similar blends obtained by usual melt mixing procedures.
Mixing studies in the single screw extruder
Authors: Bigio D. I. , Boyd J. D. , Erwin L. , Gailus D. W. 
Published: May 2005

AbstractLaminar mixing in a single screw extruder between two miscible liquids is considered. Studies are presented which examine the mixing performance in single screw extruders with mixing sections, variable geometry screws, and multi‐viscosity mixtures. Model extruders, set up on engine lathes, were used to mix colored silicone rubber which eventually cured in the screw channel. The cured silicone was then removed and sliced to measure the mixing. Results show mixing as a function of both down channel location and total average strain. For the mixing section study, results support the theory of interfacial area reorientation as the key mechanism in mixing section performance. Increasing viscosity ratio for the multi‐viscosity study showed a decrease in mixing rate.
The production and properties of poly(aryletherketone) (PEEK) rods oriented by drawing through a conical die
Authors: Richardson A. , Ania F. , Rueda D. R. , Ward I. M. , Baltá Calleja F. J. 
Published: May 2005

AbstractOriented poly(aryletherketone) (PEEK) rods have been produced by drawing isotropic polymer through a conical die. Room temperature Young's moduli were measured by three‐point bending and ranged from 5 GPa at a draw ratio of about 2 to 11 GPa at a draw ratio of about 4. Dynamic mechanical properties were explored in the range −150 to 200°C; two loss peaks were observed, with the higher corresponding to Tg.