bluuebunny/crossref_metadata_2025_split huggingface dataset:
Statistical thermodynamics of blends: Equation of state and phase relations
Authors: Simha Robert , Jain R. K. 
Published: December 2004

AbstractWe discuss the free‐energy expressions for homogeneous melts and their blends, based on our hole theory. Equation of state (PVT) and free energy of mixing (ΔGm) are considered from a common point of view without the introduction of additional parameters to pass from the first to the second set of properties. Practical problems arise from the fact that ΔGm represents a difference between large quantities. As illustrations we analyze two typical systems. One is the n − C6 + n − C16 pair where PVT and ΔGm, the latter at atmospheric pressure only, have been studied experimentally. The other is n ‐ C6 with a low and high molecular weight respectively of polyethylene as solute. Here the PVT relations of the components only are known. The effects of intercomponent attractions, temperature, pressure, and molecular weight on phase behavior are investigated. Critical coordinates, lower critical‐solution temperatures (LCST) and their pressure dependence are computed. An iso‐free volume condition obtains for this dependence where free volume is defined by the hole fraction inherent in the theory. Comparisons with experimental observations and other theoretical computations for different molecular weights are limited by the effect of polydispersity. Moreover, cloud point curves are shown. We finally compute the composition and pressure dependence of the χ‐parameter which is implicit in the theory. We conclude with some comments regarding polymer blends.
Injection molding of a transparent polyurethane: A statistical evaluation
Authors: Delluca Joan J. , Petrie Stephen P. 
Published: December 2004

AbstractIn this study the effect of processing variables upon the optical properties of an injection‐molded thermoplastic polyurethane were investigated. The investigation was separated into two phases. The first phase used conventional experimental methods, the second phase used a central composite factorial design. The processing variables studied were: melt temperatures, tool temperature, injection speed, injection pressure, back pressure, screw speed, cushion size, and cycle time. The optical responses used to evaluate the processing variables were: percent haze, percent luminous transmittance, and line of sight deviation. Each of the significant parameters used was found to have some effect on at least one optical property. Statistical analysis showed interaction among the processing parameters, indicating that simultaneous control of the parameters was required. Empirical models were derived to predict responses for a given set of processing conditions. There was good agreement between the models and experiments.
Thermoplastic polyester resins for containers
Authors: Callander Douglas D. 
Published: December 2004

AbstractAn overview of the use of polyesters for containers is presented. The market for polyethylene terephthalate container resin should reach 760 million pounds by 1989. Diethylene glycol, a polymerization by‐product, and other comonomers reduce the polymer melting point and crystallization tendency, yielding wider container processing latitude. The effect of these modifications on creep and tensile strength is discussed. Improved gaseous barrier approaches and hot‐fillable container opportunities are presented, Newer applications for thermoplastic polyester containers are summarized.
Polyphenylene ethers and their alloys
Authors: Warren R. Ingrid 
Published: December 2004

AbstractPoly(phenylene ether)s (PPE) are a class of polymers which contain phenolic monomers attached via an ether linkage. Depending upon the monomer types used in the polymerization, a variety of homopolymers and copolymers can be produced. When compounded with polystyrene, these poly(phenylene ether)s combine to form single phase alloys in contrast to the separate phases obtained with most other polymer blends. Since polyphenylene ether and polystyrene are completely miscible, the alloy also has only one glass transition temperature (Tg) and behaves in a manner that is typical of single polymeric materials. By blending poly(phenylene ether)s with impact modified polystyrene at different ratios, opaque thermoplastic resins having a wide range of chemical, thermal, and mechanical properties can be manufactured. Commercially available material grades have thus been developed to meet special product requirements for flame retardancy, high impact, increased flexural and tensile strength, low creep, and good resistance to certain chemical environments. In comparison to other types of unfilled thermoplastics, poly(phenylene ether)s have a balance of properties which can overlap those of acrylonitrile‐butadiene‐styrene (ABS), polycarbonate, nylon, and other high performance polymers.
Morphological studies of oriented ultra‐high molecular weight polyethylene with enhanced planar mechanical properties
Authors: Kanamoto Tetsuo , Zacharides Anagnostis E. 
Published: December 2004

AbstractUltra‐high molecular weight polyethylene films prepared by melt flow crystallization under torsional flow conditions were characterized by wide angle (WAXS) and small angle (SAXS) diffraction techniques and scanning electron microscopy (SEM). The films had a fibrillar morphology in which lamellae having an average fold period of 650Å were stacked with their c‐axis along the circular flow lines. X‐ray analysis showed that the a and b‐axes were preferentially oriented along the thickness and radial directions of the sample.
Mathematical modeling of melting of polymers in a single‐screw extruder a critical review
Authors: Lindt J. T. 
Published: December 2004

AbstractDeterministic mathematical models of the Maddock melting mechanism based on analytical and finite‐difference solution methods are surveyed and classified according to the key assumptions involved. It has been concluded that the rigid solid bed concept coupled with a consistent non‐Newtonian analysis of the melt flow pattern, including cross‐channel circulation, leads to superior results. It is suggested that the development of the melting theory for the Maddock mechanism as an engineering analytical tool is virtually complete.
A numerical study of the effect of normal stresses and elongational viscosity on entry vortex growth and extrudate swell
Authors: Mitsoulis E. , Vlachopoulos J. , Mirza F. A. 
Published: December 2004

AbstractA general‐purpose finite element program has been used to simulate the flow of a typical polystyrene melt in the entry and exit regions of a slit die. Instead of using a general viscoelastic constitutive equation, simplified models were used that include correlations based on experimental data available in the literature for the shear and elongational viscosities and the normal stresses. With such simple models convergence of the iterative scheme is extended to relatively high Deborah numbers (De ≈ 5). The models predict vortex growth in the entry region and an increase of extrudate swell at the exit in qualitative agreement with experimental observations. It was found that the normal stresses are primarily responsible for these phenomena, while the elongational viscosity tends to increase the end (Bagley) correction and decrease the swelling.
Progress in multiphase rubber processing: Controlled‐ingredient‐distribution mixing
Authors: Lee Biing‐Lin 
Published: December 2004

AbstractThe physical properties of finished polymer blend composites are, in general, strongly influenced by the heterogeneity of the blend and the distribution of ingredients (especially reinforcement fillers) in each of the polymer phases. In this article, we review and update a processing technology specifically for the processing of multiphase rubber blend compounds in order to produce blend compounds with more desirable properties for practical applications. The basic concept is centered on the controlled‐ingredient‐distribution mixing (CIDM) process. The improvements in the following properties of rubber blend compounds are discussed: crack growth resistance, heat buildup, oil swelling, covulcanization, green strength, and permeability.
Toughened plastics consisting of brittle particles and ductile matrix
Authors: Koo Kong‐Khen , Inoue Takashi , Miyasaka Keizo 
Published: December 2004

AbstractStudies on plastic alloys consisting of particles of brittle polymers dispersed in the matrices of ductile polymers were undertaken using the miniature polymer evaluation system (CSI Mini‐Max System). For the polycarbonate/poly(acrylonitrileco‐styrene) system, which had been found to show improved impact strength by Kurauchi, et al. using the conventional methods of molding and mechanical testing, it was verified that the miniature evaluation system gave the same results as those from the conventional methods. Ten other different combinations of ductile and brittle polymers were evaluated by using the miniature evaluation system. Among them the polycarbonate/poly(methyl methacrylate) system is found to be a toughened alloy. From these results, the requirements for the development of toughening in the ductile/brittle systems are discussed.
Effect of humidity and temperature on the adhesive strength of pressure sensitive adhesives
Authors: Lai Juey H. , Knudson Curtis , Hallgren Leander , Douglas Richard B. , Griffin Patrick 
Published: December 2004

AbstractThis paper reports the effect of humidity and temperature on the adhesive strength of a pressure sensitive adhesive (Flexbond 150) used to bond Mylar films. It has been found that, ill general, the adhesive strength decreases significantly with an increase in temperature. The effect of humidity on the bonding strength, however, was found to be process dependent. The sample preparation conditions, e.g., press weight for the bonding and the press time, are important in determining the humidity effect. The water sorption isotherm A 24°C for the adhesive was also determined. The amount of water sorbed by the adhesive at 95 percent relative pressure was found to be less than one weight percent.
Dicyanate semi IPNs—A new class of high performance, high temperature plastics
Authors: Wertz David H. , Prevorsek Dusan C. 
Published: December 2004

AbstractDicyanate Semi‐Interpenetrating Polymer Networks (semi IPNs) are made by dissolving a thermoplastic in crosslinking dicyanates and then curing the resulting mixture. The semi IPNs produced are strong, with tensile strengths of 10,000 to 12,000 psi, and flexible, with elongations to break of 10 to 17 percent. Dicyanate semi IPNs also have good thermal stability and the softening temperatures of the IPNs are significantly, higher than those of the corresponding thermoplastics.
Interpenetrating bimodal networks
Authors: Mark J. E. , Ning Y.‐P. 
Published: December 2004

AbstractSequential interpenetrating networks (IPN's) were obtained from a tetrafunctionally end‐linked network [prepared from hydroxyl‐terminated poly(dimethylsiloxane) (PDMS) chains having a number‐average molecular weight of 21.3 × 103 g mol−1] by swelling it with very short vinyl‐terminated PDMS chains (∼450 g mol−1), which were then themselves tetrafunctionally end linked, Simultaneous IPN's were prepared from a mixture of the same two types of PDMS chains, with different end‐linking agents and catalysts for the two separate reactions. In elongation studies, both types of IPN's showed upturns in modulus which were similar to those shown by the usual bimodal networks, which are prepared from mixtures of chains having identical end groups, and are thus entirely interconnected. The sequential IPN's have values of the high deformation modulus close to those of the interconnected networks, possibly because their lack of connectivity is compensated for by the stretching of the long chains by the short‐chains used to form the second network, Values of the ultimate strength are smaller for the IPN's, thus demonstrating the advantage of direct bonding between the long and short network chains. The simultaneous IPN's, however, have unusually large extensibilities, which makes their energies for rupture comparable to those of the corresponding interconnected bimodal networks.
Mechanics and mechanisms of impact fracture in semi‐ductile polymers
Authors: Vu‐Khanh T. , De Charentenay F. X. 
Published: December 2004

AbstractThe method proposed by C. E. Turner and J. G. Williams for characterizing the impact resistance of polymers was reanalyzed and a new method has been developed for the study of semi‐ductile polymers. In these polymers, the fracture occurs by a set of stable and unstable crack propagation stages. The new model takes into account the first stable stage and the point of instability in order to allow the determination of two fracture energies Ḡst and Ginst. These fracture parameters characterize the material impact behavior. The model has been applied to polyamide 11 and 12. Molding condition and orientation effects on the impact fracture energies are presented.
Properties of a branched polyester ether as a function of the preparation method
Authors: Fagerburg D. R. 
Published: December 2004

AbstractProperties of a branched polyester ether elastomer have been examined by using two widely differing preparation methods: (1) prepared to final molecular weight by using melt polycondensation (MP) and (2) prepared to an intermediate molecular weight by using melt polycondensation followed by solid phase polycondensation to the final molecular weight (SP). Differences in Tm were attributed to annealing during the SP process and also to apparent changes in monomer sequence distribution in the polymer chains. Crystallization during cooling (DSC) and melt viscosity appeared to be solely a function of molecular weight rather than of preparation history. Molecular weight distribution was exponentially dependent on viscosity average molecular weight for the MP samples, but the distribution was linearly dependent for the SP case which more nearly represents equilibrium conditions. Polymer mechanical properties did not vary much in spite of the pronounced differences observed.
Simulation of foaming process of polyurethane integral skin foams
Authors: Yokono Hitoshi , Tsuzuku Susumu , Hira Yasuo , Gotoh Masao , Miyano Yasushi 
Published: December 2004

AbstractThis paper deals with a procedure to simulate the foaming process of polyurethane integral skin foams. The process involves heat generation by chemical reaction, heat loss through the mold, and local vaporization and condensation of the solvent. To simulate this dynamic process, a boundary mobile cell model was proposed. Each cell contains a certain mass of the solvent. The volume, temperature, and pressure of each cell call be estinlated by the quantity of heat which is generated and/or transferred in the cell, assuming that no pressure gradient exists and the total volume of each cell is constant. For a typical polyurethane system, apparent density profiles were predicted theoretically, as well as chemical conversion, temperature, and pressure profiles. Experimental results were compared with the theoretical values. Rather good agreement between them was obtained, though no adjusting parameter was introduced.
Molecular orbital conformational energy calculations of the aromatic heterocyclic poly(5,5′‐bibenzoxazole‐2,2′ diyl‐1,4‐phenylene) and poly(2,5‐benzoxazole)
Authors: Welsh W. J. , Mark J. E. 
Published: December 2004

AbstractInterest in potential high‐performance polymers, leading to characterization and development of the rodlike poly(p‐phenylene benzobisoxazoles) (PBO) and poly(p‐phenylene benzobisthiazoles) (PBT), has recently been extended to a related group of polymers referred to as AAPBO, ABPBO, AAPBT, and ABPBT. In this study, geometry‐optimized CNDO/2 molecular orbital calculations have been carried out on AAPBO and ABPBO model compounds to determine conformational energies as a function of rotation about each type of rotatable bond within the repeat units. For AAPBO, which contains two types of rotatable bonds per repeat unit, the bond between the benzoxazole group and p‐phenylene group prefers the coplanar conformation with a barrier to free rotation of 2.1 kcal mol−1, while the bond between the benzoxazole groups prefers a conformation approximately 60 degrees away from coplanarity with a barrier to coplanarity and to free rotation of 3.6 kcal mol−1. For ABPBO, which contains only the former type of rotatable bond per repeat unit, the coplanar conformations were preferred with a barrier to free rotation of 1.6 kcal mol−1. These results are in excellent agreement with the results of both theoretical and experimental studies on the structurally analogous PBO. They are also consistent with the liquid crystalline behavior found for ABPBO but not for AAPBO.
A survey of the configuration and conformation of chlorinated cis‐ and trans‐ polybutadienes and their model compounds
Authors: Kondo S. , Takeda M. 
Published: December 2004

AbstractThis review is mainly concerned with the conformational changes that depend on the dielectric constants for solvents for chlorinated polybutadienes (Cl‐PBD) and their model compounds. The conformational equilibria of the rotational isomers of both meso and racemie 2,3‐dichlorobutanes and 3,4‐dichlorohexanes as the model compounds are discussed by analyzing infrared and NMR spectra. The solvent effect on the conformational parameter in Cl‐PBD is explained by the variation in the conformation of the chlorinated part having polar C‐Cl bonds. The matrix method is also described to calculate the temperature and solvent dependences of conformer populations.
Comparison of impact and compact tension fracture properties of poly(methyl methacrylate)
Authors: Umar‐Khitab S. A. , McCammond D. , Venter R. D. 
Published: December 2004

AbstractThis paper presents the results of a testing program carried out on the fracture properties of poly(methyl methacrylate) (PMMA). The objective of the program was to determine the validity of using standard impact test methods to obtain fracture data, as opposed to the more expensive fracture toughness tests. It was found that impact test results may be used to evaluate fracture properties for PMMA with correlation being obtained with fracture toughness test data.
Miscibility in poly(vinyl chloride)/chlorinated poly(vinyl chloride) blends, and blends of different chlorinated poly(vinyl chlorides)
Authors: Lehr Marvin H. 
Published: December 2004

AbstractBlends of poly(vinyl chloride) with chlorinated poly(vinyl chloride) (PVC), and blends of different chlorinated poly(vinyl chlorides) (CPVC) provide an opportunity to examine systematically the effect that small changes in chemical structure have on polymer‐polymer miscibility. Phase diagrams of PVC/CPVC blends have been determined for CPVC's containing 62 to 38 percent chlorine. The characteristics of binary blends of CPVC's of different chlorine contents have also been examined using differential calorimetry (DSC) and transmission electron microscopy. Their mutual solubility has been found to be very sensitive to their differences in mole percent CCl2 groups and degree of chlorination. In metastable binary blends of CPVC's possessing single glass transition temperatures (Tg) the rate of phase separation, as followed by DSC, was found to be relatively slow at temperatures 45 to 65° above the Tg of the blend.
Predictions of nucleation theory applied to ehrenfest thermodynamic transitions: II. The effects of pressure and stress
Authors: Campbell K. W. , Barker R. E. 
Published: December 2004

AbstractThis paper is a sequel to an earlier one on the applicability of classical nucleation theory to second‐order transitions in the Ehrenfest sense (1). In each case the approach was to obtain the critical size rc and energy barrier ΔGc for the growth of a nucleus of β‐phase in an α‐phase matrix by a Maclaurin series expansion of the free‐energy‐density g = (Gβ − Gα)/vβ as a function of θ (in BC‐I) and of ΔP and Δσ in this paper where θ = (T − Tt) is the degree of undercooling and ΔP and Δσ are analogous terms for the hydrostatic pressure shift and tensile stress shift away from the equilibrium transition. The expansion coefficients were determined by the use of thermodynamic relationships. For second‐order transitions, rc = 4γvβ Tt/ΔCpθ2, rc = 4γ/Δβ(Δp)2, and rc = 4γ/YαYβ(Δσ)2, respectively, for the three cases. The terms ΔCp, Δβ, and ΔY denote the differences in heat capacity, compressibility, and Young's modulus, e.g., ΔY = Yβ − Yα. The interfacial energy γαβ is denoted by γ. The activation energy barriers for the cases developed in this paper were ΔGc = (16π/3)γ3/(Δβ)2 (Δp)4 and ΔGc = (64π/3)γ3Yα2Yβ2/(ΔY)2(Δσ)4. More complicated expressions are given in the paper for the rc and ΔGc for first‐order transitions. In the long run, these expressions may prove more useful than the ones for second‐order because of the modifications expressions for the kinetics of transformations.
Phase diagram of polymer blends containing block copolymers
Authors: Roe Ryong‐Joon 
Published: December 2004

AbstractThe phase transition and phase separation behavior occurring in mixtures containing an A–B block copolymer and an A homopolymer is discussed. With a pure block copolymer an order‐disorder transition can be induced by raising the temperature, whereby the ordered lattice of segregated microdomains becomes unstable and gives way to a homogeneous liquid structure. Small amounts of a homopolymer added to a block copolymer can be accommodated in the microdomains consisting of the same type of monomeric units, up to a solubility limit that depends on the relative lengths of the homopolymer and the copolymer block and on the temperature. The order‐disorder transition temperature of the block copolymer is also affected by the added homopolymer. At the other extreme of concentration, spherical micelles of block copolymer are formed when a small amount of the copolymer is added in the bulk homopolymer, and the critical micelle concentration again depends on the relative lengths of the molecules and blocks involved and on the temperature. Measurements were made with light scattering and small‐angle X‐ray scattering techniques to determine the phase behavior of mixtures containing a styrene‐butadiene block copolymer and either a polystyrene or a polybutadiene. The resulting phase diagram exhibits a fascinating complexity. Comparison with recent theories treating these phenomena shows that a good agreement is generally obtained on a qualitative or semi‐quantitative level, but a quantitative agreement is often not attained.
Solid‐state polymerization in poly(butylene terephthalate): The Equilibrium constant
Authors: Kosky P. G. , Guggenheim E. A. 
Published: December 2004

AbstractPoly(butylene terephthalate)PBT or Poly‐1, 4‐butanediyl 1, 4‐diearboxylate.
polycondenses readily in the presence of small amounts of organo‐titanium compounds to form progressively higher molecular weight polymers, The reaction is reversible in the presence of the condensation byproduct, 1,4‐butanediol. Usually this reaction is carried out in the melt phase, but the viscosity is soon limiting. In the current work the polymerization is carried out in the solid phase just below the melting point of 227°C. The equilibrium constant for this reaction is measured by subjecting the polymer to a nitrogen stream saturated with a controlled quantity of butanediol. The reaction is followed by measuring the change in the number of alcoholic end‐groups by infrared spectroscopy. At about 220°C the equilibrium constant is 0.31 (σ = 0.08).