bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphology of polyethylene‐polypropylene blends
Authors: Noel Oscar F. , Carley James F.
Published: December 2004

The morphology of blends of high‐density polyethylene (PE) and isotactic polypropylene (PP) was studied by mesans of optical and scanning‐electron microscopy. In the range of 10 to 90 percent by weight PE, these blends are two‐phase systems, the components of which crystallize separately into discrete phases. The presence of PE has a definite and pronounced effect on the crystalline structure of the PP, whose spherulitic structure becomes increasingly irregular and coarse with increasing PE content. The light transmission of these blends during melting and crystallization was also studied in an attempt to characterize them.
Isothermal swell of extrudate from annular dies; effects of die geometry, flow rate, and resin characteristics
Authors: Orbey N. , Dealy J. M.
Published: December 2004

An experimental study was made of the effects of die geometry and extrusion velocity on parison swell for three high‐density‐polyethylene blowmolding resins. Four annular dies were used: a straight, a diverging, and two converging dies. Diameter and thickness swells were measured as functions of time under isothermal conditions and in the absence of drawdown. This was accomplished by extruding into an oil having the same density and temperature as the extrudate. It was observed that 60 to 80 percent of the swell occurs in the first few seconds and that equilibrium swell is attained only after 5 to 8 minutes have elapsed. The diameter and thickness swells appear to be independent phenomena, as the relationship between them depends strongly on die design. The ranking of the resins in terms of the magnitude of the swell was found to be the same for all die geometries and extrusion rates used.
Inter‐ and intrachain elastic interactions in polymers and polymer blends
Authors: Lin Kenneth S. C. , Aklonis J. J.
Published: December 2004

The damped Debye lattice or damped torsional oscillator model for viscoelastic relaxation in the primary transition region takes into account elastic interchain interactions as well as the more usually invoked intrachain interactions. To test the importance of these interchain interactions, we have applied this model to compatible blends formed from atactic polystyrene (PS) and poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO). Qualitative predictions of the variation of stress relaxation behavior of the blends as a function of PPO concentration have been made. Also, predictions concerning properties of these blends upon dilution suggest very distinctive behaviors. We have measured stress relaxation master curves in the primary transition region of PS‐PPO blends of various concentrations and have found that the predicted behavior is indeed observed. Furthermore, the unusual effects of dilution on the properties of these blends have been observed with dioctyl phthalate used as diluent. These results show that inter‐ as well as the more familiar intramolecular elastic interactions are important factors in determining viscoelastic behavior of bulk polymers in this transition region.
Liquid‐liquid equilibria in polymer blends–molecular weight effects
Authors: Somani R. H. , Shaw M. T.
Published: December 2004

Flory's equation‐of‐state theory has been successfully used by several scientists to predict the qualitative nature of the liquid‐liquid phase equilibria in polymer blends. This theory in its most simple form requires characteristic PVT parameters for each component plus an interaction energy parameter for the mixture. The melt titration technique was used to measure the miscibility of a series of polystyrene fractions (Mw = 4000 to 1,800,000) in low density polyethylene. Because the PVT properties of both of these polymers are well known, the experimental results could be compared with the predicted equilibrium compositions from Flory's equation‐of‐state theory using the interaction energy as an adjustable parameter. This comparison led to the conclusion that the interaction energy parameter may have some molecular weight dependence.
Poly(butyleneterephthalate)‐poly(ethylene‐co‐vinylacetate) polymer blends. Part II
Authors: Pilati Francesco , Pezzin Giovanni
Published: December 2004

The more distinctive morphological features which appear in the micrographs of fracture surfaces of polymer blends of poly(butyleneterephthalate)(PBTP) with poly(ethylene‐covinylacetate) (EVA), obtained by polymerizing in different conditions dimethylterephthalate (DMT) and 1,4‐butanediol (4G) in the presence of EVA (with 4 percent w/w of vinylacetate, VA,), are shown and discussed. The micrograph investigation clearly points out that the adhesion between EVA particles and PBTP matrix increases with the extent of reaction between PBTP and EVA and, for the same time of reaction, by changing from an anchor to a paddle agitator. The mean diameter of the particles is also affected by time of reaction and by the geometry of the agitator, decreasing when the adhesion increases.
Computerization of wire insulating lines–An industrial approach
Authors: LeNir V. L.
Published: December 2004

The two main materials used for insulating wire are plastic and pulp. With the introduction of digital transmission techniques, there has been an increasing demand for improved cable quality, thereby stimulating an investigation of the insulating process in order to improve quality. The increasing availability of digital computers enabled mathematical models of the insulating process to be constructed, which together with experimental work, provided a basis for the installation of computerized control systems. This paper reviews three such models which were developed and are being used. These comprise a model for screw extrusion, a model for melt flow in the wire coating die, and a model for the subsequent cooling of the insulated wire (or cable). Relatively little work was done in the area of dynamic simulation of the insulating process and we found computer control systems could be relatively easily installed in production provided high level software process modules with interfaces to a high level programming language were available on the system. It was found that simplified control schemes were usually the most effective in production. Two computer control installations to illustrate this viewpoint are described—a multiline central computerized control system, and a single‐line microprocessor‐based system.
A study in injection molding dynamics
Authors: Kamal M. R. , Patterson W. Ian , Fara D. Abu , Haber A.
Published: December 2004

Some aspects of injection‐molding dynamics were studied using a laboratory injection‐molding machine operated under the control of a microprocessor‐based servocontrol system. Two types of experiments were performed: deterministic tests which introduced step changes in the servovalve opening and stochastic tests using pseudo‐random binary sequence (PRBS) perturbations of the servovalve. Deterministic models were written for the hydraulic and nozzle pressures which were in good agreement with the experimental data. A stochastic transfer function‐noise model was obtained for the nozzle pressure, but an adequate model was not found for the hydraulic pressure. The agreement between the nozzle pressure stochastic model and the corresponding step test model was satisfactory.
Statistical thermodynamics of blends: Equation of state and phase relations
Authors: Simha Robert , Jain R. K.
Published: December 2004

We 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

In 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

An 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

Poly(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

Ultra‐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

Deterministic 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

A 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

The 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

Studies 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

This 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

Dicyanate 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

Sequential 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

The 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

Properties 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

This 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

Interest 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

This 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

This 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

Blends 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

This 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

The 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

Poly(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).
Oriented structure formation during polymer film extrusion
Authors: Sakellarides S. L. , McHugh A. J.
Published: December 2004

An experimental technique is described for producing fiberreinforced polymer films by inserting needle‐like obstructions in a film‐extrusion die. The, needles act as nucleation sites, generating a highly extensional local flow field, which causes sufficient orientation to induce the formation of oriented fibrillar crystallites embedded in a much less oriented matrix. To study the effectiveness of the above technique, linear low density polyethylene (LLDPE) and blends of linear low density with high density polyethylene (HDPE) were extruded through a film die with converging walls, with one or five needles inserted parallel to the extrusion direction, Microscopy observations, birefringence, and differential scanning calorimetry (DSC) measurements performed on the produced films showed in all cases that the presence of the needle induced the formation of a more oriented phase, which in most cases had a birefringence at least an order of magnitude higher than the film matrix. The best results were obtained in the case when blends of HDPE and LLDPE were extruded. The oriented structures obtained in this case consisted of HDPE and exhibited not only high birefringence but melting point elevation as well, indicating their fibrous nature.
Characterization of crystallinity, orientation, and mechanical properties in biaxially stretched poly(p‐phenylene sulfide) films
Authors: Maemura Eiji , Cakmak Mukerrem , White James L.
Published: December 2004

In this paper, we describe the preparation and structural characterization of biaxially oriented poly(p‐phenylene sulfide) (PPS) films. These films were prepared in a biaxial stretching machine at various stretching temperatures, rates, and stretching ratios. Selected samples were constrained annealed at elevated temperatures. The state of orientation was determined by wide angle X‐ray diffraction (pole figure determination) and birefringence measurements. The results are expressed in terms of the biaxial orientation functions (ƒ,ƒ). Mechanical properties (tensile modulus, tensile strength, and elongation to break) were obtained as a function of processing conditions and direction in the plane of the films.
The effect of hot drawing on the properties of thermotropic polymer fibers
Authors: Dibenedetto A. T. , Nicolais L. , Amendola E. , Carfagna C. , Nobile M. R.
Published: December 2004

Thermotropic liquid crystal polymers have been modeled as an array of highly ordered polyhedric nematic domains immersed in a less‐ordered, nearly isotropic matrix. A function has been defined that expresses the elastic moduli of drawn fibers as a function of orientation and geometry of the nematic domains. When such a material is hot drawn in extension, the domains orient and elongate to produce an orthotropic fibrous phase. Equations are proposed to relate the elastic moduli of the fibers to the draw ratio and the extrusion conditions. Upon annealing of the hot drawn fibers, shrinkage occurs. It is proposed that the shrinkage is the result of a physical transformation from the fibrous state back to the nematic domain structure present before extrusion and drawing. The Avrami equation is used to describe the nucleation and growth processes controlling the shrinkage at constant annealing temperature. The model is shown to correlate experimental data on the elastic properties and the shrinkage of hot drawn PET/PHB60 liquid crystal polymer with the processing conditions.
Relationship between electron sensitivity and chemical structures of polymers as electron beam resists. VI: Electron sensitivity of various acetalized poly(vinyl alcohol)s
Authors: Oguchi Kiyoshi , Sanui Kohei , Ogata Naoya , Takahashi Yoichi , Nakada Tomihiro
Published: December 2004

Acetalized poly(vinyl alcohol)s which were synthesized from poly(vinyl alcohol) (PVA) and aldehyde or ketone were evaluated as electron beam (EB) resists, in order to investigate the relationship between EB sensitivity and chemical structures of the polymers. It was found that the acetalized PVAs were easily crosslinked by EB exposure. The main mechanism of crosslinking may be radical reaction at acetal group. The sensitivity of the acetalized PVA depended on the structure of the acetal group. Acetalized PVAs synthesized from benzaldehyde, in which the electron attracting group was substituted on the benzene ring and from linear aliphatic aldehyde having a long alkyl chain, had high sensitivity. A high sensitivity of 7.2 × 10−7 C/cm2 was attained when the acetalized PVA synthesized from p‐chloro‐benzaldehyde was used. Acetalized PVAs synthesized from PVA and aldehyde having a cyclic structure had an excellent dry etching durability and were suitable as negative EB resists.
Chemistry of the ternary blends of poly(ethylene terephthalate), bisphenol‐a‐polycarbonate, and polypropylene
Authors: Halder R. S. , Misra A. , Deopura B. L.
Published: December 2004

Poly(ethylene terephthalate) (PET) and bisphenol‐a‐polycarbonate (PC) are known to form a miscible blend whereas ternary blends of PET, PC, and polypropylene (PP) form two phases. This is based on the considerations of various chemical events which may occur in these systems. The role of ester‐carbonate interchange reactions during melt mixing and fabricating is found to be unimportant. Differential scanning calorimetric analysis of the ternary blends shows that there appears to occur an exothermic transition in the heating mode of the instrument. This exothermic event was found to be suppressed considerably by incorporating suitable additives into the system. Degradation reactions studied by thermogravimetric analysis and a dilute solution viscometric technique reveal that there exists some kind of interaction among the components even with the immiscible PP component.
Structure‐Property‐Processing relationships of polyurethane‐polyester interpenetrating polymer networks
Authors: Wang K. J. , Hsu T. Jeffrey , Lee L. James
Published: December 2004

Interpenetrating polymer networks of polyurethane and unsaturated polyester were prepared by reaction injection molding (RIM) and transfer molding. The structures of the molded samples were analyzed by electron microscopy and dynamic mechanical analysis. It was found that polymer morphology and dynamic mechanical properties depend strongly on the molding temperature, reaction rate and reaction sequence. Simplified structure models based on Takayanagi's model and sample morphology can predict the storage modulus reasonably well but not the tanδ.
Pumping characteristics of self‐wiping twin‐screw extruders—A theoretical and experimental study on biopolymer extrusion
Authors: Lai‐Fook R. A. , Senouci A. , Smith A. C. , Isherwood D. P.
Published: December 2004

The flow of Newtonian and non‐Newtonian fluids which obeys a power law relationship between shear stress and shear rate has been modeled in the melt conveying section of a self‐wiping co‐rotating twin‐screw extruder using a finite element analysis of an unwound channel section. Predictions of throughput against pressure gradient are compared with experimentally obtained results for maize grits which is represented as a power law material. Rheological data applicable to extrusion simulation were obtained from capillary rheometry. Comparisons are reasonable with predicted characteristic showing similar behavior.
On the increase of viscoelastic modulus with advancement of reaction of an epoxy resin
Authors: Serrano D. , Harran D.
Published: December 2004

Log G* = f(X) isothermal variation curves were determined at various temperatures for two epoxy‐aromatic amine systems widely used in industry. G* = G′ + jG″ is the viscoelastic modulus, determined by sinusoidal shearing at constant frequency between parallel plates; X represents the degree of reaction, determined by calorimetry. These curves clearly show the phenomena of gelation and glass transition. In the temperature range studied, the value of X at the gel point varies between 0.7 and 0.9 for the DGEBA‐DDS system, and from 0.3 to 0.8 for the TGDDM‐DDS system. These variations reflect a major modification of the reaction mechanism, particularly before the gel point.
Evaluation of surface treatments for glass fibers in composite materials
Authors: Dibenedetto A. T. , Lex P. J.
Published: December 2004

The thermomechanical stability of a number of organosilane surface treatments for glass fibers was evaluated for use in a fiber reinforced epoxy resin. All of the silane coatings were found to improve the tensile strength of E‐glass filaments, particularly at large gauge lengths. A phenylamino silane and an amino silane were particularly effective in this regard. The fiber/matrix interface was evaluated as a function of temperature and after exposure to boiling water using a single‐fiber composite test. All silane coatings transmitted a higher interfacial shear stress than obtained in composites with no coatings, and in all cases the shear stress transmission was considerably higher than would be expected from the yield properties of the resin. Measurements of the glass transition temperature of the epoxy resin, as well as Fourier‐Transform Infra‐Red analysis, indicated modification of resin properties in a zone around the glass fibers. Each of the silane coatings provided more stable thermomechanical properties than those obtained with uncoated glass, at least until the silanes were irreversibly degraded by boiling water. A phenylamino silane provided the most thermally stable properties. Finally, unidirectional E‐glass fiber reinforced laminae were fabricated and the measured values of longitudinal strength were compared favorably to theoretical predictions.
Surface structure, topology, and liquid wetting behavior in oriented polymers
Authors: Sung N. H. , Lee H. Y. , Yuan P. , Sung C. S. P.
Published: December 2004

The structure and the properties of oriented polymer surfaces were studied for three series of uniaxially oriented films of polypropylene (PP), polystyrene (PS), and poly(ethylene terephthalate) (PET). The surface structure was characterized in terms of relative crystallinity and molecular orientation along with topology and roughness by using FT‐IR‐ATR dichroism technique, optical microscopy and surface profilometer. In all three polymers, the surface orientation function increases with draw ratio. The relative surface crystallinity and the trans con‐former also increases for PP and PET, respectively. In uniaxially drawn PP, the surface becomes rough with increasing draw ratio and the roughness is anisotropic with peaks and valleys elongated along the draw direction. For drawn PP, the equilibrium contact angles for four different liquids all exhibit anisotropy with higher values in perpendicular direction than that in parallel to the draw direction. In contrast, both drawn PET and PS films show smooth surfaces, and the equilibrium contact angles were all isotropic. When roughness is removed from the drawn PP by polishing without altering the molecular orientation, the anisotropy becomes negligible and the contact angles approach the value for undrawn PP. When surface roughness was created deliberately on undrawn PET and PS films, the contact angle anisotropy was clearly observed. Therefore, the anisotropy in surface topology rather than the molecular orientation seems to play a dominant role in developing anisotropic wetting behavior. The equilibrium contact angles for smooth surfaces have been calculated using the experimentally obtained roughness and anisotropic contact angle data from the rough surface. These values are in reasonable agreement with the measured contact angles for smooth surfaces, suggesting that the observed contact angle anisotropy can be attributed entirely to the roughness anisotropy rather than to the molecular orientation.
Elastomeric latex domain‐interpenetrating polymer networks: Physical and rheological properties
Authors: Silverstein M. S. , Narkis M.
Published: December 2004

The combination of rubbery and rigid polymers in a multiphase structure using staged emulsion polymerization has yielded materials with properties ranging from reinforced elastomers to high impact plastics. The many different particle morphologies that result from a two‐stage latex (TSL) polymerization include core/shell, domain, interpenetrating polymer networks (IPN), and various combinations thereof. The sequence of polymerization, crosslinking, grafting, and composition are among the significant parameters that determine the particle morphology. Elastomeric TSL with soft polyacrylates (PA) as the seed particles and polystyrene (PS) as the second stage, with each stage lightly crosslinked, may yield IPN‐microdomain particles.

The particle morphology has been elucidated through a combination of microscopy and mechanical property analyses. The significant modulus of elastomeric latex interpenetrating polymer networks (LIPN) results from reinforcement by PS intra‐particle microdomains and their significant tensile strength from a strength forming mechanism of PS inter‐particle microdomains. The increase in the PA seed crosslinking increases the crosslinked PS (xPS) level of molecular mixing with, and grafting via residual unsaturation to, the crosslinked PA (xPA) network and decreases particle deformnability. At higher xPS concentrations the formation of an xPS‐rich shell enhances xPS continuity in the molded material through the partial coalescence of the shells, diminishing the PA continuity, and yielding more PS‐like properties.

The submicron lightly crosslinked latex particles with these different morphologies flow as a pseudoplastie material through a particle slippage flow mechanism exhibiting neither a Newtonian plateau nor a yield stress at low shear rates. The deformable lightly crosslinked particles with interchangeable PS ties which disintegrate at elevated temperatures retain their identity and regain their shape at the cessation of shear. The LIPN can be processed using standard thermoplastic methods and machinery, with power law constants and shear insensitive flow activation energies that are similar to those of thermoplastics at high levels of shear. Uncrosslinked PS shells around crosslinked PA seed particles, on the other hand, completely coalesce upon molding to form a continuous thermoplastic PS matrix that may essentially flow through molecular deformation.
Positive excimer laser resists prepared with aliphatic diazoketones
Authors: Sugiyama Hisashi , Ebata Keisuke , Mizushima Akiko , Nate Kazuo
Published: December 2004

A new class of alkali‐developable positive excimer laser (KrF) resists is described. Novel α‐diazoacetoacetates derived from aliphatic polyfunctional alcohols were synthesized. These compounds undergo photolysis upon deep UV exposure to yield carboxylic acids, and exhibit excellent bleaching effects. Some of them, especially those having steroid skeletons, act as effective dissolution inhibitors. The composites prepared from these compounds and poly(p‐hydroxybenzylsilsesquioxane) were used as alkali‐developable positive deep UV resists, whose sensitivities depend on the number of photoactive groups in one photoactive molecule. Imaging results of KrF excimer laser projection printing are presented.
Polysilanes: Photochemistry and deep UV lithography
Authors: Miller R. D. , Wallraff G. , Clecak N. , Sooriyakumaran R. , Michl J. , Karatsu T. , McKinley A. J. , Klingensmith K. A. , Downing J.
Published: December 2004

The photochemistry of poly(cyclohexylmethylsilane) (PCHMS) has been studied, and PCHMS homopolymer has been shown to be useful for high resolution, deep UV pattern generation either by using a commercial 1:1 projection printer operating in the deep UV or by an excimer laser stepper at 248 nm. In the case of the excimer laser stepper, images 0.5 μm and smaller have been printed, which represents an improvement over the 0.8 μm limit previously reported for polysilane copolymers.
A new contrast enhanced lithography (cel) process using “chinese rosin” as a binder
Authors: Tomo Yoichi , Jinbo Hideyuki , Yamashita Yoshio , Ohno Seigo , Asano Takateru , Nishibu Satoshi , Umehara Hiroshi
Published: December 2004

A new contrast enhanced lithography (CEL) process using Chinese rosin as a binder is described. This binder is soluble in both non‐polar organic solvent and aqueous alkaline solution. Good coatability with organic solvent, no formation of mixing layer, and direct development without removing the CEL layer are the major advantages of this process. Among the three different kinds of photobleachable dyes, DZ‐2 (diazonium salt) has the best optical property and the resist profile is improved on g‐line reduction projection printing at the smallest dose. Moreover, this DZ‐2—Chinese rosin system is also effective at 365 nm, and the resist profile and the focus margin are improved on i‐line reduction projection printing by using this system.