bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase continuity and inversion in polymer blends and simultaneous interpenetrating networks
Authors: Jordhamo G. M. , Manson J. A. , Sperling L. H.
Published: December 2004

A semi‐empirical expression for predicting phase continuity and inversion in polymer blends and simultaneous interpenetrating networks (SINs) was developed and examined experimentally. A rheological model based on the volume fraction, ϕ, and viscosity, η, led to the equation

as the criteria for dual phase continuity for phases 1 and 2. This relation was evaluated for two systems: a castor oil polyester‐urethane/polystyrene SIN, and a mechanical blend of polystyrene and polybutadiene. Literature data was also examined. A gradual phase inversion was found, with a region of dual phase continuity in between. While predictions of phase continuity were confirmed for the mechanical blends, they were not confirmed for the SIN system. This was probably due to rapid gelation at the point of phase inversion.
The kinetics of the in situ polymerization of glycidyl methacrylate in wood using dynamic mechanical measurements
Authors: Balaba W. M. , Subramanian R. V.
Published: December 2004

The in situ polymerization of glycidyl methacrylate in wood, in the presence of uranyl nitrate, (UN), and/or 2,2′‐azo‐bis‐isobutyronitrile, (AIBN), has been investigated in the temperature range 55°‐72°C. The course of the polymerization reaction was followed by measurement of tan 5 in an automated Rheovibron viscoelastometer. The kinetics, studied by applying the Guggenheim method to the data, showed the polymerization to be first order whether catalyzed by UN or initiated by AIBN. The activation energy (Eα) for AIBN‐initiated polymerization was 121 kJ/mol, and was unaffected by varying monomer concentration in acetone. On the other hand, Eα for the UN‐catalyzed polymerization was found to be 59.1 and 73.5 kJ/mol respectively for the neat and 50 percent monomer concentration reaction mixture. The enhancement in Eα is attributed to the complexatton of the dioxouranium (VI) ion in the presence of solvent acetone, with consequent reduction in catalytic activity.
Dimensional stability of polystyrene/polymeric liquid crystal blends
Authors: Apicella A. , Iannelli P. , Nicodemo L. , Nicolais L. , Roviello A. , Sirigu A.
Published: December 2004

Recovery experiments above Tg have been performed on polymeric liquid crystal (PLC) ‐ polystyrene (PS) blend sheets obtained from extrusion and subsequent hot drawing. The data reported show that a significant improvement of the dimensional stability of a drawn thermoplastic material can be obtained by adding a low percentage of non‐compatible polymeric liquid crystals that are oriented during the hot drawing process. The fibrils formed act as a constraint for a certain amount of polymer surrounding them and consequently these highly oriented sheets, once exposed to high temperature, will mainly stress relax and do not creep. This effect disappears when the melting temperature of the oriented crystalline phase is reached. Compatible PLC‐PS blends do not show any improvement on the dimensional stability compared to the unfilled matrix.
Multiple crazing at crack tips in PVC under plane strain conditions
Authors: Lee L. H. , Mandell J. F. , Mc Garry F. J.
Published: December 2004

The nature of the yield zone at the crack tip of poly(vinyl chloride) (PVC) pipe materials has been investigated. Microscopy studies employing a plasma etching technique reveal the presence of multiple crazes ahead of the crack tip in the interior of specimens of pure PVC, CaCO3 filled PVC, and PVC pipe compound. The craze zone and the fracture toughness of blade‐notched specimens are compared with those of fatigue pre‐cracked specimens. Both types of specimens have similar fracture toughness values and form multiple crazes upon loading, suggesting that multiple crazing Is an intrinsic property of the material. The kinetics of craze initiation and the development of the multiple craze zones have also been explored.
An injection molding study. Part I: Melt and barrel temperature dynamics
Authors: Kamal M. R. , Patterson W. I. , Gomes V. G.
Published: December 2004

The dynamics of the key variables in the plastication phase of injection molding were studied using a microcomputer controlled laboratory scale injection molding machine. Interfaces for the measurement and manipulation of suitable variables were developed. An approximate theoretical analysis provided a preliminary understanding of the effect of a step input in heating power on melt and barrel temperatures. Deterministic and stochastic models were derived from experimental data for the melt and the front and rear zone barrel temperatures with heater power manipulation. Experiments were performed for evaluating the effects of back pressure manipulation, heating zone interaction, and process disturbances on the melt and barrel temperatures. Experiments showed that it is desirable to directly control the melt temperature rather than the barrel temperatures.
An injection molding study. Part II: Evaluation of alternative control strategies for melt temperature
Authors: Gomes V. G. , Patterson W. I. , Kamal M. K.
Published: December 2004

Melt temperature is a key variable of the injection molding process. The evaluation of different control strategies for the melt temperature was based on the process dynamics presented in Part I of this work. The controllers tested were: PID (proportional‐integral‐derivative) control of barrel temperatures, direct PID control of melt temperature, Dahlin control, and Smith Predictor control of melt temperature. The controllers were tuned by simulation studies and were evaluated by a comparison of performance indices. The controller responses obtained through experiments were evaluated by comparing the rise time, peak overshoot, damping, settling time, and control effort. Analyses were performed to ascertain the sensitivity characteristics of the controllers.
Boundary conditions in the modeling of injection mold‐filling of thin cavities
Authors: Soh Sung Kuk , Chang Chin Jui
Published: December 2004

A governing equation for injection mold‐filling of thin cavities with a power‐law fluid is derived. The interaction between upstream delivery channel flow and cavity flow results in a continuously changing gate condition as the total viscous dissipation of the delivery channel‐cavity assembly is minimized. Depending upon the relative magnitude of pressure drops or viscous dissipation across the channel and the cavity, the boundary conditions which determine the cavity filling process will lie between the following two limiting cases: a Cauchy type gate condition such that the location of the melt front is completely determined by the upstream flow; a Cauchy type melt front condition in which the gate condition is controlled by the downstream flow. For most injection molding cases this may be manifested as equilibration of dissipation density on the melt front. Experimentally observed melt front locations from isothermal, Newtonian filling of a constant gap rectangular cavity and of a bi‐gap rectangular cavity are reported and the validity of the limiting cases are tested.
Adhesion and the surface behavior of the silicone elastomer RTV‐142
Authors: Bretzlaff R. S. , Freitag T. A. , Lee Andréa
Published: December 2004

The silicone elastomer RTV‐142 is often used as a particle‐getter material inside electronics packages. The adhesion mechanism that forms the bond between the particle and the cured adhesive has been investigated. One expects, theoretically, that polymer chains exhibit a temperature‐dependent mobility. This is consistent with the hypothesis that the flow of polymer chain segments around asperities on the foreign particles causes adhesion. Calculations of the surface energy of an idealized polymer system are presented which support the concept of a free‐energetically driven flow of chain segments into pores and around asperities. Polymer surface‐chain mobility is investigated experimentally by the scanning electron microscope analysis of a fractured, cut, and particle‐decorated surface. Surface appearance changes were noted as a function of temperature. Scanning electron micrographs indicate that polymer chain movement is temperature dependent. Such findings support the proposed adhesion mechanism.
Rheological and mechanical properties of poly(vinyl chloride)/chlorinated poly(vinyl chloride) miscible blends
Authors: Lehr Marvin H.
Published: December 2004

The properties of poly(vinyl chlorlde)/ehlorinated poly(vinyl chloride) (61.6 percent C1) blends, prepared by melt and solution blending, were measured by various tests. Based on the chlorinated poly(vinyl chloride) (CPVC) composition, percent chlorine, and mole percent CC12 groups, these blends were expected to show intermediate properties between miscible and immiscible systems. Indicative of miscible behavior were the single glass transition temperatures over the entire composition range for both melt and solution blended mixtures. A single phase was also indicated by transmission electron microscopy. However, the yield stress showed a minimum value less than either of the pure components in the 50 to 75 percent CPVC range, which is characteristic of two‐phased systems. Specific volume, glass transition temperature, and heat distortion temperature were linear with binary composition. The storage modulus showed a small maximum, suggesting a weak interaction between the two miscible polymers. Heats of melting for the residual PVC crystallinity were also less than expected from linear additivity. At 160°C and 210°C, the logarithm of the complex viscosity was essentially linear with volume fraction of CPVC, except for a very slight decrease in the 50 to 75 percent CPVC range, which may have been a result of lower crystallinity. At 140°C, the complex viscosity of the CPVC was less than that of PVC owing to the higher crystallinity of the latter. The viscosities were similar at 160°C, but at 210°C, where most of the crystallites had melted, the complex viscosity of the CPVC was higher because of its higher glass transition temperature.
Power consumption of partially filled twin‐screw extruders
Authors: Secor R. M.
Published: December 2004

Twin‐screw extruders are used very effectively, when partially filled, for mixing and surface renewal of high‐viscosity fluids. The rate of energy input, often sufficiently high to be a major design consideration, determines the drive power, the heat input to the fluid, and the cooling requirements. Operating limitations may be fixed by thermal degradation of the material being processed. A simple model for the rate of energy dissipation in twin‐screw extruders predicts that the power input is proportional to the square of the screw speed. Measurements were made of shaft torque and screw speed for polyisobutylene passing through a large twin‐screw extruder having co‐rotating shafts. The experimental procedure avoids the problems of changes in holdup and temperature that accompany changes in screw speed under steady state conditions. The power input was found to be proportional to the screw speed raised to the exponent 1.90. This result was attributed to slightly pseudoplastic behavior of the fluid in the radial clearances.
Optimization of nonvaporizing nylon 6 reactors with stopping conditions and end‐point constraints
Authors: Ray Ajay K. , Gupta Santosh K.
Published: December 2004

In this study, optimal temperature profiles (or histories),T(t), are obtained for nonvaporizing plug‐flow (or batch) Nylon 6 reactors using the minimum principle. Two objective functions are studied, one in which the monomer conversion, convtf, is maximized, and the other in which the undesirable side product (cyclic dimer) concentration in the output stream, [C2]tf, is minimized. The control variable, temperature, is constrained to lie between 220°C and 270°C in order to ensure single phase polymerization. The most significant difference between this study and earlier ones is that the residence (or reaction), time tf, is not specified a priori, but is determined optimally by the use of a ‘stopping’ condition such that the polymer product has a number‐average chain length, μn, equal to some desired value μn.d. Simultaneously, an end‐point constraint is used, which, depending on the objective function used, forces either the cyclic dimer concentration or the monomer conversion at the end of the reactor to lie at a specified value, [C2]d or convd. Thus, this algorithm incorporates stopping conditions as well as end‐point constraints and so is more complex than earlier ones, but the results are more meaningful. Different nonisothermal optimal temperature profiles are obtained for the two objective functions studied, depending on the values of μn.d, convd, [C2]d, and the feed water concentration, representing the complex interplay of several opposing factors.
A negative resist, LMR (low molecular weight resist), for deep UV lithography
Authors: Itoh Toshio , Yamashita Yoshio , Kawazu Ryuji , Kawamura Kazutami , Ohno Seigo , Asano Takateru , Kobayashi Kenji , Nagamatsu Gentaro
Published: December 2004

A negative deep UV resist, LMR, has been developed. LMR is a diazonaphthoquinonesulfonate of cresol novolac resin and possesses a high sensitivity of 15 mJ/cm2 and a high resolution up to 0.2 μm by contact printing. An important feature of LMR is the production of negative images with overhung profiles. Such profiles are attributed to LMR possessing a large absorbance in the deep UV region (12 μm−1 at 250 nm), which is of great advantage to the lift‐off process in the fabrication of GaAs‐FET, surface acoustic wave (SAW) devices, and so on. Furthermore, because of the good thermal stability of LMR, it can liftoff hard metals such as Ni and Mo. In order to elucidate the phenomenon that deep UV irradiation retards the dissolution rate of LMR, a mechanistic study has been carried out. In both LMR and its analog lacking diazoquinone moiety, their molecular weights Increase upon deep UV irradiation, which suggests that crosslinking occurs in the base resin. This is supported by 13C NMR analyses of photochemical reaction products and by detection of radical species produced from the base resin. The photochemical reaction of the base resin is important to understand the overall lithographic performance of LMR.
Spun‐On contour coating characterizations for advanced optical lithography
Authors: White L. K.
Published: December 2004

Spun‐on contour coating properties are characterized for two absorptive undercoats, AUCs, and a contrast‐enhanced layer, CEM‐388. A low‐pass frequency filter contour modeling procedure is used to simulate the coating contours on a real silicon‐on‐sapphire epi‐island layout. The computed thickness variations are used to estimate the variation in optical densities of these spun‐on films on the topography. The variations in optical densities arc discussed in terms of the expected dimensional deviations introduced into the patterned resist layer. At the same spun‐on thickness, one absorptive undercoat offers improvement in dimensional control when compared to the other. Changes in the thickness of the CEM‐388 layer may also introduce significant dimensional deviations in the underlying positive resist layer. In, both cases the more conformal spun‐on contour coating properties produce improved resist imaging.
Excimer laser projection patterning with and without resists
Authors: Ehrlich D. J.
Published: December 2004

Projection imaging with the deep‐UV (193 nm) and VUV (157 nm) output of an excimer laser has been applied to submicrometer patterning of thin films by injected‐defect, surface‐chemical, and solid‐transformation processing. The methods have been designed to take advantage of the short‐wavelength, high‐peak‐intensity pulsed radiation from these sources. Examples are described of pattern definition by exposure of multilayer organic resists, by maskless etching and doping of solids in reactive vapors, and by solid‐state chemical transformations in inorganic Al/0 films. Well‐resolved 0.4‐μm lines and spaces have been achieved. Required doses, between 0.04 and 1 J/cm2, are compatible with single‐ or multi‐pulse step‐and‐repeat projection patterning with a small excimer laser.
Dry developable resist in e‐beam and sr lithography
Authors: Tsuda Minoru , Oikawa Setsuko , Yabuta Mitsuo , Yokota Akira , Nakane Hisashi , Atoda Nobufumi , Hoh Koichiro , Gamo Kenjj , Namba Susumu
Published: December 2004

Dry developable resists comprised of poly(methyl isopropenyl ketone) (PMIPK) and 4‐methyl‐2,6‐dI‐(4′‐azldoben‐zylidene)‐cyclohexanone‐1 gave excellent results in SK lithography, i. e., high aspect ratio resist patterns with vertical walls were easily obtained by maskless dry etching in the single layer resist process. Because of the simplicity of single layer resist processing and the high etch rate in maskless dry etching for the formation of thick resist patterns, the dry developable resist in SR lithography may be advantageous to the multilayer resist for the purpose of generating high resolution, thick resist patterns with vertical walls. The resolution limit of the dry developable resist which reproduces the designed dimensions was 100 nm line and 200 nm space when a conventional e‐beam apparatus was used at 20 KV in the dry developable multilayer resist process.
Synchrotron lithography: The way to sub‐micron features with single layer resists
Authors: Huber H.‐L. , Betz H. , Heuberger A.
Published: December 2004

Soft X‐ray radiation is affected neither by scattering in the resist nor by reflection from the substrate surface, so that a one‐layer resist system can be maintained even in the sub‐micron range. This holds primarily for the parallel synchrotron radiation avoiding all the geometrical distortions connected with X‐ray tubes and even plasma sources. It has been shown that a minimum feature size of 0.2 μm can be achieved in this case. Different resist systems applicable in X‐ray lithography have been tested regarding resolution, sensitivity, and etch stability. The optical resists Kodak ‘HPR 204’ shows very high process stability, good resolution, but low sensitivity. It is, therefore, suitable for an X‐ray pilot process but not for high throughput production. The high sensitive X‐ray resist TBM 120′ a fluorized poly(methyl methacrylate) which shows originally a very poor etch stability can be stabilized by post exposure with synchrotron radiation.
Solute diffusion in swollen membranes. Part V: Solute diffusion in poly(2‐hydroxyethyl methacrylate)
Authors: Moynihan Humphrey J. , Honey Martha S. , Peppas Nikolaos A.
Published: December 2004

Studies with phenylalanine diffusing in well‐characterized poly(2‐hydroxyethyl methacrylate) (PHEMA) membranes swollen in water at 37°C were conducted. Films were prepared by reaction of HEMA monomer with the cross‐linking agent ethylene glycol dimethacrylate (EGDMA) at cross‐linking ratios, X, of 0.005, 0.01, 0.0128, 0.025, and 0.050 mole EGDMA/mole HEMA in the presence of 40 weight percent water at 60°C for 12 hours. These membranes were subsequently swollen in water at 37°C and their structure analyzed using a modified Gaussian distribution equation of swelling. The calculated values of M̄c varied between 1,700 and 3,425 daltons, which corresponded to a correlation length of the mesh size, egr, of 24 to 35 A. The phenylalanine solute diffusion coefficient varied from 0.17 × 10−6 to 0.97 × 10−6 cm2/s, and depended on the aforementioned structural parameters of the membranes.
Notes on chlorinated polyethylene: Its preparation, some mechanical and thermal properties
Authors: Akovali G. , Vatansever A.
Published: December 2004

Low density polyethylene was chlorinated via a mixed solution‐suspension technique at three different temperatures. The products obtained at different conditions had properties ranging from hard brittle to tough elastomeric consistencies. Static mechanical, chemical, and thermal characterization of the products were made and the possibility of two different crystal structures is pointed out, one of which is consumed preferentially during chlorination.
A computer interface for the fabrication and testing of surfactant films
Authors: O'Brien Kevin C. , Lando Jerome B.
Published: December 2004

A computer interface was developed for a commercially available film balance to aid in the fabrication and characterization of surfactant films spread on water substrates. The interface is compatible with other commercially available systems, easily programmable, and able to perform a variety of tasks. This interface aided in following chemical reactions which occurred in the films, describing the morphology of the films, monitoring the process of film deposition, and also studying the mechanical properties of the films.
Thermal stability and compatibility of polyetheretherketone (PEEK) with an oxidizer and pyrotechnic blend
Authors: Moddeman W. E. , Bowling W. C. , Tibbitts E. E. , Whitaker R. B.
Published: December 2004

Polyetheretherketone (PEEK) is a relatively new high temperature engineering thermoplastic. The stability of neat and fiberglass reinforced PEEK towards air, KClO4, and TiH1.65/KClO4 blend was studied by the surface sensitive technique of X‐ray photoelectron spectroscopy (XPS) and bulk technique of thermogravimetric (TG) analysis. Both of these examinations revealed no oxidation in the presence of air or KClO4 at temperatures of 60 or 120°C. In addition, no reduction of PEEK was observed in the presence of a reducing agent such as TiH1.65. The TG results also showed no air oxidation between 120 and 500°C.
Liquid sorption in a segmented polyurethane elastomer
Authors: Schneider N. S. , Illinger J. L. , Cleaves M. A.
Published: December 2004

The sorption and diffusion of a series of liquids in a segmented polyurethane have been studied to determine how the behavior is affected by the choice of solvent and the heterophase nature of the polymer. The polyurethane was composed of methylene‐di‐para‐phenylene isocyanate (MDI) butanediol, and poly(tetramethylene oxide) (1000) with a mole ratio 3:2:1. Immersion experiments in n‐heptane liquid, a poor solvent, and incremental sorption experiments in n‐heptane vapor showed normal Fickian havior. In the set of liquids of increasing polarity, which included 1‐chloroheptane, three dichloroalkanes and orthodichlorobenzene, the swelling increased to very high levels. Effective values of the molecular weight between crosslinks computed from the Flory Rhener equation, assuming complete phase segregation, varied widely with the different liquids. Agreement could be improved by allowing 30 percent mixing of hard segments with the soft segment phase. The sorption and desorption curves for the highly swelling liquids showed various anomalies some of which might be the result of solvent induced relaxation of hard segment domains.
The numerical simulation of boger fluids: A viscometric approximation approach
Authors: Mitsoulis E.
Published: December 2004

A general‐purpose finite element program has been used to simulate the flow of nonshear‐thinning, highly elastic polymer solutions (Boger fluids). In particular, the creeping flow through an abrupt 4:1 circular and planar contraction is studied, as well as the flow at the exit of a capillary die for the determination of extrudate swell. Experimentally measured normal stress and viscosity data are included in a simple rheological model, based on the viscometric simplification of the CEF constitutive equation. Vortex size and intensity in the die entry and extrudate swell at the die exit increase rapidly, with elasticity level, in general agreement with experimental findings. It is shown that despite the limitations of the model, the viscometric approximation can be used to study the effect of normal stresses in cases where a main flow direction can unambiguously be defined. In die exit Flows, it can also provide an upper limit for the determination of extrudate swell, while Tanner's theory of elastic recovery provides the lower limit.
Monitoring the initial phase of a slow curing epoxy through the dynamic viscoelastic properties
Authors: Ganani Ehud , Higgins Brian G. , Powell Robert L.
Published: December 2004

The isothermal curing of an epoxy mixture of diglycidyl ether of bisphenol‐A and diglycidyl ether of 1,4 butanediol was monitored through the dynamic viscoelastic properties. Measurements were made at a frequency of 37.7 s−1 using a Weissenberg Rheogoniometer Model R‐17 fitted with a piezoelectric load cell and interfaced with a microcomputer. Cures were conducted at four temperatures, 15.6 ± 0.2°C to 40.1 ± 0.2°C with the cure time varying from 35 to 11 hours, respectively. Additional measurements of the steady shear viscosity, up to three hours after cure initiation, were conducted using a Weissenberg Rheogoniometer Model R20. These results show that in the early stages of the cure cycle, the fluids show low elasticity and constant viscosity. Also, independent of temperature, the relationship, η′ = 0.05 η″, holds, although it is not maintained near the gel point. This implies that initially, the longest relaxation time is independent of the extent of reaction and the temperature.
The viscoelastic and aging characteristics of polymers
Authors: Feng William W.
Published: December 2004

The time dependent mechanical properties for incompressible polymer‐like materials subjected to finite simple extension are studied. There are two parts: the viscoelastic effects and the aging characteristics. The constitutive equation developed by Christensen for finite deformation viscoelasticity is used. With two new material properties, the constitutive equation is extended to include the aging effects. An experiment is performed, and a method for determining these mechanical properties is presented in detail.
Biaxially stretched in comparison with conventionally blown coextruded composite plastic films
Authors: Siegmann A. , Nir Y.
Published: December 2004

Multilayer composite films consisting of polyolefins, either polypropylene, linear low density or medium density polyethylene, a thin adhesive layer, and a polyamide in various ratios were prepared using two basically different processes. The first, a conventional blown film process in which the extrudate is stretched while in the molten state; and the second, a two‐stage process in which the quenched extrudate is stretched at a temperature below the polymers' melting point. The films so prepared, having identical composition and similar extents of stretching, were compared on the basis of their tensile properties, thermoelastic shrinkage, oxygen transmission rate, and thermal behavior. The effects of stretching temperature, rate, and extent on the behavior of the composite films and control single layer films were investigated. The stretching temperature was found to be the dominating single process parameter in determining the films' behavior. The overall performance including tensile properties, barrier, and shrink properties of the “cold” stretched films was found markedly superior to that of the conventionally blown films. The stretched composite films possess physical properties that cannot be attained by the conventional process.
Polyurethane elastomers containing polybutadiene and aliphatic diols: Polymerization and structure
Authors: Cohen D. , Siegmann A. , Narkis M.
Published: December 2004

The effect of aliphatic diols on the polymerization and network formation of polyurethane elastomers containing hydroxyl terminated polybutadiene and three different diisocyanates was studied. The polymerization/curing progress was followed by viscosity measurements, IR spectroscopy, swelling, extraction, and hardness measurements. The resulting networks were characterized by swelling experiments. The type of diisocyanate and the diol chain length were found to have significant effects on the reacting mixtures throughout the polymerization course. The effects observed included the phase structure of the reacting mixtures, the reaction rate, the crosslink density, and the physical interactions.
The simulation of phase diagrams for polymer blends at various pressures
Authors: Rostami Shamsedin , Walsh David J.
Published: December 2004

A procedure is described for the simultaneous prediction of the binodal and spinodal curves of polymer mixtures at various pressures using a form of the equation‐of‐state theory of Flory and co‐workers. The results of the calculation are compared with experimental results for the effect of pressure on the cloud points of both oligomer mixtures showing upper critical behavior and polymer mixtures showing lower critical behavior. The procedure successfully predicts the sign of the effect and its magnitude within the experimental and theoretical uncertainties for the systems studied.
Linear low density polyethylenes and their blends: Part 3. Extensional flow of LLDPE's
Authors: Schlund B. , Utracki L. A.
Published: December 2004

The uniaxial extensional flow at 150°C of 11 linear low density polyethylenes (LLDPE) and one low density polyethylene was measured in a Rheometrics Extensional Rheometer. The presence of silicone oil did not affect the results. However, large effects of the molding time were observed. For specimens molded for 14 min, strain hardening was not observed for any gas‐phase polymerized LLDPE. As the molding time was increased to 40 min, the strain hardening was quite apparent, the elongational viscosity nearly doubled, the equilibrium plateau vanished, and the maximum strain at break Increased by about 20 percent. Explanation for the molding time effects can be found in the concept of low entanglement density in the virgin gas‐phase resins. The entanglement increases with time at temperatures above the melting point. The specimens molded for longer time show strain hardening.
The melt rheology of chloro‐polyether and polyepichlorohydrin blends
Authors: Liming Lu , Kebin Li , Shijin Li
Published: December 2004

The melt rheological behavior of chloro‐polyether and polyepichlorohydrin blends was studied. It was found that both the coupled and uncoupled blends at different blending ratios are pseudoplastic, but there was a great difference in pseudoplastic behavior between them. All the blends obeyed the principles of temperature superposition and composition superposition for plots of shear stress vs. shear rate. A model is proposed to describe and predict the rheological behavior of the blends.
Molecular entanglement for rigid rod molecular composites: Poly(p‐phenylene‐2,6‐benzbisthiazole)/poly(hexamethylene adipamide)
Authors: Wiff Donald R. , Timms S. , Helminiak Thaddeus E. , Hwang Wen‐Fang
Published: December 2004

The entanglement molecular weight necessary for integrity of processed fiber and film for rigid rod molecular composites is discussed. The case presented is one where the matrix flexible coil polymer has a marginal molecular weight for entanglement. The molecular weight of the rigid rod reinforcement was increased to offset this deficiency. No significant phase separation was observed for solutions undergoing high shear. Steady state shear measurements on rigid rod molecule solutions show that the zero shear viscosity results agree very well with recent theoretical rigid rod molecule behavior predictions.
Styrene/butyl acrylate copolymerization with layer morphology: Kinetics and viscoelastic properties
Authors: Garcia‐Rejon Andres , Rios L. , Lopez‐Latorre L. A.
Published: December 2004

Styrene/butyl acrylate copolymers with layer morphology were synthesized using an emulsion copolymerization process, The kinetic parameters studied include monomers composition, initiator and transfer agent content, feeding time, and monomer addition sequence. The final product consists of a homopolymer nucleus surrounded by concentric shells of copolymers with different composition; the initial composition is quite rich in the monomer that forms the nucleus while the process ends with an enriched layer of the second homopolymer. Since the middle copolymer layer tends to increase the compatibility among the original homopolyers, we expected to have a set of core‐shell products with completely different properties. However, the experimental results showed that this was not the case. The composition effect on the viscoelastic properties shows, on one hand, that an increase in the butyl acrylate content lowers the elastic response of the final product, and on the other hand, that the elasticity increases with copolymer content. As the initiator content in the reaction media increases, the viscosity of the coreshell products decreases because of the existence of a media flooded with free radicals. If the butyl acrylate is first added, a graft polymerization is favored because of the polar nature of this homopolymer and, therefore, the molecular weight level increases.
The nucleation of microcellular thermoplastic foam with additives: Part II: Experimental results and discussion
Authors: Colton J. S. , Suh N. P.
Published: December 2004

Experiments were performed to validate the model for the nucleation of microcellular foams in amorphous thermoplastic polymers. The polystyrene‐zinc stearate system was chosen as the model system. Other additives such as stearic acid and carbon black were also investigated. Molecular weight and orientation effects were studied. Nitrogen and carbon dioxide were used to produce the microcellular bubbles. Results show that amounts of soluble additives at levels just below their solubility limit and high gas saturation pressures yield the most acceptable foams—ones with a large number of uniform small bubbles. In this region, the bubble number is sensitive to both the gas saturation pressure and the concentration of solutes. Increasing the concentration of soluble additives above the solubility limit has little effect on bubble number and almost eliminates the dependence on saturation pressure. Molecular weight and orientation had no effect on the number of bubbles produced. Similarly, carbon black, which is insoluble in and which bonds well to polystyrene, produced no effect on bubble numbers. The agreement between theoretical predictions and experimental results is reasonably good.
Structural investigations of powder processed poly(phenylene sulfide) blends
Authors: Nadkarni V. M. , Radhakrishnan S.
Published: December 2004

The crystalline structure and morphology have been investigated for powder processed poly(phenylene sulfide) blended with high‐density polyethylene and poly(tetrafluoroethylene). The crystallinity in the former case showed large deviations from those estimated from rule of mixtures, while in the latter blends it closely followed the values predicted from the linear relation for homogeneous mixtures. Pronounced changes in some reflections were found in the X‐ray pattern on thermal curing of the samples. These results have been explained on the basis of compaction behavior of the powder blends together with the orientations induced during the processing steps.
Properties of biaxially oriented Nylon 66 film
Authors: Kohno Mitsuo , Tamemoto Kazuo
Published: December 2004

Biaxially oriented Nylon 66 film has been developed by a new tubular process. The relationship between the structure resulting from the manufacturing conditions and properties have been examined. A key technology of manufacturing is quenching of the melt, because of the high rate of polymer crystallization. The properties of biaxially oriented Nylon 66 film are found to be determined mainly by the degree of polymerization, the molecular and hydrogen bond plane structure, orientation within the film, and the degree of crystallinity. Toughness and high thermal resistance are also properties of this film. Therefore, applications for packaging have been examined, and a “retortable pouch” seems especially promising.
Mechanical properties and permeability of polypropylene and poly(ethylene terephthalate) mixtures
Authors: Bataille P. , Boissé S. , Schreiber H. P.
Published: December 2004

The synthetic membranes currently used for soil stabilization and road construction are mainly made of polypropylene and of polyesters. They are used separately for each application. The polymer used has an effect on the wettability and, the permeability of the membrane. The polypropylene membranes, for instance, have a zero wettability, whereas it is high for polyester membranes. This paper reports on the mechanical properties and the permeability of mixtures of polypropylene (PP) and poly(ethylene terephthalate) (PET). The elastic modulus of the mixture was at a minimum for a 50/50 mixture. For the other compositions, the moduli gave a positive deviation as compared with the additivity equation results. This is probably due to the fact that pure PET has a fragile behavior at the temperature at which the mechanical tests were run. This 50/50 composition corresponds to the domain where a phase inversion occurs. The permeability to water vapor gave an S‐shape curve that is typical of a “mixture” of immiscible polymers. The diffusion of the water molecules is controlled by the continuous phase. To compatibilize the two homopolymers, a 94/6 copolymer of PP and of polyacrylic acid was added, at various levels, to a 60/40 mixture of PET and PP: This did not affect markedly the elastic modulus. The yield stress increased, however, indicating that we had a better adhesion and that the copolymer seems to have a certain emulsifier effect, increasing the quality of the dispersion.
Fracture toughness of urethane‐modified methacrylate resins
Authors: Sterrett Terry , Wong Ray , Kidd Patrick
Published: December 2004

This paper reports the synthesis of a series of urethanetoughened methacrylate resins and evaluation of the fracture toughness (KIC) of these materials. The incorporation of high‐molecular‐weight polyfunctional urethanes produced resins with the best mechanical properties, important to applications as dental biomaterials.
Aliphatic polyurethane elastomers with high performance properties
Authors: Dieter Janice W. , Byrne Catherine A.
Published: December 2004

A new diisocyanate, 1,4‐eyclohexane diisocyanate (CHDI), has been used in a series of polyether‐based polyurethane elastomers. The slightly opaque samples are semicrystalline in nature with high performance properties, including high softening temperature, very good thermal stability, high tensile and tear strengths, excellent solvent resistance, and low hysteresis in compressive fatigue. Polymer properties are in part due to the small, compact, symmetrical structure of the aliphatic CHDI. Comparison of the physical, mechanical, and thermal properties of polyurethanes prepared from the aliphatic diisocyanate 4,4′‐dicyclohexylmethane dilsocyanate (H12MDI) reveal the H12MDI polymers to be more flexible and transparent elastomers with lower softening temperatures and tensile moduli and higher hysteretic heat build up. They are generally soluble in organic solvents.
Morphology in thermally oxidized high density polyethylene pipes
Authors: Gedde U. W. , Jansson J.‐F. , Terselius B.
Published: December 2004

In a continuation of previous work (1), the melting and crystallization behavior of the layered oxidized skin on thermally oxidized inner wall surfaces of different high density polyethylene (HDPE) pipes was studied. By hot stage polarized light microscopy on 5 μm thick cross‐sections of the skin, melting was shown to proceed successively as a front moving inwards as temperature was raised. Analogously, crystallization of the skin layers proceeded with the front advancing outwards towards the skin surface at decreasing temperature. The kinetics were followed and the data was compared with previous DSC thermograms (1) on similar samples. The high temperature melting peak of the oxidized skin reported in earlier DSC‐work (1) is shown to be associated with material with normal spherulitic texture.
Some problems associated with the puncture testing of plastics
Authors: Carapellucci L. M. , Yee A. F. , Nimmer R. P.
Published: December 2004

Glassy polycarbonate specimens with different degrees of aging were tested in puncture for the purpose of determining the ductile/brittle transition temperature in biaxial tension. The results show that increasing amounts of aging increase the transition temperature from −95 to −70°C. All transitions appear too low In temperature. This was confirmed by using strip‐biaxial specimens that become brittle at a significantly higher temperature. In addition to this problem, the load deflection curve also can lead to an overestimation of the load and energy to initiate cracking. A finite element model of the puncture test suggests that the compressive stress under the dart may have shifted the onset of brittleness to much lower temperatures.
Rate process analysis applied to the mechanical behavior of glassy bisphenol‐A‐polycarbonate
Authors: Mattioli Theresa K. , Quesnel David J.
Published: December 2004

The mechanical behavior of bisphenol‐A‐polycarbonate has been studied. The principle mode of deformation studied was fatigue with monotonic tests and stress relaxation tests also performed. Testing was conducted at different strain rates and polycarbonate was found to be a rate sensitive material. In addition, it was found that polycarbonate's data show a good fit to the rate process theory of deformation first proposed by Eyring, whereby molecules move over a potential barrier in an activated process. A hard ball model is presented as a first approximation to this activated process of deformation. Finally, a potential mechanism of deformation during fatigue loading is discussed.
Orientability of liquid crystal polymers in elongational flow
Authors: Kenig S.
Published: December 2004

The orientation development in elongational flow (spinning) of liquid crystal polymers (LCP) has been studied and a physical model derived which relates the modulus development and extensional deformation. The model defines an orientability parameter, λ, which in addition to the total elongational deformation (drawdown ratio) are related to the orientation (modulus) level of the final spun fiber. Five LCPs were included in the study—a lyotropic polymer: Poly (p‐phenylene‐terephthalamide) and four wholly aromatic naphthalene‐containing polyesters. The experimental results have shown good agreement with the proposed model and indicate that λ is independent of the spinneret size and is characteristic of the orientability in elongational flow of each of the polymers investigated.
Small angle and wide angle x‐ray pole figure studies on simultaneous biaxially stretched poly(ethylene terephthalate) (PET) films
Authors: Cakmak Mukerrem , Spruiell Joseph E. , White James L. , Lin J. S.
Published: December 2004

Biaxially oriented poly(ethylene terephthalate) (PET) films have been characterized by small angle and wide angle x‐ray scattering. The films were studied at various rotational angles to the impinging beam and orientations relative to axes in three directions in the film were obtained. Pole figures were developed for both the major small angle scattering peak and wide angle diffraction peaks. These are used to interpret structural changes in the films associated with various degrees of biaxial stretching and subsequent constrained annealing.
The effect of the chemical structure of low‐profile additives on the curing behavior and chemorheology of unsaturated polyester resin
Authors: Lee Dai‐Soo , Dae Han Chang
Published: December 2004

An experimental study was conducted to investigate the effect of the chemical structure of low‐profile additives on the curing behavior and chemorheology of unsaturated polyester resin during isothermal cure. For the study a general‐purpose unsaturated polyester resin was cured in the presence of t‐butyl perbenzoate as Initiator. The curing behavior of the resin was investigated using differential scanning calorimetry (DSC). Three different thermoplastic low‐profile additives were used, namely poly(vinyl acetate) (PVAc), poly(styrene‐co‐butadiene), which is also known as KRATON DX‐1300, and dehydrochlorinated Isobutylene/isoprene copolymer, often referred to as conjugated diene butyl (CDB) rubber. Each of the these additives, about 30 weight percent, was first dissolved in styrene. The solution was then mixed with unsaturated polyester resin and CaCO3. The CaCO3 particles helped stabilize the emulsions consisting of resin and KRATCN, and of resin and CDB. For each resin formulation, a series of isothermal DSC runs were made at various levels of cure pressure. It was found that for all three low‐profile resins investigated, the final degree of cure went through a maximum as cure pressure was increased from atmospheric to 6.21 MPa (900 psi). We have observed evidence that in the presence of an initiator generating free radicals, the unsaturated double bonds in the KRATON and CDB undergo grafting reactions with the styrene monomers and unsaturated polyester resin, increasing the glass transition temperature of KRATON and CDB, to an extent which varies with the cure conditions employed. Both steady and oscillatory shearing flow properties were determined using a cone‐and‐plate rheometer. The rheological measurements indicate that the resin/CaCO3/KRATON and resin/CaCO3/CDB systems give rise to gel times shorter than the resin/CaCO3/PVAc system. It is concluded that both KRATON and CDB are more effective, both for enhancing the rate of cure of unsaturated polyester resin and imparting impact properties to the cured composites, than those thermoplastic low‐profile additives that contain neither unsaturated double bonds nor a chemical structure that has rubber‐like properties in the solid state.
Shear yielding of biaxially oriented styrene‐acrylonitrile copolymer films
Authors: Chau C. C. , Rubens L. C.
Published: December 2004

The shear yielding processes in the deformation of biaxially oriented styrene‐acrylonitrile (SAN) copolymer films (machine oriented with draw ratio = 6.9 in the machine direction and 2.9 in the transverse direction) were studied. In the transverse direction, two sets of shear bands with an intersection angle of about 123.6 degrees (61.8 degrees with the tensile axis) were developed. When necking occurred, the bands in the necked region were thin and discontinuous with an intersection angle of about 81 degrees. In the machine direction, shear bands appeared to be short and diffused with an intersection angle of about 119.2 degrees. Only a slight necking effect was observed. The Luders strain in the transverse direction was about 0.56 and in the machine direction, about 0.16. The shearstrain‐volume of activation obtained from the strain rate dependence of shear stress was about 3440 ± 400 Å3 in the machine direction and 2700 ± 500 Å3 in the transverse direction. The work hardening behavior in both directions seemed to follow a linear relationship between 1n (tensile stress) and tensile strain at large strains. From a consideration of localized shearing toward tensile axis, the fraction of deformed materials was calculated. These observations indicated that (1) a strong orientation hardening effect existed in unbalanced biaxially oriented films, resulting from the difference of the amount of deformable materials between individual directions; and (2) deformation proceeded by shear banding with the high orientation direction involved more correlated molecular segments than the low orientation direction during the activation process.
Prediction of polymer‐filler redistribution in injection molding
Authors: Emerman Steven H.
Published: December 2004

Polymer‐filler redistribution is the process whereby a polymer melt with an initially homogeneous distribution of filler obtains an inhomogeneous distribution upon injection molding. The purpose of this paper is to develop a set of rules for predicting polymer‐filler redistribution. The predictions are based upon experiments on lateral particle migration in pseudoplastic fluids and theoretical calculations on lateral particle migration in second‐order fluids. Predictions are made concerning the existence of a “surface of accumulation,” the dependence of filler concentration on distance from the gate, and the effects of injection time and barrel temperature. The predictions compare favorably with experiments in a dumbbell specimen using polymers Luran 378P and Ultraniid B3, both containing glass beads.