bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of added salt on dynamic viscoelasticity of carboxymethylcellulose aqueous systems
Authors: Matsumoto Takayoshi , Mashiko Kimio
Published: December 2004

Using three series of sodium carboxymethylcellulose (NaCMC) in the range of the degree of substitution (the average number of carboxymethyl groups/glucose unit) from 0.5 to 1.3, weight‐average molecular weight Mw was determined by light scattering in solution of triethylenediamine cadmium hydroxide (cadoxene). It was found that the relation between Mw and the limiting viscosity number [η] in 0.1 N sodium chloride (NaCl) aqueous solution can be represented by Staudinger's equation. Dynamic viscoelasticity of aqueous disperse systems of NaCMC with various added salts was measured by means of a cone‐and‐plate rheometer. If the concentration of added salt is less than the concentration at which polymer begins to salt out, frequency dependence curves of the dynamic modulus, which is measured at various salt concentrations, can be superposed into a master curve by horizontal shift only. The shift factor depends on the salt concentration and the kind of salt.
Engineering analysis of reaction injection molding process of nylon 6
Authors: Lee Kwang Hee , Kim Sung Chul
Published: December 2004

A computer simulation model was established to analyze the reaction injection molding process of nylon 6. A numerical calculation was carried out to predict the temperature, conversion, and crystallinity profile within a disc type mold. The effects of the feed temperature, wall temperature, and overall reaction constant on the eject time were discussed for searching the optimum processing conditions.
Chemorheology of an epoxy resin for pultrusion
Authors: Tajima Yuji A. , Crozier Donald G.
Published: December 2004

The Williams‐Landel‐Ferry (W‐L‐F) equation was shown to describe the temperature dependence of the viscosity of a sulfonium accelerated, amine cured epoxy resin that had been formulated for pultrusion. The reference temperature and the viscosity at the reference temperature of the W‐L‐F equation were found to be simple functions of the resin advancement as determined by isothermal differential scanning calorimetry, A method is described of constructing the baseline for temperature‐programmed differential scanning calorimetry analyses in which the heat capacity is changing due to reaction.
Efficiency of polymer fractionation—A review
Authors: Mencer H. J.
Published: December 2004

With respect to molecular masses, polymers are polydispersive. Since many of their properties depend on the distribution of molecular masses, to study this correlation it is necessary to have samples of narrow molecular mass distribution or samples with accurately defined distribution. In spite of the developmental progress of fast instrumental methods (analytical and preparative gel chromatography) used to determine the molecular mass distribution curve and to obtain higher amounts of fractions of narrow molecular mass distributions, there still exists an interest in classical methods of fractionation. On the basis of a survey of monographs on polymer fractionation, numerous publications and personal experience, this review describes primarily what is an efficient fractionation. Afterwards, factors that affect fractionation efficiency according to the type of effects arc given and causes of their action are described. Conditions under which efficient fractional precipitation and fractional solution methods are applied are considered separately. At the end of the review, criteria on the basis of which fractionation efficiency is evaluated are considered in detail.
Heat transfer effects on the processing‐structure relationships of polyetheretherketone (PEEK) based composites
Authors: Velisaris Chris N. , Seferis James C.
Published: December 2004

An analytical methodology was developed capable of describing interrelations between thermal processing and polymer structure for thermoplastic based composite laminates. Specifically, this modeling methodology was used to describe experimental results generated with a specially designed match die quench mold by processing both neat PEEK polymer and carbon fiber reinforced laminate samples at different cooling rates. The developed model accurately predicted temperature profiles for PEEK laminates of different thicknesses, under normal as well as extreme quenching conditions of 114°C/s. surface cooling rates that are possible to generate with the quench mold. In general, the modeling methodology is capable of predicting a part's thermal profile during processing in terms of the composite's microscopic intrinsic properties (fiber and matrix), composition, and lamina orientation. Furthermore, by coupling to the thermal profile description, a previously developed crystallization kinetics model for PEEK polymer and its carbon reinforced composite, a quantitative description of structural development during processing was obtained. Thus, with this analytical methodology, a skin‐core crystallinity profile, where the crystallinity varies with part‐thickness as a result of uneven cooling experienced during processing, was predicted both for the neat PEEK polymer and its carbon reinforced laminate forms. Finally, the developed methodology clearly established the interplay of both microscopic heat transfer and kinetics of crystallization/solidification of the matrix that must be accounted for in predicting the final structure of a carbon fiber reinforced laminate that will, in turn, govern microscopic and macroscopic performance.
Interlaminar fracture toughness testing of composite mode I and mode II DCB specimens
Authors: Ilcewicz L. B. , Keary P. E. , Trostle J.
Published: December 2004

A computer controlled test procedure for evaluating mode I and mode II interlaminar fracture behavior was used in experiments with eight different resin matrix/graphite fiber composites. Four analytical methods for calculating fracture toughness were compared. These included an energy rate determination of theJ‐integral, a compliance calibration procedure, equations based on linear beam bending, and an Area method calculation. Methods that account for nonlinear material behavior, such as theJ‐integral, were needed for characterizing the systems with high fracture toughness. The ratio of mode II to mode I fracture toughness ranged from 1.5 to 8.0, depending on the material system. Finally, preliminary work with a technique for constant strain rate testing of mode I DCB specimens is presented.
Polymer fatigue fracture diagrams: BPA polycarbonate
Authors: Takemori Michael T.
Published: December 2004

A fatigue fracture diagram for BPA polycarbonate has been created from fatigue lifetime data obtained from knit line notched samples. This fatigue fracture diagram maps out stress‐temperature zones where fatigue fracture is dominated by crack growth through leading crazes and zones where fatigue fracture occurs through shear fracture at 45 degrees to the load direction. Both craze and shear planes coexist in the fatigue crack tip plastic zone, and both compete to determine the ultimate crack growth behavior. The shear planes preferentially develop (and fracture) at higher temperatures and stresses, but this fracture process is quite slow. Consequently, an inversion in the fatigue lifetime curve is observed, with longer lifetimes at higher stresses. This inversion is easily understood as a transition between a craze branch and a shear branch on the fatigue lifetime plot. When the fatigue lifetime curve is plotted for data at different temperatures, with the stresses normalized to the yield stress at the respective test temperatures, the craze branch data from different temperatures overlap. This overlap can be explained by the N = 2 power law dependence of crack growth in the discontinuous crack growth regime.
Vibration welding of thermoplastics. Part I: Phenomenology of the welding process
Authors: Stokes V. K.
Published: December 2004

In vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. The main process parameters in vibration welding are the weld frequency, the amplitude of the vibratory motion, the weld pressure, and the weld time. How these parameters affect weld quality, the conditions that result in the best welds, the weldability of dissimilar plastics, and the effect of fillers such as glass are of interest. To address these issues, a research vibration welding machine in which all the parameters can be independently and accurately controlled and monitored was designed and fabricated. The phenomenology of welding, as determined by experiments on the four thermoplastics polycarbonate, poly (butylene terephthalate), polyetherimide, and modified poly (phenylene oxide), is described.
Modeling of extrusion with slip boundary conditions
Authors: Meijer H. E. H. , Verbraak C. P. J. M.
Published: December 2004

Slip at boundaries is possible in viscous flows; for instance, in the extrusion of foodstuffs, water‐containing materials, and some polymers. There are two phenomenological descriptions of slip: The first is based on the presence of a very thin, low viscosity boundary layer and has been derived for capillary flow and extrusion; the second is based on a Coulomb‐friction mechanism and has been derived for capillary flow only. After a survey of these results, the friction model is derived for the extrusion process. All calculations are as simple as possible: two‐dimensional, Newtonian, isothermal, and with constant boundary layer parameters of coefficients of friction. A strong dependence of pumping characteristics and efficiency on the slip boundary conditions, and also on the extruder length in the case of friction, was found, especially when slip is only allowed for at the screw surface. Exercises like these may help in understanding abnormal extrusion behavior of slippery materials in practice.
Transmission of mechanical energy through polymeric liquid crystals and their blends
Authors: Brostow Witold , Dziemianowicz Theodore S. , Romanski Janusz , Werber Walter
Published: December 2004

Molecular composites, also called polymeric liquid crystals (PLC), are contrasted with the traditional composites; the name heterogeneous composites is proposed for the latter. Advantages of blending PLCs with ordinary engineering polymers are discussed. Results reported for blends of poly(ethylene terepthalate) (PET) with a PLC containing sequences of PET and p‐hydroxybenzoic acid (PHB) include thermophysical properties, melt rheology, mechanical properties of solid blends, and scanning electron microscopy of fracture surfaces. A model called the island model was developed to explain the results: One assumes that the lines of force as well as propagating cracks tend to concentrate in the phase rich in the more flexible engineering polymer, avoiding the islands rich in the liquid‐crystalline phase. This prevails until the phase inversion occurs. Predictions from the model are fully confirmed by the experimental evidence.
Preparation, structure, and properties of two‐phase co‐continuous polymer blends
Authors: Miles Isabel S. , Zurek Andrew
Published: December 2004

Phase continuity has been explored as a function of composition for three two‐phase polymer blends produced by mixing in the melt: polystyrene/poly(methyl methacrylate), polystyrene/cis‐polybutadiene, and poly(methyl methacrylate)/ethylene‐propylene rubber. The condition for dual phase continuity Is the application of shear close to phase inversion and this can be predicted fairly accurately using the relation

where 1 and 2 are the blend components, η is viscosity, \documentclass{article}\pagestyle{empty}\begin{document}$\mathop \gamma \limits^.$\end{document} is the shear rate in the mixing device used to produce the blend and ϕ is volume fraction. The co‐continuous materials, which we call Interpenetrating polymer blends (IPBs) are non‐equilibrium structures and are subject to disruption by changes in flow regime.
Pattern generation in polyimide coatings and its application in an electrophoretic image display
Authors: Minnema L. , Van Der Zande J. M.
Published: December 2004

Direct photo‐patterning of polyimide (PI) films was done in two ways, both based upon the modification of the PI‐precursor, the polyamic acid (PAA), by derivatives of methacrylic amide. In the first method, a photoreactive PAA is prepared by partially (25 mole percent) neutralizing PAA with N‐(N′N′‐dimethylarnino)propylmethacrylic amide and completing the neutralization with methacrylic amide (75 mole percent). In the second method the PAA is esterified, e.g. with N‐hydroxyethyl‐N‐methylmethacrylic amide, through its isourea derivative. The modified PAAs are processed like conventional negative photoresists. In the first method, the photopolymer formed by selective UV exposure is bound to the PAA by intermaeromolecular complexation, causing insolubility in the developer. The second method, which was investigated only qualitatively, provides crosslinked patterns. In both cases a pure PI film is left upon imidization at 350°C. The first method proved to be well‐suited to making the potential well structure in an electrophoretic image display. These wells must have strictly vertical walls (12 μm high) with metallized top faces. It was found that mask contact at “molecular distance” is not needed for the exposure of the photosensitive PAA: vertical walls could be made by simply adapting the developer after contact exposure. This is explained, tentatively, by the typical characteristics of the polymer‐polymer complex upon development. The potential well structure could now be made in a straightforward process.
Biaxially oriented polypropylene film in power capacitors
Authors: Nash James L.
Published: December 2004

The use of polymer dielectrics, particularly biaxially oriented polypropylene (BOPP), has revolutionized power distribution around the world. BOPP film of sub mil thickness has displaced impregnated Kraft paper because of superior dielectric performance, lower cost, and small volume. The polypropylene molecule has a unique set of properties which combine stable dielectric properties in the operating temperature and frequency range along with an adequate dielectric constant. High levels of orientation and a small unbalance of orientation are required to produce films of high dielectric strength over large areas of film. Control of thickness uniformities to approximately ± 5 percent are critical to the reliable operation of the capacitor under load and to control of capacitance in the product. A special fibrillated surface is required which promotes complete impregnation by the dielectric fluid.

This surface is acquired by the development of a specific crystal morphology at one surface of the film. No additives are used to promote this crystalline structure since most additives effect dissipation factor and generate unwanted heat. Similarly, control of contamination (ppm and ppb) is a key factor in the manufacture of film power capacitors.
The spin‐coating process mechanism related to polymer solution properties
Authors: Weill A. , Dechenaux E.
Published: December 2004

Coating the substrate with an amorphous polymer layer is a very common process in the manufacturing of integrated circuits, but the fundamental spin‐coating mechanism has not yet been precisely determined. This study examines the influence of the macromolecular characteristics on the spin‐coating process both experimentally and from a phenomenological point of view. It is concluded that the weight‐average molecular weight of the spun‐on solution is a pertinent parameter, and that chain entanglements in polymer solutions may be considered as the basic phenomenon responsible for the formation of the solid polymer layer.
Simulation of foaming in reaction injection molding
Authors: Tighe S. C. , Manzione L. T.
Published: December 2004

Blowing agents are often used in the reaction injection molding process to compensate for the shrinkage that occurs upon polymerization, thereby creating a structural foam part. Controlling the thickness of the solid skin and foamed core is essential to achieve the intended mechanical properties of the molded part. A numerical model was developed to predict the foaming behavior in reaction injection molding. This algorithm employs a novel primitive cell construction to enable it to analyze complex rectangular geometries, including inserts, with a two‐dimensional, finite difference solution method. The analysis was applied to foaming of polyurethane in a rectangular cavity. The predicted skin thickness was found to be in good agreement with actual structural foam parts. Foaming as a function of cavity thickness was also treated. The algorithm Is useful for understanding and interpreting nonlinear phenomena of rapid, exothermic polymerizations such as foam formation adjacent to the mold wall or around a metal insert. The results can be used to formulate design guidelines for achieving desired skin/core thicknesses as a function of design, material, and process parameters.
Reaction injection molding of polyureas I. Kinetics study
Authors: Hsu T. J. , Lee L. J.
Published: December 2004

Summarized in this paper are the experimental results and mathematical modeling of processing of polyureas. The experimental part includes the applications of solution polymerization to study the reaction kinetics of polyureas. The theoretical part includes a kinetic and heat transfer model that can apply solution polymerization data to predict the bulk polymerization of polyurea in the reaction injection molding process.
A coextrusion process for the manufacture of short‐fiber‐reinforced thermoplastic pipe
Authors: Doshi S. R. , Charrier J.‐M, , Dealy J. M.
Published: December 2004

The advantageous use of short‐fiber‐reinforced thermoplastic (SFRTP) resins in the manufacture of pipe requires that the fiber orientation be controlled and that the surface finish not be adversely affected by the presence of the fibers. It is proposed here that a coextrusion process be combined with the use of a Specially designed, expanding channel die to achieve these objectives. Conventional pipe dies tend to promote the axial orientation of fibers, which has an undesirable effect on the hoop properties of pipe. The use of an expanding channel die promotes fiber orientation in the hoop direction. However, even in this case, there is still a strong component of the shear field near the wall of the die, and in this region, axial orientation still predominates, The use of a three‐layer, coextrusion process in which unreinforced resin is used for both the inner and outer layers makes it possible to minimize the shear effects on the fiber orientation in the middle SFRTP layer. At the same time, it provides a smooth, fiber‐free pipe surface. A theoretical analysis of this process is presented. The analysis shows that the presence of unreinforced surface layers increases the level and uniformity of fiber orientation. The results of an experimental study of fiber orientation in the middle SFRTP layer are found to be in qualitative agreement with the predictions of the theory.
Interface determination in bicomponent extrusion
Authors: Karagiannis A. , Mavridis H. , Hrymak A. N. , Vlachopoulos J.
Published: December 2004

The unidirectional flow of two immiscible fluids with different viscosities in a long die of arbitrary shape is considered. Mathematically, the problem has a continuum of solutions corresponding to arbitrarily prescribed interface shapes, but experimental evidence indicates the existence of a unique interface shape with the less viscous fluid encapsulating the more viscous fluid. With the introduction of the minimum viscous dissipation principle, which postulates that the amount of viscous dissipation is minimized for a given flow rate, the problem becomes a nonlinearly constrained optimization problem. A generalized reduced gradient/finite element method combination is used to predict the interface shape when two inelastic fluids are considered. The effect of the viscosity ratio and flow‐rate ratio on the interface shape is examined for different die geometries. Inner layer breakup phenomena are predicted and explained for complex die geometries.
X‐ray determination of encapsulation stresses on silicon wafers
Authors: Nguyen L. T. , Noyan I. C.
Published: December 2004

Preliminary results of a systematic investigation of the behavior of encapsulating materials used in electronic packaging are reported. In this study, the radii of curvature of silicon wafers encapsulated with a filled epoxy are obtained by X‐ray diffraction. The values recorded agree closely with Dektak scanning for thin coatings. However, deviations occur with thicker layers due to the fundamental difference in the parameter measured by both techniques. Analytical solutions are proposed for both one‐and two‐sided encapsulation. Results predicted for the one‐sided coating describe a more severe state of stress within the package, and a correspondingly higher curvature than observed. X‐ray radiographs and optical micrographs of molded packages reveal the presence of internal voids and surface cracks. Such defects relax the stresses within the composite system and may account for the discrepancy observed.
A new differential scanning calorimetry based approach for the estimation of thermal conductivity of polymer solids and melts
Authors: Khanna Y. P. , Taylor T. J. , Chomyn G.
Published: December 2004

A new concept based on differential scanning calorimetry (DSG) is introduced which enables us to make a rapid estimation of the thermal conductivity of materials. This technique is shown to give reasonable agreement with the literature data and offers unique advantages, e.g. short analysis time, no instrument modification, small thermal radients across the sample, spall sample size requirements, and most importantly it can be applied to polymer melts. Although our data falls within the literature range, it is difficult to comment on its accuracy since the literature itself shows a wide variation. The precision of our measurements is better than ±20 percent which is considered adequate for thermal conductivity evaluation. As a matter of convenience, we have also presented briefly, a background of the thermal conductivity measuring techniques.
Application of nitrile butadiene rubber for flexible, chemically protective coating
Authors: Hoontrakul Pat , Szamosi Janos , Tobing Singa D.
Published: December 2004

Rheological properties of toluene solutions of nitrile butadiene rubber, of different molecular weights (Mw, 290,000,320,000, and 450,000) and acrylonitrile contents (30 and 40 percent), were investigated at low (0.1 S−1) to medium (20,0 S−1) shear rates, in order to determine their feasibility for dip‐coating applications. The effect of a surface‐active additive, bentonite, and the solid content (15 and 20 wt percent) on solution viscosity was of main interest. At low zero‐shear viscosity (<50 Pa·S) an excessive sagging of the wet film was experienced; at high zeroshear viscosity (>100 Pa‐·S) the coating showed poor leveling. Zeroshear viscosity was found to be less affected by bentonite than oligomer‐based solutions, at the same time, the solid content and the molecular weight of the polymer had more pronounced effects. With a proper balance of the parameters, seamless coating films were achieved, with excellent tensile and tear properties, and good permeation resistance against benzene.
Thermal analysis of polycarbonate/linear low‐density polyethylene
Authors: Mielke W.
Published: December 2004

In a cooperative testing of polymer blends of polycarbonate (PC) and linear low‐density polyethylene (LLDPE), 17 laboratories from six countries contributed measurements of differential scanning calorimetry (DSC) or differential thermal analysis (DTA) and of thermogravimetric analysis (TGA). This work is part of the activity of the VAMAS* Technical Working Party–Polymer Blends (TWP–PB), which provided the samples and coordinated the tests. Thermal analysis proved to be a, rapid means of assessing the miscibility of polymers using small samples. The system PC/LLDPE investigated in this test is found immiscible. The results of this cooperative test are a basis to elaborate a standard procedure for the characterization of polymer blends.
Miscibility and morphology of the poly(vinyl chloride)/styrene‐acrylonitrile copolymer/poly(methyl methacrylate) ternary blend system
Authors: Huarng J. C. , Min Kyonsuku , White James L.
Published: December 2004

The phase equilibrium of the ternary system poly (vinyl chloride) (PVC)/styrene‐acrylonitrile copolymer (77/23) (SAN)/poly (methyl methacrylate) (PMMA) was investigated using a combination of turbidity, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) measurements. Both turbidity and DSC were used to determine room temperature ternary phase diagrams. The results are basically similar, but the formulation based on the DSC results and the presumed phase model would seem more reliable since it is possible that immiscible blends may well have different phases with similar refractive indices.
Characteristics of hydroxybenzoic acid‐ethylene terephthalate copolymers and their blends with polystyrene, polycarbonate, and polyethylene terephthalate
Authors: Zhuang Ping , Kyu Thein , White James L.
Published: December 2004

We present a basic study of the thermal, dielectric, Theological, and mechanical properties of hydroxybenzoic acid‐ethylene terephthalate copolymers (PHB‐PET). It is argued that they have two‐phase structures, one rich in ethylene terephthalate (PET) and one rich in hydroxybenzoic acid (PHB). Polystyrene (PS) is immiscible in 60% PHB‐PET (60‐PHB‐PET) blends. Polycarbonate (PC) is partially miscible with the high PET phase of 60‐PHB‐PET. PET seems completely miscible with this high PET phase. Shear viscosity measurements on blends indicate that 60‐PHB‐PET gives rise to large reductions of viscosity. Extrudates and melt‐spun fibers have been prepared. The phase morphologies of low PHB‐PET blends as determined by scanning electron microscopy indicate ellipsoids or long fibrils of the, 60‐PHB‐PET in PS or PC matrices. High extrusion rates and melt spinning produce fibrillar structures. The mechanical properties of films, extrudates, and melt‐spun fibers were studied. Blends with 10% 60‐PHB‐PET exhibited significant increases in Young's modulus and tensile strength.
Blends of a chlorinated poly(vinyl chloride) compound and a thermotropic liquid crystalline copolyester: Some rheological behavior and spiral mold flow
Authors: Lee Biing‐Lin
Published: December 2004

Rheological and spiral mold flow measurements were made on blends of a chlorinated poly (vinyl chloride) (CPVC) compound and a thermotropic liquid crystalline copolyester of p‐hydroxybenzoic acid/poly (ethylene terephthalate) (60/40), hereafter referred to as LCC, at 210°C. Several interesting flow phenomena have been observed. While the shape of the flow curve (i.e., G′ vs. ω; G″ vs. ω) of LCC is solidlike, those of the blends are pseudoplastic. The dynamic viscosity of the blends increases as the concentration of LCC increases. However, the shear viscosity of the blends is reduced with LCC and may be described using the relationship of additivity of fluidity. Although the melt elasticity of the blends is increased with the concentration of LCC, the extrudate swell of the blends after extrusion from a capillary is decreased. This phenomenon, however, is complicated. A Theological analysis based on an idealized runner system is used to describe the spiral flow length as a function of the Theological properties of the molten polymers and also the operating conditions. The relative improvement of the spiral flow length of the CPVC compound due to blending with LCC could be correlated with the power‐law fluid model at high shear rates.
Mechanical behavior of polycarbonate/phenoxy blends before and after interchange reactions
Authors: Mondragón I. , Gaztelumendi M. , Nazábal J.
Published: December 2004

Melt‐mixed blends of polycarbonate/phenoxy were obtained before and after Interchange reactions by controlling the processing time. The dynamic mechanical analysis of the physical and reacted blends confirmed the immiscibility of the pair and the displacement of the glass‐transition temperatures of the mixtures; this displacement was seen more clearly in the reacted mixtures, and at phenoxy‐rich contents, even a single phase can appear. The exchange reactions resulted in a mechanical behavior that showed both a higher modulus and greater tensile strength in the reacted blends. The ductility was close to linearity for the physical blends and probably would be improved in the reacted mixture with a lower processing time.
Thermal, dynamic mechanical, and rheological behavior of linear low‐density polyethylene/poly(octadecene‐co‐maleic anhydride) blends
Authors: O'Connor K. M. , Orler E. B.
Published: December 2004

Blends of linear low‐density polyethylene (LLDPE) and a 50:50 copolymer of octadecene and maleic anhydride (C18‐MAH) were characterized by calorimetry, dynamic mechanical testing, and rheometry. In the solid state, the blends are essentially immiscible. No evidence was obtained for cocrystallization of the LLDPE with the paraf‐finic side‐chains of the C18‐MAH. Interactions between the blend components were observed in three ways. First, presence of the C18‐MAH in the LLDPE melt increases the nucleation rate for LLDPE crystallization. Second, side‐chain crystallization in a portion of the C18‐MAH component equivalent to approximately 15% of the total blend is apparently suppressed in the blends. Third, although the mechanical loss of the blends is essentially a sum of the pure components, the β relaxation of the LLDPE is absent in blends containing more than 20% C18‐MAH. The blends are also immiscible in the melt. The steady and dynamic shear rheology is dominated by the immiscibility and mismatch in viscosity, η, between the two polymers. A linear dependence on blend composition was found for log η in dynamic (small strain) tests. Nonlinear behavior with positive and negative deviations from linearity was found for log η in steady shear (large strain) tests.
Tg‐Composition analysis of miscible polymer blends
Authors: Aubin Madeleine , Prud'Homme Robert E.
Published: December 2004

Several authors have suggested a monotonic variation of the glass transition temperature (Tg) of miscible polymer blends as a function of composition. They usually express the results in terms of equations proposed by Couchman‐Karasz, Gordon‐Taylor, Fox, and several others. However, we have noticed that numerous systems exhibit a cusp when Tg is plotted as a function of composition (after correction for the presence of crystallinity when semi‐crystalline polymers are involved). This cusp cannot appear when the Tg's of the two homopolymers involved are separated by less than about 52 degrees., It will be shown that this observation is quite general since it has been observed with several polyester/chlorinated polymer blends, polycaprolactone/nitrocellulose blends, and polystyrene/poly(vinylmethylether) blends; It will also be shown that this behavior is predicted in the framework of the free volume theory, with equations derived by Kovacs. According to this theory, above a critical concentration ϕc (relative to the plasticizer) and below a critical temperature Tc, the high‐Tc, polymer no longer contributes to the free volume of the mixture whereas it does above Tc. This difference leads to a Tg‐composition variation which has to be expressed by two different equations, one below Tc and the other above Tc, the cusp defining the limit of applicability of each equation.
Solution blending of polystyrene and poly(methyl methacrylate)
Authors: Burns Charles M. , Kim Woo Nyon
Published: December 2004

Blends of poly(methyl methacrylate) (PMMA) and polystyrene (PS) have been investigated by differential scanning calorimetry and scanning electron microscopy. Blends were made of a low molecular weight PS with three PMMAs having number‐average molecular weights of (1) 18,300, (2) 37,000, and (3) 211,000, The blend was found to be partially miscible. The composition‐dependent values of the polymer‐polymer interaction parameter (g12) were determined and found to be from 0.015 to 0.029 for solution casting at 25°C. The interaction parameter (g12) increases with increasing PMMA molecular weights in the PMMA/PS blend systems. This result is consistent with the behavior of the glass transition temperatures and with the microscopy study which indicate that compatibility is greater in the PMMA‐1/PS blends having the low molecular weight of PMMA than in the PMMA‐3/PS blends having the higher molecular weights of PMMA.
Viscoelastic behavior of polymer blends
Authors: Utracki L. A.
Published: December 2004

There is a reciprocal relation between flow and structure in multiphase systems such as polymer blends or composites. For this reason characterization of these materials must be carried out under conditions which guarantee minimum modification of structure. Capillary rheometry is particularly ill suited as a test tool, but the small strain dynamic oscillatory method may provide the true material responses, Most frequently these are expressed as frequency, ω, dependent storage and loss shear moduli, G′ and G″, or real and imaginary viscosities, η′ = G″/ω and η″ = G′/ω. However, two other methods of data presentation seem to be more sensitive to melt structure. They are the Cole‐Cole plot of η″ vs. η′ and the relaxation spectrum. Frequently, both of them indicate a binomial response. Various mechanisms leading to such behavior will be discussed.
The effect of cryogenically ground rubber on some mechanical properties of an unsaturated polyester resin
Authors: Rodriguez E. L.
Published: December 2004

The effect of Cryogenically Ground Rubber (CGR) from old tires on some mechanical properties of an unsaturated polyester resin is presented. A delay in the free radical cure reaction of the unsaturated polyester resin was observed upon the addition of ground rubber. This delay in the cure reaction could be overcome with the further addition of the free radical initiator. The particle size, surface chemistry, and the chemical composition of the rubber had an effect on the cure and on the final properties of the rubber‐filled composites. It was also found that the rubber particles decreased the tensile, flexural, and storage shear modulus of the unsaturated polyester. Composites made from silane‐treated ground rubber showed better mechanical properties than composites made from untreated CGR. Finally, the particle size of the ground rubber was apparently too large to produce a toughening effect on the filled materials.
Classification of ionic polymers
Authors: Ibidapo T. Adesanya
Published: December 2004

Ionic polymers are polymers, either organic or inorganic, which contain both covalent and ionic bonds in their molecular structure. This is the basic characteristic feature that distinguishes the ionic polymers from their conventional counterparts. There is no accepted definition of, or method of classifying, ionic polymers. The few previous classifications were not only restricted to particular groups but also cannot completely accommodate the current existing range of ionic polymers. This work considers the existing modes of classification of ionic polymers as well as the range of ionic polymers in the establishment of a simple and straightforward classification. It ensures, firstly, that a reflection of their different background structures can always be obtained; secondly, materials with similar properties or behavior are brought together; and lastly, it enables the prediction of new entries that might subsequently have to be Included in the scheme.
Rheology and processing of linear low density polyethylene resins as affected by alpha‐olefin comonomers
Authors: Kalyon Dilhan M. , Yu Dong‐Woo , Moy Francis H.
Published: December 2004

The effects of the higher alpha‐olefin comonomers on the rheology and processing behavior of linear low density polyethylenes were investigated. Four linear low density polyethylene resins polymerized with butene, hexene and octene comonomers and a low density polyethylene were characterized in terms of their shear viscosity, first normal stress difference, storage and loss moduli, shear stress growth, stress relaxation upon step strain, stress relaxation upon the cessation of steady shear, and uniaxial extensional stress growth material functions. Differences in first normal stress difference, relaxation moduli, damping function parameters, and uniaxial extensional stress growth behavior were noted. The observations were elucidated in terms of the processability considerations in blown film extrusion process.
Ultimate properties of blown films of linear low density polyethylene resins as affected by alpha‐olefin comonomers
Authors: Kalyon Dilhan M. , Moy Francis H.
Published: December 2004

Blown film samples of linear low density polyethylene resins copolymerized with butene, hexene, and octene were characterized in terms of various mechanical and optical properties which included tensile, impact, tear, puncture, haze, and gloss. The microstructure development aspects were also investigated employing crystallinity and density, infrared dichroic ratio, and birefringence, and focusing on various positions along the circumference of the bubble. The ultimate properties, and the microstructure of the blown film samples, were found to depend strongly on the extent of short chain branching and on the comonomer employed.
Temperature measurements of polymer melts in the heating barrel during injection molding. Part I. Temperature distribution along the screw axis in the reservoir
Authors: Amano Osamu , Utsugi Shirou
Published: December 2004

A new procedure has been developed to measure the temperature distribution of the polymer melts along the screw axis during injection by using a small sheath thermocouple. At the same time, the effects of molding conditions on temperature distribution has been studied. The temperature distribution of the polymer melt along the screw axis during injection can be obtained from the difference between the standard temperature profile and the temperature profile of the polymer melt with unknown and non‐uniform temperature measured under the same rate of injection. The temperature of a polymer melt within a shot is not uniform. The difference between the maximum and the minimum temperature within a shot may exceed 10°C in some cases. There are two major factors which govern the effects of molding conditions on the temperature distribution of the polymer melts during injection. The first is the amount of shear heating in the metering zone. The second is the amount of heat absorbed into the polymer in the compression and feed zones.
Modeling the packing stage in injection molding of thermoplastics
Authors: Huilier D. , Lenfant C. , Terrisse J. , Deterre R.
Published: December 2004

A model, for the packing stage In injection molding of thermoplastics is proposed. It allows one to calculate the time evolution of pressure and temperature fields and mass variations in simple geometries. The model holds for amorphous as well as for crystalline polymers if the kinetics of crystallization are known for temperatures far from the melting point, It applies after filling stage; initial temperature and pressure conditions are available from filling‐simulating software. The principles rest on finite difference schemes computing simultaneously temperature and velocity of compressible non‐Newtonian fluid in a filled cavity. The pressure field is determined from an equation of state at any time, owing to a mass balance in each gridmesh. The meaningful results of the simulation are local shrinkage and a good approximation of final weights of finished products. The algorithm is essentially checked for the influence of physical, thermal, and processing parameters on the cavity pressure for the injection of a polystyrene (Gedex 1541) into a rectangular mold cavity.
A kinetic study of the thermal decomposition of poly(aryl‐ether‐ether‐ketone) (PEEK) in nitrogen
Authors: Day M. , Cooney J. D. , Wiles D. M.
Published: December 2004

The kinetic parameters of the thermal decomposition of poly(aryl‐ether‐ether‐ketone) (PEEK) in a nitrogen atmosphere have been obtained using an isothermal weight‐loss method. Several mathematical approaches have been used to obtain the Arrhenius parameters based upon the use of different reaction models. The values obtained for the activation energy (E = 198.4 to 219.7 kJ/mol) and preexponential factor (log A = 11.1 to 12.3 min−1) fall within a narrow range, irrespective of the method of calculation. Although the kinetic data most closely fits an Avrami two‐dimensional nucleating model, the data can be just as easily described by a first‐order rate law.
Effect of physical aging on tensile stress relaxation and tensile creep of cured EPON 828/epoxy adhesives in the linear viscoelastic region
Authors: Vleeshouwers S. , Jamieson A. M. , Simha R.
Published: December 2004

The effect of physical aging on viscoelastic properties was studied for several cross‐linked epoxies in the glassy state. Tensile creep and tensile stress relaxation were measured during isothermal physical aging, following rapid quenching of samples annealed above the glass‐transition temperature (Tg). The momentary creep curves measured at 21°C, 45°C, and 61°C below Tg for different epoxies could be fitted to an empirical equation for the creep compliance D(t):

Values for β and to were obtained, and the dependence of to on the aging time was determined. Shift factors were calculated to investigate changes in molecular mobility during physical aging. The momentary stress relaxation was measured on the same epoxy materials as used for the creep studies. The stress relaxation curves were fitted to the following equation for the tensile modulus E(t):

Values for α and to were obtained. The influence of physical aging on‐to was again studied by calculating shift factors as a function of the aging time. The results are compared with the results of the creep tests and discussed in the context of current molecular theories of physical aging of glassy polymers.
Effect of die wall cooling or heating on extrudate swell
Authors: Vlcek J. , Vlachopoulos J.
Published: December 2004

A general purpose finite element program was used to study polymer extrudate swelling. It is shown that viscosity variations due to externally applied cooling or heating have a significant influence on the swelling ratios of axisymmetric and planar extrudates. The effect is more pronounced at high Peclet and Weissenberg numbers. Swelling due to thermal effects and swelling due to viscoelasticity are not additive because of interrelations between the various mechanisms.
3‐D structure‐property relationships in rolltruded polymers. Part I: Mechanical property enhancement in three directions
Authors: Berg E. M. , Sun D. C. , MaGill J. H.
Published: December 2004

The effect of rolltrusion, a solid state deformation process, on the three dimensional mechanical properties of several polymers has been measured. Polymers studied included isotactic polypropylene (iPP), polyvinylidene fluoride (PVDF), and propylene/ethylene block copolymers. It was found that mechanical strength is enhanced triaxially for all these specimens upon rolltrusion. Material stiffness also exhibits 3‐D improvement, depending on the polymer type and processing conditions. These new results are discussed in regard to some structural models in the literature.
Rheology‐morphology relationships in nylon 6/liquid‐crystalline polymer blends
Authors: La Mantia F. P. , Valenza A. , Paci M. , Magagnini P. L.
Published: December 2004

Extrusion measurements have been carried out on blends of nylon 6 and a liquid‐crystalline copolyesteramide (LCP). The flow curves at low temperature show a behavior similar to that of pure LCP with a rapid rise of the viscosity at low shear rates. At high shear rates the viscosity is lower than that for each of the two components. This minimum has been attributed to the lack of interactions between the two phases and to the formation of fibrils of the LCP phase. The SEM analysis shows, indeed, that fibrils of the LCP phase are produced in the convergent flow at the inlet of the capillary at high shear rates. These fibrils are lost during the flow in the long capillary.
The interface in binary mixtures of polymers containing a corresponding block copolymer: Effects of industrial mixing processes and of coalescence
Authors: Plochocki A. P. , Dagli S. S. , Andrews R. D.
Published: December 2004

In theories of the minor phase (domain) formation in polyblends rendered as emulsions it is usually assumed that the size and shape of the domains are the result of melt viscosity effects (Taylor, Wu) or viscoelasticity effects (VanOene, Elmendorp) being balanced by interfacial tension. This assumption would predict a monotonic decrease of the domain size to a final limiting size with increasing energy of mixing. However, a systematic study of the dependence of domain morphology on industrial mixing processes which was carried out on a “model” LDPE/PS (2/1) mixture and the related polyalloy (i.e., the same mixture with a corresponding block copolymer as compatibilizer) does not support this expectation. Doirain size was found to go through a minimum as mixing energy was increased. A similar minimum was seen in data on specific volume of the melt vs. mixing energy, which indicates a correlation between melt specific volume and domain size. Calculation of the approximate surface area of the domains using a simple model of domain shape indicated that total interfacial energy in the polyblend and/or polyalloy is a trivial part of the mixing energy introduced. These calculations also indicated that if compatibilizer was located entirely at the interface, the surface layer would have a thickness of about 90 nm. Some micrographs seem to show such a surface layer. We propose that an abrasion mechanism is responsible for the early stage of the dispersion process, and that the final domain size may be controlled by a dispersion‐coalescence equilibrium. This is compared with the theories of final particle size proposed by VanOene and Wu.
Development of an in‐line rheometer suitable for reactive extrusion processes
Authors: Pabedinskas A. , Cluett W. R. , Balke S. T.
Published: December 2004

This paper presents the development of a novel in‐line extrusion rheometer based on the flow of polymer through a wedge (vertically tapered slit). This rheometer is suitable for measuring changes in rheological properties on‐line during reactive extrusion, because it can be used to estimate the viscosity for a range of shear rates without the need to change the polymer flow rate (i.e., extruder throughput). Equations have been developed to estimate the parameters of the power‐law equation, used to describe the viscosity‐shear rate relationship, from measurements of pressure drops along the wedge. An experimental in‐line wedge rheometer has been built and used to measure the viscosity for a series of polypropylenes prepared via reactive extrusion. Viscosity measurements from the experimental in‐line wedge rheometer are compared with measurements from a capillary rheometer. Good agreement is found between the capillary and wedge rheometer measurements.