bluuebunny/crossref_metadata_2025 huggingface dataset:
Composites with planar reinforcements (flakes, ribbons)—A review
Authors: Rexer J. , Anderson E.
Published: December 2004

Unlike fibers, planar reinforcements, such as flakes and ribbons, provide reinforcement in two directions. If such reinforcements are arranged parallel to their principal plane in a composite material, they thus provide a distinctly higher performance than fiber reinforcements for two‐dimensional loading conditions. This higher performance amounts to about a factor three for the Young's modulus and a factor two for the tensile strength. However, in spite of this obvious advantage, composites with planar reinforcements are as yet relatively unknown. This is mainly due to the fact that planar reinforcements are not as readily available as fiber reinforcements and therefore not much work has been done on them. The present article gives first a short outline of the theory of the elastic and tensile properties of composites with planar reinforcements. Then, a non‐exhaustive review is presented of the work on composites with planar reinforcements, with particular attention given to recent developments. A final aim of this article is that by showing the merits of planar reinforcements as compared to presently existing fiber reinforcements, it may contribute to their use in the design of composite structures.
Application of small system thermodynamics to polymer molecules. II. Secondary nucleation
Authors: Lindenmeyer P. H. , Beumer H. , Hosemann R.
Published: December 2004

Statistical mechanical methods can be used to relate not only structure and thermodynamics but also structure and kinetics. Methods are developed for calculating the crystal growth rate kinetic models. When the usual macroscopic thermodynamics are applied, the resulting surface energies, σ and σe extracted from the experimental growth rates are quite comparable to those obtained from kinetic models. However, when one applies small system thermodynamics, a substantially smaller σ is obtained. This latter assumption has the advantage of explaining why extended chain seed crystals do not promote crystal growth and why folded chain crystals grow on such seeds. The statistical mechanical methods in both of these cases predict the observed decrease in the rate constant, Kg with decreasing molecular length without the necessity of a separate theory for varying σe with molecular length.
Dynamic mechanical and broad line nuclear magnetic resonance behavior of some aromatic polyamides
Authors: Frosini V. , Levita G. , Butta E.
Published: December 2004

The results of dynamic mechanical and broad‐line proton magnetic resonance studies carried out over a broad, temperature range on a series of aromatic polyamides are presented. At temperatures lower than 300 K, the NMR data show no relaxation for the all‐meta linked benzene rings polyamide, whereas processes for the other polyamides are found, the magnitude of which is dependent on the polymer structure. Between 400 and 500 K further decreases in the second moment take place for all materials. Two secondary mechanical loss peaks are evident in these polymers, one in the 200‐380 K region (β) and one in the 380‐500 K region (β*), at about 104 cps. In particular, the relaxation strength of the β* peak depends on the conditions of isolation of the polymers from solution. The results are discussed in terms of possible motional processes of these polymers characterized by a long range intramolecular uniaxial order. An attempt is made to correlate the relaxational properties of aromatic polyamides to the existence of a phase of low regularity such as the nematic or smectic mesophases.
Geometry design of a coat‐hanger die with uniform flow rate and residence time across the die width
Authors: Matsubara Yutaka
Published: December 2004

This article provides an approximate but sufficiently practical method of geometry design of a coat‐hanger die having both uniform flow rate and residence time across the full width of the die. Such a die is often needed when a heat‐sensitive resin such as poly(vinyl chloride) is sheeted, because different residence times across the die width are apt to cause a sheet defect in the transverse direction of the sheet. Although some assumptions were made facilitating mathematical analysis, an application of this method to a sheeting die 1 m wide gave good uniformity of flow rate and residence time.
A method for the determination of the internal particle structure of poly(vinyl chloride) suspension resins by analyses of vinyl chloride desorption rate data
Authors: Daniels C. A. , Longeway G. D.
Published: December 2004

A method has been developed for analyzing the vinyl chloride desorption rate data from poly(vinyl chloride) resins. This technique, based on Fickean diffusion kinetics already demonstrated for this system, yields fundamental internal particle morphology information, which is in agreement with that determined by other methods. The approach detailed in this manuscript can be applied to other particle‐penetrant systems for which the nature of the diffusion kinetics is known.
A study of chain‐addition polymerizations with temperature variations. IV. Copolymerizations—Experiments with styrene‐acrylonitrile
Authors: Sebastian D. H. , Biesenberger J. A.
Published: December 2004

Free‐radical copolymerizations were studied under nonisothermal conditions with emphasis on their thermal runaway and ignition behavior. Computational models are presented in generalized form and compared with experiments on the system styrene‐acrylonitrile. A new, useful method is proposed for the evaluation of runaway parameters from scant kinetic data.
Processability of raw elastomers and its relation to deformational and failure behavior
Authors: Nakajima N.
Published: December 2004

A method was proposed for a scientific description of processability of raw elastomers involving a master curve representing deformation behavior and a failure envelope representing the ultimate properties. When a specific machine is given, the mechanical and environmental conditions may be defined from the geometry and operating condition of the machine. Matching these conditions, specific information on processability may be extracted from the master curve and failure envelope. In constructing the master curve, we have proposed to use the strain‐time correspondence principle including the behavior at both small and large deformation. The necessary measurements may be considerably simplified; for example, the Rheovibron and the Mooney rheometer provide necessary data over the entire range of the rubbery behavior. The latter instrument may be operated at a slow speed, i.e., 0.05 RPM and the torque‐rise curve is used. With the rotational viscometer, the stress often reaches a maximum before reaching steady state, particularly with rubbers. We have shown that the curve leading to the peak is the shear stress‐strain curve. The maximum was found to correspond to the failure point in the tensile deformation. The stress‐time correspondence principle is not applicable to some rubbers. In these cases, the same calculation may still be conducted to evaluate the deviation from the master curve. Then, the extent of deviation may be used to represent the degree of long chain branching.
Poly(ethylene terephthalate) nucleation as studied by shrinkage of film of low orientation level
Authors: Adams G. C.
Published: December 2004

Poly(ethylene terephthalate)s of weight average MW 74,000 and 30,000 have been uniaxially stretched, cooled under restraint, reheated, and shrunk unrestrained. Five stretch temperatures between 80 and 120°C and elongations up to 280 percent have been employed. Density and wide‐angle X‐ray diffraction results indicate conventional crystallization to have occurred only for the highly oriented samples, e.g., stretching above 200 percent at 90°C. The majority of stretching conditions studied produced only nucleated polymer. A sensitive, qualitative measure of nucleation is the degree of stretch imposed. Sufficiently high stretch temperature and low stretch rate lead to negligible nuclei formation. Nucleation in stretched, unshrunk films correlates with relatively high shrinkage, low orientation, low density and the absence of crystallinity until after the film has been shrunk. Crystallization on the other hand correlates with relatively high density, relatively low shrinkage and high orientation.
Scaleup factors of tubular emulsion polymerization reactors
Authors: Vatanatham T. , Forsyth T. H.
Published: December 2004

This paper examines the important dimensionless numbers that control emulsion polymerization in a tubular reactor. It was found that the activation energy of polymerization was of major importance, while the role of monomer diffusion was not very significant. By selecting certain combinations of the dimensionless numbers, changes occurring during scaleup from a small tubular diameter to a larger diameter can be approximated.
Elastic moduli of the crystalline regions in the direction perpendicular to the chain axis of ethylene‐vinyl alcohol copolymers
Authors: Nakamae Katsuhiko , Kameyama Masao , Matsumoto Tsunetaka
Published: December 2004

In order to clarify the crystal structure and intermolecular cohesion forces of ethylene‐vinyl alcohol copolymers (EVA), the elastic modulus (Et) of EVA copolymers was measured. We proposed that EVA copolymers are crystallizable over the entire range of copolymer composition and can produce, an isomorphous crystallite. On the basis of these crystal structures, the value of Et was expected to be dependent on the copolymer composition. Et values are indeed closely dependent on composition and decrease with decreasing VA segment. From the anisotropy of Et for (100) and (002) planes, which means the anisotropy of the intermolecular interaction, the direction of hydrogen bonding seems to be in the a‐axis direction.
Order‐disorder transitions in the extrusion of fiber‐filled poly (ethylene terephthalate) and blends
Authors: Wu Souheng
Published: December 2004

Order‐disorder transitions occur in fiber orientation and distribution during extrusion of fiber‐filled poly (ethylene terephthalate) and its blends with other polymers. Associated with these transitions are three characteristic regimes of extrudate surface morphology, cross‐sectional structure and fiber distribution. Low wall shear rates result in a “smooth porcupine” surface, polygonal cross section, and uniform fiber distribution. Medium wall shear rates produce a “rough porcupine” surface, irregular cross section and tubular depletive fiber distribution with fibers depleting at a relative radial position r/R of 0.63 and accumulating at the surface and the axis. This is exactly opposite to the tubular pinch effect observed for neutrally buoyant rigid spheres which accumulate at r/R of 0.63 and deplete at the surface and the axis. High wall shear rates give a “shorn porcupine” surface, rounded or distorted polygonal cross section and radial migration of fibers toward the axis. The extant of disorder decreases with increasing pseudoplasticity, of the fluid, suggesting that the characteristic fiber orientation, distribution and transitions arise from normal stress effect and/or the eccentric rotation of fibers dictated by the complex velocity profile of the flowing fluid. These phenomena have not been previously reported.
Award address formation and properties of network polymeric materials
Authors: Gillham John K.
Published: December 2004

A general model for thermosetting materials which relates polymerization to properties is discussed. In particular, a phase diagram relates the four states of matter encountered (i.e., liquid, rubber, ungelled glass and gelled glass) to gelation and vitrification phenomena. The model is extended to rubber‐modified thermosetting systems to show that, by control of the time to gelation, a given chemical formulation can provide different morphologies and hence different material behavior. The principal experimental approach uses a torsional braid analyze (TBA), an automated version of which is described. Use of the technique to measure gelation and vitrification times is discussed.
Pyrolysis‐molecular weight chromatography‐vapor phase infrared spectrophotometry: An on‐line system for analysis of polymers—a review
Authors: Kiran Erdoǧan , Gillham John K.
Published: December 2004

An instrumental system consisting of a combination of a programmable pyrolyzer, a thermal conductivity detector, a mass chromatograph, a gas chromatograph, a fast‐scan vaporphase infrared spectrophotometer and a computer is reviewed with examples which show the utility of the system in the analysis of decomposition phenomena in polyolefins, polyolefinsulfones, polymethacrylates, polystyrenes, and polybutadienes. The system records the thermal history before and during pyrolysis of the sample and provides chromatographic retention times, infrared spectra, mass numbers and relative amounts of the volatile products of pyrolysis. Identification of the constituents is thus facilitated and mechanisms for decomposition become easier to estimate and verify.
Viscoelastic properties of epoxy polymer concrete
Authors: Tolbert R. N. , Hackett R. M.
Published: December 2004

The viscoelastic nature of polymer concrete was investigated utilizing an epichlorohydrin/bisphenol A‐type epoxy resinaggregate system. Compression specimens were tested for linearity of viscoelastic behavior, the effect of size of mass on creep, and for determination of the specific creep compliance and the associated elastic modulus. The creep compliance was determined by least squares curve fitting of the experimental creep data. Collocation, a numerical Laplace transform inversion routine, was used to develop the equation for the relaxation modulus.
A new technique for determining the oxidative stability of molten polymers
Authors: Trizisky J. D.
Published: December 2004

A new method and apparatus for determining the oxidative stability of molten polymers, especially polyolefins, is described. The apparatus consists of a laboratory scale mixer modified to allow for the continuous determination of the oxygen absorbed by the polymer. The oxygen uptake curve observed for polyolefins is of the type normally associated with the autocatalytic oxidation of hydrocarbons and yields an induction period—a traditional measure of stability. Typical results from experiments concerning the antioxidant type, antioxidant level and temperature on polyethylene stabilization are presented to illustrate the usefulness of the technique in both quality control and research applications.
An approach towards the reduction of sink marks in sheet molding compound
Authors: Smith Kenneth L. , Suh Nam P.
Published: December 2004

Sink marks are shallow depressions normally observed above reinforcing ribs in molded Sheet Molding Compound (SMC) parts. In this paper, the effect of mold geometry, particularly the rib entrance shape, on the flow pattern of molding compound and the resulting sink marks in molded parts is presented. Flat plate specimens with a single reinforcing rib in the center were used in this work. Rib entrance shape was varied and its effect on both sink depth and fiber orientation measured. A reduction in sink depth from 0.0007 in. to less than 0.0001 in. was observed when comparing rounded and protruding rib entrances, respectively. The effect of inducing unequal flow rates from the two sides of the rib was also investigated and found to give a reduction in sink depth of about one‐third. A computer simulation of the flow during molding was, used to compare observed flow patterns with simple theoretical predictions. The SMC was modeled as a highly viscous Newtonian fluid and finite difference methods were used to solve the Navier‐Stokes equations. Extension of this modeling procedure to more complex geometries will aid in the design of nearly sink free molds.
Application of a chemical group contribution technique for calculating solubility parameters of polymers
Authors: Ahmad Husain , Yaseen M.
Published: December 2004

A chemical group contribution technique, based on the principle of additivity of molar attraction constants for groups in a molecule, has been used for determining the solubility parameters for several polyesters, polyethers and a few other types of polymers. The solubility parameter for a polymer is calculated by using the contributions for chemical groups reported in the literature with the resultant values found to compare favorably. For geometrical isomers of polymers, the calculated solubility parameters are identical but differ for positional substitution.
The confined chain approach to the deformation behavior of bulk polymers
Authors: Gaylord Richard J.
Published: December 2004

A theoretical “two wall” model of polymer chains confined between a pair of infinite parallel walls is developed to represent the amorphous regions in filled or reinforced elastomers, block copolymers and semicrystalline polymers. The free energies of the various types of confined chains are determined using statistics which incorporate nearest‐neighbor interactions. The stress‐strain, tensile ii odulus and swelling properties of the individual chains as a function of chain contour length and temperature are discussed. A mean field, free energy expression is used to account for interactions between confined chain segments: The free energy due to the direct interaction between the walls is given by a van der Waals potential. The equilibrium wall separation of the two wall model is determined as a function of the number of each type of chain, chain contour length and temperature. The two wall model is shown to display several deformation phenomena, including: yield, stress softening; draw; stress hardening; the Mullins effect; set; and crack or craze propagation.
Prediction and measurement of the thermal expansion coefficient of crystalline polymers
Authors: Kardos J. L. , Raisoni J. , Piccarolo S. , Halpin J. C.
Published: December 2004

Among the increased structural demands now being made on both unfilled and reinforced plastics is that of dimensional stability under various performance environments. Crystalline polymers are heterogeneous materials consisting of two distinct phases and, as such, can be treated as molecular versions of engineering composites. This paper first outlines the general physical model whereby a crystalline polymer is considered to be a multi‐ply laminate of unidirectionally reinforced plies. The calculational format is then detailed for the prediction of the stiffness and thermal expansion coefficient of an isotropic sheet of crystalline polymer and a sample calculation is given for quenched high density polyethylene. A data base is presented for the stiffness and thermal expansion coefficient of low and high density polyethylene having quenched, slowcooled, and annealed thermal histories. Comparison between experimental and predicted results yields good agreement in all cases to better than 25 percent. Implications and limitations of the predictive technique are discussed.
Interfacial effects on the NMR of composite polymers
Authors: Douglass Dean C. , McBrierty Vincent J.
Published: December 2004

Several NMR experiments can provide estimates of the scale of spatial inhomogeneity in solid materials in the range of nanometers to microns. The effects underlying these experiments their interpretation, and models used in their interpretation are discussed and illustrated with applications to polymers. Examples chosen from the literature include semicrystalline polymers (polyethylene, polyvinylidene fluoride, polychlorotrifluoroethylene), filled elastomers (carbon‐filled butadiene), copolymers (styrene: butadiene, dimethylsiloxane: bisphenol‐A polycarbonate, polyurethane) and blends (polymethylmethacrylate‐polystyreneacrylonitrile, polyvinylidene fluoride‐polymethylmethacrylate). Comparison of examples directs attention to the similarity in anisotropic motional behavior of highly constrained interfacial material in semicrystalline and filled polymers. While no one experiment is applicable to all dimensions, or all systems, NMR has proven especially useful for dimensions in the range of tens of nanometers, where other techniques are often less revealing.
Capillary viscometry: A complete analysis including pressure and viscous heating effects
Authors: Kamal Musa R. , Nyun Hla
Published: December 2004

Capillary viscometers have been used extensively, because of their simplicity and reliability, to measure the viscosity of fluids over a wide range of shear rates. However, in capillary flow, the shear rate is not uniform throughout the capillary, a pressure gradient is established in the direction of flow, and the temperature of the fluid is nonuniform due to viscous dissipation. In the present work, a general, simple and practical method is proposed for correcting for the effects of pressure variation and viscous dissipation in determining the viscosity of polymer melts at high pressures. The method essentially involves the estimation of temperature, pressure, shear rate, and shear stress under a variety of experimental conditions at a predetermined point in the capillary. As such, it may be considered as a generalized extension of the classical Rabinowitsch‐Mooney method for estimating true viscosity in capillary flow.
Experimental and theoretical investigation of extrudate swell of polymer melts from small (length)/(cross‐section) ratio slit and capillary dies
Authors: Huang David , White James L.
Published: December 2004

An experimental and theoretical study is presented of extrudate swell from short capillary and slit dies. The polymer melts studied were polystyrene and polypropylene. The swell from slit dies is greater than the swell from capillaries. Decreasing die entry angle for capillary dies decreases swell. The argument is made that elongational How existing in the die entry region and for short dies determines extrudate swell. Dimensional analysis arguments are used to relate extrudate swell to a Weissenberg number based on elongational flow at the die entrance and the detailed die geometry. Correlations are developed. The theoretical study is based on unconstrained elastic recovery following elongational How through the die entrance region.
Differential scanning calorimetry analysis of morphological changes in segmented elastomers
Authors: Hesketh T. R. , Van Bogart J. W. C. , Cooper S. L.
Published: December 2004

Investigations of morphological changes which are induced in segmented elastomers by annealing and quenching are reported. Four different polymers were studied each based on the same soft segment—1000 or 2000 molecular weight poly(tetramethylene oxide). The hard segments were 4,4′‐diphenylmethane diisocyanate (MDI) chain extended with 1,4‐butane diol (ET series), piperazine coupled with 1,4‐butane diol bischloroformate (BN‐1,4), or dimethyl terephthalate condensed with 1,4‐butane diol (H‐50). Following annealing at various temperatures (120, 150, 170, or 190°C), the polymers were quenched to ambient conditions, and their properties measured by differential scanning calorimetry (DSC) as a function of time following the quench. DSC measurements taken immediately after the quench show that the soft segment Tg is higher than that of the control, suggesting that the applied thermal history promoted increased mixing of hard and soft segments. As time passes after quenching, the Tg values decrease and approach an equilibrium value. This effect is much smaller for those samples having crystalline hard segments. Endotherms attributed to the disruption of long range ordering in the hard segment domains resulted from the annealing process. These endotherms appeared at higher temperatures for higher annealing temperatures. The positions of crystalline melting endotherms were independent of the annealing/quenching conditions investigated.
The carrier dyeing of synthetic fibers
Authors: Ingamells W. , Peters R. H.
Published: December 2004

The mode of action of carriers in augmenting the rate of dyeing of disperse dyes with acrylic and polyester fibers is discussed in terms of the plasticizing action of the carrier. It is shown that the effectiveness of a carrier is determined by its ability to reduce the glass transition temperature of the fiber and not by the fiber swelling. The rate of dyeing as measured by the diffusion coefficient of the dye is shown to be uniquely related to the difference between the dyeing temperature and the glass transition temperature (T – Tg). In the light of these results, some aspects of carrier action in dyeing from perchlorethylene are discussed. Treatment of polyester fibers with carrier also increases crystallinity. Changes in diffusion for a series of copolyesters have been correlated with the long spacing obtained from small angle X‐ray scattering (SAXS).
Residual solvent and its diffusion in acrylic fibers
Authors: Armstrong A. A. , Borie R. D. , Lanier W. W.
Published: December 2004

A survey showed that some commercial acrylic fiber products contain small quantities of residual solvent (dimethylacetamide). No diffusion of solvent from these products could be detected on laundering, dry cleaning, or exposure to synthetic perspiration. Acrylic carpets containing residual solvent were enclosed in sealed boxes to simulate a closed room. Air in the boxes was monitored for solvent content over a 14‐day period at 24°C (75°F) and 38°C (100°F) at both low and high humidity conditions. In all cases the solvent content of the air was below the detection limit of the best analytical procedure available (below 0.1 ppm). Diffusion rates of sol vent from 15‐denier carpel fiber into nitrogen were measured over the temperature range of 25–100°C. There was no detectable diffusion below 60°C measured over a 24‐h period. Mass diffusivities ranged from 2.5 × 10−19 cm2/s at 60°C to 6.4 × 10−14 cm2/s at 100°C. Under the conditions of expected use, the rate of diffusion of residual solvent from acrylic fibers is very low. Based on the low concentrations of residual solvent and its very low diffusion rate, there is an extremely low probability of any exposure to solvent from the residual solvent present in commercial acrylic fiber products.
A sorption theory for gas mixtures
Authors: Dent R. W.
Published: December 2004

From kinetic theory, an equation has been developed for the multilayer sorption of each of two competing gases or vapors onto sites on or within a sorbing material. The thermodynamic characteristics of sorption in the first layer are assumed to differ from those of the second and higher layers, which are all assumed to be identical, as in the Brunauer, Emmett and Teller (B.E.T.) Model. However, in contrast to the B.E.T. Model, these outer layers are not taken to be identical to bulk liquid. The model gives a closed form solution involving seven constants of which five can be obtained from the corresponding pure component sorption. The version of this equation for single gas sorption has three constants and differs from the classical B.E.T. equation, by having the extra constant. The Langmuir and B.E.T. equations are in fact limiting forms of this single gas equation. Examples are given which show excellent fits to experimental, sigmoidal isotherms from the literature up to about 95 percent of the saturation pressure, whereas the B.E.T. generally deviates above 40–50 percent of saturation. The equation can also be partitioned to give important information regarding the distribution of the sorbed molecules, and gives values for the ‘bound’ first layer content and for the ‘mobile’ higher layer sorbed fraction at equilibrium for any relative pressure.
The thermodynamic state of water in cellulose acetate membranes
Authors: Burghoff H.‐G. , Pusch W.
Published: December 2004

Using experimental sorption data and corresponding experimental results from calorimetric investigations, the state of water in cellulose acetate (CA) membranes is discussed by applying a theoretical treatment of sorption reported previously (1–3). The sorption of water can be attributed to a gain in surface energy at the polymer/vapor interface. Using differential thermodynamic potentials of sorbed water together with experimentally determined heat capacities of sorbed water, the thermodynamic potentials G, H, and S of sorbed water are estimated for the temperature interval −40 to + 40°C. At constant temperature, each thermodynamic potential depends on the water content. The resulting distribution function of G indicates that the sorbed water exists in different states. Comparing the Gibbs free energy of sorbed water with that of ice or liquid water at the same temperature leads to the conclusion that none of the sorbed water freezes to ice within the temperature interval used. Based on the Gibbs free energy of water in electrolyte solutions and the distribution function of G for sorbed water, partition coefficients of salts within CA membranes may be estimated. The results are in good agreement with experimentally determined partition coefficients which are available from the literature. As the partition coefficient of a salt is directly related to the salt rejection of the membrane, this provides a method of estimating the desalination performance of a membrane from its water sorption isotherm.
Water vapor transport in an epoxy resin based on TGMDA and DICY
Authors: Illinger Joyce L. , Schneider Nathaniel S.
Published: December 2004

Water uptake has been measured in an epoxy resin based on tetraglycidylmethylenedianiline curved with dicyanidamide. The curing behavior of this system as elucidated by differential scanning calorimetry and Fourier transform infrared is complex. Based upon this information we selected curing temperatures and times in addition to the “standard” cure. The kinetics of the sorption of water by the materials which have undergone the standard cure indicate that the two modes of sorption are involved at high humidity and only a single mode at lower humidity (as seen by changes in the slope of the log Mt vs log t plots). The kinetics of the sorption in the resins which have undergone post cure at higher temperatures also indicate two or more modes of sorption at high humidities. However the slopes of the log Mt vs log t plots differ from those for the resin with standard cure. Subsequent sorption/desorption cycles on the standard cure resin showed marked increases in the initial sorption rate as well as changes in mode, suggesting that irreversible changes in the resin had occurred.
Epoxy‐water interactions
Authors: Moy P. , Karasz F. E.
Published: December 2004

It has been shown that sorbed moisture plasticizes epoxy resins with a resultant depression in the glass transition temperature of the polymer. The nature of the epoxy‐water interaction still requires further investigation. The equilibrium sorption and diffusion of water in a high Tg epoxy is examined. Other analytical techniques including differential scanning calorimetry, infrared spectroscopy, electron microscopy and nuclear magnetic resonance are applied to the system. Experimental results suggest that the sorbed water at low concentrations is strongly localized at specific segments or groups in the polymer. Discussion is given relative to the structure‐properties of the epoxy and its possible correlation to the experimental data obtained.
Preparation of an ionomer elastomer by continuous sulfonation in an extruder and neutralization in static mixers
Authors: Siadat B. , Lundberg R. D. , Lenz R. W.
Published: December 2004

Rapid and efficient sulfonation of ethylene‐propylene terpolymer elastomer (EPDM) was achieved in a continuous melt mixing process. A mixture of sulfuric acid and acetic anhydride was used as the sulfonating agent. The reaction of EPDM polymer and the sulfonating agent was carried out in an extruder. It was shown that the continuous melt sulfonation of EPDM polymer may be used as an alternative to the batch solution methods previously reported for the preparation of sulfonated EPDM polymer. The extruder‐reactor method offers advantages of shorter process time, elimination of solvent handling hazards, and abatement of solvent removal and recovery problems.
Hydrostatic extrusion of linear polyethylene in tubular and non‐circular sections
Authors: Hope P. S. , Gibson A. G. , Parsons B. , Ward I. M.
Published: December 2004

Tubular and non‐circular section components have been produced by solid‐phase hydrostatic extrusion of linear polyethylene. Although the extrusion pressures were found to increase with the degree of complexity of the product sections, the module of the products were greatly enhanced and increased linearly with deformation ratio in the manner reported previously for circular section extrusions. Factors influencing the mechanics and stability of the process are discussed.
Melting performance in the single screw extrusion of thermoplastics
Authors: Cox A. P. D. , Fenner R. T.
Published: December 2004

Melting performance experiments involving three different thermoplastics and three different screw designs have been carried out on a well‐instrumented single screw extruder equipped for cold screw extractions. In the case of the particular polystyrene used it was possible to deduce, from measurements made on the extracted screw, the velocity, and hence acceleration, of the solid bed of compacted polymer at points along the screw channel. The experimental results are successfully compared with the performance predicted by a previously established model, the most important feature of which is the ability to allow the solid bed to deform freely and hence to accelerate. The results show that the bed does indeed suffer significant and non‐uniform acceleration and that the model can predict both this acceleration and the resulting bed break‐up which leads to surging.
Mixing in an intermeshing twin screw extruder chamber: Combined cross and down channel flow
Authors: Maheshri Jagdish C. , Wyman Charles E.
Published: December 2004

The cross and down channel flows are analyzed in the center of an idealized leakproof intermeshing twin screw extruder chamber. The respective velocity components are assumed to vary only with channel depth. Because the screw flights block the cross channel flow, fluid circulates between two complementary channel depths in the cross channel direction just as predicted for single screw extruders. In addition, fluid circulates between an independent set of channel depths in the down channel direction due to the seal provided by the second screw lands. When the two fluid motions are considered simultaneously, a fluid particle is predicted to follow a complex path over a number of channel depths during its residence time in the extruder. This unique flow also causes particles which are initially near one another to eventually move to significantly distant locations. Furthermore, a wide range of velocities and shear rates is experienced by a fluid particle as it moves to the various channel depths. The strain predicted by two approaches is nearly uniform for the twin screw extruder product in striking contrast to the distribution of absolute strains found in single screw devices. The strain uniformity, wide shear history, and fluid separation predicted by this analysis of a limiting case may help explain the good mixing capabilities of these devices.
Conformal mapping analysis of infection mold filling
Authors: Ryan M. E. , Chung T.‐S.
Published: December 2004

A conformal mapping analysis of the mold filling behavior in rectangular cavities is developed. The polymer melt is assumed to behave as a purely viscous Generalized Newtonian Fluid. The shape of the advancing flow front, the pressure distribution in the mold cavity, streamlines, constant temperature lines, and the required filling time may be readily determined using the techniques described. The theoretical results are in good agreement with experimental data previously reported in the literature.
Investigations on thermal and hydrolytic degradation of poly(ethylene terephthalate)
Authors: Zimmerman Heinz , Kim Nguyen Thac
Published: December 2004

The thermal properties of poly(ethylene terephthalate) (PET) are sensitively affected by polycondensation catalysts and temperature. The kinetics of thermal degradation were investigated by determining the rates of formation of carboxyl groups on isothermal heating. Carboxyl groups in PET were not only a result of thermal exposure but they were also an influence on hydrolytic stability. The hydrolytic cleavage of polyester chains, i.e., the formation of carboxyl groups, was found to be an autocatalytic reaction.
Photodegradation of polymers in solution as studied by laser flash photolysis
Authors: Schnabel Wolfram
Published: December 2004

By applying the light scattering detection method during flash photolysis experiments, causing main chain degradation of polymers, it is possible to study disentanglement diffusion of coiled macromolecules or the kinetics of the chemistry of main chain breakage. Results of typical experiments are presented. Poly(phenylvinylketone) was degraded at 347 nm in various solvents (disentanglement diffusion). Polystyrene was degraded at 265 nm in CHCl3 containing O2 (chemical reaction).
Direct evidence for the existence of a craze at the crack tip in environmental stress cracking of polyethylene
Authors: Bandyopadhyay S. , Brown H. R.
Published: December 2004

Liquid nitrogen fracture tests have been carried out to produce direct evidence of the existence of a voided region, the craze, ahead of the crack in environmental stress cracking of polyethylene. Evidence of crazing is presented for both low and high density polyethylenes.
Calendering poly(vinyl chloride): Theory and experiments
Authors: Vlachopoulos J. , Hrymak A. N.
Published: December 2004

An isothermal model for the calendering of power‐law fluids which exhibit a slip boundary condition is presented. This model is based on lubrication approximation and Gaskell's theorxy. It Predicts sheet thickness, pressure distribution, velocity profiles, torque and power from rheological data for the melt and machine parameters. The predictions (sheet thickness, pressure distribution and torque) are compared with a set of experimental data for rigid poly(vinyl chloride)(PVC) provided to the authors by Solvay & Cie S.A.
An anomaly in the necking behavior of polyethylene, Part 3
Authors: Gedde U. W. , Terselius B. , Jansson J.‐F.
Published: December 2004

Differential scanning calorimetry (DSC) measurements, polarized light microscopy and scanning electron microscopy (SEM) studies are reported on neck fibers formed by constant uniaxial tensile loading of polyethylene specimens at temperatures ranging from 298 to 353 K. The DSC measurements indicate that the temperature of the melting peak (Tpeak) of the neck fibers is closely related to the fibrilinity, i.e., the content of complete fibrillar structure, and that Tpeak and thus fibrillinity of the fractured neck fibers is sensitive to the nominal stress in the region of marked transition. A previously proposed hypothesis concerning the appearance of a marked transition in the necking/fracture behavior of high density and high molecular weight polyethylene is thereby supported. The polarized light microscopy showed a correlation between the zone length of the transformation from spherulitic to fibrillar structure and the previously reported distinctness in neck formation. The crystallinity determinations obtained from the DSC measurements and the SEM observations confirmed the suggestion previously made that the density decrease in the fractured neck fibers of a high density polyethylene with Mn = 21.6 × 103 and Mw = 199 × 103 is a result of void formation.
Rheological characterization of polycaprolactam anionically synthesized in the presence of lithium chloride
Authors: Acierno D. , D'Amico R. , La Mantia F. P. , Russo S.
Published: December 2004

Melt viscosity and dynamic‐mechanical data are reported for samples obtained by anionic polymerization of caprolactam, in the presence of LiCl. The full body of results is essentially in line with those previously reported relative to mixtures of inorganic salts and commercial nylon 6, In particular a drastic‐decrease of the melting point and of the rate of crystallization is confirmed as well as an increase of the glass transition temperature and of the melt viscosity. Some quantitative differences exist, which may be attributed to the different molecular weight distribution in the polymers employed in the present work.
A basic experimental study of sandwich injection molding with sequential injection
Authors: Young Sai S. , White James L. , Clark Edward S. , Oyanagi Yasushi
Published: December 2004

An experimental study of sandwich injection molding is reported which involves sequential injection of polymer melts with differing melt viscosity into a mold. In isothermal injection molding the relative viscosity of the two melts is the primary variable determining the phase distribution in the mold. Generally the most uniform skin‐core structure occurs when the second melt entering the mold has a slightly higher viscosity than the first melt injected. Large viscosity inequalities lead to nonuniform skin thicknesses. The influence of blowing agents and non‐uniform temperature fields on the extent of encapsulation is described. Temperature fields are very important especially if the first polymer melt injected has a greater activation energy of viscous flow (or a greater temperature dependence of the viscosity function).
Polymer compatibility: Nylon‐epoxy resin blends
Authors: Wang Yung‐Yun , Chen Show‐An
Published: December 2004

Dynamic mechanical and differential scanning calorimetric studies of cured blends of alcohol soluble nylon with up to 40 percent epoxy resin indicate that the blends contain three phases: crystalline nylon phase, crosslinked nylon‐epoxy resin phase, and crosslinked epoxy resin phase. There are unreacted nylon chains distributed in the former two phases. The crystalline nylon phase is composed of partially reacted nylon chains and a small amount of unreacted nylon chains. Degree of ordering in this phase, both unreacted and partially reacted nylon chains, decreases with increasing epoxy resin content. Stress‐strain studies show that stress‐induced crystallization in partially reacted nylon chains in the crystalline nylon phase does occur during elongation resulting in the occurrence of a maximum tensile strength (at 5 percent epoxy resin content) as in the case of crosslinked rubber. Lap shear studies using the blend as an adhesive indicate a maximum strength at 30 percent epoxy resin content, implying that adhesion and crosslinking effects due to incorporation of epoxy resin play a major role in the adhesion performance.
Bulk density versus hydrostatic pressure characteristics of plastics in powder and pellet form
Authors: Smith N. M. , Parnaby J.
Published: December 2004

Isothermal bulk density data measured for a number of commercially important plastics are presented for practical ranges of uniform hydrostatic pressure. Regression fitted polynomials are given for each plastic to facilitate the use of the data in computer‐aided lumped‐parameter, extrusion screw feed‐zone design methods. The cylindrical pressure‐test cell used for determining the data is described together with the theory governing its reliable operation.
Reactive rotational molding
Authors: Throne J. L. , Gianchandani J.
Published: December 2004

In order to identify the major fluid mechanical effects and catalog their domains of influence, an extensive study of flow behavior of reactive polyester resin systems in uniaxial, horizontal rotating systems has been undertaken. Four general flow phenomena are identified: cascading, where resin is withdrawn from the recirculating pool arid drains back; rimming, where resin is taken around the top of the cylinder by viscous forces; stable hydrocyst formation, where rings of fluid perpendicular to the axis of rotation are formed; and solid body rotation, where the resin on the mold wall is quite uniform and time‐independent. For most flow conditions, the desired region of solid body rotation apparently can be reached only by passing through each of the other flow regimes. Experimental work on polyester resin systems is compared with theoretical studies on flow stability, hydrocyst formation, and withdrawal from quiescent pools, and suitable correlations are developed. It is noted that the current correlations for stable hydrocyst formation are invalid for polyester resins and a simpler correlation is proposed.
The disk cure test—an evaluation method for flow and curing characteristics of thermosetting molding compounds
Authors: Tonogai Saburo , Hasegawa Kiichi , Fukuda Akinori
Published: December 2004

A new and useful method, the Disk Cure Test, has been developed for evaluating the curing characteristics and moldability of thermosetting resins. The change of flowability during heating in a thin state at given temperatures is examined as a measure of curing rate. The optimum test conditions were established. The feature of this method was also clarified by comparing it with the conventional tests, such as Brabender plastometry, Curelastometry, and solvent‐extraction. Based on this information on curing, the moldability and the optimum molding conditions were established for various commercial and laboratory compositions, including phenolics, aminos, diallyl phthalates, epoxies, and poly(bismaleimide).
Use of “penalty” finite elements in analysis of polymer melt processing
Authors: Roylance David
Published: December 2004

The finite element method is an approximate numerical analysis approach of great applicability to a wide variety of field problems. This paper describes the formulation of a convenient method for treating fluid‐flow problems relevant to analysis of polymer processing operations, and illustrates its use by means of some linear and nonlinear problems in melt extrusion.
An integrated experimental study of the injection molding behavior of some polyethylene resins
Authors: Kamal Musa R. , Kalyon D. M. , Dealy J. M.
Published: December 2004

The present study reports on the results of an integrated experimental program to determine some of the important interactions between resin properties, moldability, and the microstructure and ultimate properties of molded articles. As part of the program, resins are characterized as to their rheological, thermal, and crystallization behavior. Then, the resins are injection molded in a laboratory machine employing simple, but highly instrumented molds in order to evaluate moldability and to produce moldings for testing and analysis. Microstructural analysis to determine morphology and orientation of the moldings is carried out utilizing polarized light microscopy and differential scanning calorimetry. Finally, shrinkage and tensile properties of the moldings are determined experimentally. To illustrate the utility of the proposed techniques, results are reported for two polyethylene resins' that exhibit superficially similar properties but, according to tests, show significant differences in moldability and product properties.