bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chlorinated high density polyethylene. II. Solid state structure
Authors: Chang B. H. , Dai J. W. , Siegmann A. , Hiltner A. 
Published: December 2004

AbstractChlorination of high density; polyethylene results in polymers which consist of unmodified methylene units and chlorinated methylene co‐units. The effect of the concentration and distribution of chlorinated units on the solid state structure has been examined by thermal, wide angle X‐ray diffraction and dynamic mechanical analysis. As the substitution becomes more random, the crystallinity, crystallite size, and crystalline perfection decrease for a given chlorine content. The chlorinated units are shown to be capable of co‐crystallizing, and the concentration of chlorine in the crystalline phase increases as the distribution is made more random. Concurrently, the chlorine concentration of the amorphous phase decreases. Segregation of chlorine into the amorphous regions is most efficient when the substitution is blocky.
Application of the parallel Avrami model to crystallization of poly(etheretherketone)
Authors: Cebe Peggy 
Published: December 2004

AbstractWe have reexamined the parallel Avrami model recently proposed by Velisaris and Seferis (1) to describe the non‐Isothermal crystallization of poly(etheretherketone), PEEK. We show that, based on considerations of morphology development, the crystallization process with the larger Avrami exponent has the higher melting point, whereas the process with the smaller Avrami exponent has the lower melting point. This assignment differs from that of Velisaris and Seferis. In addition, we have used the infinite crystal melting point, as required by crystallization theory, to determine the Avrami rate parameters for the two processes. With this revision of the parallel Avrami model, we have applied the model to non‐isothermal crystallization of APC‐2 PEEK composite. Under the assumption that the linear growth rate determines the Avrami rate parameter, both the transport activation energy, U, and the kinetic parameter, Kg, are found to compare favorably with the values previously determined from isothermal crystallization of neat resin PEEK.
Microstructure in injection molded samples of liquid crystalline poly(P‐hydroxy‐benzoic acid‐Co‐ethylene terephthalate)
Authors: Hedmark Per G. , Lopez J. Manuel Rego , Westdahl Marianne , Werner Per‐Erik , Jansson Jan‐Fredrik , Gedde Ulf W. 
Published: December 2004

AbstractThe microstructure of injection molded bars (2.9 and 5.8 mm thick) of thermotropic liquid crystalline poly(p‐hydroxy‐benzoic acid‐co‐ethylene terephthalate) has been studied by SEM on samples etched with n‐propylamine, SEM fractography, DSC, IR, ESCA, WAXS and polarized microscopy. The 2.9 mm bar consists of three different layers: a highly oriented surface skin, an oriented intermediate layer and a non‐oriented core. The 5.8 mm bar has a more complex microstructure and is composed of five different layers: a highly oriented surface skin, an oriented layer just beneath, a non‐oriented layer, another oriented layer and a non‐oriented core. The thicknesses of the different layers vary, significantly, with distance from the mold gate. The thickness of the core increases, significantly, with increasing distance from the mold gate at the expense of the oriented layers. The structure within the different morphological layers is not perfectly uniform. Tensile testing demonstrated the mechanical anisotropy of the surface material (a ratio of almost 20 between the longitudinal and transverse moduli) and the isotropy of the central core material.
A study of miscibility of blends of polybutadienes of varying microstructure
Authors: Shah Ketan , Min Kyonsuku , White James L. 
Published: December 2004

AbstractThe miscibility of various amorphous polybutadienes with mixed microstructures of 1,4 addition units (cis, 1,4 and trans 1,4) and 1,2 addition units have been investigated. The studies here involved optical transparency, differential scanning calorimetry, and small angle light scattering. It was found that a 90 percent (cis) 1, 4 addition polybutadiene was immiscible with high (91 percent) 1,2 addition polybutadiene. Reduction of the 1,2 content to 71 percent induced an upper critical solution temperature (UCST) with the cis 1,4 polymer. Polybutadienes with 50 percent and 10 percent 1,2 contents were miscible above the crystalline melting temperature of the cis 1,4 polybutadiene. Immiscibility of the 91 percent 1,2 addition polymer was also found with a 10 percent 1,2 polybutadiene. The latter polymer also exhibits an UCST with the 71 percent 1,2 polymer. The results are used to interpret the characteristics of blends of polybutadienes of varying microstructure.
Processing‐morphology relationships of compatibilized polyolefin/polyamide blends. Part I: The effect of an lonomer compatibilizer on blend morphology
Authors: Willis J. M. , Favis B. D. 
Published: December 2004

AbstractThe morphology of compatibilized polyolef in/polyamide blends was found to be significantly dependent on the concentration of an ionomer compatibilizer (polyethylene‐methacrylic acid‐isobutyl acrylate terpolymer) in the blend. For a dispersed phase content of 10% by weight, a maximum reduction in phase size was observed when only 0.5% by weight of ionomer was added to the blend, A more significant reduction of the dispersed phase size was observed when the minor phase was nylon, due to interactions which exist between the ionomer and the polyamide. These interactions have been confirmed by Fourier transform infrared spectroscopy. At high concentrations of the ionomer, flocculation of the nylon dispersed phase was observed. In comparison to one‐step mixing, blends prepared by two‐step or batch mixing were characterized by a smaller dispersed phase when nylon was the matrix, and a larger particle size when nylon was the minor phase. The results observed are explained in terms of a speculative model of the interactions occurring across the nylon‐polvolefin interface.
Rubber toughening of polystyrene through reactive blending
Authors: Fowler M. W. , Baker W. E. 
Published: December 2004

AbstractAcrylonitrile‐butadiene rubber having carboxylic acid groups (XNBR) and polystyrene having oxazoline groups, were melt blended in a Rheomix mixer under optimized conditions, The ratio of rubber to polystyrene phase was kept constant at 1:4 by weight. The concentration of the reactive oxazoline groups in the polystyrene phase was varied by mixing polystyrene (PS) with a copolymer of styrene and vinyl oxazoline (OPS). A torque rise observed during blending was found to be related to the concentration of oxazoline‐carboxylic acid pairs. This torque rise, and independently measured increases in viscosity, both indicate inter‐polymer crosslinkihg. Scanning electron microscopy was used to observe the morphology of the blends. Improved rubber phase dispersion was observed with increasing oxazoline concentration. Instrumented impact strength measurements were made using an unnotched Charpy technique. The plastic yielding was then quantified with the use of a ductility ratio. The impact strengths and ductility of the reactive blends are found to be up to 73% greater than those of the corresponding non‐reactive blends. Increasing the OPS concentration beyond 5% results in decreasing impact strength, for as the compatibility increases, the rubber particle size decreases below an effective size for rubber toughening. Similar impact improvement is observed when the major PS phase is substituted with high impact polystyrene (HIPS) containing some OPS.
Reactive extrusion of polystyrene/polyethylene blends
Authors: van Ballegooie Peter , Rudin Alfred 
Published: December 2004

AbstractThe feasibility of inducing beneficial changes to polystyrene/polyethylene (PS/PE) blends via reactive extrusion processes is considered. Experiments have been conducted on 50:50 wt.% PS/PE blends that were treated with different levels of dicumyl peroxide and triallyl isocyanurate coupling agent. Both a low molecular weight and a high molecular weight blend series have been investigated. A “more reactive” polystyrene was synthesized by incorporation of a minor amount of ortho‐vinylbenzaldehyde. Blends containing this modified polystyrene were subjected to identical processing' conditions on a counter‐rotating twin screw extruder. Examination of the tensile properties of the extrusion products suggested that a judicious level of peroxide and coupling agent additives would be beneficial to the ultimate physical properties. The quantity of styrenic phase becoming chemically grafted to the polyethylene matrix was influenced most strongly by the level of the chosen coupling agent. As determined by scanning electron microscopy, the phase morphologies of the tensile test fracture surfaces were strongly dependent upon the reaction extrusion process; those extruded blends that had been exposed to the additive pre‐treatment displayed substantially finer microstructure. The enthalpy of fusion of the polyethylene melting endotherm was likewise influenced by both the presence or absence of the additives as well as the molecular weight nature of the blend series.
Determination of the nature and content of antioxidant and antioxidant synergist in polyethylene and crosslinked polyethylene used in cables
Authors: Crine J.‐P. , Haridoss S. , Cole K. C. 
Published: December 2004

AbstractIt is shown that polyethylene and crossllnked polyethylene resins used for cable applications contain an antioxidant synergist in addition to an antioxidant. Their nature and content have been determined by a combination of ultraviolet and Fourier transform infrared spectroscopy and neutron activation analysis measurements. The results thus obtained suggest that part of the antioxidant compound is grafted to polymer chains during crosslinking.
Dielectric analysis of epoxy/amine resins using microwave cavity technique
Authors: Jow J. , Hawley M. C. , Finzel M. , Kern T. 
Published: December 2004

AbstractDielectric properties (permittivity and dielectric loss factor) of stoichiometric mixtures of DGEBA (diglycidylether of bisphenol A) epoxy (DER 332) and amine (diaminodiphenyl sulfone; DDS) as a function of temperature and extent of cure have been measured at a microwave frequency of 2.45 GHz. Permittivity and dielectric loss factor of this resin increase with increasing temperature and decrease with increasing extent of cure. Dielectric loss factor is more dependent on temperature in the early stages of cure but becomes less dependent on temperature as the cure proceeds. Dielectric loss data can be related to extent of cure in order to monitor the cure process. Online measurements of temperature‐ and cure‐dependent dielectric loss factor show three material structure stages and significant changes in dielectric loss factor during the microwave cure process. Dielectric Joss factor is also found to be the same for both thermal and microwave cured samples.
A process for the simultaneous oligomerization and copolymerization of ethylene
Authors: Benham E. A. , Smith P. D. , McDaniel M. P. 
Published: December 2004

AbstractHigh density polyethylene becomes more flexible and tough by adding short branches onto the otherwise linear backbone. Commercially, this is achieved by adding 1‐butene or 1‐hexene comonomer to reactor and copolymerizing it with ethylene. A process has now been developed which uses low pressure to produce new forms of branched polyethylene without addition of comonomer to the reaction mixture.
Computer‐aided analysis of a linearly tapered coat‐hanger die
Authors: Liu Ta‐Jo , Hong Chin‐Nan , Chen Kun‐Chou 
Published: December 2004

AbstractWe describe the computer‐aided engineering analysis of a linearly tapered coat‐hanger die in this paper. The general governing equation for flow distribution inside the die was derived first. On the basis of this equation, we have developed the design formula for a die to deliver uniform flow. In addition, we have also examined the variations of lateral flow uniformities and residence time distributions of polymeric liquids under several different design and operating conditions: (1) using manifolds with non‐circular cross‐sections, (2) adjusting production widths, (3) delivering fluids with different viscosities, and (4) enlarging manifolds for practical production considerations.
On the role of coupling agents in zirconia‐polypropylene suspensions for ceramic injection molding
Authors: Hunt K. N. , Evans J. R. G. , Woodthorpe J. 
Published: December 2004

AbstractThe effect of titanate, zirconate, and zircoaluminate coupling agents on the viscosity of zirconia‐polypropylene injection molding blends was investigated. The zircoaluminate did not influence viscosity while the two former additives effected a considerable reduction. The titanate coupling agent also reduced the viscosity of the polymer in the absence of ceramic powder, and was more efficient in this respect, as a flow modifier than dioctyl phthalate. A comparable effect on the ceramic suspension was obtained by adding a species similar in molecular structure to the titanate coupling agent but without coupling ability.
Memory effects in polymers. II. Processing history vs. crystallization rate of nylon 6—observation of phenomenon and product behavior
Authors: Khanna Y. P. , Reimschuessel A. C. , Banerjie A. , Altman C. 
Published: December 2004

AbstractThe observation of a novel phenomenon is reported whereby the processing history of a nylon 6 leads to a memory effect which in turn affects its crystallization rate from the molten state. Differential scanning calorimetry (DSC) and optical microscopy are the primary techniques used to demonstrate that the melt‐crystallization behavior of nylon 6 can be controlled by processing variables. Characterization data is presented to show that obvious parameters such as molecular weight, impurities, monomer and oligomers, etc. are not responsible for the observed changes in crystallization behavior upon processing. It is shown that the mechanical properties and/or morphology of a nylon 6 article can depend upon the processing technique (e.g., compression or injection molding) as well as the processing history of the nylon 6 resin itself.
A study of bubble nucleation in a mixture of molten polymer and volatile liquid in a shear flow field
Authors: Han James H. , Han Chang Dae 
Published: December 2004

AbstractBubble nucleation in a mixture of volatile liquid and polymer melt under shear flow conditions was investigated, using a light scattering technique. In the study, a mixture of polystyrene and trichlorofluoromethane was extruded through a slit die having glass windows and bubble nucleation in the flow channel was observed optically. A He‐Ne laser was used to illuminate the nucleating and growing bubbles. The light flux scattered by the growing bubbles at a fixed angle was detected by a photomultiplier with the aid of a high‐voltage power supply. The bubble nucleating site in the flow channel was located using a computer controlled tracking system, which was designed to move the entire optical system automatically in the three dimensional space, and also had the ability to follow the software control command and cooperate with the data acquisition system. When the site of bubble nucleation was located, the coordinates of this site in the flow channel and the experimental conditions were automatically recorded on a floppy diskette by entering a software command. The pressure profile along the flow channel was measured by pressure transducers, with the aid of a microprocessor‐based pressure reading system. It has been found that the site of bubble nucleation varies with the position in the direction perpendicular to the flow direction, which is attributed to the nonuniform velocity and stress distributions in the slit flow channel. The present investigation suggests that bubble nucleation can be induced either by flow and/or shear stress; specifically, flow‐induced bubble nucleation is the dominant mechanism at positions near the center of the die opening, and shear‐induced bubble nucleation is the dominant mechanism at positions near the die wall. It should be mentioned that the bubble near the die wall may also be generated by cavitation brought about by the surface roughness of the wall and also by thermal fluctuations due to the heat transfer between the metal (die wall) and the mixture of polymer and volatile component. The present study indicates that bubble nucleation in a shear flow field can occur at an unsaturated condition. This is in contrast to bubble nucleation under static conditions, where supersaturation is necessary.
Laboratory simulation of space and salt water environmental effects on polymers
Authors: Garton Andrew , Henry Jacqueline L. , McLean Paul D. , Stevenson William T. K. 
Published: December 2004

AbstractMost polymers are eroded rapidly (>0.1 μm/h) in the low earth orbit (LEO) environment when facing the direction of flight. The rate of erosion varies little with the polymer type, except for fluoropolymers and silicones. Methods for simulating such an environment are reviewed. Secondly, the oxidation lifetime of stabilized and unstabilized polyolefins can be reduced 50 to 90 percent, with a, high yield of carboxylic acid (i.e. chain scission) oxidation products, when thermal oxidation at 70 to 90°C takes place in 0.01 to 0.1 molar sodium chloride solutions, as compared to thermal oxidation in air. Both sets of observations illustrate the need for detailed mechanistic investigations before accelerated test procedures can be developed to predict material lifetime.
Effect of mixing history on phase morphology of a polyalloy and a polyblend
Authors: Plochocki A. P. , Dagli S. S. , Curry J. E. , Starita J. 
Published: December 2004

AbstractThis paper details some of the immediate findings for phase morphology formation and persistence in an industrial melt mixing of a polyblend/alloy (‘PB’/‘PBA’). Estimation of the minor phase domain size in a polyblend is feasible if the viscoelasticity functions, interfacial tension of the component‐polymers, and the mixing process shear stress level are available. Clusters of domains are formed in the mixer (following streamlines). During steady flow in capillaries the clusters are forming rings which result from the flow velocity profile. Quantitative description of the clusters requires an expansion of image analysis software to account for the interdomain spacing in the clusters, as well as for their pattern. The on‐line rheometry was found useful for monitoring coalescence and the effectiveness of the compatibilizer: higher “stiffness” of the PAB melt compared with that of PB shows up in measurements of complex viscosity and modulus. Further study is required, however, for correlating domain spacing and the real time rheometry data (esp. the relaxation spectrum plateau [13]). Finally, the study of phase morphology for the “model” polyblend provides an insight into the melt deformation history in an industrial mixer. It is expected that the distribution of domain sizes would correlate with the pass frequency in the mixing blocks [41], stress distribution in the extruder, and coalescence of the dispersed (“minor”) phase.
Sheet molding compound compression‐molding flow
Authors: Castro J. M. , Griffith R. M. 
Published: December 2004

AbstractMost available descriptions of sheet molding compound (SMC) flow are based on a generalized Hele‐Shaw type model. These analyses have several deficiencies. SMC slip at the wall is neglected, and unrealistic rheological models are used. Consequently, molding pressures are incorrectly predicted but, nonetheless, the fill patterns for thin, large area charges typical of exterior automotive body panels are reasonably well predicted as is shown here by comparison with experiment. Recently, a model has been developed that allows for slip at the wall and assumes extensional resistance controls in the interior of the SMC. The model contains the Hele‐Shaw approximation as an extreme case. The predicted molding forces during fill are compared with experiment for some commercial moldings. A dimensionless group to predict when the Hele‐Shaw type models fail in predicting the charge shape is developed and its applicability demonstrated.
Molecular weight distributions of tetrafluoroethylene‐hexafluoropropylene copolymers
Authors: Tuminello W. H. 
Published: December 2004

AbstractA new methodology has been developed to determine molecular weight distributions (MWD) from dynamic rheometry data. The present work extends and modifies previous results and illustrates that the MWDs of tetrafluoroethylenehexafluoropropylene copolymers (FEP) are broader than previously thought. The major change in methodology involves the relationship between a reduced form of the elastic shear modulus as a function of frequency, G′(ω), and the cumulative weight fraction as a function of molecular weight. The new method uses a square root versus the former linear relationship. Spectroscopic analysis of the end group concentration was used to determine the number‐average molecular weight. These data were used to reference the MWDs determined by dynamic rheometry and indicate that the molecular weights of these polymers are 20% lower than previously found.
Measurement of polymer viscoelastic response during an impact experiment
Authors: Nairn J. A. 
Published: December 2004

AbstractInstrumented impact data on polymers typically show high frequency oscillations that decay in amplitude during the impact event. By undertaking a complete impact analysis including effects of inertial loading, external damping (friction), and internal damping (viscoelastic relaxations), we have been able to predict all the details of the high frequency oscillations. The most consistent analysis of impact data on Delrin® 100 polyacetal is one that ignores friction and attributes the decay of the high frequency oscillations to the effect of viscoelastic relaxations in the polymer. The impact analysis therefore allows us to extract viscoelastic relaxation information from Instrumented impact data. It is further suggested that this direct observation of viscoelastic relaxations during impact testing should make it possible to make a quantitative assessment of the role that viscoelastic relaxations play in influencing the impact toughness of polymers.
Fracture toughness of impact‐modified polymers based on the J‐integral
Authors: Narisawa I. , Takemori M. T. 
Published: December 2004

AbstractThe fracture toughness characterization of four impact‐modified polymers based on the J‐integral concept was studied. We have discovered that the use of the “crack blunting line” concept needs revision. Direct measurements of the crack growth can be made (as opposed to indirect readings from the fracture surface) that test the applicability of the crack blunting concept. Our results indicate that for rubber‐toughened polymers the use of the blunting line fails to specify properly the critical J‐integral value for crack initiation.
Stress development in plastic sheet extrusion
Authors: Chan T. W. David , Lee L. James 
Published: December 2004

AbstractThe development of flow‐induced stresses in extruded sheet made of polypropylene was analyzed. A theoretical model was developed to simulate velocity, temperature, and stress profiles for polymeric materials flowing inside a slit die. The output of this simulation was then used to compute temperature and stress profiles as the extrudate emerged from the die, cooled, and relaxed under no draw conditions. Simulated surface stresses and stress profile across the extruded sheet agreed well with the experimental data for the die temperature effect and the die gap effect at low draw ratios.