bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rheological evaluation of polystyrene/polyethylene blends
Authors: Utracki L. A. , Sammut P. 
Published: December 2004

AbstractThe dynamic shear behavior at 200°C of low density polyethylene, LDPE, polystyrene, PS, and their blends was studied. Two series of blends were prepared containing LDPE:PS = 1:2, 2:1 and 17:3; the first series contained 0, the second 5 wt% of the compatibilizing, partially hydro‐genated poly(styrene‐b‐isoprene) di‐block copolymer, SEB. From the Casson plot the relative values of apparent yield stress were found to be G′y > G″y the addition of SEB decreased both these functions, but the inequality remained valid. After subtracting the yield stress values the frequency relaxation spectrum was computed from the relation G″ = G″(ω). The linear viscoelastic functions determined from the spectrum were found to agree with experimental values within a range of error below 5%. The blends were found to be thermorheologically complex with the time‐temperature shift factors depending on both temperature and frequency. A compositional dissymmetry of blend morphology was observed: PS dispersed in LDPE formed spheres, while at corresponding concentration LDPE in PS formed fibers. A difference in surface tension of the two polymers, leading to different spreading coefficients (SPE/PS≠SPS/PE), or dissymmetry of the interfacial tension coefficient, could provide a possible explanation.
J Integral measurements of ultra high molecular weight polyethylene
Authors: Rimnac Clare M. , Wright Timothy M. , Klein Robert W. 
Published: December 2004

AbstractFracture of ultra high molecular weight polyethylene (UHMWPE) contributes to damage modes occurring on the articulating surfaces of total joint replacement components. To minimize damage through the optimization of component design requires an understanding of the fracture behavior of UHMWPE. A fracture/mechanics approach was taken in which J integral tests were performed on three‐point bend specimens of two thicknesses. JIC was determined to be 99.5 kJ/m2 and was independent of specimen thickness. The fracture surfaces for both specimen thicknesses showed extensive orientation and failure through multiple layers of material, suggesting that UHMWPE experiences plane stress conditions at the crack tip, regardless of thickness.
Phase equilibrium in the binary and ternary blend system: Polycaprolactone‐polyvinyl chloride‐styrene acrylonitrile copolymer
Authors: Huarng Jyh Chiarng , Min Kyonsuku , White James L. 
Published: December 2004

AbstractAn experimental study of binary and ternary phase equilibrium in the system polycaprolactone (PCL) poly(vi‐nylchloride) (PVC)‐77/23 styrene‐acrylonitrile copolymer (SAN) is described. Miscibility is determined using differential scanning calorimetry (DSC) and turbidity. PCL/PVC and PCL/SAN are largely miscible systems but PVC/SAN is immiscible. The ternary system shows considerable miscibility. The blends are characterized by polarized light microscopy and wide‐angle X‐ray diffraction. The former measurement characterizes the structure of the spherulites. Additions of PVC, SAN, or PVC/SAN causes the spherulites observed in PCL to grow in size and become coarse. X‐ray diffraction shows no movement of crystallographic peaks indicating the crystallographic unit cell is composed of PCL. Melting point depression measurements are used to calculate Flory χ interaction parameters for PCL/PVC and PCL/SAN. The melting point depression is also considered and used to investigate PVC/SAN interaction. An effort is made to compute the ternary phase diagram and tie lines.
Memory effects in polymers. IV. Processing history vs. crystallization rate—effect of polymer structure
Authors: Khanna Y. P. , Kumar R. , Reimschuessel A. C. 
Published: December 2004

AbstractOur earlier work on this series has shown that the processing history, e.g., melt‐extrusion, freeze‐grinding, or solution precipitation of virgin nylon 6 leads to a marked increase in the crystallization rate. Similar studies have now been extended to several other polymers. Results indicate that the processing history effects on the crystallization rate are most pronounced for polymers with high intermolecular forces, e.g. nylon 6, nylon 66, nylon 6/66, nylon 11, and nylon 12. Interestingly, polymers of intermediate polarity, e.g., polyethylene terephthalate (PET) and chlorotrifluoroethylene (CTFE)/vinylidene fluoride (VDF) copolymer (96/4, Aclar®) also reveal similar effects although to a much lesser extent. On the other hand, non‐polar polymers, e.g. polyethylene, are not influenced in terms of crystallization behavior by the processing history.
Polyesters II: A review of phase behavior in binary blends: Amorphous, crystalline, liquid crystalline, and on transreaction
Authors: Porter Roger S. , Jonza James M. , Kimura Masao , Desper C. Richard , George Eric R. 
Published: December 2004

AbstractThermal and mechanical studies on many linear polyesters have revealed their behavior in crystalline, liquid crystalline, and amorphous phases. Their phase behavior in binary compositions has also been studied by a range of additional techniques and in combinations including the polycarbonate of bisphenol‐A. Regions of amorphous compatibility and incompatibility have been identified and measures made of transition temperature changes with composition. The conditions for transreaction have also been determined and the properties measured for the resultant new copolymers.
4,4′‐Isophthaloyidiphthalic anhydride polyimides
Authors: Pratt J. R. , Blackwell D. A. , St. Clair T. L. , Allphin N. L. 
Published: December 2004

AbstractA series of polyimides based on 4.,4′‐isophthaloyldiphthalic anhydride (IDPA) was prepared and characterized by inherent viscosity, differential scanning calorimetry (DSC), solubility, wide‐angle X‐ray scattering (WAXS), and isothermal thermogravimetric analysis (ITGA). Film forming, tough, insoluble polyimides were obtained with most of the 11 diamines used for evaluation. Two materials were semicrystalline. Several compositions showed excellent thermooxidative stability by ITGA at 300 and 350°C in air, as compared to Kapton‐H (Du Pont) film. The IDPA‐m‐phenylenediamine (m‐PDA) composition, for example, gave a flexible, amorphous film having a Tg of 259°C (identical with LARC‐TPI) and insoluble in a wide range of solvents. It is based on a potentially low‐cost dianhydride (IDPA) and, unlike LARC‐TPI, a low‐cost, domestically available diamine which gives a negative Ames test.
Effect of crosslinking density on the diffusion of antioxidant in XLPE matrices
Authors: Sheu Kueiying , Huang Samuel J. , Johnson Julian F. 
Published: December 2004

AbstractA Fourier Transform Infrared spectrometer equipped with a microbeam accessary and a linear translation stage with a pinhole mask was used to monitor the diffusion of antioxidant in crosslinked polyethylene (XLPE) matrices crosslinked with controlled amounts of crosslinking agent. Integration of the peak area for a characteristic peak of the antioxidant at different positions along the sample indicated the changing concentration due to diffusion within 30 days. This technique allowed us to study an antioxidant with a molecular weight in the thousand range. The diffusion coefficients calculated were in the order of 10−11 – 10−10 cm2·s−1. It was observed that the diffusion constants dramatically changed with the crosslinking density.
Shear and nonisothermal elongational characterization of a liquid crystalline polymer
Authors: La mantia F. P. , Valenza A. 
Published: December 2004

AbstractA commercial liquid crystalline polymer (LCP) sample was characterized both in shear and in nonisothermal elongational flow over a wide range of temperatures (240–350°C). The LCP sample employed was a copolyesteramide of 2,6 hydroxynaphthoic acid, terephthalic acid, and aminophenol manufactured by Celanese and commercially known as Vectra B950. The viscosity decreases dramatically at temperatures above the crystal‐nematic transition of the polymer. At lower temperatures, the extrusion of the sample is mainly due to plastic flow. Die‐swell values are very small and contraction of the extrudate is also revealed, but the sample shows high elasticity. The polymer is not spinnable at very low temperatures, and the melt strength rapidly decreases with increasing temperature.
Gas transport in multilayer packaging structures
Authors: Alger M. M. , Stanley T. J. , Day J. 
Published: December 2004

AbstractCalculation of gas permeation in food packaging structures can be done using a steady‐state analysis employing the permeability coefficient. While this approach is adequate for some applications, for many others a time‐dependent transport analysis must be considered to make quantitative predictions of shelf life. The limitation of the simple permeability analysis for multilayer structures is illustrated for Saran‐coated polycarbonate and poly(ethylene terephthalate) soda cans. These more detailed calculations on package structures can be done using standard computer library routines to include both the effect of gas sorption and diffusion.
Morphology of polyamide and polyether block amide blends
Authors: Boublil H. , Okoroafor E. , Belhoucine M. , Rault J. , Atochem M. Glotin 
Published: December 2004

AbstractThe morphology of polyamide 12 and polyether block amide blends was investigated by electron microscopy and dynamic mechanical techniques. The blends are not miscible, and phase segregation is observed. In each phase, the lamellar structure of the pure components is observed. The stability of these micro phases is pointed out. When the mass ratio of the hard and soft sequences in the block copolymer is about 4, a partial miscibility takes place.
Cure analysis of sheet molding compound in molds with substructures
Authors: Fan Jyh‐Dar , Lee L. James , Kim Junil , Im Yong‐Taek 
Published: December 2004

AbstractThe effects of material flow, heat transfer, part geometry, and curing agents on the cure of sheet molding compounds (SMC) in molds with substructures were analyzed both experimentally and numerically. It was found that heat transfer during mold filling has a profound effect on the cure pattern, especially for fastcure resins molded for parts with thin dimensions.
Speculation on interfacial adhesion and mechanical properties of blends of PET and thermotropic polyester with flexible spacer groups
Authors: Shin Boo Young , Chung In Jae 
Published: December 2004

AbstractA thermotropic liquid crystalline polyester (LCP) with a long flexible spacer group in the main chain was prepared by melt polymerization and mixed with poly(ethylene terephthalate) (PET). Differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) studies revealed that the crystallization of PET was accelerated by the addition of LCP in the matrix. Interfacial adhesion between PET and LCP was much improved by introduction of a long flexible spacer in the main chain. Fibers of the blend with 30 wt percent of LCP had fine microfibrillar structure with a large aspect ratio formed in the matrix. Initial modulus and ultimate strength were highly elevated by the addition of LCP due to good interfacial adhesion and microfibrillar structure of LCP in the blend.
Helical flow of curing highly viscous liquids
Authors: Jepsen C. , Mewes D. 
Published: December 2004

AbstractFor profile extrusion of rubber, a shear head is frequently placed at the outlet of the extruder. In the shear head, the rubber compound is heated to its cure temperature by means of internal friction between two coaxially rotating cylinders (annulus). The aim of this examination is to find suitable operating parameters for all rubber compounds. The highest possible temperatures and an even cure profile are the characteristics of suitable operations. The degree of cure should be as close as possible to the maximum cure permitted. For examination of the processes in the annulus, a coupled system of differential equations is set up and solved numerically. The cure profiles established along the annulus are of special interest. The effects of the geometry, the rotational speed of the inner cylinder, the volumetric flow, the operating temperatures, and the viscosity as a function of the shear rate and the temperature are examined. The results of the calculations show that the viscosity, which increases with increasing cure, has a strong effect on the velocity and dissipation profiles. The results of the experimental investigations on a shear head coincide well with theoretical prediction.
An experimental study of multiobjective dynamic optimization of a semibatch copolymerization process
Authors: Choi K. Y. , Butala D. N. 
Published: December 2004

AbstractOptimal open loop control strategies are developed for a semibatch free radical copolymerization of methyl methacrylate and vinyl acetate using the multiobjective dynamic optimization method. A detailed kinetic model is validated through experimentation and used for the design of optimal controls. Both monomer feed rate and reactor temperature are varied to produce the copolymer of desired composition and molecular weight. The open loop control policies are implemented in a process control computer and tested on an experimental stirred tank polymerization system. Excellent agreement between the model predictions and the experimental data have been obtained.
Effects of thermal modification on the structural properties of thermotropic liquid crystalline copolyester and phenoxy resin blends
Authors: Kodama Minekazu 
Published: December 2004

AbstractThe effects of thermal modification on the structural properties were studied for a poly(ethylene terephthalate‐co‐p‐hydroxybenzoic acid) liquid crystal bended with phenoxy resin. Poor miscibility and phase separation between the blend components are observed by the temperature dependence of dynamic mechanical properties of sample molded at 260°C, over the composition range studied. The miscibility of the blends is increased by molding at 280°C, and the blends molded by increasing the processing time show a dynamic mechanical transition to a homogeneous blend. These changes are the result of an interchange reaction between the blend components. A rubbery modulus has been observed for such blends. This implies the formation of cross‐linked structures that accompany the interchange reactions.
Relationships in a bismaleimide resin system. Part I: Cure mechanisms
Authors: Donnellan Thomas M. , Roylance David 
Published: December 2004

AbstractA series of bismaleimide resin systems has been examined in order to identify the molecular features responsible for the mechanical response of these materials. A range of network structures was produced both by formulation of resins with different ratios of N,N′‐bismaleimido‐4,4′‐diphenylmethane (BMI) and methylene dianiline (MDA), and by the use of different thermal processing cycles. Spectrographic and chromatographic techniques were used to study the reactions that occurred during the cure. Two principal reactions were confirmed: a Michael addition reaction which provides linear chain growth, and an addition reaction which produces crosslinking through the double bonds of the maleimide group. In general, curing at a lower temperature or increasing the MDA content served to favor chain extension over crosslinking, which might be expected to increase molecular mobility in the resin.
Static shear strength and adhesion friction of some thermoplastics
Authors: Benabdallah S. H. 
Published: December 2004

AbstractThe static shear strength and static friction of three thermoplastics have been investigated for the case of contact between a bulk plastic sample and a very smooth metallic plate. The minimum tangential force required to shear the interfacial adhesion bonds between the two surfaces was measured and defined as the adhesion component of friction Fa. Experimental results showed that Fa is large when the surface energy is high or the interfacial energy is small and that a correlation may exist between this force and the work of adhesion evaluated from Dupré equation. The real area of contact Ar was also measured using an optical device designed to handle samples and experimental conditions similar to the static friction tests. It was found that Ar is proportional to Pa0.9 where Pa is the apparent pressure of contact and an increase of Fa with Pr was observed. The static shear strength τ has been evaluated as the ratio Fa/Ar, and its relationships with the real contact pressure P approximated by linear functions. It was concluded that τ increases at high P, although it has not been verified for ultra‐high‐molecular‐weight polyethylene. An attempt has been made to explain the observed break in the data. The results indicated that (τ/τb) = κ′(τa/Pa) where b refers to bulk, a to apparent values, and κ′ is a proportionality constant that depends on the plastic material.
Electrical degradation of homo‐ and copolymers of styrenes and of styrene/2‐vinylnaphthalene
Authors: Gustafsson A. , Wiberg G. , Gedde U. W. 
Published: December 2004

AbstractA variety of different styrene monomers [styrene (S), p‐fluorostyrene (p‐FS), pentafluorostyrene (PFS), p‐chlorostyrene (p‐ClS), p‐bromostyrene (p‐BrS), p‐methylstyrene (p‐MS), p‐tert‐butylstyrene (p‐tBS), p‐methoxystyrene (p‐MOS), p‐ethoxystyrene (p‐EOS), and p‐propoxystyrene (p‐POS)] have been polymerized by radical and cationic mechanisms. Copolymers of S/PFS, S/p‐ClS, S/2‐vinyl‐naphthalene (2‐VN), and S/p‐phenylstyrene (p‐PhS) were prepared by radical polymerization. All polymers were fully amorphous and transparent and exhibited only one glass transition temperature in the temperature range 77 to 141°C. Thin films of the polymers were subjected to external electrical partial discharges (PD). Typically, 20 PD experiments were conducted for each polymer and the data for the time to breakdown were adapted to the two‐parameter Weibull distribution function. The resistance towards PD of the various polymers was found to depend strongly on the monomeric structure. Complementary PD experiments on a series of narrow molecular mass polystyrenes confirmed that the minor variation in molecular mass between the different styrene polymers is of no importance for the PD resistance. The PD resistance of the homopolymers decreased in the following order: PS ≈︁ P(p‐MS) > P(p‐tBS) ≈︁ P(p‐BrS) > P(p‐POS) > P(p‐ClS) ≈︁ P(p‐MOS) > P(p‐EOS) ≈︁ P(p‐FS) > P(PFS). The time to breakdown for copolymers of S and PFS decreased monotonously with increasing PFS content. Styrene copolymers with low molar contents of 2‐ VN and p‐PhS exhibited a higher resistance towards PD than PS. The results are discussed with reference to various properties of the studied polymers, such as segmental mobility, ionization potential, resonance stabilization, and reactivity of the radicals formed.
Electrical noise characteristics of carbon black–filled linear low density polyethylene near the percolation threshold
Authors: Bengtsson Per , Kubát Josef , Klason Carl , McQueen Douglas H. 
Published: December 2004

AbstractElectrical noise measurements have been used to study electrical conduction in carbon black‐filled linear low density polyethylene. Measurements of the resistivity, real part of the relative permittivity, thermal noise, and current noise have been carried out for carbon black contents and temperatures below, near, and above the percolation threshold for electrical conduction. The current noise shows a 1 /fα frequency dependence, with α near unity close to the percolation threshold, but increasing to 1.5 at higher resistivities or temperatures.
Investigation of the three region flow curve of polymeric liquid crystals by rheo‐optical methods
Authors: Asada Tadahiro 
Published: December 2004

AbstractSteady flow behavior of bulk liquid crystals and polymeric liquid crystals are summarized into a three region flow curve. Changes in the internal structure during deformation and flow were investigated by rheo‐optical methods. Two different optical geometries were used. In one method, a light beam passed through perpendicular to the shear plate, and in the other method a light beam passed perpendicular to the edge of the lamina flow. The results indicate that the details of the internal texture do not necessarily appear in the rheological properties, such as viscosity, and that the molecular orientation mechanism under shear force is fundamentally different in a liquid crystal of rod‐like molecules and a suspended solution of rod‐like molecules. In the isotropic solution, the rod‐like molecules float or are suspended in a solvent and are oriented by the flow field of the solvent fluid. However, in a liquid crystal, the torque propagates directly on the individual rod‐like molecules, affecting their orientation. They flow as if it were a plastic solid.
Interfacial stress concentration and the effect of residual microstress on tensile fracture in filled epoxy resins
Authors: Wang Hong‐Bing , Li Shan‐Jun , Yu Tong‐Yin 
Published: December 2004

AbstractInterfacial stress concentrations in rubber‐filled epoxy resin and glass bead–filled epoxy resin systems were studied by a photoelastic method. We found that the stress concentration is independent of the applied stress and the particle size, but decreases with increasing chemical bonding at the interface between rubber and matrix. For the rubber‐filled system, stress concentration is present at the equator of particles, while for either the untreated or treated glass bead‐filled system, it is on the two poles. The effect of interfacial residual microstress on tensile fracture was studied, and results showed that the function of residual microstress is limited as tensile elongation increases.
Analysis of polymer membrane formation through spinodal decomposition. III: Two‐dimensional simulations of early‐stage behavior
Authors: Chen Yuh‐Ling , Solc Karel , Caneba Gerard T. 
Published: December 2004

AbstractA nonlinear diffusion equation is used to study early‐stage spinodal decomposition of polymer solutions, in relation to the membrane formation, in two dimensions. The effects of overall polymer composition and composition‐dependent mobility and diffusivity are included in our simulations. Our results show a kinetically stable structure is established during the early stages, which corresponds to a circular range of peaks in the two‐dimensional frequency spectrum. Such a spectrum is found to result in an interconnected cell structure in the two‐dimensional real space. A decrease in the level of polymer interdomain interconnectedness is obtained as time increases, which indicates the influence of interfacial tension. As the overall polymer composition is increased, an increase in interdomain distances is observed, although the same early stage morphological structure is obtained. Finally, calculated interdomain distances from the two‐dimensional simulation are larger than those obtained in equivalent one‐dimensional model systems.
Injection molding using a generalized eulerian lagrangian formulation
Authors: Alexandrou Andreas N. , Armed Alauddin 
Published: December 2004

AbstractA mathematical and a numerical approach to model the injection mold filling stage is presented. The approach is based on a Generalized Eulerian Lagrangian (GEL) formulation. In purely Lagrangian formulations the solution is obtained at mesh points which follow the local fluid velocity. On the other hand, in Eulerian formulations the mesh is fixed and the solution is obtained at fixed spatial locations. In injection molding different parts of the flow domain are best analyzed by one but not both formulation methods. The Generalized Eulerian Lagrangian formulation combines the advantages of both formulations: In the same flow problem but different regions the GEL formulation allows the selective application of an Eulerian, Lagrangian, or a mixture of the two formulations. In this work the melt is described using the White‐Metzner constitutive relation and results are shown and discussed for the filling of a cavity from a single gate and from a fully open end under different process conditions.