bluuebunny/crossref_metadata_2025_split huggingface dataset:
High orientation of toughened chalk‐filled isotactic polypropylene: Preparation and properties
Authors: Galeski A. , Kryszewski M. , Kowalewski T. 
Published: December 2004

AbstractChalk‐filled isotactic polypropylene (iPP) toughened by modifying the interfaces with liquid oligomer of ethylene oxide was subjected to high deformation at elevated temperature. Oriented chalk‐filled material exhibits interesting properties: high concentration of open interconnected pores, high elastic modulus, high tensile strength, ability to absorb large quantities of liquids, white color and roughness of the surface. A continuous process for the production of oriented, toughened, chalk‐filled isotactic polypropylene is described. The stretching ratios which can be achieved range from 4 to 8 for modified chalk concentrations with compositions of 60 and 40 wt%, respectively. Solid state extruded, toughened, chalk‐filled iPP prepared for comparison exhibits similar morphology and properties as drawn toughened chalk‐filled iPP although it contains much less voids.
Model filled polymers. XIII: Mixing and time‐dependent rheological behavior of polymer melts containing crosslinked polymeric particles
Authors: Sun L. , Park M. , Aklonis J. J. , Salovey R. 
Published: December 2004

AbstractThe rheological properties of polystyrene (PS) and poly(methyl methacrylate) (PMMA) composites filled with monodisperse sized crosslinked polymeric particles are sensitive to processing history and chemical composition. Particles compatible with the matrix, such as PMMA or copolystyrene‐vinylphenol in a PMMA matrix, are randomly dispersed on mixing, yielding (almost) Newtonian fluids. Particles incompatible with the matrix, such as PS or copolystyrene‐acetoxystyrene in PMMA, produce composites whose steady shear viscosities depend on shear rate and whose dynamic moduli are elevated at low frequency. Particles in incompatible composites tend to cluster, producing a structure that is destroyed at high shear rates and that reforms on aging at elevated temperatures.
Photoinitiated crosslinking of low density polyethylene. V: Orientation in stretched samples
Authors: Qing Yan , Rånby Bengt 
Published: December 2004

AbstractLow density polyethylene (LDPE) is extruded, stretched, and photocrosslinked at different temperatures with different stretch rations in a continuous production line. Three different sequences are adopted: crosslinking before drawing, crosslinking after drawing, and crosslinking during drawing. The effect of drawing is studied by measuring the tensile properties. The increase of tensile strength and the decrease of elongation at break after stretching are related to chain orientation in crystalline morphology measured by X‐ray diffraction. Thermal analysis by differential scanning calorimetry (DSC) supports these results. Owing to chain relaxation, the effects of orientation by stretching are significant only when the samples are drawn at a temperature not much higher than the melting point. Annealing of the drawn samples at a temperature above the melting point shows that the orientation in a crosslinked sample is retained for a much longer time than in an uncrosslinked sample. For the crosslinked samples, it is found that crosslinking after or during drawing gives a material with lower shrinkage upon heating; however, crosslinking before drawing gives a heat‐shrinkable material.
Injection molding of unsaturated polyester compounds
Authors: Blanc R. , Agassant J. F. , Vincent M. 
Published: December 2004

AbstractA bulk‐molding compound made of unsaturated polyester resin, glass fiber, calcium carbonate fillers, and low profile additives is studied. The viscosity of the compound in the absence of cure reaction is measured by capillary rheometry. The compound exhibits a shear‐thinning behavior. Injection molding in a rectangular plaque equipped with pressure transducers shows that the crosslinking reaction can begin during mold filling for low flow rate or high mold temperature. Fiber orientation in the plaque is complex as the reinforcement appears under two aspects, bundles or filaments. Their lengths and orientations are different. A layered structure throughout the thickness is observed at the mold entrance, whereas the orientation becomes progressively unidirectional in the plaque. Two fiber‐free layers near the the mold walls are observed. A numerical simulation of mold filling assuming inelastic non‐Newtonian kinetic dependent behavior is presented. The results agree well with pressure measurements. A simplified decoupled fiber motion calculation is finally proposed. A qualitative explanation of the basic phenomena which induce fiber orientation is presented.
Some considerations on equation of state and phase relations: Polymer solutions and blends
Authors: Xie Hankun , Nies Erik , Stroeks Alexander , Simha Robert 
Published: December 2004

AbstractWe review briefly the general assumptions underlying hole theories of the configurational thermodynamic functions for single and multiconstituent systems. From the original Simha‐Somcynsky theory several important modifications have recently evolved. First, there is a revision of the combinatorial entropy originating from the mixing of segments and holes in the spirit of Huggins's theory. With consistent additional modifications of the configurational free energy, quantitatively significant consequences for certain aspects of phase equilibria can arise. Finally, allowance for nonrandom mixing of constituents species and holes has been made. We illustrate the theory's potentials first in terms of pressure‐volume‐temperature (PVT) data for high and low molar mass species and their miscible mixtures. The influence of PVT properties on the miscibility behavior of solutions and blends is examined next. Of particular concern are the connections between predictability of lower from upper mixing spinodals, pressure effects, and the binary interaction χ‐function.
Interfacial grafting and crosslinking by free radical reactions in polymer blends
Authors: Lambla Morand , Seadan Manus 
Published: December 2004

AbstractRelevant developments in polymer blends based on immiscible products have shown how efficient the amphiphilic species are in improving mechanical properties and morphological stabilization throughout successive processing steps. However, it appears that the amount of compatilizer that has to be introduced for reaching the expected level of global properties is largely higher than the calculated concentration based on the interfacial area. In order to obtain the required concentration of amphiphilic copolymer at the interface, it seems of interest to test the possibility of creating these species by in situ reactivity at the interface. As most of the polymers are hydrocarbon compounds, they are subjected to free radical reactivity by hydrogen abstraction on the different hydrocarbon sites, which may lead to crosslinking or grafting. Therefore, this work deals with reciprocal free radical reactivity of two immiscible semicrystalline homopolymers, namely, low density polyethylene (LDPE) and polyamide‐11 (PA‐11). The reaction has to occur mainly at the interface, where the resulting grafted copolymer has to be anchored for final stabilization of the biphasic system. Different analytical techniques help in characterizing the reacted blend and determining the level of interfacial grafting.
Compatibilized blends of polyamide‐6 and polyethylene
Authors: Padwa Allen R. 
Published: December 2004

AbstractAn increasing number of polymer alloys made by reactive processing of a compatibilizer precursor (CP) to form the compatibilizer in situ have appeared in recent years. Literature reports on compatibilization studies have focused on interactions of chemistry‐morphology, processing‐morphology, morphology‐rheology, morphology‐properties, etc. In commercial alloys, the interaction of chemistry and processing results in a material that has a balance of physical properties and rheological behavior. To maximize the contribution of each phase, it is of interest to be near the phase inversion region. In this work, maleic anhydride functionalized polyethylene is used as an effective CP for polyamide/polyethylene blends. In blends containing 50% nylon 6, the melt viscosity of the alloy increases exponentially as the ratio of CP to polyethylene increases though the morphology remains dispersed polyamide 6. High ratios of CP/PE are desired for toughness, alloys containing lesser amounts of CP exhibit better processability. The balance of toughness and processability is shown to be affected by the molecular weight of the CP.
Fluid mechanics of the formation of polymer blends. Part I: Formation of lamellar structures
Authors: Lindt J. T. , Ghosh A. K. 
Published: December 2004

AbstractThis paper deals with the early stages of blend morphology development as occurs in a screw extruder. Using combinations of similar polymers (polystyrene and styrene‐butadiene copolymer) and dissimilar polymers (PS and EVA) as model systems, it has been concluded that during melting the scale of segregation between the blend components is reduced by orders of magnitude within fraction of a second residence time. During the early stages of morphology development, the melting pellets produce fine lamellar structures (thickness of the order of μm) that extend over much of the melting zone before being broken up by capillary forces. The origin and the deformation history of the lamellar structures have been successfully interpreted by a new theory.
Spatial depth profiling of chromophores in thin polymer films using photopyroelectric spectroscopy
Authors: Prystay M. C. , Power J. F. 
Published: December 2004

AbstractFrequency domain photopyroelectric effect spectrometry (FD‐PPES) is a recent spectroscopic technique that may be used to recover depth profiles of optical absorption in thin films on a noncontact and nondestructive basis. In this work a series of well characterized thermally homogeneous samples were prepared that exhibited continuous or discrete subsurface profiles of optical absorption. Multifrequency FD‐PPES measurements made on these samples were compared to theory using a heat transfer model, which we have developed for a multilayer thermally homogeneous absorber. Excellent agreement between experiment and theory was obtained for these model studies. While both phase and magnitude channels of the FD‐PPES response give depth profiling information, the phase response is especially sensitive to variations in the subsurface profile of optical absorption. By means of the phase response it is possible to determine the number and spatial positions of absorbers in a series of discrete absorbing layers. The FD‐PPES. technique has excellent potential for analysis and nondestructive evaluation of polymer films.
Glass transition temperatures in bismaleimide‐based resin systems
Authors: Tungare A. V. , Martin G. C. 
Published: December 2004

AbstractThe glass transition temperatures in bismaleimide‐based resins were investigated using different stoichiometric ratios of 1, 1′‐(methylenedi‐4, 1‐phenylene)bismaleimide (BMI) and 4, 4′‐methylenedianiline (MDA). The resin cure involves a low temperature primary amine addition to the maleimide double bonds and a high temperature homopolymerization of the maleimide double bonds. The network topology and the glass transition temperature changes with resin composition and curing conditions were determined using differential scanning calorimetry (DSC). An empirical model was used to relate the glass transition temperature to the extents of the amine addition and the homopolymerization reactions in 1:1 and 2:1 BMI:MDA resins. The changes in thermal properties with resin post‐cure were also examined.
Plasma polymerized tetramethyl germanium films deposited at elevated substrate temperatures
Authors: Sadhir R. K. , Saunders H. E. , Byers W. A. 
Published: December 2004

AbstractThin plasma polymerized films of tetramethyl germanium are deposited at various substrate temperatures. The influence of substrate temperature on the deposition rate, composition, structure, and electrical properties of the films is discussed. With an increase in the substrate temperature from 25°C to 150°C under similar plasma deposition conditions, the conductivity of the film increased by four orders of magnitude. Films of plasma polymerized tetramethyl germanium deposited at 150°C show typical semiconducting behavior (increasing conductivity with increasing temperature) and have a sheet conductivity of 1.0 × 10−6 S cm−1 at 25°C. There is a direct correlation between the conductivity and the composition of the films, i.e., the higher the conductivity the higher the ratio of germanium to carbon at the surface. At deposition temperatures of 25 and 75°C the germanium to carbon ratio was essentially the same, but at a deposition temperature of 150°C, this ratio was considerably higher.
Effect of catalyst on the reactive processing of polyesters with epoxy‐functional polymers
Authors: Stewart M. E. , George S. E. , Miller R. L. , Paul D. R. 
Published: December 2004

AbstractThe objective this work was to determine the effects of selected polyester catalysts on the reaction of a polyester with epoxy functional polymers. Polyesters containing various catalyst metals were melt blended with either an ethylene‐co‐glycidyl methacrylate or a styrene‐co‐glycidyl methacrylate copolymer. The viscosities of the blends were monitored as a function of mixing time using torque rheometry. In addition, the molecular weight distributions of selected samples were analyzed using gel permeation chromatography. Both the torque rheometry and the gel permeation chromatography results indicate that the polyester reacts with epoxy functional polymers. This reaction occurs under conditions and at processing times which are readily obtainable in conventional melt processing equipment. Furthermore, the reaction kinetics of polyesters with glycidyl methacrylate copolymers are dramatically affected by the nature of the catalyst system used to prepare the polyester. Under the conditions used, antimony catalysts are particularly effective at promoting the reaction between polyesters and the epoxy functionality and the activity of the catalysts studied appears to decrease in the following order: antimony > gallium > tin ≃ titanium > germanium. Manipulation of the polyester catalyst system may offer a method to control the extent of reaction obtained in reactive processing of polyesters with epoxy functional compounds.
Impact toughened blends of styrene‐maleic anhydride copolymer, polyethylene, and ethylene‐propylene copolymer
Authors: Datta S. , Dharmarajan N. , Ver Strate G. , Ban L. 
Published: December 2004

AbstractImpact‐toughened, compatibilized binary blends of styrene‐maleic anhydride (SMA) copolymer/amine functionalized ethylene‐propylene (amine‐EP) polymer and ternary blends consisting of SMA/amine‐EP/high density polyethylene (HDPE) are described. In both blends 0.02 to 4 μm range rubbery inclusions, which toughen the SMA matrix, are formed. SMA sub‐inclusions exist in the amine‐EP phase. In the ternary blend substantially all of the polyethylene is embedded in the EP phase. Compatibilization of the SMA and the commingled polyolefin phase is promoted by a graft copolymer formed by the reaction of amine groups on the EP with the maleic anhydride groups on the SMA. We describe the morphology, rheology, aging characteristics and impact properties of these blends. SMA modification by SMA‐g‐(amine‐EP) polymers formed in situ in the melt, with HDPE, has not been previously reported.
Plasticity and fracture initiation in rubber‐toughened poly(methyl methacrylate)
Authors: Gloaguen J. M. , Steer P. , Gaillard P. , Wrotecki C. , Lefebvre J. M. 
Published: December 2004

AbstractThe deformation behavior of rubber toughened poly(methylmethacrylate), RT‐PMMA, has been investigated in terms of the ability of the material to nucleate plasticity. Work‐hardening rate parameter K measurements in the early stages of the nonelastic response in a constant strain‐rate test are used to probe the development of micro shear zones as a function of rubber volume fraction. The results reveal the existence of a sharp transition from difficult to easy shear band nucleation for a critical rubber volume fraction Vc. This abrupt change in mechanical behavior also shows in the evolution of the critical stress intensity factor K measured at the onset of crack initiation. These findings are discussed in terms of the morphological parameters of the blends.
Characterization and analysis of defects in extruded/coagulated films of heterocyclic aromatic polymers for nonlinear optics studies
Authors: Mehta R. , Lee C. Y.‐C. 
Published: December 2004

AbstractThe high degree of electron delocalization in heterocyclic aromatic molecules makes this class of chemistry ideal for hyperpolarizability and NLO (nonlinear optics) polymer developments. This type of polymer is usually insoluble in common solvents and is not amenable to common optical film processing techniques like spin coating. A study of the approach in using an acidic solution extrusion followed by coagulation for optical quality film forming is reported in this paper. The polymers studied are: PBZT, (poly (p‐phenylene benzobisthiazole)); 6F‐PBO (polybenzobisoxazole containing hexaflorinated moities); and Zytel 330 (an amorphous nylon). Some of the resulting films showed an improved optical quality while others showed an extremely poor optical quality over the films used in a previous study. The optically clear films, however, were not of wave‐guiding quality. The defects in the films that would cause light scattering were characterized and the probable causes of these defects were discussed. The defects were: (a) optically inferior morphology, (b) micro‐voids, (c) macro‐voids, (d) solid particles, (e) lines in the transverse direction, and (f) lines in the machine direction. Identification and classification of these defects will help additional efforts in the future for improving the optical quality of heterocyclic aromatic polymer films.
Properties and morphology of oriented ternary blends of poly(ethylene terephthalate), high density polyethylene, and compatibilizing agent
Authors: Sambaru Prasad , Jabarin S. A. 
Published: December 2004

AbstractOriented blends of poly(ethylene terephthalate) (PET) and high density polyethylene (HDPE) with and without compatibilizing agent have been studied with regard to orientation temperature, stretch rate, extension ratio, mode of orientation, and blend composition. These oriented blends have been characterized using infrared spectroscopy and differential scanning calorimetry. The tensile and tensile impact properties were also investigated. The results show that blends with compatibilizer show strain hardening upon orientation, whereas the blend without compatibilizer does not strain harden upon orientation. The blends with less PET content have been difficult to orient. The morphology of these blends show fibril structure, highly oriented in the direction of stretch. Infrared measurements show that PET within the blend has undergone strain induced crystallization upon orientation. It has also been observed that the mechanical properties, such as the modulus and ultimate stress, show improvement upon orientation. Simultaneously stretched blends show better physical properties than sequentially oriented blends.
The influence of rubber‐matrix interfaces on the crystallization kinetics of isotactic polypropylene blended with ethylene‐propylene‐diene terpolymer (EPDM)
Authors: Wenig W. , Asresahegn M. 
Published: December 2004

AbstractBlends of isotactic polypropylene with amorphous and slightly crystalline ethylene‐propylene‐diene terpolymer (EPDM), prepared by solution blending, have been investigated by optical microscopy and differential scanning calorimetry. Nucleation and crystallization kinetic parameters, such as nucleation rates, nucleation half times, Avrami‐exponents and spherulitic growth rates, have been determined. It has been found that the dispersion of crystalline EPDM in iPP is different from that of amorphous EPDM. Both EPDMs are incorporated into the spherulites, causing a decrease of the maximum growth rate of the iPP spherulites. The surface free energy of the iPP crystals is diminished on adding EPDM to iPP and is accompanied by a higher secondary nucleation rate. From the decrease observed in the Avrami exponent with increasing EPDM concentration in the blend, it has been concluded that nucleation becomes predominantly heterogeneous, as there is a proportional increase in the interfacial area between the two components.
Fibers from blends of PET and thermotropic liquid crystalline polymer
Authors: Mehta Sanjay , Deopura B. L. 
Published: December 2004

AbstractBlends of poly(ethylene terephthalate‐Co‐p‐oxybenzoate), PET/PHB, with poly(ethylene terephthalate), PET, have been studied in the form of as‐spun and drawn fibers. DSC melting and crystallization results show that the PET is compatible with LCP and the crystallization of PET decreases by the addition of LCP in the matrix. Upon heating above the crystal melting temperature of PET, the blend shows good dispersion of LCP in the PET matrix. Wide angle X‐ray diffraction of drawn blended fibers show the possible formation of LCP oriented domains. The mechanical properties of drawn fiber up to 10 wt% LCP composition exhibit significant improvement in tensile modulus and tensile strength with values of 17.7 GPa and 1.0 GPa, respectively. Values of modulus are compared with prediction from composite theory, assuming the blend system as nematic domains of LCP. dispersed in PET matrix.
Sheet extrusion of in‐situ composites: Influence of processing parameters
Authors: Crevecoeur G. , Groeninckx G. 
Published: December 2004

AbstractUnidirectional sheets were extruded of an in‐situ composite of thermotropic liquid crystalline Vectra B950 in a matrix of polyphenylene‐ether and polystyrene. Three important processing parameters were systematically varied: draw‐ratio, slit opening and extruder throughput. Morphology and mechanical properties of these films were determined, and qualitatively related to the processing conditions.
Analysis of residence time distribution in the extrusion process including the effect of 3‐D circulatory flow
Authors: Joo J. W. , Kwon T. H. 
Published: December 2004

AbstractIt is of great importance to accurately measure or predict the Residence Time Distribution (RTD) in designing extruders and/or in setting up a proper operating condition, because chemical reactions depend significantly on the RTD and temperature when chemical reactions take place during the extrusion process. A previous method to predict the RTD can analytically determine RTD, Residence Time Distribution Function f(t) and Cumulative Residence Time Distribution Function F(t), based on a simplified two‐dimensional velocity field in an extruder. However, this previous method cannot accurately take into account the three‐dimensional circulatory flow inside the extruder. The present paper suggests a new method to accurately determine the RTD taking into account the three‐dimensional circulatory flow and presents a new formula derived to calculate f(t). In order to demonstrate the applicability of the new method including the circulatory flow effect, RTD, f(t) and F(t) were calculated based on a three‐dimensional velocity field obtained via a quasi‐three‐dimensional finite element analysis. It was found that the previous method has a tendency to underestimate the RTD, owing to the neglect of the three‐dimensional circulatory flow in comparison with the new method.