bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of additives on the crystallization kinetics of semicrystalline polymers. II: Selective polymer‐additive interaction in poly(vinylidene difluoride)—poly(methylmethacrylate) blends
Authors: Pillin Isabelle , Pimbert Sylvie , Levesque Guy 
Published: April 2004

AbstractThe influence of pigments and mineral fillers on the crystallization kinetics of poly(vinylidene fluoride) (PVDF) in its blends with poly(methyl methacrylate) (PMMA) was studied by Differential Scanning Calorimetry and Optical Microscopy. The introduction of organic pigments or mineral fillers into PVDF results in a more or less significant increase in non‐isothermal crystallization temperatures, depending on the additives used. In PVDF, the pigment nucleation activity is quite different from that previously found in poly(butylene terephthalate) (PBT). Attractive interactions between PVDF and additive surfaces are particularly important parameters. The competition between pigments and talc lead to the observation that some pigments are able to inhibit the nucleating power of this mineral in PVDF, probably through specific attractive interactions. In PVDF‐PMMA blends, selective interactions between polymers and additives were observed, depending on their chemical structures. Highly chlorinated pigments present a strong attraction for PMMA and then lose an important part of their nucleating power towards PVDF. On the other hand, a pigment containing carbonyl groups becomes the most active nucleating agent, illustrating the presence of strong interactions between such compounds and the PVDF C‐H bonds.
Influence of the processing conditions on a two‐phase reactive blend system: EVA/PP thermoplastic vulcanizate
Authors: Joubert Catherine , Cassagnau Philippe , Michel Alain , Choplin Lionel 
Published: April 2004

AbstractThe elaboration of a TPV based on copolymer of ethylene and vinyl acetate (EVA) and polypropylene (PP) as thermoplastic phase was investigated in a batch mixer. The crosslinking reaction is carried out through a transesterification reaction between ester groups of EVA and alcoxysilane groups of the crosslinker agent tetrapropoxyorthosilicate (TPOS). The main advantage of this crosslinking reaction is that it can be well controlled and suitable for different processing conditions. The aim of the present study is to get a better understanding of the dispersion mechanism and of the phase inversion of the EVA major phase during its dynamic vulcanization into the PP minor phase. It was proved that the initial viscosity ratio, λ = ηpp/ηEVA, between EVA and PP plays an important part in the morphology development of the reactive blend. The viscosity ratio must be close to the critical ratio expressed by Utracki's model of phase inversion mechanism. Furthermore, the influence of different processing parameters on the variation of the morphology and on the mechanical properties of the ultimate TPV was investigated. The main conclusion of this study is that the characteristic time of crosslinking must be of the same order than the time of mixing. Indeed, better mechanical properties are obtained when a progressive phase inversion occurred and when it is controlled by rheological aspects and transient morphology equilibrium of the two phases and not by the mechanical fragmentation of the crosslinked EVA. For example, in our experimental conditions (concerning the amounts of catalyst and crosslinker reagents), high shear rates can be avoided (\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma} $\end{document} < 80 s−1) as the self‐heating of the blend under shear considerably increases (ΔT ≈ 50°C for \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma} $\end{document} = 225 s−1), leading to faster kinetics and consequently to a phase inversion controlled by the fragmentation of the crosslinked EVA phase.
Numerical prediction of residual stresses and birefringence in injection/compression molded center‐gated disk. Part I: Basic modeling and results for injection molding
Authors: Lee Young Bok , Kwon Tai Hun , Yoon Kyunghwan 
Published: April 2004

AbstractThe present study attempted to numerically predict both the flow‐induced and thermally‐induced residual stresses and birefringence in injection or injection/compression molded center‐gated disks. A numerical analysis system has been developed to simulate the entire process based on a physical modeling including a nonlinear viscoelastic fluid model, stress‐optical law, a linear viscoelastic solid model, free volume theory for density relaxation phenomena and a photoviscoelasticity and so on. Part I presents physical modeling and typical numerical analysis results of residual stresses and birefringence in the injection molded center‐gated disk. Typical distribution of thermal residual stresses indicates a tensile stress in the core and a compressive stress near the surface. However, depending on the processing condition and material properties, the residual stress sometimes becomes tensile on the surface, especially when fast cooling takes place near the mold surface, preventing the shrinkage from occurring. The birefringence distribution shows a double‐hump profile across the thickness with nonzero value at the center: the nonzero birefringence is found to be thermally induced, the outer peak due to the shear flow and subsequent stress relaxation during the filling stage and the inner peak due to the additional shear flow and stress relaxation during the packing stage. The combination of the flow‐induced and thermally‐induced birefringence makes the shape of predicted birefringence distribution quite similar to the experimental one.
Numerical prediction of residual stresses and birefringence in injection/compression molded center‐gated disk. Part II: Effects of processing conditions
Authors: Lee Young Bok , Kwon Tai Hun , Yoon Kyunghwan 
Published: April 2004

AbstractThe accompanying paper, Part I, has presented the physical modeling and basic numerical analysis results of the entire injection molding process, in particular with regard to both flow‐induced and thermally‐induced residual stress and birefringence in an injection molded center‐gated disk. The present paper, Part II, investigates the effects of various processing conditions of injection/compression molding process on the residual stress and birefringence. The birefringence is significantly affected by injection melt temperature, packing pressure and packing time. However, the thermally‐induced birefringence in the core region is insignificantly affected by most of the processing conditions. On the other hand, packing pressure, packing time and mold wall temperature affect the thermally‐induced residual stress rather significantly in the shell layer, but insignificantly in the core region. The residual stress in the shell layer is usually compressive, but could be tensile if the packing time is long, packing pressure is large, and the mold temperature is low. The lateral constraint type turns out to play an important role in determining the residual stress in the shell layer. Injection/compression molding has been found to reduce flow‐induced birefringence in comparison with the conventional injection molding process. In particular, mold closing velocity and initial opening thickness for the compression stage of injection/compression molding have significant effects on the flow‐induced birefringence, but not on the thermal residual stress and the thermally‐induced birefringence.
Crystalline forms in melt‐crystallized syndiotactic polystyrene/clay nanocomposites
Authors: Wu Tzong‐Ming , Hsu Sung‐Fu , Wu Jeng‐Yue 
Published: April 2004

AbstractX‐ray diffraction methods and polarized optical microscopy have been used to investigate the structural change of syndiotactic polystyrene/clay nanocomposites. The nanocomposite has prepared by mixing an sPS polymer solution with organically modified montmorillonite. Both X‐ray diffraction and transmission electron microscopy results indicate that most of the swellable silicate layers are exfoliated and randomly dispersed into the sPS matrix. The X‐ray diffraction data also show the presence of polymorphism in sPS/clay nanocomposites, which is strongly dependent on the thermal history of the nanocomposites from the melt and on the content of clay. In this study, the effect of premelting temperatures and crystallization temperatures of sPS and sPS/clay nanocomposites on their crystalline phases is discussed.
Carboxyl terminated polyamide 12 chain extension by reactive extrusion using a dioxazoline coupling agent. Part II: Effects of extrusion conditions
Authors: Chalamet Yvan , Taha Mohamed , Berzin Françoise , Vergnes Bruno 
Published: April 2004

AbstractCondensation reactions between a carboxyl terminated polyamide 12 and a dioxazoline carried out by reactive extrusion have been characterized in the first part of this study. In the present paper, we focus on the influence of extrusion conditions on reaction progress. Influences of screw profile, screw speed, barrel temperature and feed rate have been established. The use of a flow computation software permitted confirmation of the importance of thermal and mechanical degradations in the condensation process.
Bulk polymerization of methyl methacrylate in crosslinked NBR: The effect of the nature of boundary conditions on phase morphology and dynamic behavior of the final IPN
Authors: Omaraee I. Amiri , Mohammadi N. 
Published: April 2004

AbstractThe influence of the nature of confining walls on morphology development during bulk polymerization of methyl methacrylate in a poly(acrylonitrile‐ran‐butadiene) network was investigated by dynamic mechanical analysis and light and scanning electron microscopy. Some samples polymerized while confined by metallic walls showed broad damping properties between the Tg of the components and, consequently, a microheterogeneous morphology. On the other hand, the same compositions, polymerized while confined by glass walls, showed clear separation into a macroscopic three‐layer structure of poly(methyl methacrylate) film between NBR layers. This suggests that phase separation of polymeric systems under symmetric boundary conditions also depends on the nature of the boundaries.
Macroscopic observation of healing process in stress‐whitened polypropylene under hydrostatic pressure
Authors: Lee Jong Keun , Kim Jong Hyun , Chu H.‐C. , Pae Kook D. 
Published: April 2004

AbstractStress‐whitening and its healing phenomena in polypropylene under tensile load superposed on hydrostatic pressure up to 89.7 MPa have been investigated. Tensile samples of polypropylene were first cold‐drawn beyond the yielding at atmospheric pressure to develop stress‐whitening, and the stress‐whitened samples were further drawn under various intensities of hydrostatic pressure (P = 7.6 − 89.7 MPa). As a result of the experiment, morphological changes in stress‐whitening occurred in the necked gauge sections (RI and RII) and in the shoulders of the neck (RIII). The macroscopic observations were made by optical microscopy on the entire specimen and on the sliced sections. The stress‐whitening in the RI region was found to be either partially or nearly completely healed depending on the level of hydrostatic pressure at which the specimens were drawn. The cross sections of polypropylene specimens exhibited two concentric ring structures upon stress‐whitening. The stress‐whitened core region is surrounded by clear shell region. The size and degree of healing of stress‐whitening in the core region were affected by the applied hydrostatic pressure.
Rheokinetics of linear polymerization. A literature review
Authors: Cioffi M. , Ganzeveld K. J. , Hoffmann A. C. , Janssen L. P. B. M. 
Published: April 2004

AbstractThe dramatic increase of viscosity is a fundamental problem when designing a polymerization process. Since a thorough understanding of rheokinetics—the study of the coupled rheological changes and chemical kinetics in the reaction mixture—especially at high degrees of conversion, is still missing, industrial polymerization processes are often designed on basis of trial and error procedures and operate in far‐from‐optimal conditions. Even at laboratory scale the measurement of the viscosity of systems rapidly changing with time is troublesome and predicting quantitatively the increase of viscosity is not an easy task. The non‐Newtonian character of polymeric systems makes rheokinetics an even more challenging field, and more interesting as well. In this review article the difficulties encountered by the research community, the results obtained so far and the problems still to be faced are discussed.
The influence of alkyl end‐groups on the miscibility of hyperbranched polymers with polyolefins
Authors: Sendijarevic Ibrahim , McHugh Anthony J. , Orlicki Joshua A. , Moore Jeffrey S. 
Published: April 2004

AbstractPolyetherimide (PEI) hyperbranched polymers (HBPs) with alkyl terminated endgroups were blended with linear low density polyethylenes (LLDPEs) and extruded as thin films. The effects of length and concentration of the alkyl groups on the miscibility of the extruded films were examined using confocal and scanning electron microscopy (SEM). Surface properties of the blends were further characterized using contact angle measurements in de‐ionized water. Results indicate that migration of PEI HBPs to the film surfaces is predominantly driven by the surface energy differences of HBPs and polyolefins. Moreover, the addition of PEI HBPs to LLDPEs has a negligible effect on the processing properties of LLDPEs.
Effect of the compatibilizer on the physical properties of biaxially deformed in situ composites
Authors: Seo Yongsok , Kim Jinho , Kim Hyong‐Jun 
Published: April 2004

AbstractThe effect of a compatibilizer (poly(ester imide), PEsI) on the biaxial deformation of a thermotropic liquid crystalline polymer (TLCP, poly(ester amide)) in a poly(ether imide) and the properties of biaxially deformed in situ composites were studied. The compatibilizer improved dispersion of the TLCP and the adhesion between TLCP and the matrix. The properties of blown films were affected by the amount of the compatibilizer used. The morphology evidently shows that ca. 0.6 wt% PEsI provides the best morphology when 10 wt% VB phase is included. The mechanical properties, especially in the hoop direction, were significantly improved for the compatibilized films compared to uncompatibilized one. The impact strength of a compatibilized blend film with 0.6 wt% PEsI was almost twice that of an uncompatibilized blend film.
Effect of hybrid network formation on adhesion properties of polycyanurate/polyurethane semi‐interpenetrating polymer networks
Authors: Grigoryeva O. , Fainleib A. , Pissis P. , Boiteux U. 
Published: April 2004

AbstractThe adhesion characteristics of modified polycyanurates based on the principle of semi‐interpenetrating polymer networks (semi‐IPNs) have been studied. It has been shown that the formation of a polycyanurate network in the presence of linear polyurethane (LPU) leads to increasing adhesion strength to aluminum and titanium. The peculiarities of polycyanurate network (PCN) formation in the presence of different amounts of LPU are discussed. It has been found that chemical incorporation of LPU into PCN occurs during network formation owing to chemical interaction of urethane groups with cyanate groups of growing PCN. At LPU content in the initial composition up to around 20 wt% only a hybrid network is formed. The maximal values of adhesive strength to aluminum and titanium are achieved at LPU content of 20–25%, corresponding to formation of a hybrid network. The further increase of LPU content leads to the presence of non‐incorporated LPU (semi‐IPN formation) in the adhesive layer and to reduction of the adhesive strength.
Effects of temperature and strain rate on the tensile behavior of unfilled and talc‐filled polypropylene. Part I: Experiments
Authors: Zhou Yuanxin , Mallick P. K. 
Published: April 2004

AbstractThe tensile behavior of unfilled and 40 w% talc‐filled polypropylene has been determined at four different temperatures (21.5, 50, 75 and 100°C) and three different strain rates (0.05, 0.5 and 5 min−1). Experimental results showed that both unfilled and talc‐filled polypropylenes were sensitive to strain rate and temperature. Stressstrain curves of both materials were nonlinear even at relatively low strains. The addition of talc to polypropylene increased the elastic modulus, but the yield strength and yield strain were reduced. The temperature and strain rate sensitivities of these materials were also different. An energy‐activated, rate sensitive Eyring equation was used to predict the yield strength of both materials. It is shown that both activation volume and activation of energy increased with the addition of talc in polypropylene.
Effects of temperature and strain rate on the tensile behavior of unfilled and talc‐filled polypropylene. Part II: Constitutive equation
Authors: Zhou Yuanxin , Mallick P. K. 
Published: April 2004

AbstractBased on the experimental results presented in Part I of this research, a three parameter nonlinear constitutive model has been proposed to describe the strain rate and temperature dependent tensile behaviors of unfilled and talc‐filled polypropylene. One of the parameters is the elastic modulus. The other two parameters in this model are a strain exponent, m, and a compliance factor, β. Their relationships to strain rate and temperature are obtained from the experimental results. The simulated stress‐strain curves from the model are in good agreement with the test data. The analysis of the model shows that the strain exponent m, which controls the strain softening (or hardening) effect of the material, is not only strain rate independent, but also temperature independent. The compliance parameter, β, which controls the flow stress level of the material, on the other hand, varies with both strain rate as well as temperature. Results also show that the addition of talc filler in polypropylene reduces the strain exponent m, and increase the compliance parameter, β, which reduces the flow stress level of talc‐filled polypropylene to lower than that of unfilled polypropylene.
Development of rapid heating and cooling systems for injection molding applications
Authors: Yao Donggang , Kim Byung 
Published: April 2004

AbstractThe injection molding process has several inherent problems associated with the constant temperature mold. A basic solution is the rapid thermal response molding process that facilitates rapid temperature change at the mold surface thereby improving quality of molded parts without increasing cycle time. Rapid heating and cooling systems consisting of one metallic heating layer and one oxide insulation layer were investigated in this paper. Design issues towards developing a mold capable of raising temperature from 25°C to 250°C in 2 seconds and cooling to 50°C within 10 seconds were discussed. To reduce thermal stresses in the layers during heating and cooling, materials with closely matched low thermal expansion coefficient were used for both layers. Effects of various design parameters, such as layer thickness, power density and material properties, on the performance of the insert were studied in detail with the aid of heat transfer simulation and thermal stress simulation. Several rapid thermal response mold inserts were constructed on the basis of the simulation results. The experimental heating and cooling response agrees with the simulation and also satisfies the target heating and cooling requirement.
Synthesis and insecticidal activity of 5‐acyloxyimino‐5‐deoxyavermectin B1 derivatives
Authors: Xiguang Liu , Jingping Wu , Xiaomei Liang , Daoquan Wang 
Published: April 2004

AbstractFour novel 5‐acyloxyimino‐5‐deoxyavermectin B1 compounds have been synthesized from avermectin B1 by selective oxidization of the hydroxy group at C‐5, followed by oximation and convenient esterification. Their structures were confirmed by IR, 1H NMR, 13C NMR and MS. Insecticidal activities of the intermediate oxime and the four new acyl derivatives were evaluated against Helicoverpa armigera, Spodoptera exigua and Musca domestica. Copyright © 2004 Society of Chemical Industry
Tebuconazole dissipation and metabolism in Tifton loamy sand during laboratory incubation
Authors: Strickland Timothy C , Potter Thomas L , Joo Hyun 
Published: April 2004

AbstractThe fungicide tebuconazole is widely used to control soil‐borne and foliar diseases in peanuts and other crops. No published data are currently available on the extent and rate at which this compound degrades in soil. Unpublished data summarized in registration documents suggest that the compound is persistent, with 300–600 days half‐life. We conducted a 63‐day laboratory incubation to evaluate tebuconazole's dissipation kinetics and impact on soil microbial activity in Tifton loamy sand. Tifton soils support extensive peanut production in the Atlantic Coastal Plain region of Georgia and Alabama. Products containing tebuconazole are applied to an estimated 50% of the peanut acreage in the region. At the end of the incubation, 43 (±42)% of the parent compound was recovered in soil extracts. The first‐order kinetic model, which gave a good fit to the dissipation data (r2 = 0.857), yielded a soil half‐life (t1/2) of 49 days. This is 6–12 times more rapid than t1/2 values described in unpublished tebuconazole registration documents. Four degradates were identified. Tentative structural assignments indicated that degradates were derived from hydroxylation of the parent compound and/or chlorophenyl ring cleavage. Cleavage products showed a steady increase during the incubation, and on a molar basis were equal to 63% of the time zero tebuconazole concentration. No significant effect on soil microbial biomass was observed, indicating that when the compound is applied at normal agronomic rate it does not impact soil metabolic activity. Use of the soil‐half life data derived in this study should improve the accuracy of tebuconazole fate assessments for Coastal Plain peanut production. The study also indicated that environmental assessment of selected degradates may be needed to fully evaluate risks of tebuconazole use. Published in 2004 for SCI by John Wiley & Sons, Ltd.
Effect of exposure period on degree of dominance of phosphine resistance in adults of Rhyzopertha dominica (Coleoptera: Bostrychidae) and Sitophilus oryzae (Coleoptera: Curculionidae)
Authors: Daglish Gregory J 
Published: April 2004

AbstractDegree of dominance of phosphine resistance was investigated in adults of Rhyzopertha dominica F and Sitophilus oryzae L. Efficacy of the grain fumigant phosphine depends on both concentration and exposure period, which raises the possibility that dominance levels vary with exposure period. New and published data were used to test this possibility in adults of R dominica and S oryzae fumigated for periods of up to 144 h. The concentrations required for control of homozygous resistant and susceptible strains and their F1 hybrids decreased with increasing exposure period. For both species the response lines for the homozygous resistant and susceptible strains and their F1 hybrids were parallel. Therefore, neither dominance level nor resistance factor was affected by exposure period. Resistance was incompletely recessive and the level of dominance, calculated at 50% mortality level, was −0.59 for R dominica and −0.65 for S oryzae. The resistant R dominica strain was 30.9 times more resistant than the susceptible strain, compared with 8.9 times for the resistant S oryzae strain. The results suggest that developing discriminating doses for detecting heterozygote adults of either species will be difficult. Copyright © 2004 Society of Chemical Industry