bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolution of phase behavior and orientation in uniaxially deformed polylactic acid films
Authors: Kokturk G. , Piskin E. , Serhatkulu T. F. , Cakmak M. 
Published: April 2004

AbstractThe development of crystalline structure and orientation during uniaxial stretching of cast amorphous linear and branched lactic acid films were investigated in the rubbery temperature ranges that spans between glass transition temperature and cold crystallization temperature. This material exhibited almost ideal stress‐strain behavior in the temperature range 65–80°C. Because of its strain crystallizability, films with uniform thickness can be obtained at high deformation levels as a result of self‐leveling. Branching was found to retard this self‐leveling through its slightly detrimental effect on the strain hardening. Upon stretching the material undergoes rapid orientation in the amorphous state and beyond a critical level very sharp and highly oriented β crystalline form chains with −3/1 helix. If the temperature is at or below Tg, with additional stretching, the films were found to revert to a highly oriented amorphous state through the destruction of the crystalline domains. At higher temperatures, further stretching results in continuation of improvement in crystalline order.
Accelerated ultraviolet weathering of PVC/wood‐flour composites
Authors: Matuana Laurent M. , Kamdem Donatien P. 
Published: April 2004

AbstractUltraviolet weathering performance of polyvinyl chloride (PVC) filled with different concentrations of wood flour was studied. Extruded PVC/wood‐flour composite samples were subjected to cyclic ultraviolet lamps/condensation exposures and assessed over a total of 400 and 2600 hours. Each assessment consisted of DRIFTFTIR and XPS collections, contact angle measurement, color measurement, and tensile property testing. The experimental results indicated that wood flours are effective chromophore materials since their incorporation into a rigid PVC matrix accelerated the degradation of the polymeric matrix. Photodegradation converted unfilled PVC samples to a colored material of lower extensibility. Although composite samples exhibited greater discoloration than unfilled PVC samples, they retained all their original strength and stiffness properties even after 2600 hours of cyclic UV irradiation/condensation exposures.
Spatially homogeneous gelation in liquid composite molding
Authors: Comas‐cardona Sebastien , Ziaee Saeed , Advani Suresh G. 
Published: April 2004

AbstractOn‐line mixing of the resin with its curing agents prior to injection into a mold is a common industrial technique for fabricating composite parts. For vinyl‐ester resins that cure via free radical polymerization, the concentrations of retarder, accelerator, and initiator are pre‐selected and cannot be changed during the injection. Hence, the resin that enters the mold the earliest has cured longer than the resin that enters the mold later, since the gel time for the resin is the same, owing to the fixed ratio of the curing agents. This approach leads to inhomogeneous cure of the resin and consequently to longer residence time of the resin in the mold. It requires an additional 50 to 75 percent of the filling time before a part can be de‐molded. In this study, it is shown that by adjusting the concentration of curing agents during the injection, a more homogeneous gel time throughout the mold can be achieved. The time to de‐mold is reduced to 18‐24 percent of the filling time. Sensors that measure the conductivity of the resin were used to detect the location and monitor the cure of vinyl‐ester. This approach could be extended to other resin systems to control the spatial curing of the resin in the mold.
Interpenetrating polymer networks based on carboxylated nitrile rubber and poly(alkyl methacrylate)s
Authors: Manoj N. R. , Ratna D. , Dalvi V. , Chandrasekhar L. , Patri M. , Chakraborty B. C. , Deb P. C. 
Published: April 2004

AbstractA series of interpenetrating polymer networks (IPNs) based on carboxylated nitrile rubber (XNBR) and poly(alkyl methacrylate)s such as poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA) and poly(butyl methacrylate) (PBuMA) were synthesized. The compositions of the IPNs were also varied by changing the swelling time of the rubber in the methacrylate monomer. The tensile and dynamic mechanical properties of the IPNs were studied. The dynamic mechanical properties in the range of 1–105 Hz were obtained by the time‐temperature superposition of the data under multifrequency mode, which indicated high tanδ with good storage modulus in the entire frequency range. This indicates the suitability of these IPNs as vibration and acoustic dampers.
Accelerated aging of polyimide/titanium adhesive bonds using the notched coating adhesion test
Authors: Giunta Rachel Knudsen , Kander Ronald G. 
Published: April 2004

AbstractThe effect of elevated temperature aging on the interphase of a polyimide adhesive and a titanium substrate has been investigated. An interfacially debonding adhesive test was applied, and the adhesive/substrate interphase was characterized through an analysis of the failure surfaces. To facilitate the aging study, an “openfaced” adhesive geometry, the notched coating adhesion (NCA) test, was used. Use of this adhesive geometry allows an acceleration of diffusion‐related aging phenomena by up to two orders of magnitude, as compared to a traditional “sandwiched” bond. The failure surfaces were characterized using X‐ray photoelectron spectroscopy and optical microscopy. Bulk adhesive properties were investigated using differential scanning calorimetry and solvent uptake. Although there was evidence of polyimide degradation within the interphase, only minor changes in the bulk polyimide properties were detected. This indicates that the adhesive may be degrading preferentially in the interphase region.
Crown ether‐modified clays and their polystyrene nanocomposites
Authors: Yao Hongyang , Zhu Jin , Wilkie Charles A. , Morgan Alexander B. 
Published: April 2004

AbstractCrown ether‐modified clays were obtained by the combination of sodium and potassium clays with crown ethers and cryptands. Polystyrene nanocomposites were prepared by bulk polymerization in the presence of these clays. The structures of nanocomposites were characterized by X‐ray diffraction and transmission electron microscopy. Their thermal stability and flame retardancy were measured by thermogravimetric analysis and cone calorimetry, respectively. Nanocomposites can be formed only from the potassium clays; apparently the sodium clays are not sufficiently organophilic to enable nanocomposite formation. The onset temperature of the degradation is higher for the nanocomposites compared to virgin polystyrene, and the peak heat release rate is decreased by 25% to 30%.
The effect of crystallization on the structure and morphology of polypropylene/clay nanocomposites
Authors: Maiti Pralay , Nam Pham Hoai , Okamoto Masami , Kotaka Tadao , Hasegawa Naoki , Usuki Arimitsu 
Published: April 2004

AbstractThe effect of crystallization on the structure and morphology of maleic anhydride grafted polypropylene (PP‐MA)/clay (montmorillonite) nanocomposites (PPCNs) is presented. Wide‐angle X‐ray diffraction (WAXD) measurements of PPCNs crystallized at different temperatures show that the extent of intercalation increases with the crystallization temperature. The enhancement of intercalation occurs with lower clay content PPCNs, and maximum intercalation takes place for 4 wt% clay content. The mechanism of intercalation has been proposed through crystallization. Excess γ‐form of the crystallite of PP‐MA appears in presence of clay, possibly because of the confinement of the polymer chain between the clay particles. WAXD data also reveals that d‐spacing increases gradually with clay content. The decrease of spherulitic size is observed with increasing clay content, which indicates that clay particles act as nucleating agents. Lamellar textures have been explored by using small angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM), which exhibit that both the lamellar thickness and long period of the PPCNs are higher than those of PP‐MA.
Foam processing and cellular structure of polypropylene/clay nanocomposites
Authors: Nam Pham Hoai , Maiti Pralay , Okamoto Masami , Kotaka Tadao , Nakayama Takashi , Takada Mitsuko , Ohshima Masahiro , Usuki Arimitsu , Hasegawa Naoki , Okamoto Hirotaka 
Published: April 2004

AbstractPolypropylene (PP)/clay nanocomposites (PPCNs) were autoclave‐foamed in a batch process. Foaming was performed using supercritical CO2 at 10 MPa, within the temperature range from 130.6°C to 143.4°C, i.e., below the melting temperature of either PPCNs or maleic anhydride‐modified PP (PP‐MA) matrix without clay. The foamed PP‐MA and PPCN2 (prepared at 130.6°C and containing 2 wt% clay) show closed cell structures with pentagonal and/or hexagonal faces, while foams of PPCN4 and PPCN7.5 (prepared at 143.4°C, 4 and 7.5 wt% clay) had spherical cells. Scanning electron microscopy confirmed that foamed PPCNs had high cell density of 107–108 cells/mL, cell sizes in the range of 30–120 μm, cell wall thicknesses of 5–15 μm, and low densities of 0.05–0.3 g/mL. Interestingly, transmission electron microscopic observations of the PPCNs' cell structure showed biaxial flow‐induced alignment of clay particles along the cell boundary. In this paper, the correlation between foam structure and rheological properties of the PPCNs is also discussed.
Morphology and rheological properties of polypropylene/reactive elastomer blends
Authors: Marguerat Frédérique , Carreau Pierre J. , Michel Alain 
Published: April 2004

AbstractThe relation of morphology to the linear viscoelastic properties for polymer blends consisting of an inert polypropylene and an elastomeric dispersed phase, made of two miscible copolymers, EVA and EMA, was investigated. The rheological properties of the elastomeric phase were modified by crosslinking in presence of an organometallic catalyst. The activation energy for the transesterification reaction taking place between EVA and EMA has been determined by following the increases of the complex viscosity with time and temperature. The Palierne model has been used to describe the linear viscoelastic behavior of the blends, and to estimate the interfacial tension between the immiscible components. The model was shown to describe relatively well the linear viscoelastic properties of reactive and nonreactive blends containing 30% or less elastomer. In parallel, the morphology of reactive and nonreactive blends (i.e. without catalyst in the elastomeric phase), before and after rheological experiments, has been determined using scanning electron microscopy. The size of the dispersed elastomeric particles for reactive blends prepared using an internal mixer was found to be, in most cases, much smaller than that for nonreactive blends.
Effect of dynamic vulcanization on the microstructure and performance of polyethylene terephthalate/elastomer blends
Authors: Ma Pei Lian , Favis Basil D. , Champagne Michel F. , Huneault Michel A. , Tofan Florin 
Published: April 2004

AbstractBlends of polyethylene terephthalate (PET) and ethylene‐ethyl acrylate‐maleic anhydride terpolymer (E‐EA‐MAH) were dynamically crosslinked in a one‐step extrusion process. An amine‐terminated glycol reacting with MAH moieties was used as the crosslinking agent. The effect of blend composition and dynamic crosslinking on the microstructure and mechanical properties were investigated. Blend ratios ranging from 80:20 to 20:80 PET/E‐EA‐MAH were studied. The region of phase inversion was located for uncrosslinked and dynamically crosslinked blends. The rheological characterization was also carried out for these blends in comparison with the neat materials. After dynamic crosslinking, the phase inversion is shifted from the 30–40% range to the 70–80% range of elastomer content. This shift is induced by the increase of viscosity and elasticity of the network formed. Dynamically crosslinked blends show significant improvements in impact strength but also exhibit a decrease in elongation at break.
Effect of the dispersed phase fraction on particle size in blends with high viscosity ratio
Authors: Cho Y. G. , Kamal M. R. 
Published: April 2004

AbstractIt has been reported that for polymer blends with high viscosity ratio (>1), the size of the dispersed particles decreases with increasing volume fraction of the dispersed phase. In order to explain this effect, an equation was derived for the affine deformation of an imaginary plane of the dispersed phase in stratified two‐phase steady, simple, shear flow. The model predicts that for viscosity ratio >1, the deformation rate increases with volume fraction of the dispersed phase, and the shear stress also increases, leading to an increase of the breakup time. Therefore, the total deformation of the dispersed phase, before breakup, increases with increase of volume fraction, resulting in a decrease of the size of the dispersed phase particles. Accordingly, one can expect that in industrial mixers, the particle size of the blends should decrease as the volume fraction increases, if coalescence is suppressed. Experiments were carried out in a Haake batch mixer, using polyethylene/polyamide‐6 blends compatibilized by adding maleic anhydride grafted polyethylene. Particle size decreased up to 20 wt% polyamide‐6, at 100, 150, and 200 RPM, and increased between 20 and 30 wt%. The decrease of the particle size is mainly due to increased deformation of the dispersed phase. The increase of the particle size above 20 wt% is due to coalescence at high fractions.
Transient compositional effects from feeders in a starved flow modular co‐rotating twin‐screw extruder
Authors: Kim Eung Kyu , White James L. 
Published: April 2004

AbstractA process dynamics model of transient output composition variations in a moduar self‐wiping twin‐screw extruder caused by input disturbances from feeders is developed. The changes of output mass flow rate and weight fraction of additives in the output stream were predicted for various time dependent input modes into a second feeder and other ports part way along the length of the machine.
Continuous microcellular polystyrene foam extrusion with supercritical CO2
Authors: Han Xiangmin , Koelling Kurt W. , Tomasko David L. , Lee L. James 
Published: April 2004

AbstractThe continuous production of polystyrene microcellular foams with supercritical CO2was achieved on a two‐stage single‐screw extruder. Simulations related to the foaming process were accomplished by modeling the phase equilibria with the Sanchez‐Lacombe equation of state and combining the equations of motion, the energy balance, and the Carreau viscosity model to characterize the flow field and pressure distribution in the die. The position of nucleation in the die was determined from the simulation results via a computational fluid dynamics code (FLUENT). Experimental parameters were selected according to the Tgand phase equilibria. The effects of CO2concentration and die pressure are explored. Below the solubility limit, higher CO2concentrations lead to smaller cell size and greater cell density. With an increase of die pressure, the cell size decreases and the cell density increases.
Toughening mechanisms in annealed high density polyethylene under impact
Authors: Ravi S. , Takahashi K. 
Published: April 2004

AbstractImpact fracture behavior of annealed high density polyethylene (HDPE) has been studied. Charpy impact test results show that annealing increases the total fracture energy of HDPE and also that the increase in fracture energy is mainly due to the increase in the propagation energy with annealing time. Microscopic studies have been carried out to elucidate the origin of the rise in the propagation energy of the annealed HDPE. It is found that as annealing time increases, microscopically, the failure is more ductile with the formation of fibrillar structure. Based on the morphological study, it is proposed that the increased toughness observed in annealed HDPE is due to the occurrence of micro‐voids (or cavities) as the material yields under mode I dynamic tension. The void generation promotes the formation of fibrous structure, which absorbs greater energy than as‐received HDPE.
Effect of blending sequence on the microstructure and properties of PBT/EVA‐g‐MAH/organoclay ternary nanocomposites
Authors: Li Xiucuo , Park Hwan‐Man , Lee Jang‐Oo , Ha Chang‐Sik 
Published: April 2004

AbstractTernary nanocomposites based on poly(butylene terephthalate) (PBT), maleic anhydride grafted poly(ethylene‐co‐vinyl acetate) (EVA‐g‐MAH), and organically modified montmorllonite (organoclays) were prepared through four different blending sequences in a Haake rheocord mixer: (1) To blend PBT, EVA‐g‐MAH and organoclays in one step; (2) First to prepare EVA‐g‐MAH/organoclay nanocomposite, then mix it with PBT to get the final nanocomposite; (3) To mix PBT with organoclays first, then the PBT/organoclay nanocomposite with EVA‐g‐MAH. (4) To mix organoclays with the PBT/EVA‐g‐MAH blend. The microstructure of the PBT/EVA‐g‐MAH/organoclay ternary hybrids was characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that the blending sequence significantly influences the microstructure of PBT/EVA‐g‐MAH/organoclay ternary hybrids and the dispersion behavior of the organoclays in the polymer matrix. Tensile and impact properties of the hybrids were also studied. The results showed that the mixing sequence (2) gives the best tensile and impact strength due to its fine “sea‐island” morphology of PBT/EVA‐g‐MAH blend and good dispersion of the organoclays in the continuous PBT matrix.
Microwave absorbing properties of carbon black/silicone rubber blend
Authors: Kwon Soon Kil , Ahn Joon Mo , Kim Geun Hong , Chun Chang Hwan , Hwang Jun Sik , Lee Jeong Hwan 
Published: April 2004

AbstractIn the frequency range of 2–18 GHz, the microwave absorbing properties of a carbon black/silicone rubber blend were investigated by changing the carbon black content and the thickness. The real part (ε′) and the imaginary part (ε″) of permittivity of the blends were calculated from the S‐parameters measured by a network analyzer. The reflection loss was simulated by using ε′ and ε″. The reflection loss less than −10 dB could be obtained in the frequency range of 9.6ε13.5 GHz from the sample with 10 wt% of carbon black at 1.9 mm of thickness.
Tear strength of ductile polyolefin films
Authors: Chang A. C. , Inge T. , Tau L. , Hiltner A. , Baer E. 
Published: April 2004

AbstractA reinforced trouser tear test was developed to evaluate the tear resistance of thin ductile films. Tests with blown film of linear low‐density polyethylene blended with up to 30 wt% of a high melt strength polypropylene (hmsPP) demonstrated that the test differentiated among films based on composition and thickness. Increasing the amount of hmsPP in the film decreased the tear resistance. Also, thinner films were less tear‐resistant than thicker films. Stable crack growth occurred with transformation of a crack tip damage zone into a continuous yielded zone at the fractured edge. The tear energy was directly proportional to the width of the yielded zone. Correspondence between the energy to deform the material in the yielded zone and the measured tear energy demonstrated that yielding in the vicinity of the propagating crack provided the resistance to tearing in these films.
Measurement and prediction of LDPE/CO2solution viscosity
Authors: Areerat Surat , Nagata Takefumi , Ohshima Masahiro 
Published: April 2004

AbstractWhen CO2is dissolved into a polymer, the viscosity of the polymer is drastically reduced. In this paper, the melt viscosities of low‐density polyethylene (LDPE)/supercritical CO2solutions were measured with a capillary rheometer equipped at a foaming extruder, where CO2was injected into a middle of its barrel and dissolved into the molten LDPE. The viscosity measurements were performed by varying the content of CO2in the range of 0 to 5.0 wt% and temperature in the range of 150°C to 175°C, while monitoring the dissolved CO2concentration on‐line by Near Infrared spectroscopy. Pressures in the capillary tube were maintained higher than an equilibrium saturation pressure so as to prevent foaming in the tube and to realize single‐phase polymer/CO2solutions. By measuring the pressure drop and flow rate of polymer running through the tube, the melt viscosities were calculated. The experimental results indicated that the viscosity of LDPE/CO2solution was reduced to 30% of the neat polymer by dissolving CO2up to 5.0 wt% at temperature 150°C. A mathematical model was proposed to predict viscosity reduction owing to CO2dissolution. The model was developed by combining the Cross‐Carreau model with Doolittle's equation in terms of the free volume concept. With the Sanchez‐Lacombe equation of state and the solubility data measured by a magnetic suspension balance, the free volume fractions of LDPE/CO2solutions were calculated to accommodate the effects of temperature, pressure and CO2content. The developed model can successfully predict the viscosity of LDPE/CO2solutions fromPVTdata of the neat polymer and CO2solubility data.
Wood‐flour‐reinforced polyethylene: Viscoelastic behavior and threaded fasteners
Authors: Farid S. I. , Kortschot M. T. , Spelt J. K. 
Published: April 2004

AbstractThe tensile stress relaxation and flexural creep properties of wood‐fiber‐reinforced low‐density polyethylene (WFRP) were measured at various temperatures and stress levels. Power law relations were used to correlate the data, and time‐temperature superposition was applied to tensile stress relaxation results. Stress relaxation in WFRP was similar to that of LDPE and greater than that in spruce. The clamping force and torque characteristics of self‐threading screws and internally threaded inserts were measured in WFRP, and the viscoelastic model was extended to predict the relaxation in screw clamping force as a function of time. Both screw pullout force and the amount of clamping force relaxation were greater in WFRP than in spruce.
Transparent multiphasic polystyrene/epoxy blends
Authors: Hoppe C. E. , Galante M. J. , Oyanguren P. A. , Williams R. J. J. , Girard‐Reydet E. , Pascault J. P. 
Published: April 2004

AbstractBlends of polystyrene (PS) with an epoxy monomer (DGEBA) and a tertiary amine (BDMA), were initially miscible at 120°C but phase‐separated at very low conversions in the course of polymerization. Although there was a significant difference between the refractive indices of polystyrene and the DGEBA/BDMA solution, the refractive index of the epoxy network increased in the course of polymerization, attaining a value close to that of PS at complete conversion. A sharp decrease of the light transmittance was observed at the cloud‐point, observed at very low conversions. However, the continuous increase of the refractive index of the epoxy phase with conversion produced an approximate matching of both refractive indices, leading to transparent materials at complete conversion. Morphologies generated by reaction‐induced phase separation depended on the molar mass distribution of polystyrene and its mass fraction in the blend. For a PS with a high value of the mass‐average molar mass (Mw), it was possible to generate a dispersion of PS particles in the epoxy matrix (blends containing 5 wt% PS), phase‐inverted morphologies (blends containing 15 wt% PS) and double‐phase morphologies (blends with 10 wt% PS). Therefore, PS/DGEBA/BDMA blends could be used to obtain transparent epoxy coatings toughened by polystyrene particles or transparent polystyrene parts reinforced by a dispersion of epoxy particles.