bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation of exfoliated high‐impact polystyrene/MMT nanocomposites via in situ polymerization under controlling viscosity of the reaction medium
Authors: Uthirakumar Periyayya , Kim Hee Joo , Hong Chang‐Hee , Suh Eun‐Kyung , Lee Youn‐Sik 
Published: December 2007

AbstractExfoliated high‐impact polystyrene (HIPS)/montmorillonite (MMT) nanocomposites were prepared via in situ polymerization of styrene in the presence of polybutadiene, using an intercalated cationic radical initiator‐MMT hybrid (organoclay). In the solution polymerization in toluene, the silicate layers of the clay were well exfoliated, due to the low extra‐gallery viscosity that can facilitate the diffusion of styrene monomers into the clay layers during the polymerization. The exfoliated HIPS/MMT nanocomposites were also successfully prepared by controlling the viscosity of the reaction medium with prolong swelling of the organoclay in styrene, prior to bulk polymerization. The HIPS/MMT nanocomposites, obtained from bulk polymerization, exhibited a significant improvement in thermal stability, compared to those obtained from solution polymerization as well as the pure polymer counterparts. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers
Influence of gamma irradiation on waste poly(propylene) composites containing talc and high crystallinity poly(propylene)
Authors: Hassan Medhat M. , El‐Kelesh Nabil A. , Dessouki Ahmed M. 
Published: December 2007

AbstractCommercial polyolefin, such as poly(propylene), are widely used because of their easy processing and their excellent mechanical and thermal properties. Although their recycling is well established, the mechanical and thermal properties of the recycled waste poly(propylene)(WPP) are normally lower than those of the virgin material. The introduction of talc can improve the toughness, without compromising the processability and recycling capabilities. However, the thermal properties of these blends should be assessed to limit degradation during recycling. The effect of gamma radiation on the thermal and mechanical properties of WPP/High Crystallinity Poly(propylene)/Talc was studied. TGA, DSC, and electrical conductivity performed the characterization of WPP composites. Mechanical properties and electrical conductivity of the composites were evaluated. The results showed that the addition of Talc to WPP was found to improve the thermal stability of WPP composites. The compatibilisation of the blends using gamma radiation resulted decrease the weight loss with increasing the temperature. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers
Preparation and nonisothermal cure kinetics of DGEBA‐nanosilica particles composites
Authors: Ghaemy M. , Nasab S.M. Amini , Barghamadi M. 
Published: December 2007

AbstractNanocomposites from nanoscale silica particles (NS), diglycidylether of bisphenol‐A based epoxy (DGEBA), and 4,4′‐diaminobiphenyl benzidine (DAPB) as curing agent were obtained from direct blending of these materials. This homogenous mixture was cured in the oven at a particular temperature for a certain time or scanned from room temperature up to 300°C in differential scanning calorimeter (DSC). Mechanism and kinetic of the cure reaction of nanocomposite and thermal stability of the cured sample were studied with FTIR, DSC, and thermogravimetric analysis, respectively. The effect of amount of nanosilica (NS) particles as catalyst on the cure reaction of DGEBA/DAPB system was studied by the Kissinger and Ozawa equations. The existence of NS particles with hydroxyl groups in the structure catalyzes the cure reaction of DGEBA/DAPB system, increased the rate constant, and shifted the exothermic peak toward lower temperatures with increasing amount of NS particles. The activation energies of cure reaction of pure DGEBA/DAPB system obtained from two methods were in good agreement and decreased when NS particles were present in the mixture. The isothermal cure reaction at 145°C in an oven was followed by measuring the disappearance peak of epoxide group at 916 cm−1 using FTIR. The diffusive behavior of cured samples was investigated during water sorption at 25°C and the experimental results fitted well according to Fick's law. Diffusion coefficient of cured sample containing 10% NS decreased in comparison to the sample without NS particles. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers
Organic–inorganic hybrid boron‐containing phenol–formaldehyde resin/SiO2 nanocomposites
Authors: Gao Jungang , Jiang Chaojie , Ma Weitao 
Published: December 2007

AbstractThe organic–inorganic hybrid boron‐containing phenol–formaldehyde (BPFR) resin/SiO2 nanocomposites was synthesized in‐situ from boric acid, phenol, and tetramethoxysilane. The structure of BPFR modified and the distributions of silicon element were studied by Fourier‐transform infrared spectroscopy, energy dispersive X‐ray spectrometry, and transmission electron microscope, respectively. The glass transition temperature (Tg) was determined by torsional braid analysis. The results show that silicon element distribution is homogeneous, and the size of nanosilica is about 40–60 nm. The thermal stability and kinetics parameters of thermal degradation were determined by thermogravimetry analysis (TGA). TGA results show that the resin modified has higher heat resistance property when the additive quantity of SiO2 was 3 wt%. The temperature of 5% weight loss is 487.7°C, which is 12.4°C higher than that of common BPFR. The residual ratio of 3 wt% SiO2/BPFR was 62.3% at the temperature of 900°C, which is 11.2% higher than that of common BPFR. The mechanics loss peak Tp of 3% SiO2/BPFR is 33°C higher than common BPFR. Fiberglass‐reinforced BPFR modified by 3 wt% SiO2 has better mechanical and dielectric properties than that of common BPFR. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers
Sliding wear and friction characteristics of sisal fibre reinforced polyester composites: Effect of silane coupling agent and applied load
Authors: Chand Navin , Dwivedi U.K. 
Published: December 2007

AbstractChopped sisal fibre‐reinforced polyester composites with and without silane modification were prepared. Wear and friction measurements on the chopped sisal fibre reinforced polyester composites have been performed at different loads for different weight percentages of sisal fibre by using a pin‐on‐disc wear and friction tester. It has been found that increase of chopped sisal fibre content increased the Pressure‐Velocity (PV) limit of composites. Silane modification improved the wear resistance of untreated sisal fibre reinforced polyester composite. Coefficient of friction increased with increase of fibre content and decreased with increase of load. Wear mechanism has been discussed with the help of SEM observations. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers
Novel biodegradable flame retardant, poly(butyl methacrylate)/sodium silicate/Mg(OH)2 nanocomposite
Authors: Samal Ramakanta , Rana Pradeep K. , Mishra Girija P. , Sahoo Prafulla K. 
Published: December 2007

AbstractFlame retardant poly(butyl methacrylate)/sodium silicate/Mg(OH)2 (MH) nanocomposite has been prepared via in situ emulsion polymerization of BMA, benzoyl peroxide, layered silicate, and conventional fire retardant additive, MH. The morphology, thermal stability, and flammability properties of the nanocomposite were characterized by IR, XRD, TEM, TGA, cone calorimetry, and limiting oxygen index. The thermal stability and the flame retardant properties of the polymer‐silicate‐MH showed significant improvements in the decomposition temperature and the lower heat release rates due to the formation of nanocomposites with layered silicates. Biodegradation testing by Bacillus cereus (gram‐positive) revealed the ecofriendly nature of the nanocomposite. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers
Effect of hygrothermal aging on the diffusion of seawater in epoxy/glass composites studied by positron lifetime spectroscopy
Authors: Radha J.C. , Ranganathaiah C. 
Published: December 2007

AbstractThe effect of hygrothermal aging on the free volume controlled diffusion of seawater in the epoxy/glass (E/G) composite samples with E‐glass fibers woven at 0° and 45° to the epoxy matrix has been studied using Positron lifetime technique. The equilibrium mass uptake of seawater is assessed by the gravimetric method. The positron results indicate that the free volume hole size increases with hygrothermal aging in the composite E/G (0°) suggesting swelling while the hole size shows continuous decrease in the E/G (45°) composite up to 45°C. We also found that hygrothermal aging process in the present composites is an exothermic process. Although the equilibrium uptake of seawater decreases with the increasing temperature in both the cases, the magnitude of decrease is more in 0°‐oriented composite than in 45°‐oriented composite. The heat of absorption calculated from the temperature dependence of equilibrium mass uptake is found to be negative in both the cases. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers
Recent developments in chemical modification and characterization of natural fiber‐reinforced composites
Authors: John Maya Jacob , Anandjiwala Rajesh D. 
Published: December 2007

AbstractA critical review of the literature on the various aspects of natural fibers and biocomposites with a particular reference to chemical modifications is presented in this paper. A notable disadvantage of natural fibers is their polarity which makes it incompatible with hydrophobic matrix. This incompatibility results in poor interfacial bonding between the fibers and the matrix. This in turn leads to impaired mechanical properties of the composites. This defect can be remedied by chemical modification of fibers so as to make it less hydrophilic. This paper reviews the latest trends in chemical modifications and characterizations of natural fibers. The structure and properties of natural fibers have been discussed. Common chemical modifications and their mechanisms have also been elaborated. The importance of chemical modifications and the resultant enhancement in the properties of the composites have also been reviewed. Recent investigations dealing with chemical modifications of natural fiber‐reinforced composites have also been cited. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers
Coefficient of thermal expansion for Twaron® fibers using crystallographic data
Authors: Jain Anjana 
Published: December 2007

AbstractThe effect of in situ heating on the unit cell dimensions of crystalline aramid fiber (Twaron® fibers) has been studied in the temperature range 20–280°C. The changes in the unit cell dimensions have been used to estimate the coefficients of thermal expansion along the axial directions. On heating, the a and b axes expand, the coefficients of thermal expansion being αa = 35.84 × 10−6/°C and αb = 38 × 10−6/°C at room temperature. The c‐axis contracts on heating, giving negative coefficient of thermal expansion αc = −5.38 × 10−6/°C at room temperature. Volume coefficient of thermal expansion αV however is positive, being 101.22 × 10−6/°C. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers
Morphology of PA‐6 vibration welded joints and its effect on weld strength
Authors: Chung Young‐Mi , Kamal Musa R. 
Published: December 2007

AbstractThe microstructure of the heat affected zone (HAZ) in vibration welded joints of polyamide‐6 were studied using polarized light microscopy (PLM), Fourier transform infrared (FTIR) microspectrometry, scanning electron microscopy (SEM), and modulated differential scanning calorimetry (MDSC). PLM images showed the existence of two distinct HAZ layers: an inner layer (HAZ‐I) with small spherulites and an outer deformed layer (HAZ‐II) adjacent to the bulk zone. The thickness of the HAZ‐I and HAZ‐II layers and the size of spherulites in HAZ‐I depended on welding parameters, such as weld pressure and amplitude. The microstructure study of molecular orientation, using birefringence, and crystal phase type, using FTIR, suggests that HAZ‐I originates from a molten polymer film, while HAZ‐II arises in the polymer in the rubbery state. Etched HAZ surfaces also show clear distinction between the two HAZ layers. Therefore, HAZ‐I is renamed as the recrystallized layer and HAZ‐II as the deformed layer. Fracture tests show that the weakest part of the joint occurs in the recrystallized layer region adjacent to the deformed layer. MDSC analysis indicates that the determining factor of the weld strength is the crystallinity of the recrystallized layer, not the thickness of HAZ. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers
Optical monitoring of polypropylene crystallization during injection molding
Authors: Favaro Márcia M. , Marinelli Alessandra L. , Farah Marcelo , Bretas Rosario E.S. 
Published: December 2007

AbstractThe nonisothermal crystallization of polypropylene resins, i‐PP, during injection molding, using an optical device inserted in the injection mold cavity was monitored. The device detected the change of optical properties which occurs in polymers during their crystallization process; thus the intensity of a laser beam after it passed through the crystallizing polymer was measured during an injection molding cycle. The collected light intensity after the end of the cycle was correlated with the morphologies and final crystallinity degree of the samples. The influence of nucleating agents and the change of the parameters of the injection molding process on the morphology and optical signals were also investigated. The morphologies were analyzed by polarized light optical microscopy, PLOM. The % of crystallinity of the samples was measured by wide angle X‐rays diffraction, WAXS. It was concluded that the optical device was sensible to different polymer crystallization kinetics, morphology type, and changes in the injection molding parameters. It was also found that the mold temperature and packing pressure and time were the factors that affected most the kinetics of crystallization of these polymers in this particular disk geometry. The WAXS results showed that the lower the final light intensity the higher the % of crystallinity in the samples. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers
Thermal residual stress development for semi‐crystalline polymers in rotational molding
Authors: Xu H. , Bellehumeur C.T. 
Published: December 2007

AbstractIn rotational molding, polymer powders are subjected to heating, melting, cooling, and subsequent crystallization processes. Because of the asymmetrical cooling condition, thermally induced residual stresses are created inside molded parts leading to part warpage. A detailed theoretical heat transfer model is presented for the entire rotational molding process including the consideration of endothermic and exothermic transitions. At the same time, the development of residual stress inside the molded parts is simulated with thermoelastic model. The warpage values are calculated under different processing cases, and the generated numerical results are in good agreement with data reported in the literature. Our results show that both crystallinity and temperature gradients developing within the polymer during the cooling process greatly affect the dimensional stability of ethylene copolymers typically processed in rotational molding. The latter is found to be the determining factor in evaluating the effect of cooling conditions on the warpage generated in a molded product. Our results also demonstrate the importance of the crystallization kinetics, the material stiffness, and its evolution during the solidification process on the dimensional stability of the molded products. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers
Tribological properties of blends of melamine‐formaldehyde resin with low density polyethylene
Authors: Brostow Witold , Datashvili Tea , Huang Bernard 
Published: December 2007

AbstractTribological properties of blends of melamine‐formaldehyde resin (MFR) with low density polyethylene (LDPE) containing 1, 5, 10, 20, 25 wt% MFR were investigated. We have determined sliding wear by multiple scratching along the same groove using a micro scratch tester. Instantaneous penetration depth is lowered by the MFR addition to LDPE. However, there is less viscoelastic recovery and the residual (healing) depths increase with increasing MFR concentration. Microindentation hardness increases along with the MFR content. Since MFR is only partially miscible with LDPE, MFR‐rich islands in the PE matrix offer more interfaces and so increase hardness. Friction determined with a pin‐on‐disk tribometer using silicon nitride balls as a function of MFR concentration shows a minimum. The result is explained in terms of surface morphology seen in scanning electron microscopy. At the same time, all blend friction values are lower than for neat LDPE. Wear determined in the pin‐on‐disk tribometer decreases along with the MFR concentration increase. Thus, pin‐on‐disk wear and friction show different faces of blends tribology. Blending can be used to improve tribological properties of LDPE. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers
Thermoplastic polyurethane elastomers based on polycarbonate diols with different soft segment molecular weight and chemical structure: Mechanical and thermal properties
Authors: Eceiza A. , Martin M.D. , de la Caba K. , Kortaberria G. , Gabilondo N. , Corcuera M.A. , Mondragon I. 
Published: December 2007

AbstractA series of thermoplastic polyurethane elastomers based on polycarbonate diol, 4,4′‐diphenylmethane diisocyanate and 1,4‐butanediol was synthesized in bulk by two‐step polymerization varying polycarbonate diol soft segment molecular weight and chemical structure, and also hard segment content, and their effects on the thermal and mechanical properties were investigated. Dynamic mechanical analysis termogravimetric analysis, differential scanning calorimetry, Fourier transform infrared‐attenuated total reflection spectroscopy and mechanical tests were employed to characterize the polyurethanes. Thermal and mechanical properties are discussed from the viewpoint of microphase domain separation of hard and soft segments. On one hand, an increase in soft segment length, and on the other hand an increase in the hard segment content, i.e., hard segment molecular weight, was accompanied by an increase in the microphase separation degree, hard domain order and crystallinity, and stiffness. In phase separated systems more developed reinforcing hard domain structure is observed. These hard segment structures, in addition to the elastic nature of soft segment, provide enough physical crosslink sites to have elastomeric behavior. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers
A macroscopic mathematical model for tensioned‐web slot coating
Authors: Lin Fang‐Ho , Liu Chi‐Ming , Liu Ta‐Jo , Wu Ping‐Yao 
Published: December 2007

AbstractA mathematical model was developed to predict the performance of tensioned‐web slot coating (TWSC), in particular, the minimum wet thickness. The model was based on the lubrication approximation for the coating solution flow and a simplified membrane theory for the moving web. The theoretical predictions compared reasonably well with available experimental data. The effects of fluid viscosity, web tension, coating speed, and wrapping angle on the performance of TWSC were evaluated. An example was presented to illustrate how die lip design could be varied to improve its performance. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers
Numerical study of nonisothermal polymer extrusion flow with a differential viscoelastic model
Authors: Mu Yue , Zhao Guoqun 
Published: December 2007

AbstractA numerical study of nonisothermal viscoelastic flow is conducted to investigate the complex flow characteristics of polymer melts in the extrusion process. A general thermodynamic model for the energy conversion related to viscoelastic fluid flow is introduced. The mathematical model for three‐dimensional nonisothermal viscoelastic flow of the polymer melts obeying a differential constitutive equation (Phan‐Thien and Tanner model) is established. A decoupled algorithm based on the penalty finite element method is performed on the calculation. The discrete elastic‐viscous split stress (DEVSS) algorithm, incorporating the streamline‐upwind Petrov‐Galerkin (SUPG) scheme is employed to improve the computation stability. Essential flow characteristics of polymer melts in the extrusion die for hollow square plastic profile is investigated based on the proposed numerical scheme with ignoring the outer thermal resource. The energy partitioning, which quantified the conversion of mechanical energy into thermal energy, is discussed. The effects of volume flow rate and die contraction angle upon the flow patterns are further investigated. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers
From peripheral to central, the story of Melanie's metamorphosis in an urban middle school science class
Authors: Tan Edna , Barton Angela Calabrese 
Published: December 2007

AbstractIdentity formation is a critical dimension of how and why students engage in science to varying degrees. In this paper, we use the lens of identity formation, and in particular identities in practice, to make sense of how and why Melanie, over the course of sixth grade, transformed from a marginalized member of the science class with a failing grade to a highly valued member of the sixth‐grade science community with a perfect score of a 100% for the sixth‐grade exit project. Our findings reveal that the different figured worlds of the science classroom, such as whole class, small group work, and individual work, offered Melanie different affordances for identity formation that were built upon across such spaces, in both productive and unproductive ways. Our findings also take up the kinds of critical roles that members of her classroom community, in particular teacher and peers, play in supporting and constraining such a transformation. We discuss the implications identity formation has for understanding issues of gender equity and science learning. © 2007 Wiley Periodicals, Inc. Sci Ed 92:567–590, 2008
rAAV‐asPLB transfer attenuates abnormal sarcoplasmic reticulum Ca2+‐ATPase activity and cardiac dysfunction in rats with myocardial infarction
Authors: Zhao Xiao‐Yan , Hu Shen‐Jiang , Li Jiang , Mou Yun , Bian Ka , Sun Jian , Zhu Zhao‐Hui 
Published: December 2007

AbstractBackground:Diminished myocardial sarcoplasmic reticulum Ca2+‐ATPase (SERCA) activity and upregulated phospholamban (PLB) level during cardiac dysfunction, had been reported in many studies.Aims:The current study was designed to examine the effects of rAAV‐antisense phospholamban (asPLB) gene transfer on cardiac function, SERCA expression and activity, as well as PLB expression and phosphorylation (Pser16‐PLB), in a rat myocardial infarction (MI) model.Methods and results:Rat MI model was generated by ligating the left anterior descending coronary artery. Four weeks later, left ventricular ejection fraction (LVEF), left ventricular systolic pressure (LVSP), the maximal rates of increase and decrease in intraventricular pressure (±dp/dtmax) were significantly depressed, and left ventricular end diastolic pressure (LVEDP) was increased. Myocardial PLB was markedly increased while both SERCA activity and Pser16‐PLB level were decreased. In rAAV‐asPLB transfected rats, rAAV‐asPLB, which was injected into the myocardium around the infarction area immediately after the coronary artery ligation, effectively attenuated the depression of cardiac function, significantly inhibited the expression of PLB, restored Pser16‐PLB level and enhanced myocardium SERCA activity.Conclusion:rAAV‐asPLB transfer in rats with MI effectively prevented the progression of heart failure.