bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of prior aging at 288°C in air and in argon environments on creep response of PMR‐15 neat resin
Authors: Ruggles‐Wrenn M. B. , Broeckert J. L. 
Published: October 2008

AbstractThe creep behavior of PMR‐15 neat resin, a polyimide thermoset polymer, aged in air and in argon environments at 288°C for up to 1000 h was evaluated. Creep tests were performed at 288°C at creep stress levels of 10 and 20 MPa. Creep periods of at least 25‐h in duration were followed by 50‐h periods of recovery at zero stress. Prior isothermal aging increased the elastic modulus and significantly decreased the polymer's capacity to accumulate creep strain. The aging environment had little influence on creep and recovery behaviors. However, aging in air dramatically degraded the tensile strength of the material. Dynamic mechanical analysis revealed an increase in the glass transition temperature from ∼330°C to ∼336°C after 1000 h in argon or in air at 288°C. The rise in the glass transition temperature with aging time is attributed to an increase in the crosslink density of the PMR‐15 polyimide. Increase in the crosslink density due to aging in both air and argon environments is likely behind the changes in the elastic modulus and the decreased capacity for inelastic straining. A visibly damaged surface layer of ∼0.16 mm thickness was observed in specimens aged in air for 1000 h. Results indicate that the unoxidized core material governs the overall mechanical response, whereas the oxidized surface layer causes a decrease in tensile strength by acting as a crack initiation site and promoting early failures. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Fabrication and morphology control of poly(methyl methacrylate) hollow structures via coaxial electrospinning
Authors: Chan Kok Ho Kent , Kotaki Masaya 
Published: October 2008

AbstractA modified electrospinning method known as coaxial electrospinning was used to fabricate poly(methyl methacrylate) (PMMA) hollow structures. In this study to understand morphology control, the effect of processing parameters such as concentration of polymer sheath solution, size of core/sheath capillaries, feed rate, and applied voltage had been evaluated. Morphological observations via scanning electron microscope (SEM) revealed that via the control of polymer concentration within the sheath solution, morphologies such as hollow particles and fibers could be obtained. With the use of fine core/sheath capillaries, micron hollow fibers with walls of less than 20 nm were obtained. This study has demonstrated how the investigated processing parameters have a direct influence on the structures and how these parameters have supported the notion that effective encapsulation process is the key to the dual layer bicomponent structures. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Mechanism of bubble formation in the drying of polymer films
Authors: Pourdarvish Reza , Danner Ronald P. , Duda J. Larry 
Published: October 2008

AbstractA common problem in making thin polymer films by solution processing is the undesirable formation of bubbles during the drying process. These bubbles appear well below the boiling point of the solvent. Experience indicates, however, that the degassing of the polymer solutions reduces bubble formation, indicating a relationship with the presence of air. This work is based on a hypothesis that if the solubility of air in the polymer solution increases with solvent concentration, then the solution can become supersaturated with air as the concentration of the solvent is reduced during the drying process. To test this hypothesis the system poly(vinyl acetate)‐toluene‐nitrogen was chosen. Previously published data on the solubility and diffusion of nitrogen in the polymer‐solvent system were used. Different diffusion models based on the friction coefficients and free‐volume model were then used to correlate the diffusivity data so that the diffusion behavior of the ternary system can be predicted over a broad range of conditions. Finally, the thermodynamic and diffusivity correlations were incorporated into a multicomponent drying model which included main and cross‐diffusion terms to predict saturation behavior in the polymer solution during the drying process. The model without the cross‐diffusion terms represents the ideal system in which the diffusion of one component does not affect the diffusion of others. The drying model did not predict supersaturation of nitrogen when cross‐diffusion terms were neglected. Supersaturation of nitrogen was predicted, however, when the cross‐diffusion terms are included. Therefore, the cross‐diffusion terms in the mass transfer model are essential for the development of nitrogen supersaturation. Also different diffusion models based on the friction coefficients led to qualitatively similar predictions for the supersaturation of nitrogen. The simulation's results supported our experimental observations regarding bubble formation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Evaluation and simulation of the peel behavior of polyethylene/polybutene‐1 peel systems
Authors: Nase Michael , Langer Beate , Baumann Hans Joachim , Grellmann Wolfgang , Geißler Gordon , Kaliske Michael 
Published: October 2008

AbstractThe peel characteristics of sealed low‐density polyethylene/isotactic polybutene‐1 (PE‐LD/iPB‐1) films, with different contents of iPB‐1 up to 20 m.‐% (mass percentage), were evaluated and simulated in dependence on the iPB‐1 content, and in dependence on the peel rate. Sealing involves close contact and localized melting of two films for a few seconds. The required force, to separate the local adhered films, is the peel force, which is influenced, among others, by the content of iPB‐1. The peel force decreases exponentially with increasing iPB‐1 content. Transmission electron microscopy studies reveal a favorable dispersion of the iPB‐1 particles within the seal area, for iPB‐1 concentrations ≥6 m.‐%. Here, the iPB‐1 particles form continuous belt‐like structures, which lead to a stable and reproducible peel process. The investigation of the peel rate‐dependency on the peel characteristics is of important interest for practical applications. The peel force increases with increasing peel rate by an exponential law. A numerical simulation of the present material system proves to be useful to comprehend the peel process, and to understand the peel behavior in further detail. Peel tests of different peel samples were simulated, using a two‐dimensional finite element model, including cohesive zone elements. The established finite element model of the peel process was used to simulate the influence of the modulus of elasticity on the peel behavior. The peel force is independent of the modulus of elasticity, however, the peel initiation value increases with increasing modulus of elasticity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Effect of bis(3‐triethoxysilylpropyl) tetrasulfide on the crosslink structure, interfacial adhesion, and mechanical properties of natural rubber/cotton fiber composites
Authors: Zeng Zheng , Ren Wentan , Xu Chi , Lu Weiqiang , Zhang Yong , Zhang Yinxi 
Published: October 2008

AbstractBis(3‐triethoxysilylpropyl) tetrasulfide (TESPT) was used to improve the interfacial adhesion between cotton fiber and natural rubber (NR). The crosslink density, interfacial adhesion, mechanical properties, dynamic mechanical properties, and morphology of NR/cotton fiber composites were investigated. The composites with TESPT had higher crosslink density, better mechanical properties, higher initial modulus, and higher yield strength than the composites without TESPT because of the difference in interfacial adhesion. The results of an interfacial adhesion evaluation, the high storage modulus and low damping values of the composites with TESPT, and the coarse surfaces of the pullout fibers implied the enhancement of interfacial adhesion. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
A novel method for the determination of cell infiltration into nanofiber scaffolds using image analysis for tissue engineering applications
Authors: Semnani Dariush , Ghasemi‐Mobarakeh Laleh , Morshed Mohammad , Nasr‐Esfahani Mohammad‐Hossein 
Published: October 2008

AbstractOne of the major themes in tissue engineering is scaffold fabrication. The porosity and pore size of scaffolds play a critical role in tissue engineering. Different methods are used to measure the porosity and pore size of scaffolds, although none can predict the cell infiltration for various cell sizes, shapes, and configurations. The aim of this study was to predict the cell infiltration of various cells with different sizes, shapes, and configurations through the use of image analysis. In this study, cell models were used to predict cell infiltration into nanofiber scaffolds. The results of this study showed that with increases in the cell size and the number of layers of nanofibers, the number of cells that could infiltrate the scaffolds decreased. In addition, the cell configuration had some effect on cell infiltration into the nanofiber scaffolds. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Reactivity ratios and monomer partitioning in the microemulsion copolymerization of vinyl acetate and butyl acrylate
Authors: Ovando‐Medina Víctor M. , Martínez‐Gutiérrez Hugo , Mendizábal Eduardo , Corona Miguel A. , Peralta René D. 
Published: October 2008

AbstractThe true monomer reactivity ratios for the vinyl acetate/butyl acrylate system were determined with experimental data from the cumulative copolymer composition at low, intermediate, and high conversions and with the monomer partitioning among the aqueous, microemulsion droplet, and polymer particle phases taken into account. A mixture of sodium dodecyl sulfate and poly(ethylene oxide) (23) dodecyl ether (Brij‐35; 3 : 1 w/w) was used as a stabilizer. Potassium persulfate was used as an initiator. The true values of the monomer reactivity ratios were 0.028 ± 3.2 × 10−3 for vinyl acetate and 6.219 ± 3.1 × 10−1 for butyl acrylate, and these were in agreement with those reported in the literature for bulk copolymerizations but differed from values reported for other compartmentalized copolymerizations. Thus, these results indicate that the monomer partitioning and cumulative copolymer composition throughout the reaction have to be duly accounted for in the determination of monomer reactivity ratios in heterogeneous polymerizations. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Water‐soluble poly(ethylene glycol) prodrug of pemetrexed: Synthesis, characterization, and preliminary cytotoxicity
Authors: Min Tao , Ye Hai , Zhang Peng , Liu Jun , Zhang Can , Shen Wenbin , Wang Wan , Shen Longsheng 
Published: October 2008

AbstractPemetrexed is a novel antifolate of antimetabolite with multiple enzyme targets involved in both pyrimidine and purine synthesis. It has entered the clinical usage due to favorable profiles especially in the cancer treatment of mesothelioma and non–small‐cell lung carcinoma. But it presents numerous challenges associated with poor water solubility and unstability in its original form of glutamic acid. The aim of this study is to solubilize pemetrexed by designing and synthesizing its aqueous‐soluble prodrug using high aqueous‐soluble polymeric carrier poly(ethylene glycol) (PEG). A new type of soluble pemetrexed prodrug was synthesized with dihydroxyl PEG and a single amino acid linkage, and was extensively characterized using 1H‐NMR, 13C‐NMR, Fourier‐transform infrared, and matrix‐assisted laser desorption time of flight mass spectrometry. In addition, the prodrugs were evaluated for the drug loading capability, the aqueous solubility, and the preliminary in vitro cytotoxicity. The results indicate that the new PEGylated pemetrexed conjugates possess enhanced water solubility and stability, and provide another feasible choice of the pharmaceutical form of pemetrexed in the clinical application. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Surface treatment of phosphate glass fibers using 2‐hydroxyethyl methacrylate: Fabrication of poly(caprolactone)‐based composites
Authors: Khan Ruhul A. , Parsons A. J. , Jones I. A. , Walker G. S. , Rudd C. D. 
Published: October 2008

Abstract2‐Hydroxyethyl methacrylate (HEMA) solution (1–10 wt %) was prepared in methanol and phosphate glass fibers were immersed in that solution for 5 min before being cured (irradiation time: 30 min) under UV radiation. Maximum polymer loading (HEMA content) was found for the 5 wt % HEMA solution. Degradation tests of the fibers in aqueous medium at 37°C suggested that the degradation of the HEMA‐treated fibers was lower than that of the untreated fibers. X‐ray photoelectron spectroscopy revealed that HEMA was present on the surface of the fibers. Using 5 wt % HEMA‐treated fibers, poly(caprolactone) matrix unidirectional composites were fabricated by in situ polymerization and compression molding. For in situ polymerization, it was found that 5 wt % HEMA‐treated fiber‐based composites had higher bending strength (13.8% greater) and modulus (14.0% greater) than those of the control composites. For compression molded composites, the bending strength and modulus values for the HEMA‐treated samples were found to be 27.0 and 31.5% higher, respectively, than the control samples. The tensile strength, tensile modulus, and impact strength of the HEMA composites found significant improvement than that of the untreated composites. The composites were investigated by scanning electron microscopy after 6 weeks of degradation in water at 37°C. It was found that HEMA‐treated fibers inside the composite retained much of their original integrity while the control samples degraded significantly. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Experimental determination of concentration‐dependent carbon dioxide diffusivity in LDPE
Authors: Tendulkar J. , Upreti S. R. , Lohi A. 
Published: October 2008

AbstractIn this work, we experimentally determine the concentration‐dependent diffusivity of carbon dioxide in low‐density poly(ethylene) (LDPE). For this purpose, experiments are carried out to obtain pressure‐decay data for isothermal diffusion of the gas in the polymer. Based on a detailed mass transfer model, variational calculus is used to establish the conditions necessary to yield the concentration‐dependent diffusivity that enables the model‐predicted mass of absorbed gas in polymer to match with the experimental counterpart. A computational algorithm is implemented to solve the model and the conditions and obtain the diffusivities. Determined at 120 and 130°C for four different pressures in the range 0.352 to 1.232 MPa, the diffusivities are strong unimodal functions of gas concentration in polymer and of the order 10−9 m2 s−1. Mathematical correlations are developed to calculate the diffusivity at a given temperature, pressure, and gas concentration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis and pH‐induced phase transition behavior of PAA/PVA nanogels in aqueous media
Authors: Yao Ri‐Sheng , You Qi‐Dong , Liu Peng‐Ju , Xu Yu‐Fu 
Published: October 2008

AbstractPolyacrylic acid (PAA) and polyvinyl alcohol (PVA) are well‐known FDA‐approved biocompatible polymers. A novel method for preparing PAA/PVA complex nanoneedles in PVA aqueous solution is presented in this article. The PAA/PVA complex nanogels are obtained via polymerization of acrylic acid monomer after PVA nanoparticles formed in water/acetone cosolvent. The results of TEM images showed that the PVA chains were aggregated to form gel particles with some erose nanoparticles. As AA monomers polymerized around PVA nanoparticles, PAA/PVA complex nanogels formed. The PAA/PVA nanogels had an average diameter of 300–100 nm with AA concentration of 0.5–2 g/100 mL. As acetone concentration varied, TEM images demonstrated that the morphologies of resulting nanogels are different. Without acetone in PVA aqueous solution, however, PAA/PVA complexes aggregated to form earthnut‐like particles. These results show that the shape and size of PVA/PAA nanogels can be tailored as a template or core for the formation of PAA/PVA nanogels. These PAA/PVA nanogels exhibited pH‐induced phase transition due to protonation of PAA chains. The novel PVA/PAA nanogels promise to be developed into pH‐controlled drug delivery system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Batch emulsion polymerization of vinyl chloride: Application of experimental design to investigate the effects of operating variables on particle size and particle size distribution
Authors: Pourmehr Mahdi , Navarchian Amir H. 
Published: October 2008

AbstractIn this article, the influences of operating variables on the particle size (PS) and particle size distribution (PSD) of emulsion poly(vinyl chloride) in batch reactor were investigated using Taguchi experimental design approach. The variables were temperature (T), water to monomer weight ratio (R), concentrations of initiator ([I]) and emulsifier ([E]), and agitation speed (S). Scanning electron microscope was used together with image analysis software to determine the PS and PSD. Statistical analysis of results revealed that the PS of emulsion poly(vinyl chloride) strongly depends on emulsifier and initiator concentrations, respectively, whereas the other factors have no significant effects in the range of levels investigated in this study. Except initiator concentration, all factors have important influence on the PSD (significance sequence: S > R > T > [E]). It is implied from the greater influence of agitation speed relative to temperature on PSD that the shear coagulation predominates the Brownian coagulation in this system. The relative optimum condition for a typical paste application was also determined using overall evaluation criteria. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Thermal degradation behavior of PMMA synthesized by emulsifier‐free emulsion polymerization with a Cu2+/HSO3− redox system
Authors: Chiu Tso‐Pei , Don Trong‐Ming 
Published: October 2008

AbstractIn this study, poly(methyl methacrylate) (PMMA) latex was synthesized in an emulsifier‐free emulsion polymerization at 60°C using a Cu2+/HSO redox initiator system with different concentrations of Cu2+. The experimental results showed that the monomer conversion reached above 90% for all systems. Zeta potential was all negative due to the bonded bisulfite ion and the magnitude was greater than 30 mV, providing the stability of PMMA emulsion. The morphology of the latex observed by scanning electron microscope revealed a uniform particle size, and the average particle size increased from 181.9 to 234.2 nm as the Cu2+ ion concentration increased from 2.0 to 6.0 mM in 1M of MMA solution. Thermal degradation behavior of synthesized PMMA was studied by thermogravimetric analysis, in which a two‐stage degradation behavior was observed. These two stages were found to be caused by the degradation of unsaturated end group (PMMACRCH2) and saturated end group (PMMAH), respectively. In addition, the higher the concentration of Cu2+ ion, the greater the proportion of PMMACRCH2 in the final product, and in turn rendering more weight loss in the first‐stage degradation. The copper ion not only played a role in the redox initiation, but also acted as a chain transfer agent to terminate growing polymer chains, thus producing PMMACRCH2. The apparent activation energies of the first stage (Ea1) and second stage (Ea2) were calculated by Ozawa's and Boswell's method. The results showed that Ea1, representing the degradation of PMMA‐CRCH2, was lower than Ea2 for the degradation of PMMA‐H. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Determination of the phase diagram of HBA‐HNA liquid crystalline polymer/polycarbonate blends
Authors: Lee Kam‐Wa D. , Chan Philip K. , Kamal Musa R. 
Published: October 2008

AbstractThe phase diagram of blends of liquid crystalline polymer (LCP) and polycarbonate (PC) was constructed. The effect of temperature on morphological development in melt‐blended samples was examined with a polarized light microscope, in conjunction with a heating stage. Phase separation in the blend was observed as the temperature was increased. For a particular LCP/PC blend composition, two‐phase separation temperatures (Tsp1 and Tsp2) were determined. Consequently, the corresponding phase diagram relating to phase separation was constructed. It was divided into three regions. No phase separation occurred when the blend was below Tsp1. However, a slight phase separation was detected when the temperature was between Tsp1 and Tsp2. Moreover, pronounced phase separation was observed when the blend was at a temperature above Tsp2. The phase‐separated structure varied according to the initial composition of the blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Optimization of operating conditions in a single‐zone drier for two‐layer polymer coatings
Authors: Khandelwal A. , Singhania M. , Vinjamur M. 
Published: October 2008

AbstractIn industrial dryers, hot air is blown over wet coatings either from top or from both top and bottom sides to remove the solvent. Drying of multilayer coatings is a complicated process that involves simultaneous heat and mass transfer, transport, and thermodynamic behavior of polymer solutions. Airflow and its temperature are important operating conditions in a dryer. We report optimization of the operating conditions to minimize residual solvent without inducing blisters for two‐layer coatings using mathematical modeling. Our results reveal that optimal air flow on the bottom side of the coating is always greater than or equal to that on its top side—an agreement with the common notion of “backside drying.” Furthermore, the effect of coating thickness, residence time, individual layer thickness, initial solvent concentration, and reversal of the two layers on the optimal conditions is discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Miscibility of polymethylmethacrylate and polyethyleneglycol blends in tetrahydrofuran
Authors: Selvakumar M. , Bhat D. Krishna , Renganathan N. G. 
Published: October 2008

AbstractThe miscibility of polymethylmethacrylate (PMMA) and polyethyleneglycol (PEG) blends in tetrahydrofuran (THF) has been investigated by viscosity, density, refractive index, and ultrasonic velocity studies. Various interaction parameters such as polymer–solvent and blend–solvent interaction parameters and heat of mixing have been calculated using the viscosity, density, and ultrasonic velocity data. The results indicated the existence of positive interactions in the blend polymer solutions and that they are miscible in THF in the entire composition range. The study also revealed that variation in the temperature does not affect the miscibility of PMMA and PEG blends in THF significantly. The presence of hydrogen bonding in the blends in the solid state has also been indicated by FTIR studies. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009