bluuebunny/crossref_metadata_2025 huggingface dataset:
Screen printable epoxy/BaTiO3 embedded capacitor pastes with high dielectric constant for organic substrate applications
Authors: Jang Kyung‐Woon , Paik Kyung‐Wook
Published: July 2008

In this article, embedded capacitor pastes (ECPs) with various BaTiO3 (BTO) powder contents were formulated and screen‐printed on PCBs to fabricate capacitors. The material properties of the ECPs that included their rheology, curing behavior, and dielectric constant were investigated. Embedded capacitors were fabricated for reliability tests related to the thermal cycling and high temperature and humidity potential of optimized ECPs. Additionally, changes in the dielectric properties were discussed. ECPs were formulated with various powder contents from 0 to 70 vol %. ECP resin was cured at temperatures ranging from 130 to 220°C. All ECPs had the viscosities below 30 Pa · s at a shear rate of 100 s−1 to be easily screen‐printable. The dielectric constant of the cured ECPs increased to 60 at 70 vol %, and the dielectric loss was approximately 0.023 for all ECPs regardless of BTO volume content. For the reliability test, ECPs with 50, 60, and 70 vol % BTO powder contents were selected and embedded capacitors were fabricated. After a thermal cycling test with a temperature range from −55 to 125°C for 1000 cycles, capacitance decreased by approximately 5 ∼ 10%, but the dielectric loss did not change. After a 85°C/85RH% test for 1000 h, the capacitance and dielectric loss increased by nearly 20%. Cyanoresin (CRS) was used to form the high dielectric polymer/ceramic composite material. The newly formulated resin system had a dielectric constant that is double that of a conventional epoxy resin system. Additionally, the dielectric constant of the polymer/ceramic composite material increased 50% at 50 vol %. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Preparation and properties of cyclo‐olefin copolymer/titania hybrids
Authors: Ou Cheng‐Fang , Hsu Ming‐Chieh
Published: July 2008

A series of organic–inorganic hybrid materials consisting of an organic cyclo‐olefin copolymer (COC) and inorganic titania (TiO2) were successfully synthesized by a sol–gel process. TiO2 was obtained through the hydrolysis of titanium n‐butoxide (TNBT) with the catalysis of HCl. Differential scanning calorimetry analysis indicated that the glass‐transition temperature of the hybrids was higher than that of pure COC, and it rose significantly as the TNBT content was increased from 1 to 15 wt %. Scanning electron microscopy observations showed that the morphology of fractured surfaces of the COC/TiO2 hybrid with 5 wt % TNBT was a single homogeneous phase, indicating that the miscibility between COC and TiO2 was good for the hybrids. According to ultraviolet–visible analysis, the transmittance of pure COC at 550 nm was high up to 91.7%. The light transmittance of the COC/TiO2 hybrids was still higher than 80% with the TNBT content up to 5 wt %. The decomposition temperatures of the hybrids, investigated with thermogravimetric analysis, were not affected significantly by the addition of TNBT. The oxygen barrier property of the hybrid films showed significant improvements in comparison with pure COC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Effect of silica‐based nanofillers on the properties of a low‐density polyethylene/ethylene vinyl acetate copolymer based thermoplastic elastomer
Authors: Hui S. , Chaki T. K. , Chattopadhyay S.
Published: July 2008

The effect of pristine silica nanoparticles on a model low‐density polyethylene (LDPE)–ethylene vinyl acetate copolymer (EVA) thermoplastic elastomer blend system is explored in this article. Pristine silica nanoparticles were melt‐blended with the LDPE–EVA system at 1.5, 3, and 5 wt % loadings through the variation of the sequence of addition. In one of the compositions, coupling agent bis[3‐(triethoxysilyl)propyl] tetrasulfide (Si‐69) was used to improve the interaction of hydrophilic silica fillers with the polymer matrix. The blends were compression‐molded, and their mechanical, dynamic mechanical, and thermal properties, X‐ray diffraction patterns, and morphology were evaluated. The properties of the blends were found to be strong functions of the sequence of addition of nanofillers during their preparation. With Si‐69 as a coupling agent, the dynamic storage modulus of nanosilica‐based composites was found to increase up to 35%. An appreciable improvement in the tension set properties of the thermoplastic elastomer nanocomposites was observed in all the nanosilica‐based films. Morphological studies and dynamic properties clearly indicated that the differential properties of these blend systems primarily stemmed from the extent of dispersion and alternation of crystalline morphology, which in turn was a strong function of preferential incorporation in the LDPE or EVA matrix and the agglomeration tendency of the nanofillers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Thermal stabilization effect of biphenol monoacrylate on polyamide 6
Authors: Yang Tao , Ye Lin , Shu Ying
Published: July 2008

Biphenol monoacrylate (AL) was combined with a traditional hindered phenolic‐based binary antioxidant system to form a ternary stabilization system for the purpose of further improving the thermal–oxidative stability of polyamide 6 (PA6). The thermal stabilization effect of the antioxidant AL on PA6 was studied in terms of the reduced viscosity, the chemical structure, the yellow index, and the mechanical properties. The results showed that the antioxidant AL, with the proper chemical structure, could improve the thermal stability of PA6 effectively through a unique bifunctional stabilizing mechanism. The interaction of the molecules of PA6 with the antioxidant AL was investigated. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Optomechanical properties of the morphology of viscose fibers due to the cold‐drawing process
Authors: Fouda I. M. , Seisa E. A.
Published: July 2008

This study sheds light on the changes produced by the effects of cold‐drawn fibers on the microstructure and macrostructure of viscose fibers. The optical properties and strain produced in viscose fibers were measured interferometrically at room temperature. Structural parameters were calculated, such as the work per unit of volume, the reduction in entropy due to elongation, and the harmonic mean specific refractivity. In addition, the resulting data were used to calculate the optical stress coefficient and optical configuration and to apply the Mooney–Rivlin equation to determine the constants. Also, the number of crystals per unit of volume and the average orientation angle for uniaxial stretching were calculated with the extension ratios. The relation between the true stress and strain hardening was calculated. The average value of the maximum birefringence was determined to equal 0.046. The relations between the optical and mechanical changes with different parameters were established for the studied fibers. Microinterferograms and curves were drawn for illustration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Polyhydroxybutyrate/acrylonitrile‐g‐(ethylene‐co‐ propylene‐co‐diene)‐g‐styrene blends: Their morphology and thermal and mechanical behavior
Authors: de Carvalho Fabiana Pires , Quental Antonio Carlos , Felisberti Maria Isabel
Published: July 2008

Polyhydroxybutyrate (PHB) is a biodegradable bacterial polyester emerging as a viable substitute for synthetic, semicrystalline, nonbiodegradable polymers. An elastomer terpolymer of acrylonitrile‐g‐(ethylene‐co‐propylene‐co‐diene)‐g‐styrene (AES) was blended with PHB in a batch mixer and in a twin‐screw extruder to improve the mechanical properties of PHB. The blends were characterized with differential scanning calorimetry, dynamic mechanical analysis, scanning electron microscopy, and impact resistance measurements. Despite the narrow processing window of PHB, blends with AES could be prepared via the melting of the mixture without significant degradation of PHB. The blends were immiscible and composed of four phases: poly(ethylene‐co‐propylene‐co‐diene), poly(styrene‐co‐acrylonitrile), amorphous PHB, and crystalline PHB. The crystallization of PHB in the blends was influenced by the AES content in different ways, depending on the processing conditions. A blend containing 30 wt % AES presented impact resistance comparable to that of high‐impact polystyrene, and the value was about 190% higher than that of pure PHB. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and characterization of dicyanate monomers containing methylene spacers
Authors: Anuradha G. , Sarojadevi M.
Published: July 2008

The bisphenols containing methylene spacer were prepared by treating eugenol/2‐allyl phenol with 2,6‐dimethyl phenol/guiacol/o‐cresol in the presence of AlCl3. All the bisphenols were converted to their respective cyanate esters by treating with CNBr. The structural confirmation was done by FTIR, 1H NMR, 13C NMR spectral methods, and elemental analysis. Thermal characterization was done by DSC and TGA. DSC transition shows that the Tg is in the range of 208–239°C. The Tg is highest for the cyanate ester Cy(b) with symmetric structure. The Tg of the cured network depends on the length and symmetry of the monomer, Tg being higher for shorter and the para‐substituted monomers. The T10 values are in the range of 364–381°C. The char yield is in the range of 47–53%. From the char yield, the limiting oxygen index (LOI) value was determined, which is used to confirm the flame retardancy of the cyanate ester resins. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Antimicrobial finishing of regular and modified nylon‐6 fabrics
Authors: Shalaby S. E. , AL‐Balakocy N. G. , Abdel‐Fatah O. M. , Elshafei A. M.
Published: July 2008

A simple, efficient, and practically applicable functional approach for improvement antimicrobial properties of nylon‐6 fabrics and increase the washing durability of biofunctions was developed. This finishing approach is based on grafting of the fabrics with methacrylic acid (MAA) to create additional carboxylic groups in nylon‐6 macromolecules, followed by subsequent reaction with dimethylalklbenzyl ammonium chloride (DMABAC) solution under alkaline conditions. The carboxylic groups react with cationic agent through ionic interaction, which led to the immobilization of QAS on nylon‐6 fabrics. This immobilization was proofed through determination of nitrogen content, applying scanning electron microscopy (SEM), and FTIR microscopy. The effect of treatment conditions on salt uptake (SUT) on nylon‐6 fabrics and reaction efficiency (RE) was investigated. The antimicrobial assessment of regular and grafted with PMAA nylon‐6 fabrics treated with DMABAC revealed that both types of fabrics are characterized before washing, by quite strong biocide effect on Bacillus mycoides, Escherichia coli and Candida albicans. The role of grafting nylon‐6 fabrics before treatment with salt on durability of antimicrobial functions seems to be more significant as the samples were repeatedly washed. Even after Laundring 10 times the grafted samples could still provide 80%, 100%, and 87.5% microbial reduction against B. mycoides, E. coli and C. albicans, respectively, in contrast with 42.6%, 65.6%, and 42.5% in case of regular nylon‐6 fabrics. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008.
Fabrication, structure, and properties of chitin whisker‐reinforced alginate nanocomposite fibers
Authors: Watthanaphanit Anyarat , Supaphol Pitt , Tamura Hiroshi , Tokura Seiichi , Rujiravanit Ratana
Published: July 2008

Calcium alginate yarn (30 fibers) and calcium alginate nanocomposite yarn (30 fibers) containing 0.05–2.00% w/w chitin whiskers were both prepared by wet spinning process. The whiskers were prepared by acid hydrolysis of chitin from shrimp shells. The average length and width of the whiskers were 343 and 46 nm, with the aspect ratio being ∼ 7.5. Incorporation of a low amount of the whiskers in the nanocomposite fibers improved both the mechanical and the thermal properties of the fibers significantly, possibly a result of the specific interactions, i.e., hydrogen bonding and electrostatic interactions, between the alginate molecules and the homogeneously dispersed chitin whiskers. Biodegradation of the calcium alginate fibers and the nanocomposite fibers was tested in Tris‐HCl buffer solution and the same buffer solution that contained lysozyme. The addition of the chitin whiskers in the nanocomposites fibers accelerated the biodegradation process of the fibers in the presence of lysozyme, whereas the presence of Ca2+ ions in the Tris‐HCl buffer solution helped to improve the tenacity of both the alginate and the nanocomposite fibers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Kinetics of glycidyl azide polymer‐based urethane network formation
Authors: Manu S. K. , Sekkar V. , Scariah K. J. , Varghese T. L. , Mathew S.
Published: July 2008

Reactions between hydroxyl‐terminated glycidyl azide polymer (GAP) and different isocyanate curatives such as toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), and methylene diicyclohexyl isocyanate (MDCI) at various temperatures viz. 30, 40, 50, and 60°C were followed by Fourier transform infra red spectroscopy. The reactions were found to follow second‐order kinetics. With TDI and IPDI at 30°C, a two‐stage reaction was observed. For GAP‐TDI system, the second stage was slower than the first while for GAP‐IPDI system, the second stage was faster than the first indicating dominance of autocatalytic effect. The stage separation occurred due to the difference in reactivity of the isocyanate groups and was found to narrow down with increase in temperature. The viscosity build up due to the curing reaction was followed for GAP‐TDI system for comparison. The stage separation was evident in the viscosity build up also. Rheokinetic analysis done based on data generated showed a linear correlation between viscosity build up and fractional conversion. The kinetic and activation parameters evaluated from the data showed the relative difference in reactivity of the three diisocyanates with GAP. Both the approaches suggested that the reactivity of the isocyanates employed for the present study could be arranged as TDI > IPDI ≫ MDCI. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Curing reaction of amino‐terminated aqueous‐based polyurethane dispersions with triglycidyl‐containing compound
Authors: Wang Shih‐Chieh , Chen Po‐Cheng , Yeh Jen‐Taut , Chen Kan‐Nan
Published: July 2008

Amino‐terminated anionic aqueous‐based polyurethane (PU) dispersion was obtained from NCO‐terminated PU prepolymer, which was neutralized with an excess triethylamine (TEA) and chain extended by ethylenediamine (EDA) during water dispersion process. That PU prepolymer was obtained from a polyaddition reaction of isophorone diisocyanate (IPDI), polypropylene glycol‐2000 (PPG‐2000), and 2,2′‐dimethylol propanoic acid (DMPA). This aqueous‐based PU dispersion was treated with trimethylolpropane triglycidyl ether (TMPTGE) as a latent curing agent and resulted in a self‐cured PU resin on drying. A model ring‐opening curing reaction between oxirane group of TMPTGE with terminal amino group of PU was demonstrated by glycidol with n‐butyl amine. The physical and mechanical properties as well as thermogravimetric analyses of these self‐cured PU resins were evaluated in this article. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Study on the long‐term thermal‐oxidative aging behavior of polyamide 6
Authors: Shu Ying , Ye Lin , Yang Tao
Published: July 2008

The long‐term thermal‐oxidative aging behavior of polyamide 6 (PA6) was studied by comparison with the stabilized sample in this work. The variation of mechanical properties of the pure and the stabilized samples of PA6 with aging time at 110°C, 130°C, and 150°C were investigated, respectively. The aging mechanism of PA6 under heat and oxygen was studied in terms of the reduced viscosity, crystallization behavior, dynamic mechanical behavior, and chemical composition through the methods of polarized light microscopy (PLM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), X‐ray photoelectron energy spectrum (XPS), and so on. The results indicated that at the initial stage of aging, the molecular crosslinking reaction of PA6 dominated resulting in the increase of the mechanical strength, reduced viscosity, and the glass transition temperature of the sample. And the molecular degradation dominated in the subsequent aging process resulting in the decrease of the melting temperature, the increase of the crystallinity, and the formation of the oxides and peroxides products. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Jute fiber reinforced polypropylene produced by continuous extrusion compounding, part 1: Processing and ageing properties
Authors: van den Oever M. J. A. , Snijder M. H. B.
Published: July 2008

This article addresses the processing and ageing properties of jute fiber reinforced polypropylene (PP) composites. The composite has been manufactured by a continuous extrusion process and results in free flowing composite granules, comprising up to 50 weight percent (wt %) jute fiber in PP. These granules have similar shape and diameter as commercially available PP granules. Rheological analysis shows that viscosity of the compounds follows the same shear rate dependency as PP and is on the same level as glass‐PP compounds. The mechanical properties show very little variation and exhibit strength and stiffness values at the upper range of competing natural fiber reinforced compounds for injection molding. The mechanical performance reduces gradually upon prolonged thermal loading and immersion in water. The low water diffusion coefficient of the 50 wt % jute‐PP composites indicates that the fibers are not forming a continuous network throughout the polymer. The jute fibers exhibit a stabilizing effect against ultra violet irradiation (UV) on PP polymer and, as a consequence, the mechanical properties of jute‐PP composites hardly decrease during an accelerated UV ageing test. Bacteria, fungi, and garden mold grow easily on the compound material, but only have a limited effect on mechanical properties. The resistance to growth of bacteria on the materials surface can be increased using a biostabilizer. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis, characterization, and curing of a new acrylate‐based dental restorative resin
Authors: Ghaemy Mousa , Bekhradnia Sara , Heidaripour Maryam
Published: July 2008

The synthesis of monomer 1,3‐bis [(2‐hydroxy‐3‐acrylate) propyloxy]2‐hydroxy propane (BHAPP) is reported for the possible use in dental restoratives. The monomer was prepared by the reaction of acrylic acid with diglycerol diglycidyl ether (DGE) in the presence of triethyl amine as a catalyst. The progress of the reaction at 60°C followed by measuring the intensity of the epoxide absorption peak at 915 cm−1 which has reached to its minimum value after 5 h. The structure of the monomer was characterized by FTIR and 1H‐NMR. The monomer was a moderately viscous light yellow color liquid having a refractive index of 1.544. Thermal curing of the monomer in DSC in the presence of benzoyl peroxide showed exothermic peak with maximum temperature (Tp) varied from 89 to 107°C depending on the heating rate and activation energy of 83 kJ/mol. Photopolymerization of the monomer by visible light in the presence of camphorquinone and N,N‐dimethylaminoethyl methacrylate as the photoinitiating system showed maximum 60% conversion after 40 s exposure. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Silk grafting with methacrylic and epoxy monomers: Thermal process in comparison with ultraviolet curing
Authors: Ferrero Franco , Periolatto Monica , Songia Michela Bianchetto
Published: July 2008

Silk grafting with methacrylic and epoxy monomers was studied with the aim to obtain high graft yields. With both monomer types optimum operating conditions of thermal grafting in water bath were established. In particular, three epoxy monomers were tested at various concentrations, at different temperatures and reaction times, with sodium chloride or sodium thiosulphate as catalysts. Optimum yields (76–82%) were found with Araldite DY‐T for 2 h at 70°C with 3Msodium chloride. The results were compared with those obtained with the same monomers by UV curing, radical with methacrylates and cationic with the epoxy resin. The UV curing efficiency was tested by gel content determinations. Thermal and UV cured fibers were then subjected to measurements of fibroin solubility in ethanol–calcium chloride–water mixture to evaluate the crosslinking degree. Except in the case of methacrylamide, radical UV curing yielded fibers more crosslinked than thermal treatment, or crosslinked to the same extent, whereas cationic UV curing showed lower crosslinking effects. The grafted fibers were characterized through DSC measurements and FTIR‐ATR spectrometry. Finally, surface morphology of UV‐cured samples was investigated through SEM analyses which showed that the better products could be obtained with UV curing at low add‐on, mainly with dimethacrylates and Araldite DY‐T, whereas the thermal grafting seems to be preferable for high add‐on. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Impact of curing temperature on microstructures and properties of isobutylene–isoprene rubber/clay nanocomposites
Authors: Lu Yong‐Lai , Li Zhao , Mao Li‐Xin , Li Yao , Wu You‐Ping , Liang Yu‐Rong , Zhang Li‐Qun
Published: July 2008

In this work, the influence of curing temperature on microstructures of isobutylene–isoprene rubber/clay nanocomposites (IIRCNs) prepared by melt compounding was characterized using wide‐angle X‐ray diffraction and TEM. The gas barrier and tensile properties of IIRCN cured under different temperature were examined. The results reveal that high pressure, curing reactions, and reactions of amine intercalants with curing agents together play important roles on determining the final microstructures of cured IIRCNs. Changing curing temperature would dramatically alter intercalated structure, dispersion homogeneity, filler–rubber interaction strength, and crosslinking density of obtained IIRCN, resulting in great difference in final properties. Finally, some suggestions for the preparation of successful RCNs were proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Preparation and characterization of water‐blown polyurethane foams from liquefied cornstalk polyol
Authors: Yan Yongbin , Pang Hao , Yang Xiaoxu , Zhang Rongli , Liao Bing
Published: July 2008

Polyurethane foams were prepared from the liquefied cornstalk polyol, which was obtained by the liquefaction of cornstalk in the presence of polyhydric alcohols using sulfuric acid as catalyst. The advisable liquefaction reaction conditions were selected by investigating their influences on the properties of liquefied cornstalk polyol, taking account of the requirement for the preparation of appropriate polyurethane foams. The influences of the contents of catalysts, water, surfactant, and isocyanate on the properties of polyurethane foams were also discussed, and feasible formulations for preparing cornstalk‐based polyurethane foams were proposed. The results indicated that the foams prepared from such liquefied cornstalk polyol exhibited excellent mechanical properties and thermal properties, and could be used as heat‐insulating materials. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Photoinitiating polymerization to prepare biocompatible chitosan hydrogels
Authors: Hu Xiaohong , Gao Changyou
Published: July 2008

Chitosan hydrogels were prepared from water soluble chitosan derivatives (chitosan‐MA‐LA, CML) by photoinitiating polymerization under the existence of Irgacure2959 and the irradiation of UV light. The CML was obtained by amidation of the amine groups of chitosan with lactic acid and methacrylic acid. Gelation time of the hydrogel could be adjusted within a range of 5–50 min, and controlled by factors such as the degree of MA substitution, initiator concentration, existence of oxygen, and salt. The dry hydrogel adsorbed tens to hundred times of water, forming a highly hydrated gel. The swelling ratio was smaller at the higher degree of MA substitution, higher pH, and higher salt concentration. Rheological test showed that the hydrogel is elastomeric in the measuring frequency range, with a storage modulus and loss modulus of 0.8–7 kPa and 10–100 Pa, respectively. In vitro culture of chondrocytes demonstrated that the cells could normally proliferate in the extractant of the hydrogels, showing no cytotoxicity at lower initiator concentration. By contrast, the extractant of the hydrogel made by the redox initiating system, i.e., ammonium persulfate (APS) and N,N,N′,N′‐tetramethylethylenediamine (TEMED), showed apparent cytotoxicity. Thus, the chitosan hydrogels initiated by the Irgacure2959 have better comprehensive properties, in particular better biocompatibility, and are more suitable for biomedical applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis of poly(methyl methacrylate)/silica nanocomposite through emulsion polymerization using dimethylaminoethyl methacrylate
Authors: Barari Mohammad , Sharifi‐Sanjani Naser
Published: July 2008

Polymer/Silica nanocomposite latex particles were prepared by emulsion polymerization of methyl methacrylate (MMA) with dimethylaminoethyl methacrylate (DM). The reaction was performed using a nonionic surfactant and in the presence of silica nanoparticles as the seed. The polymer‐coated silica nanoparticles with polymer content and number average particle sizes ranged from 32 to 93 wt % and 114–310 nm, respectively, were obtained depending on reaction conditions. Influences of some synthetic conditions such as MMA, DM, surfactant concentration, and the nature of initiator on the coating of the silica nanoparticles were studied. Electrostatic attraction between anionic surface of silica beads and cationic amino groups of DM is the main driving force for the formation of the nanocomposites. It was demonstrated that the ratio of DM/MMA is important factor in stability of the system. The particle size, polymer content, efficiency of the coating reaction, and morphology of resulted nanocomposite particles showed a dependence on the amount of the surfactant. Zeta potential measurements confirmed that the DM was located at the surface of the nanocomposites particles. Thermogravimeteric analysis indicated a relationship between the composition of polymer shell and polymer content of the nanocomposites. The nanocomposites were also characterized by FTIR and differential scanning calorimetry techniques. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Cross‐linked and uncross‐linked biodegradable nanocomposites. I. Nonisothermal crystallization kinetics and gas permeability
Authors: Shih Y. F. , Wang T. Y. , Jeng R. J. , Wu J. Y. , Wuu D. S.
Published: July 2008

Various nanocomposites of poly(butylene succinates) (PBS) with different ratios of organically modified layered silicates (OMLS) were prepared. Moreover, such PBS nanocomposites cross‐linked by dicumyl peroxide (DCP) were also prepared in this work. Effects of cross‐linking and OMLS on nonisothermal crystallization kinetics and the gas permeability of PBS samples were investigated further. WAXD indicates that the layers of clay were intercalated by the modifiers, and that the interlayer distance of OMLS in the nanocomposites could be expanded to about 2.96 nm. The results of DSC analysis revealed that the crystallization temperatures of nanocomposites shifted to the lower temperature with the increase of OMLS content. With the addition of OMLS, crystallinity was decreased, whereas the half‐life of crystallization was increased. On the other hand, even the cross‐linked effects also increased the half‐life of crystallization of the materials, but did not necessarily decrease crystallinity in all cases. Moreover, the PBS/OMLS nanocomposites showed a 23.87–46.64% decrease in permeability of oxygen when compared with the pristine PBS sample. Yet, the cross‐linked nanocomposites exhibited decrements of 6.38–39.53%. This indicates that the gas permeability of PBS was more effectively depressed by the addition of OMLS than by the cross‐linking reaction. The cross‐linked structure of polymer seemed not to be very effective in decreasing the gas permeability of PBS. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Interferometric study of creep deformation and some structural properties of polypropylene fiber at three different temperatures
Authors: Fouda I. M. , EL‐Farahaty K. A. , Seisa E. A.
Published: July 2008

Influence of temperature on creep deformation for polypropylene PP fiber under a constant load was studied interferometrically. The automated multiple‐beam Fizeau system in transmission was equipped with a mechanical creep device attached to a wedge interferometer. This system was used to determine the optical properties (n∥, n⟂, and Δn) of PP fiber during the creep process at constant loading with varying temperature. The creep compliance was drawn as a function of both time and temperature. An empirical formula was suggested to describe the creep compliance curves for PP fibers and the constants of this formula were determined. Two Kelvin elements combined in series were used to provide an accurate fit to the experimental compliance curves. The stress–strain curve via creep was studied to determine some mechanical parameter of PP fibers, Young's modulus E, yield stress σy, and yield strain εy. The optical orientation function f(θ), the dielectric constant d, the dielectric susceptibility χ, the surface reflectivity $ \overline R $, and the average work per chain W′ were also calculated. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Effect of fiber length on processing and properties of extruded wood‐fiber/HDPE composites
Authors: Migneault Sébastien , Koubaa Ahmed , Erchiqui Fouad , Chaala Abdelkader , Englund Karl , Krause Cornelia , Wolcott Michael
Published: July 2008

Fiber length and distribution play important roles in the processing and mechanical performance of fiber‐based products such as paper and fiberboard. In the case of wood–plastic composites (WPC), the production of WPC with long fibers has been neglected, because they are difficult to handle with current production equipment. This study provides a better understanding of the effect of fiber length on WPC processing and properties. The objectives of this study were therefore to determine the role of fiber length in the formation process and property development of WPC. Three chemithermomechanical pulps (CTMP) with different lengths, distributions, and length‐to‐diameter ratios (L/D) were obtained by mechanical refining. Length, shape, and distribution were characterized using a fiber quality analyzer (FQA). The rheometer torque properties of high‐density polyethylene (HDPE) filled with the pulps at different loads were studied. Variations in fiber load and length distribution resulted in significant variations in melting properties and torque characteristics. Composites from the three length distributions were successfully processed using extrusion. Physical and mechanical properties of the obtained composites varied with both length distribution and additive type. Mechanical properties increased with increasing fiber length, whereas performance in water immersion tests decreased. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and characterization of an amphiphilic pluronic‐poly(D,L‐lactide‐co‐glycolide) copolymer and their nanoparticles as protein delivery systems
Authors: Wu Yan , Che Fu‐Bin , Chen Jiang‐Han
Published: July 2008

A new amphiphilic Pluronic (F68)‐PLGA copolymer, which can be used to prepare the stealth or long‐circulating nanoparticles, was synthesized with Pluronic (F68), DL‐Lactide, and glycolide. The structures of Pluronic (F68)‐PLGA copolymer as the products were characterized with infrared spectrometry, nuclear magnetic resonance and their molecular weights were determined by gel permeation chromatography. Two methods, double emulsion (DE) and nanoprecipitation (NP), were employed to fabricate the polymeric nanoparticles. Bovine serum albumin (BSA) was loaded into nanoparticles as a model protein. Influence of the preparation conditions on the nanoparticles size, encapsulation efficiency, and release profile in vitro was investigated. They showed the entrapment efficiency of 42.9–63.4% and the average diameter of 119.1–342.8 nm depending on the fabrication technique of nanoparticles and the type of copolymer. The stability maintenance of BSA in the nanoparticle release in vitro was also measured via sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE), circular dichroism (CD), and fluorescence spectrometry. The results showed that the new copolymer could load BSA effectively and BSA kept stable after it was released from the nanoparticles. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
A comparison of the properties of rice husk ash, silica, and calcium carbonate filled 75 : 25 NR/EPDM blends
Authors: Arayapranee Wanvimon , Rempel Garry L.
Published: July 2008

The effects of incorporation of three different fillers, i.e., rice husk ash (RHA), silica, and calcium carbonate (CaCO3), over a loading range of 0–60 phr on the curing characteristics, processability, mechanical properties, and morphology of 75 : 25 natural rubber (NR)/ethylene‐propylene‐diene monomer (EPDM) blends were studied using a conventional vulcanization system. Filler loading and type influence the processability of the blends in which RHA and CaCO3 offer better processing advantage over silica. The best improvement in the tensile and tear strength and abrasion resistance of the 75 : 25 NR/EPDM blends with additional fillers was achieved when filled with silica. However, RHA and CaCO3 were better in resilience property compared to that of silica. The RHA filled blends showed higher failure properties and abrasion resistance but lower ozone resistance than that containing CaCO3. Scanning electron micrographs revealed that the morphology of the blend filled with silica is finer and more homogenous compared to the blend filled with RHA and CaCO3. According to these observations, RHA can be used as a cheaper filler to replace CaCO3 in rubber blends where improved mechanical properties are not so critical. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis–structure–performance relationship of cocondensed phenol–urea–formaldehyde resins by MALDI‐ToF and 13C NMR
Authors: Du Guanben , Lei Hong , Pizzi A. , Pasch H.
Published: July 2008

Matrix assisted laser desorption ionization time of flight (MALDI‐ToF) mass spectrometry has consistently confirmed on a number of PUF resins that phenol–urea cocondensates exist in phenol–urea–formaldehyde (PUF) resins. A noticeable proportion of methylene‐linked phenol to urea cocondensates were detected in all the PUF resins tried, alongside methylene bridges connecting phenol to phenol and urea to urea. The PUF, PF, and UF oligomers formed were identified. Variations of the PUF preparation procedure did always yield a certain proportion of the mixed phenol to urea cocondensates. Their relative proportion was determined and related the synthesis procedure used. Comparison of the MALDI‐ToF results with a 13C NMR investigation showed that in a real PUF resin in which phenol to urea cocondensates were identified the methylene bridge NMR signal at 44 ppm, characteristic of phenol to urea unsubstituted model compound cocondensates, does not appear at all. This confirmed that this peak cannot be taken as an indication of the existence of phenol and urea condensation under actual resin preparation conditions. The peak indicating cocondensation in PUF resins in which the phenolic nuclei and urea are substituted appears instead at 54.7–55.0 ppm. Thermomechanical analysis has again confirmed that the resin gel times greatly accelerates with increasing urea molar content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Alkali resistance of a casein‐acrylonitrile graft copolymer fiber
Authors: Tang Ren‐Cheng , Mei Jie
Published: July 2008

The casein‐acrylonitrile graft copolymer fiber was treated in sodium hydroxide, sodium carbonate, and sodium bicarbonate solutions to evaluate its alkali resistance which was very important for wet processing. The weight loss and whiteness of the treated fibers were examined. UV spectra of the alkaline treatment solutions and IR spectra of the treated fibers were analyzed. The study showed that the fiber exhibited poor alkali resistance. Treating temperature, alkali concentration, and strength affected the weight loss and whiteness of the treated fibers. A high weight loss was found even at low alkali concentration, and the obvious yellowing was observed at higher alkali concentration and temperature. The weight loss was primarily due to the hydrolysis of casein, whereas the yellowing was caused by the hydrolysis of nitrile groups and induced formation of CN conjugated system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis of morphologically different, metal absorbing aniline‐formaldehyde polymers including micron‐sized sphere using simple alcohols as morphology modifier
Authors: Koner Rik Rani , Albino Kumar Potsangbam , Chakraborty Saswati , Ray Manabendra
Published: July 2008

Aniline‐formaldehyde condensate (AFC) is an amine functional group containing polymer. The sticky resinous nature of the polymer limits its usefulness. Synthesis of AFC in presence of methanol, isopropanol, t‐butanol, n‐octanol or glycerine formed solid cakes instead of resinous material. The scanning electron microscopic (SEM) picture of the polymer synthesized in presence of t‐butanol shows the formation of micron sized spheroids while the presence of methanol, isopropanol, n‐octanol and glycerine leads to amorphous polymer. The polymers were characterized with IR, MALDI‐TOF mass and Energy Dispersive X‐ray (EDAX) analysis. To probe the accessibility of the amine functional groups by external reagents and as an application, metal removal property of the polymers were tested using aqueous Cr(VI) solution. All the polymers remove Cr(VI) efficiently at pH 3 with extent of metal removal depends on their morphology. Polymer synthesized in presence of isopropanol removes ∼ 66% Cr(VI) removal from an initial concentration of 9 mg/L. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Biogenic amine levels change in the brains of stressed honeybees
Authors: Chen Yi‐Ling , Hung Yu‐Shan , Yang En‐Cheng
Published: July 2008

Three different stress treatments, CO2 anesthesia, chilling anesthesia, and vertical spin, were applied to test whether honeybee (Apis mellifera) workers express stress responses in rewarding behaviors. In the present work, we defined the rewarding behaviors as the bees flying between the hive and feeder. The results from behavioral observation show that the flight time interval of the rewarding behavior of bee workers, flying between hive and feeder, was longer when they were stressed, suggesting that the stress treatments affected the workers' rewarding behavior. The biogenic amine levels in the workers' brains were measured to examine the rapid biochemical brain response to the stressors. After the chilling anesthesia, the dopamine (DA) and octopamine (OA) levels were significantly decreased; with the CO2 anesthesia for durations of both 2 min and 4 min, only DA showed a significant decrease. In the non‐anesthesia treatments, the vertical spin with a velocity of 50 and 60 rpm for 90 s, the DA and OA levels were significantly decreased. Our results suggest that when the bees were under stress, the brain levels of OA and DA were depressed, and this may have caused latency in the rewarding behavior. The serotonin (5‐HT) levels under these stress treatments were not changed. Arch. Insect Biochem. Physiol. 68:241–250, 2008. © 2008 Wiley‐Liss, Inc.
Effects of RH‐5992 on ecdysteroidogenesis of the prothoracic glands during the fourth larval instar of the silkworm, Bombyx mori
Authors: Gu Shi‐Hong , Lin Ju‐Ling , Lin Pei‐Ling , Kou Rong , Smagghe Guy
Published: July 2008

Stage‐dependent effects of RH‐5992 on ecdysteroidogenesis of the prothoracic glands during the fourth larval instar of the silkworm, Bombyx mori, were studied in the present report. When larvae were treated with RH‐5992 during the early stages of the fourth larval instar (between day 0 and day 1), initially ecdysteroid levels in the hemolymph were inhibited. However, 24 h after RH‐5992 application, ecdysteroid levels were greatly increased as compared with those treated with acetone. The examination of the in vitro prothoracic gland activity upon RH‐5992 application during the early stages of the fourth larval instar confirmed a short‐term inhibitory effect. When RH‐5992 was applied to the later stages of the fourth larval instar, no effects on both hemolymph ecdysteroid levels and prothoracic gland activity were observed. Addition of RH‐5992 to incubation medium strongly inhibited ecdysteroid secretion by the prothoracic glands from the early fourth instar, indicating direct action of RH‐5992 on ecdysteroidogenesis by prothoracic glands. Four hours after application with RH‐5992 on day 1.5, prothoracic glands still showed an activated response to PTTH in both PTTH‐cAMP signaling and the extracellular signal‐regulated kinase (ERK) signaling. Moreover, addition of RH‐5992 to incubation medium did not interfere with the stimulatory effect of the glands to PTTH in ecdysteroidogenesis. These results indicated that both PTTH‐cAMP signaling and PTTH‐ERK signaling may not be involved in short‐term inhibitory regulation by RH‐5992. Arch. Insect Biochem. Physiol. 68:197–205, 2008. © 2008 Wiley‐Liss, Inc.
Total Synthesis and Biological Potential of Psammosilenin A
Authors: Dahiya Rajiv
Published: July 2008

The present work reports the synthesis of a plant‐originated cyclooctapeptide – psammosilenin A 8 by cyclization of linear peptide fragment phe‐pro‐phe‐phe‐ala‐pro‐leu‐pro‐Opfp which was prepared by coupling of tetrapeptide units Boc‐phe‐pro‐phe‐phe‐OH and ala‐pro‐leu‐pro‐OMe followed by proper deprotection of terminal groups and activation of the acid functionality. During synthesis, dicyclohexylcarbodiimide (DCC) and N,N‐diisopropylcarbodiimide (DIPC) were used as the coupling agents and N‐methylmorpholine (NMM)/triethylamine (TEA) were used as bases. Structure of the synthesized peptide was elucidated by spectral as well as elemental data. The newly synthesized peptide was subjected to biological screening and found to possess potent cytotoxic activity against DLA and EAC cell lines with IC50 value of 7.93 and 17.06 μM, respectively. Furthermore, good anthelmintic activity against earthworms M. konkanensis and Eudrilus species at 1 and 2 mg/mL was also observed for the synthesized cyclic peptide. Studies indicated that N‐methylmorpholine was a more useful base for cyclization of linear peptide unit in comparison to pyridine.
Synthesis and In‐Vitro Antibacterial Activity of 5‐Substituted 1‐Methyl‐4‐nitro‐1H‐imidazoles
Authors: Letafat Bahram , Emami Saeed , Aliabadi Alireza , Mohammadhosseini Negar , Moshafi Mohammad Hassan , Asadipour Ali , Shafiee Abbas , Foroumadi Alireza
Published: July 2008

A series of 5‐substituted 1‐methyl‐4‐nitro‐1H‐imidazole derivatives were synthesized and evaluated for in‐vitro antibacterial activity against a panel of microorganisms including Staphylococcus aureus, Staphylococcus epidermidis, Bacillus subtilis, Esherichia coli, Klebsiella pneumonia, Entrobacter aerogenes, and Helicobacter pylori using conventional agar dilution method. Among the test compounds, 1‐methyl‐4‐nitro‐5‐(phenylsulfonyl)‐1H‐imidazole was the most potent against Gram‐positive bacteria, with a MIC value of ⪇8 μg/mL. All compounds showed no significant activity against Gram‐negative bacteria at concentrations ⪇64 μg/mL The MIC values against 15 clinical isolates of H. pylori indicated that compounds 10 and 11 were the most active compounds in this series in terms of inhibiting the growth of H. pylori (MIC = 2 μg/mL). It was also demonstrated that their corresponding activities were four times larger than that of metronidazole.
Synthesis and Evaluation of the Luciferase‐Oligodeoxynucleotide for the Sequence‐Selective Detection of Nucleic Acids
Authors: Nagatsugi Fumi , Nakahara Ryusuke , Inoue Kaori , Sasaki Shigeki
Published: July 2008

A new method for the synthesis of ODN‐luciferase conjugate was investigated as a signal‐amplifying sensor of the target nucleic acids. The conjugation of the luciferase was successfully achieved between the cysteine residue and the 2‐amino‐6‐vinylpurine nucleoside of the ODN probe without significant inactivation of luciferase. The ODN‐luciferase conjugate modified with PEG retained the luciferase activity and selectivity during the hybridization with the target ODN.
Synthesis of Nitroxyl Radicals for Overhauser‐enhanced Magnetic Resonance Imaging
Authors: Yamada Ken‐ichi , Kinoshita Yuichi , Yamasaki Toshihide , Sadasue Hiromi , Mito Fumiya , Nagai Mika , Matsumoto Shingo , Aso Mariko , Suemune Hiroshi , Sakai Kiyoshi , Utsumi Hideo
Published: July 2008

Non‐invasive measurement and visualization of free radicals in vivo would be important to clarify their roles in the pathogenesis of free radical‐associated diseases. Nitroxyl radicals can react with free radicals and be derivatized to achieve specific cellular / subcellular localizing capabilities while retaining the simple spectral features useful in imaging. Overhauser‐enhanced magnetic resonance imaging (OMRI), which is a double resonance technique, creates images of free radical distributions in small animals by enhancing the water proton signal intensity via the Overhauser Effect. In this study, we synthesized various nitroxyl probes having 15N nuclei and deuterium, and measured the enhancement factor for Overhauser‐enhanced magnetic resonance imaging experiments. 15N‐D‐4‐Oxo‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (15N‐D‐oxo‐TEMPO) has the highest enhancement factor compared with other nitroxyl probes. The proton signal enhancement was higher for 15N‐labeled nitroxyl probes when compared to the 14N‐labeled analogues because of the reduced spectral multiplicity of the I = 1/2 nucleus. Furthermore, this enhancement is proportional to the line width and number of electron spin resonance lines of nitroxyl radicals. Finally, we compared the Overhauser‐enhanced magnetic resonance image of 15N‐labeled, deuterated 4‐Oxo‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl with that of 14N‐H‐TEMPOL. These results suggested that the selective deuteration of the nitroxyl probes enhanced the signal‐to‐noise ratio and thereby improved spatial and temporal resolutions.
Is multidisciplinary research more highly cited? A macrolevel study
Authors: Levitt Jonathan M. , Thelwall Mike
Published: July 2008

Interdisciplinary collaboration is a major goal in research policy. This study uses citation analysis to examine diverse subjects in the Web of Science and Scopus to ascertain whether, in general, research published in journals classified in more than one subject is more highly cited than research published in journals classified in a single subject. For each subject, the study divides the journals into two disjoint sets called Multi and Mono. Multi consists of all journals in the subject and at least one other subject whereas Mono consists of all journals in the subject and in no other subject. The main findings are: (a) For social science subject categories in both the Web of Science and Scopus, the average citation levels of articles in Mono and Multi are very similar; and (b) for Scopus subject categories within life sciences, health sciences, and physical sciences, the average citation level of Mono articles is roughly twice that of Multi articles. Hence, one cannot assume that in general, multidisciplinary research will be more highly cited, and the converse is probably true for many areas of science. A policy implication is that, at least in the sciences, multidisciplinary researchers should not be evaluated by citations on the same basis as monodisciplinary researchers.