ISSN:0959-8103    

DOI:10.1002/pi.1995.210380201

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractEpoxidized natural rubber (ENR) was first precured with 3‐aminopropyltriethoxysilane (APS) by the normal compression molding technique. The resultant sheet was further subjected to moisture cure, via hydrolysis and condensation reactions, by soaking it in water. The moisture‐cured sample, when prepared under appropriate reaction conditions, demonstrated partial strain‐induced crystallization behavior and moderate tensile strength, as opposed to typical peroxide‐cured and sulfur‐cured vulcanizates. The suitability of the ENR–APS precured sample for in‐situ silica reinforcement by the sol–gel process, using tetraethyl orthosilicate (TEOS) as the silica precursor, was also demonstrated. Silica content as high as 36% by weight could be incorporated into the rubber, and TEOS‐to‐silica conversion of over 60% was observed. Comparative analysis with a typical peroxide‐cured sample that was subjected to the same sol–gel process indicates that the silica in the final ENR–APS sol–gel vulcanizate is chemically

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380202

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractNew types of complex salts of 7,7′,8,8′‐tetracyanoquinodimethane with aromatic ionenes and their model compounds were prepared. The electrical conductivity and the activation energy were measured and discussed in relation to their structure. The effects of the nature of the aromatic unit, and the flexibility and rigidity of the polymer backbone were compared with the corresponding model compounds. The effects of frequency and temperature are discussed in terms of the molecular strucuture of the complex. The electroconductivity at room temperature of the 1 : 1 polymer complex salts was found to be between 2 × 10−4and 7 × 10−5S/cm, while that of the model complex salts was between 1.3 × 10−3and 6.3 × 10−3S/cm. The activation energy was found to be 0.14 eV on average. The limitation of the concept of polycationic complex salts of TCNQ for electrically conductive plastics for commerical application in the plastics indu

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380203

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe role of certain cations as homopolymer inhibitors in the direct radiation grafting of acrylic acid to nylon‐6 fabric was investigated. The grafting solution was methanol and water at a ratio of 30 : 70 vol%. The maximum graft yield was obtained at 0·08 wt% when using Fe2+and at 0.7% for Fe3+. In addition, the graft yield obtained with the latter ion was higher than that for the former. Moreover, the presence of Na+and K+salts in concentrations as low as 0·1 wt% caused an increase in the graft yield. The hydrophilic properties investigated indicated that the water absorption of nylon‐6 fabric after 9 days increased by 44 times after grafting with poly(acrylic acid) at 166% graft yield. This ratio became 123 times, when this graft copolymer was transformed to the sodium salt. These ratios became 105 and 490 times for the corresponding recrystallized forms, respectively. A study was made to gain a better understanding of the observed super water absorption using SEM and DSC analysis. SEM micrographs of the recrystallized copolymer indicated the formation of large pores with a dendritic structure. Moreover, DSC showed a decrease in both the heat of fusion and melting point. The grafted nylon‐6 fabric showed a noticeable affinity for different dy

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380204

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractSBR compounds containing ammonium derivatives as neutral analogues of the oligoamidephosphates were studied with respect to their vulcanization characteristics and mechanical properties. Several differences between the effects of the neutral ammonium derivatives and the oligoamidephosphates were discovered, which may be connected with the different pHs of these products. As in the case of isoprene rubber compounds, the neutral products showed increased efficiency in comparison with the oligoamidephosphates. They offer the possibility of four‐fold reduction of the optimum cure time and partial replacement of the base sulphenamide accelerator. All SBR compositions containing neutral ammonium derivatives (NADs) were relatively well crosslinked and had cure characteristics and mechanical properties equal to, or better than, the corresponding compositions without neutral ammonium derivatives, even in the cases when the NAD amount was predominant. The results of our experiments give reason to assume that NADs participate in the vulcanization process with the formation of a different number of chemical bonds of various types. The NADs probably affect some physical interactions als

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380205

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe divinyl ester monomers were prepared by reacting glycidyl methacrylate (GMA) with dioic acids (adipic acid, glutaric acid, succinic acid, malonic acid and oxalic acid). The reaction between the active epoxy groups of GMA and the carboxylic group of the dioic acid was catalysed by triphenyl phosphine. the curing kinetics of divinyl ester monomers were studied using benzoyl peroxide as a free radical initiator. The kinetic studies were made by differential scanning calorimetry (DSC) using the isothermal method. An explanation for the difference in the kinetic parameters with different monomers is given. A shift in the kinetic model from autocatalytic tonth order was observed in all cases. A reaction mechanism for the radical polymerization is supported by a detailed mathematical derivation and experimental results.

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380206

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractTransient currents in double‐sided vacuum aluminized polyvinyl formal (PVF) film samples of thickness 40 μm were investigated in the charge and discharge modes at different temperatures and fileds. The results observed suggest that the transient currents are governed by charge injection processes leading to space charge effects. Comparative studies of the isochronal characteristics (i.e. current–temperature plots at fixed times) with the thermally stimulated discharge current (TSDC) indicated a strong resemblance between the two techniques. These studies suggest that the simultaneous mechanism of movement of charges through microscopic distances coupled with dipolar orientation may be responsible for the TSDC peak observed at 1

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380207

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe rate of the scavenging reaction of hyaluronic acid with hydroxyl radicals was investigated by means of competitive reaction with 4‐nitrosodimethylaniline. It was found that the reactivity of hyaluronic acid with hydroxyl radicals depends on both the molecular weight and the concentration of hyaluronic acid. These features were accounted for by the characteristic molecular properties of hyaluronic acid in solutio

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380208

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper reports the synthesis of amorphous polymer electrolytes. Polymer–salt complexes in the ternary system were prepared by mixing two polymers, namely poly(oxyethylene) and poly(oxypropylene glycol), with sodium iodide. This three component system is represented on a ternary pseudophase diagram. The ternary compositions are completely amorphous in a certain composition range and the composition POE–12%POPG–Nal with O/Na = 10 exhibited record high conductivity of 2 × 10−4(Ω cm)−1at ambient temperature. Formation of the amorphous electrolyte and the enhanced miscibility of the polymers were analysed using differential scanning calorimetry, X‐ray diffraction and ionic conductivity studies. The cation was found to play a major role in enhancing the miscibility of

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380209

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe tear failure and processing characteristics of short sisal fibre reinforced styrene butadiene rubber (SBR) composites were investigated. Tear strength was examined with special reference to the effects of fibre length, fibre orientation, fibre concentration and bonding agent. It was observed that the tear strength depends on all the above factors. The tear failure mechanism was analysed from fractographs taken using a scanning electron microscope (SEM). During tear testing, the composites failed by a shearing process. Microscopic examination of cracks propagating in SBR composites revealed that the amorphous SBR matrix developed cracks, leaving ligaments of rubber attached to the broken fibres. The rubber particles were stretched as the crack opened and failure occurred at large critical extensions. It was observed that an increase in the concentration of fibres increased the tear strength in both longitudinal and transverse directions. The tear strength values were almost three to four times higher than those of the unfilled vulcanizates under similar conditions. In order to analyse the processing behaviour, the green strength, mill shrinkage and Mooney viscosity of the compounds were determined. Finally, the polymer–filler interaction was studied using the Lorenz–Park and Kraus equati

ISSN:0959-8103    

DOI:10.1002/pi.1995.210380210

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY