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Polymers and Polymer Composites

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Title: ORGANIC VAPOUR SENSOR FROM CARBON BLACK FILLED AMORPHOUS POLYMER COMPOSITE: EFFECTS OF PROCESSING, CARBON FIBRES AND IRRADIATION
Page Range: p.213-221
Author(s): Xian Ming Dong; Ruo Wen Fu; Ming Qui Zhang; Bing Zhang; Min Zhi Rong
File size: 209K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 3

Abstract
Carbon black filled polybutyl methacrylate composites for use as organic vapour sensors were fabricated by polymerisation filling. It was found that the composites have a wide synthesis window, giving composite materials with high gas sensitivity under different conditions. In comparison with composites made by solution mixing, these composites made by polymerisation filling were shown to have a much higher responsivity to organic vapours because of the superior distribution of the filler particles. The addition of a third component, vapour-grown carbon fibres and the post-treatment of the composites by gamma-irradiation is claimed to have proven effective in enhancing response stability. This paper focuses on the effects of synthesis conditions such as reaction time, reaction temperature and initiator content, on the number-average molecular weight of the resultant polymer matrix, and the electrical responsivity of the resultant composites against organic vapours. Also evaluated, were the inclusion of the vapour-grown carbon fibres and the irradiation treatment. 20 refs.

Title: COMMERCIAL DENTAL COMPOSITE: DETERMINATION OF REACTION ADVANCEMENT AND STUDY OF THE MIGRATION OF ORGANIC COMPOUNDS
Page Range: p.223-234
Author(s): Sanglar C; Defay M; Waton H; Bonhommme A; Alamercery S; Baudot R; Piasse O; Grenier-Loustalot M F
File size: 201K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 3

Abstract
This work investigates the role of residual reactive methacrylate functions a the end of the photopolymerisation cycle of organic dental composites, and examines the behaviour of the residual monomers and oligomers in organic (ethanol) and aqueous (water and artificial saliva) media. Results indicate that all the methacrylate monomers present in dentine migrate into ethanol, whereas in aqueous media, only the most hydrophilic monomer (urethane dimethacrylate(UDMA)) migrated into water and artificial saliva. The desorption in the three media is accompanied by the hydrolysis of monomers, leading to the formation of monohydrolysed UDMA and bisphenyl glycidyl dimethacrylate (BISGMA). UDMA and BISGMA were completely hydrolysed in the artificial saliva. It was suggested that the alkalinity of the medium favoured the hydrolysis of methacrylate functions. 26 refs.

Title: CURE SIMULATION OF HEMP FIBRE ACRYLIC BASED COMPOSITES DURING SHEET MOLDING PROCESS
Page Range: p.235-244
Author(s): Behzad T; Sain M
File size: 173K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 3

Abstract
This aim of this study is to provide a model to predict the cure behaviour and temperature variations of hemp fibre acrylic based composites during the process of sheet moulding, and to evaluate the predicted values with experimental results. The composites are designated for use in the automotive industry. A finite difference method was applied to predict the cure behaviour and temperature variation of hemp fibre acrylic based composites during the process. Dynamic differential scanning calorimetry was used to determine the kinetic parameters for the curing reaction at different heating rates. It was found that the experimental and predicted values were in good agreement at the lower heating rate. The thermophysical properties of the resin, fibre and composite were obtained to use in the model. The temperature profile and the degree of cure of the composite with 40% resin and 60% fibre were simulated, and a comparison of numerical results with known experimental data confirmed the approximate validity of the model. 19 refs.

Title: COVALENTLY CONNECTING NANOPARTICLES WITH EPOXY MATRIX AND ITS EFFECT ON THE IMPROVEMENT OF TRIBOLOGICAL PERFORMANCE OF THE COMPOSITES
Page Range: p.245-252
Author(s): Ying Luo; Min Zhi Rong; Ming Qui Zhang
File size: 345K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 3

Abstract
Graft polymerisation of glycidyl methacrylate, which can form chemical bonding with epoxy during the subsequent composites manufacturing, onto the surface of nanoparticle-sized silicon carbide, proved to be an effective method of producing nano-silicon carbide epoxy composites with high tribological performance. Graft polymerisation by means of soapless emulsion polymerisation resulted in composite particles consisting of silicon carbide core and polymeric shell, in which the polyglycidyl methacrylate (PGMA) was bonded to the nanoparticles by the double bonds introduced during the pretreatment with a coupling agent. Compared with untreated such particles, the grafted versions were shown to exhibit improved dispersibility, and in addition were able to establish chemical bonding between the fillers and matrix through the reaction between the epoxide groups and the curing agent when compounded with epoxy. As a result of these advantages, the epoxy composites filled with PGMA-grafted nano silicon carbide particles demonstrated high sliding wear resistance and low frictional coefficient at a low filler loading. 19 refs.

Title: FIBRE ORIENTATION AND MECHANICAL PROPERTIES OF SHORT GLASS FIBRE REINFORCED PP COMPOSITES
Page Range: p.253-262
Author(s): Minjie Chen; Chaoying Wan; Yong Zhang; Yinxi Zhang
File size: 303K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 3

Abstract
The fibre orientation and distribution in short glass fibre reinforced polypropylene composites were measured, and an orientation function was introduced to describe the fibre orientation distribution. The fibre orientation distribution in the same level plane was shown to depend on the fibre position in an injection moulded plate. Maleic anhydride grafted PP (MAPP) was used as a compatibiliser. The use of the compatibiliser improved the interfacial adhesion between the short glass fibres and the PP, and consequently the mechanical properties. Improvements in tensile strength and impact properties are discussed with reference to the use of short glass fibre reinforcement and MAPP in the composites. 25 refs.

Title: SURFACE MODIFICATION OF PBO FIBRES BY GAMMA-RAY IRRADIATION: EFFECTS ON INTERFACIAL PROPERTIES OF THEIR EPOXY COMPOSITES
Page Range: p.263-270
Author(s): Zhang C H; Huang Y D; Liu L
File size: 179K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 3

Abstract
Surfaces of polyphenylene bezobisoxazole (PBO) fibres were grafted with epichlorohydrin by a gamma irradiation method. The influence of the irradiation dose on the interfacial shear strength (IFSS), interlaminar shear strength (ILSS) and the fibre wettability were investigated. The fibre surface composition and the shear fracture topography of PBO fibre/epoxy resin composites were also analysed by X-ray photoelectron spectroscopy and scanning electron microscopy respectively. Results were able to indicate the optimal irradiation dose for fibre surface modification, and details are given of improvements to IFSS, ILSS and wettability of the fibres. SEM indicated that the improved interfacial adhesion resulted in a change in the failure mode of PBO fibre/epoxy composite from an adhesive-type interfacial failure to a cohesive-like matrix failure. 14 refs.

Title: CAPILLARY EXTRUSION RHEOLOGY AND THERMAL STABILITY OF EVA/ORGANOMONTMORILLONITE NANOCOMPOSITES
Page Range: p.271-280
Author(s): Dazhu Chen; Weian Zhang; Pingsheng He
File size: 181K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 3

Abstract
EVA copolymer-based nanocomposites based on organomontmorillonite were prepared by melt compounding. A partially intercalated, partially exfoliated structure was revealed in the nanocomposites by X-ray diffraction and transmission electron microscopy. Attention was paid to the steady shear rheological properties of the nanocomposites via a capillary rheometer. It was found that an increased n temperature improved the flow properties, but decreased the pseudoplasticity of the melts. With increasing shear stress (or shear rate), the shear viscosity and flow activation energy dropped, while the extrudate swell ratio rose. The addition of organomontmorillonite led to a reduction in both the shear viscosity and swell ratio of the nanocomposites compared to the EVA matrix. The thermal stability of the EVA and EVA/organomontmorillonite nanocomposites was also examined by means of thermogravimetric analysis techniques. 31 refs.

Title: EVALUATION OF THE MECHANICAL AND ULTRASONIC PROPERTIES OF BUTADIENE-ACRYLONITRILE RUBBER CONTAINING SHORT ARAMID FIBRES
Page Range: p.281-299
Author(s): Helaly F M; El-Sabbagh S H; El-Latif L A
File size: 509K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 3

Abstract
Short aramid fibres were incorporated into butadiene-acrylonitrile copolymer rubber (NBR), and an adhesion system consisting of hydrated silica, resorcinol and hexamethylene tetramine, was used to strengthen the bond between the rubber and the fibres. Rheological, tensile, and ultrasonic properties and hardness were characterised. It was found that the properties of the composites improved as the fibre content increased up to 30 phr by weight. Longitudinal and transverse ultrasonic velocities were used to calculate the elastic parameters of the composites. These results were then used to assess the bonding between the fibres and the rubber matrix as well as the sound absorptive potential of the composites. SEM showed the fibre distribution in the rubber to be satisfactory. Regression analysis was used to clarify the correlation between the longitudinal tensile strength and ageing over time. It was found that the strain energy increased with fibre content, while the fatigue life decreased. 28 refs.

Title: MODIFICATION OF SODIUM SALT OF PARTIALLY CARBOXYMETHYLATED GUAR GUM BY GRAFT COPOLYMERIZATION WITH METHYL ACRYLATE
Page Range: p.301-312
Author(s): Trivedi J H; Patel N K; Trivedi H C; Kalia K
File size: 215K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 3

Abstract
The grafting of methyl acrylate onto sodium salt of partially carboxylated guar gum was carried out using ceric ammonium nitrate as the redox initiator in an aqueous medium. Reaction variables observed included varying concentrations of initiator, nitric acid, monomer and amount of the backbone, in addition to time and temperature variations, in order to establish the optimised reaction conditions for grafting. The influence of these reaction parameters on the grafting yields and the rates of polymerisation, graft copolymerisation and homopolymerisation, were also studied. A kinetic scheme of free radical graft copolymerisation was proposed and the experimental results were found to agree very well with the proposed kinetic scheme. The graft copolymer sample was characterised by IR spectroscopy, thermal and scanning electron microscopic techniques. 25 refs.

Title: AROMATIC DIAMINES AS COOPERATIVE COMPATIBILIZERS AND IMPACT MODIFIERS IN LDPE/HIPS BLENDS
Page Range: p.313-320
Author(s): Pospisil J; Michalkova D; Fortelny I; Krulis Z; Slouf M
File size: 206K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 3

Abstract
The use is examined of compatibilisers and stabilisers for blends of reclaimed polymers in order to enhance the feasibility of mechanical recycling, and to improve the mechanical properties of the recyclates. This work deals with LDPE. The impact strength of recycled or pre-aged (recyclate model) LDPE/HIPS blends, compatibilised with styrene-butadiene copolymer/ethylene-propylene rubber was enhanced and fineness of the phase structure of the system was improved by the use of N,N'-disubstituted 1,4-phenylenediamine co-additives. Mechanism of the strong synergistic compatibilisation effect was explained by LDPE grafting with styrene-butadiene copolymer, mediated by the bifunctional amine additive. 21 refs.

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