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Polymers and Polymer Composites

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Title: THERMOFORMING COMPLEX PARTS FROM UNCONSOLIDATED AND CONSOLIDATED POLYPROPYLENE/GLASS FIBRE FABRICS
Page Range: p.543-558
Author(s): Trudel-Boucher D; Fisa B; Denault J; Gagnon P
File size: 414K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 6

Abstract
Thermoforming of unconsolidated and consolidated PP/glass fibre fabrics was studied for two mould geometries: a square mould and a mould with three studs. The principal objective of this study was to evaluate the feasibility of direct thermoforming of unconsolidated fabrics in complex moulds, since this process offers the potential of reducing the cost of the raw material by eliminating the separate consolidation step performed prior to moulding. In this work, the unconsolidated and consolidated fabrics plies were heated in a convection oven and transferred to a press to be simultaneously conformed and re-consolidated using a rubber punch and a metal cavity. Results showed that a similar product quality (evaluated by the void content), could be obtained with unconsolidated and consolidated fabrics once conformation to the mould shape had been achieved. It was found that a minimal forming temperature of 215 degrees C was required to achieve conformation to the mould shape, and that minimal forming pressures of 2 and 3 MPa had to be applied to achieve the same objective for the consolidated and unconsolidated fabric. In addition, an increase in the punch hardness, variation of the fabric orientation, and an increase in the number of vents, was found to reduce the pressure necessary to produce conformation to the mould shape. 21 refs.

Title: MULTIPLE INJECTION PORT SIMULATION FOR RESIN INJECTION PULTRUSION
Page Range: p.559-70
Author(s): Rahatekar S S; Roux J A; Lackey E; Vaughan J G
File size: 243K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 6

Abstract
The aim of this research was to predict the effect of multiple resin injection ports on the magnitude of the resin injection pressure needed to achieve complete wet-out of the fibres in the injection chamber. The work focuses on the use of epoxy/glass rovings and polyester/glass rovings composites. The recommended injection pressures for complete wet-out are predicted for a variety of processing parameters. Darcy's law for flow through porous media is used for modelling the fibre/resin system of injection pultrusion. The governing equations are solved via the finite element volume method to predict the resin pressure field, the resin velocity field and the location and shape of the resin flow front. Different permeability models were used to determine the transverse and longitudinal permeabilities. 7 refs.

Title: EFFECT OF EPOXY RESIN ON THE MECHANICAL PROPERTIES AND MELT VISCOELASTIC BEHAVIOUR OF POLY(BUTYLENE TEREPHTHALATE)/MONTMORILLONITE NANOCOMPOSITES
Page Range: p.571-80
Author(s): Defeng Wu; Chixing Zhou; Xie Fan; Dalian Mao; Zhang Bian
File size: 234K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 6

Abstract
PBTP/epoxy/montmorillonite ternary nanocomposites, (PCNs) were prepared by melt intercalation, and their morphologies were investigated by XRD and TEM. The results showed that by using epoxy resin as a compatibiliser, the clay was easily intercalated and dispersed well in the matrix. As such, the PCNs exhibited superior tensile and impact properties than the PBTP alone, although any surplus epoxy dispersed in the PBTP matrix reduced the material performance. The melt viscoelastic behaviour of the PCNs was measured by means of a parallel plate rheometer. The PCN ternary hybrids showed a stronger solid-like response in the lower frequencies than did the samples without epoxy resin. This is said to have been due to the enhancement of percolation network density, and the bridge-like effect of the epoxy linking the clay and the polymer chains. The compatibiliser, therefore, was shown to influence both the morphology and performance of the nanocomposites. The optimum compatibiliser dose of 4 wt% was arrived at by means of a novel crossover point rheological method. 25 refs.

Title: NONLINEAR VISCOELASTIC CREEP CHARACTERIZATION OF HDPE-RICE HUSK COMPOSITES
Page Range: p.581-598
Author(s): Pramanick A; Sain M
File size: 337K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 6

Abstract
Rice husk plastic composites are used in load-bearing applications such as deck boards and railings. These applications, typically using 40% plastic, are subjected t creep. In order to better define, model and predict long-term creep deformation, the viscoelastic characterisation of this material and the prediction of creep as a function of time is important for its long term commercial success. This research aims to derive a relationship between deformation, time, temperature, relative humidity and stress. In this study, therefore, hollow extruded rice husk-HDPE beams were subjected to creep and recovery in flexural mode and the stress related nonlinear creep behaviour of the same was studied phenomenologically. Both linear and non-linear region constants were determined with modified models, and a predictive model was developed. 22 refs.

Title: NON-ISOTHERMAL CURE KINETICS OF POLYBENZOXAZINE/CARBON FIBER COMPOSITES BY PHASE CHANGE THEORY
Page Range: p.599-605
Author(s): Chunling Xin; Xiaoping Yang; Dingsheng Yu
File size: 124K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 6

Abstract
The curing of benzoxazines (BA-a) and benzoxazine/carbon fibre composites (BA-a/CF), was monitored and compared using non-isothermal differential scanning calorimetry, at various heating rates. The results showed that the initial cure temperature of BA-a/CF was lower that of BA-a at the same heating rate. Various kinetic parameters and apparent activation energies for both curing systems were obtained using a modified version of the Avrami equation. The change in the Avrami component with cure temperature is reported to reflect two different stages of the benzoxazine cure reaction: the microgel formation, growth stage and the diffusion-controlled stage, The activation energy obtained from the Avrami rate constant for neat benzoxazine was shown to closely agree with earlier values reported by another method. For BA-a/CF composites, the activation energies obtained from the Avrami rate constant reflected the effect of the carbon fibres on the cure behaviour of benzoxazine. The cure reaction of benzoxazines was found to be not only catalysed by carbon fibre, but also retarded by it. 19 refs.

Title: MECHANICAL AND THERMAL PROPERTIES OF OIL PALM EMPTY FRUIT BUNCH-FILLED UNPLASTICIZED POLY (VINYL CHLORIDE) COMPOSITES
Page Range: p.607-17
Author(s): Bakar A A; Hassan A; Yusof A F M
File size: 325K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 6

Abstract
The effect of oil palm empty fruit bunches (EFB) on the mechanical and thermal properties of unplasticised PVC is investigated. An increase in EFB fibre content in the uPVC matrix was shown to improve the flexural modulus and cause a slight increase in the Tg, but at the expense of impact and flexural strengths. The incorporation of EFB also decreased the thermal stability of the composites evidenced by a decrease in decomposition temperature and a change in the degradation process from two to three stages. 35 refs.

Title: EFFECT OF FLEXIBLE POLYMER COATING ON INTERFACIAL ADHESION OF GLASS FIBRE REINFORCED POLYPROPYLENE
Page Range: p.619-25
Author(s): Xiadong Zhou; Qunfang Lin; Ruohua Xiong; Xinyu Cui; Gance Dai
File size: 103K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 6

Abstract
Flexible rubber coatings were obtained with which to coat glass fibre surfaces for use in a polypropylene matrix. The polymeric coatings were obtained by using two rubbers, cis-polybutadiene rubber and EPDM, and two block copolymers, polystyrene-block-polybutadiene-block polyvinyltriethoxysilane and polystyrene-block-polyvinyltriethoxysilane. The effect of the coatings on the interfacial adhesion and thermal cycling resistance of composites were studied by a single-filament fragmentation technique which was designed to measure the interfacial shear strength of the composite. It was found that the interfacial shear strength was improved by the rubber coatings, which could graft to silane coupling agents coated onto the fibre surfaces and could undergo crosslinking under peroxide initiation. The interfacial bond strength was determined by the nature and thickness of the rubber coatings. Interfacial adhesion was also seen to improve when using block copolymers to treat glass fibres. The rubbers and those copolymers having flexible blocks in their structures both produced coatings that could relieve the thermal stresses at the composite interface during temperature cycling. The interface between the composites and the flexible polymer coatings had good thermal cycling fatigue resistance. 18 refs.

Title: TENSILE AND IMPACT PERFORMANCE OF POLYPROPYLENE MICROCOMPOSITE SYSTEM: EFFECT OF NOVEL SILICA ASH FILLER
Page Range: p.627-35
Author(s): Chaudhary D S; Jollands M C
File size: 120K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 6

Abstract
Polypropylene was used as the matrix with which to study filler-polymer interactions when rice hull ash (silica ash) was used as a microfiller. Two sizes of silica ash particles were studied to obtain quantitative data on the composites' mechanical performance. Nucleating effects were found, suggesting, it is claimed, that there was a moderate polymer-filler interaction during melt-processing. A comparison of the effects of increasing filler loading and increasing surface treatment indicated, that at higher filler loadings, the effect of surface treatment was not dominant. Reducing the filler particle size was found to improve the tensile modulus and impact strength. Furthermore, removal of silica ash impurity by burning it off resulted in a significant increase in these properties, but similar results were not obtained following surface treatment of the unburnt ash. Such results are claimed to indicate that there was a possible trade-off between using the silica ash without burning, thus saving on the cost of burning off the impurities, and using the 'burnt' ash and saving on the cost of surface modification. 17 refs.

Title: PREDICTION OF THERMAL CONDUCTIVITIES OF FIBRE REINFORCED COMPOSITES USING A THERMAL-ELECTRICAL ANALOGY
Page Range: p.637-644
Author(s): Young Jun Cho; Jae Ryoun Youn; Tae Jin Kang; Sung Min Kim
File size: 260K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 6

Abstract
A method is described with which to predict the effective thermal conductivities of fibre reinforced composites. It is based on the thermal-electrical analogy. Geometrical modelling of a laminate composite was attempted using a voxelisation method. The geometry of the woven fabric composite was discretised into yarn-type voxels and matrix-type voxels. This study used a balanced plain weave laminate composite of graphite and epoxy. Both in- and out-of-plane thermal conductivities were predicted for the composite. The effectiveness of the proposed method is claimed to be supported by the reasonable agreement between present results and previously reported research. 12 refs.

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