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Polymers and Polymer Composites

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Title: SELF-SENSING OF DAMAGE AND STRAIN IN CARBON FIBER POLYMER-MATRIX STRUCTURAL COMPOSITES BY ELECTRICAL RESISTANCE MEASUREMENT
Page Range: p.515-525
Author(s): Chung DDL; Wang S
File size: 105K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 11
Issue No: No. 7

Abstract
The use of DC electrical resistance measurement for the self-sensing of strain and damage in continuous carbon fibre polymer-matrix structural composites is examined. Carbon fibres, being electrically conductive enable composites to exhibit electrical properties which depend on parameters such as strain and damage, thereby attaining the ability to sense themselves through electrical measurement. A consequence of self-sensing structural materials is reduced cost, enhanced durability, a larger sensing volume, and an absence of mechanical property degradation.. This paper provides a review of self-sensing behaviour, in addition to addressing the design of the electrical contacts, and providing a model for relating the electrical resistance to the type and amount of damage. 37 refs.

Title: HIGH STRAIN RATE COMPRESSION CHARACTERIZATION OF AFFORDABLE WOVEN CARBON/EPOXY COMPOSITES UNDER OFF-AXIS LOADING
Page Range: p.527-539
Author(s): Hosur M V; Alexander J; Vaidya U K; Jeelani S; Mayer A
File size: 381K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 11
Issue No: No. 7

Abstract
An experimental study is described into the response of affordable plain weave carbon/epoxy composite laminates to high strain rate compression loading, using a modified Compression Split Hopkinson's Pressure Bar under off-axis loading. Laminates were manufactured using aerospace-grade woven fabrics using a vacuum-assisted resin infusion moulding technique. Samples were subsequently subjected to high strain rate compression loading and tested along 0 degrees, 15 degrees, 30 degrees and 45 degrees off-axes angles. Quasi-static tests were also conducted to compare results with the dynamic response. Failure modes were evaluated using optical micrographs, and results were analysed in terms of peak stress, strain at peak stress, failure modes and orientation. 17 refs.

Title: RHEOLOGY OF HIGHLY FILLED POLYPROPYLENES PREPARED WITH SURFACE TREATED FILLERS
Page Range: p.541-550
Author(s): Ren Z; Shanks R A; Rook T J
File size: 121K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 11
Issue No: No. 7

Abstract
This study reports on the production of highly filled PP composites by the extrusion of polypropylenes with surface treated fillers. The aim of the investigation was to include the highest proportion of filler in order to provide hardness and high density, without undue brittleness. It was shown that the viscoelastic behaviour of melt flow of highly filled polypropylene composites significantly depended on certain properties of the fillers. These included aspect ratio, specific surface area and particle size. Fillers considered included talc, calcium carbonate and barium sulphate. Traditional surface modifiers such as stearic acid were found to be useful, but titanates, and in particular, small amounts of silicones were shown to provide the greatest rheological modification. 25 refs.

Title: DUAL CURE PHENOL - EPOXY RESINS: CHARACTERISATION AND PROPERTIES (short article)
Page Range: p.551-558
Author(s): Devi K A; Nair C P R; Ninan K N
File size: 92K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 11
Issue No: No. 7

Abstract
Reactive blends of 2, 2'-diallyl bisphenol A (DABA) and a novolac epoxy resin (EPN) were investigated for their cure behaviour, and rheological, physical, mechanical and thermal properties. Cure characterization was carried out by differential scanning calorimetry and dynamic mechanical analysis. The system underwent dual curing via a sequential phenol-epoxy reaction and allyl polymerization. The former reaction was catalysed by triphenyl phosphine. Whereas the phenol-epoxy reaction was completed, the allyl polymerisation was limited to 40% by the regulation of cure conditions. It was shown that an increase in epoxy concentration in DABA-EPN blends led to an improvement in the tensile and flexural strengths of the neat castings. Flexural strength and interlaminar shear strength of the glass laminate showed an improvement with an increase in EPN concentration. Although the crosslink density of the neat casting was enhanced by epoxy concentration, this was not shown to result in any significant variations in the Tg of the cured matrix. The dual curing of the matrix system resulted in a considerable improvement, it is claimed, in the flexural properties of their glass composites. 15 refs.

Title: DEFORMATION CHARACTERISTICS OF NANO-SILICON DIOXIDE FILLED POLYPROPYLENE COMPOSITES
Page Range: p.559-562
Author(s): Wu C L; Zhang M Q; Rong M Z; Lehmann B; Friedrich K
File size: 118K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 11
Issue No: No. 7

Abstract
Polypropylene was compounded with nano-silica particles which had been subjected to surface modification via irradiation graft polymerization. Improvements were found in the mechanical properties of such nanocomposites with fairly low filler content. This work reports on the deformation characteristics of the PP nanocomposites using transmission electron microscopy. It was concluded that it was due to the interfacial entanglement between the grafting polymers attached to the nanoparticles and the matrix polymer, that the grafted nano-silicon dioxide showed much greater extensibility inn the composites than the nanoparticles as-received. This was believed to be the main cause of extensive plastic drawing of the matrix polymer surrounding the treated nanoparticles, and provided the composites with a higher static ductility. 10 refs.

Title: MECHANISM OF VOID FORMATION IN COMPOSITE PROCESSING WITH WOVEN FABRICS
Page Range: p.563-572
Author(s): Lee G-W; Lee K-J
File size: 348K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 11
Issue No: No. 7

Abstract
A mechanism for void formation is suggested, which involves an analysis of the resin flow through woven glass fabrics, at both the macro and micro levels. Both these types of flow arise from the characteristic structure of woven fabrics. In order to investigate the mechanism of void formation in woven fabrics, a new dimensionless number was defined as the ratio of the superficial velocity to the initial spreading rate. The prediction of void formation using this dimensionless number was shown to have a good correlation with the results from a cross sectional observation and void content measurement. It was confirmed that the mechanism suggested in this study is very useful and that the morphological structure of woven fabrics is conductive to void formation. 11 refs.

Title: SYNTHESIS AND PROPERTY CHARACTERISATION OF PINEAPPLE LEAF FIBER BASED FIBER COPOLYMERS VIA GRAFTING
Page Range: p.573-580
Author(s): Sahoo P K; Mohapatra R; Sahu G C; Dalei M
File size: 183K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 11
Issue No: No. 7

Abstract
This work reports on the preparation of natural fibre copolymers by the grafting of hydrophobic monomer, methyl methacrylate onto chemically modified pineapple leaf fibre using a complex initiating system. The modified pineapple leaf fibre-g-PMMA copolymers so obtained were characterized by FTIR, their thermal behaviour by TGA, and their morphology by scanning electron microscopy. In addition, their tensile strength, elongation and tenacity were measured. The extent of water absorption by the grafted PALF, showed that the grafting of MMA imparts hydrophobicity onto PALFs. Biodegradation of the copolymers was evaluated in sludge water and soil and by using cultured microorganisms. 17 refs.

Title: PROPERTIES OF GF-REINFORCED THERMOPLASTICS IN BEAM STRUCTURE
Page Range: p.581-589
Author(s): Nomura M; Makita J; Hamada H
File size: 358K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 11
Issue No: No. 7

Abstract
This study verifies that a structure in which glass fibres are apparently joined, namely, a beam structure, can be formed in the matrix resin by using the fact that the polymer resins with a high affinity for glass fibres, tend to migrate towards the glass fibre interface. Glass fibre content and glass fibre length are shown to be important factors influencing the formation of a beam structure. The larger the glass fibre content, and the greater the glass fibre length, the easier is the formation of the beam structure. It was verified that even if the resin content was so small as to form the dispersed phase in polymer blends, a continuous phase could still be formed by including glass fibres. By adding a small amount of resin having a higher heat resistance than the matrix resin, and having an affinity for glass fibres, fibres were successfully joined by selective migration of this small quantity of resin to the interface with the glass fibres. The beam structure material was found to have a HDT significantly higher than that of conventional glass fibre reinforced thermoplastic composites, and by applying this concept to glass fibre reinforced polystyrene, the HDT of GFPS improved from 100 - 110 degrees C to 200-250 degrees C. 15 refs.

Title: DETERMINANTS OF SWELLING BEHAVIOUR OF METHACRYLAMIDE AND CELLULOSICS BASED HYDROGELS
Page Range: p.591-601
Author(s): Chauhan G S; Bansal M; Mahajan S
File size: 201K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 11
Issue No: No. 7

Abstract
The synthesis and swelling response of some novel hydrogels in different swelling media is studied. Hydroxypropylcellulose based networks with methacrylamide were synthesized in aqueous media in the presence of N,N-methylene bisacrylamide by simultaneous gamma radiation. The reaction conditions such as radiation dose, amount of water and concentrations of monomer and crosslinker were evaluated for optimum network yield. Using these conditions, networks of cellulose and its other derivatives were also synthesized with methacrylamide. Resultant networks are characterized for structural properties by elemental analysis, FTIR, and scanning electron micrography. The swelling behaviour of networks was studied as a function of the synthetic reaction conditions, the nature of polymeric backbones and the nature of the swelling medium. The equilibrium swelling is shown as a function of both structural and environmental factors, since hydrogels are sensitive to their environment. 10 refs.

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