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Polymers and Polymer Composites

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Title: TENSILE PROPERTIES OF POLYMER SAMPLES CONTAINING MILLIMETRE SCALE SILICON MICROCHIPS
Page Range: p.505-516
Author(s): Kolonko A M; Metje N; Chapman D N; Kukureka S N
File size: 354K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 20
Issue No: No.6

Abstract
In order to produce monitoring systems for polyethylene pipes, one option is to distribute sensors within the plastic matrix. Currently, no information is available on the effects of small, individual sensors on the structural integrity of polyethylene pipes if these are embedded in the pipe wall. In order to assess the influence of these sensors, small samples were subjected to tensile tests with different sizes and shapes of microchips investigated at different positions and orientations. It was discovered that a square microchip improves the stiffness the most but reduces the ductility of the sample the most, while a microchip with the same area, but of circular shape also acts as reinforcement when its volume is sufficiently large relative to the volume of the polymer matrix, causing the smallest reduction in ductility. The optimal microchip orientation is parallel to the tension direction. 25 Refs.

Title: RHEOLOGY, FLEXURE AND THERMOMECHANICAL CHARACTERIZATION OF EPOXY/CNF NANOCOMPOSITES: EFFECT OF DISPERSION TECHNIQUES
Page Range: p.517-530
Author(s): Mahesh Hosur; Rajib Barua; Shaik Zainuddin; Ashok Kumar; Trovillion J; Jeelani S
File size: 879K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 20
Issue No: No.6

Abstract
The aim of this study is to investigate the optimum technique to disperse vapour grown carbon nanofibres (VGCNFs) in SC-1 epoxy uniformly and to evaluate their effect on the performance of SC-1 epoxy. In this study, ultrasonication and Thinky mixing methods were used either in isolation or in combination with 3-roll shear mixing. To achieve better dispersion, VGCNF was tested either by mixing with SC-1 resin directly or premixed with a solvent and then mixed with SC-1 resin after evaporating the solvent. Flexural tests were performed to evaluate mechanical performances, and the results exhibited 25.60% and 8.88% improvement of flexural strength and modulus, respectively over neat epoxy with only 0.2 wt.% loading. Dynamic Mechanical Analysis (DMA), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) indicated improvement in storage modulus, Tg, inflection temperature and residue content respectively over neat SC-1 epoxy. The high viscosity found by rheological analysis prevents their ubiquitous use in fibre reinforced composites. Thermal and mechanical properties at higher loading conditions were seen either to reduce or not significantly improve. These results indicate that the methods used for dispersion are suitable for low weight percent loading only.36 Refs.

Title: IN-VITRO RESPONSE OF FIBROBLASTS TO POLY-L-LACTIDE COMPOSITE MATERIALS CONTAINING BOVINE BONE
Page Range: p.531-536
Author(s): Zeqiang He; Lizhi Xiong
File size: 328K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 20
Issue No: No.6

Abstract
This study aimed to investigate the interaction between fibroblastic cells and poly-L-lactide (PLLA) composite film containing bovine bone. The effects of PLLA/bovine bone on cell cytotoxicity, attachment, proliferation and differentiation of fibroblasts in-vitro were investigated. The results of cytotoxicity tests showed that cells cultured in extracts of PLLA/bovine bone and on the surface of composites showed normal growth and proliferation, and mineralisation nodules were observed for fibroblasts cultured in PLLA/bovine bone extract at day 7 by using von Kossa staining and tetracycline staining. Compared with pure PLLA materials, bovine bone in the PLLA composites facilitated both adhesion and proliferation of rat fibroblasts on the PLLA/bovine bone composite film. In conclusion, these results suggest that the introduction of bovine bone may improve the cell response involved in the osteogenesis and thus may be beneficial to further modify poly-L-lactide as a better bone repairing material. 15 Refs.

Title: THERMAL AND GAS BARRIER PROPERTIES OF COC/SIO2 NANOCOMPOSITES
Page Range: p.537-544
Author(s): Cheng-Fang Ou; Po-Hung Shen
File size: 387K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 20
Issue No: No.6

Abstract
This study is performed primarily to investigate the effects of chemical modification on silica surface and the silica content on the thermal and gas barrier properties of a cyclo olefin copolymer (COC) matrix. The COC/ SiO2 nanocomposites were constructed from COC and three species of SiO2 nanoparticles (AEROSIL A200, R805 and R974) with different organic groups, prepared by solution blending. The thermal properties of the composites were studied by DSC and TGA. The gas barrier properties of the composites were characterized by use of a gas permeability analyzer. The glass transition temperature (Tg) and decomposition temperature (Td) of these composites increased obviously with the silica content ranging from 0.5 to 10 wt.%. The composite with 10 wt.% R805 exhibited the highest Tg, which was 14.1 degrees C higher than that of pure COC. The water and oxygen permeability decreased with increasing the content of SiO2. The composites with 10 wt.% R974 had the minimum values of water and oxygen permeability and were 32% and 36% lower than those of pure COC, respectively. The dispersion of these silica particles in the COC matrix was made by SEM and consideration was given to the relationship between the modified silica surface and the COC matrix, and thermal properties and gas barrier properties. 33 Refs.

Title: POLYVINYL ALCOHOL ENGINEERED CEMENTITIOUS COMPOSITE (PVA-ECC) FOR THE INTERFACIAL BOND BEHAVIOUR OF GLASS FIBRE REINFORCED POLYMER BARS (GFRP)
Page Range: p.545-558
Author(s): Kim B; Lee J-Y
File size: 549K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 20
Issue No: No.6

Abstract
This paper presents experimental investigations of the interfacial bond behaviour of different types of rebar (steel, sand-coated GFRP, and helically-wrapped GFRP bars) and cementitious composites with and without polyvinyl alcohol (PVA) fibre. A total of 27 cubic specimens were prepared, and different PVA fibre volume fractions of 0%, 1% and 2% were added. The effects of PVA fibre on the compressive strength and interfacial bond strength were not significant. However, PVA fibre in engineered cementitious composites apparently changed the failure mechanisms during the pullout of both the steel and the helically-wrapped GFRP bars. The increase in PVA fibre volume fraction significantly improved the ductility of the matrix. Specifically, the helically-wrapped GFRP bar demonstrated the greatest improvement in ductility, while the sand-coated GFRP bar resulted in frictional pullout of the rebar due to the complete slip failure of the resin, regardless of the fibre content. Finally, the application of PVA-ECC to the helically-wrapped GFRP bar was found to be effective as replacement for steel rebar with respect to the ductility of the interfacial bond. 24 Refs.

Title: EFFECT OF POLYPROPYLENE-GRAFTED-MALEIC ANHYDRIDE COMPATIBILIZER ON THE PHYSICAL PROPERTIES OF POLYPROPYLENE/CARBON NANOTUBE COMPOSITES
Page Range: p.559-566
Author(s): Hemmati M; Shariatpanahi H; Ghorbanzadeh Ahangari M; Fereidoon A; Narimani A
File size: 406K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 20
Issue No: No.6

Abstract
The mechanical, rheological, morphological and thermal properties of a polypropylene (PP) matrix reinforced with single-walled nanotubes (SWNTs) and poly(propylene-grafted-maleic acid) (PP-g-MA) content were investigated by melt processing. PP-g-MA was used as a compatibiliser to promote carbon nanotube dispersion. Compared to uncompatibilised PP/SWNT nanocomposites, the tensile modulus of the material increased considerably when nanotubes and compatibiliser were employed. Furthermore, the Izod impact strength and tensile strength improved when 0.5 wt.% SWNTs and 1 wt.% PP-g-MA were added to the PP matrix. The rheological characterisation results revealed that addition of SWNTs increased the storage modulus and complex viscosity at low frequencies. When PP-g-MA was introduced, the complex viscosity and storage modulus further increased. Scanning electron microscopy revealed that the SWNTs were uniformly distributed when low concentrations of SWNTs were employed. In addition, the dispersion and adhesion between SWNTs and the PP matrix were improved when 0.5 wt.% SWNTs and 1 wt.% PP-g-MA were added. The results of differential scanning calorimetry indicated that the addition of SWNTs increased the crystallinity of PP/SWNT nanocomposites. 38 Refs.

Title: SCREENING THE VIABILITY OF ROSELLE GRAFT-COPOLYMERS
Page Range: p.567-574
Author(s): Ashish Chauhan; Balbir Kaith
File size: 377K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 20
Issue No: No.6

Abstract
In this paper, graft-copolymerization of Hibiscus sabdariffa (Roselle) using methyl acrylate (MA) as principal monomer and 4-vinyl pyridine (4-VP) as secondary monomer, using ceric ammonium nitrate - nitric acid initiator system in binary vinyl monomeric mixture, has been reported. Different optimized reaction parameters such as temperature, time, initiator concentration, monomer concentration and pH were used to obtain the maximum graft yield and then to explore its change on properties and behaviour of the fibre. The graft copolymer were characterized by FTIR, SEM, XRD, TGA and DTA techniques and evaluated for swelling behaviour, chemical resistance, moisture absorbance and dye-uptake behaviour, keeping in view the use of these advanced graft copolymers for scientific and industrial application. 26 Refs.

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