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Polymers and Polymer Composites

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Title: FRACTURE TOUGHNESS OF DISCONTINUOUS LONG GLASS FIBER REINFORCED POLYPROPYLENE: AN APPROACH BASED ON A NUMERICAL PREDICTION OF FIBER ORIENTATION IN INJECTION MOLDING
Page Range: p.121-130
Author(s): Rizov V; Harmia T; Reinhardt A; Friedrich K
File size: 467K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 2

Abstract
The fracture toughness of discontinuous long glass fibre reinforced injection moulded polypropylene was characterised using the microstructural efficiency concept in combination with a numerical prediction of the fibre orientation during injection moulding, using Sigmasoft commercial computer software. In a three-dimensional numerical scheme, fibre volume fractions, shear viscosity and mean fibre aspect ratio data were input in order to perform a mould filling analysis. The resultant local fibre orientation parameters for injection moulded square plates of long glass fibre reinforced PP permitted the calculation of the local fracture toughness using the microstructural efficiency concept. This was compared with the experimental toughness values obtained by the use of compact tension test specimens. A good correlation between the calculated fracture toughness data and the measured ones was reported to indicate that a fibre orientation prediction by the Sigmasoft finite element computer code, could be used in combination with the microstructural efficiency concept for the determination of local fracture toughness values in injection moulded long glass fibre reinforced thermoplastics. It is claimed that this combined approach provides good opportunities for the optimisation of a thermoplastic workpiece in its design with respect to local fracture resistance, which will in turn provide extended areas of application within the engineering sector. 13 refs.

Title: STRUCTURAL INVESTIGATION INTO POLY-P-PHENYLENEBENZOBISOXAZOLE FIBRES
Page Range: p.131-137
Author(s): Sharma L; Mizoo O; Pezzotti G
File size: 250K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 2

Abstract
Polyparaphenylene benzobisoxazole fibres (Zylon) are characterised by heat resistance, high modulus and high strength. High resolution Raman piezospectroscopy and electron microscopy were used to quantify the relationship between the structure and the mechanical properties of the fibre. This work reports on the structural changes occurring in two poly paraphenylene benzobisoxazole fibres prepared under different processing conditions. Fibre A was coagulated in aqueous phosphoric acid and fibre B was produced by heat treating fibre A at 650 degrees C under 0.7 GPa tension. The ordered and disordered morphology relating this to probable liquid crystal formation, is revealed. The research is claimed to demonstrate the fundamental importance of polymer processing conditions to the subsequent polymer properties. By undergoing a heat treatment stage, stronger fibres were obtained. 10 refs.

Title: TOUGHENING OF POLYPROPYLENE HIGHLY FILLED WITH ALUMINIUM HYDROXIDE
Page Range: p.139-150
Author(s): Zhanpai Su; Pingkai Jiang; Qiang Li; Ping Wei; Yong Zhang
File size: 304K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 2

Abstract
The flame retardant and mechanical properties of rubber-modified, aluminium hydroxide filled PP were studied, together with its morphology. The PP was toughened with EPDM and zinc neutralised sulphated EPDM ionomer. The PP matrix, when high filled with aluminium hydroxide particles can achieve an adequate level of flame retardancy, but there is a decrease in the mechanical properties due to an inadequate adhesion between the aluminium hydroxide particles and the PP matrix, and also the tendency for the filler to agglomerate. By using zinc neutralised sulphated EPDM ionomer instead of EPDM the tensile properties were shown to improve with only a slight decrease in toughness, due to improvements in the interfacial adhesion between modifier and matrix. SEM micrographs showed that the rubber phase was dispersed in the continuous PP matrix, and that most aluminium hydroxide particles were uniformly distributed in the rubbery phase, and that much finer rubbery domains were found in the PP/Zn-S-EPDM/aluminium hydroxide composites. 28 refs.

Title: SYNTHESIS AND CHARACTERIZATION OF STARCH AND ACRYLAMIDES BASED HYDROGELS
Page Range: p.151-165
Author(s): Chauhan G S; Kumari A; Sharma R
File size: 524K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 2

Abstract
In order to synthesise a variety of hydrogels for use in drug delivery and environmental management technologies, starch was graft copolymerised with three acrylamides: acrylamide, 2-acrylamido-2-methylpropanesulphonic acid and N-isopropyl acrylamide. The synthesis was carried out at two different temperatures, including the gelatinisation temperature of starch (70 degrees C). A redox system, consisting of ammonium persulphate and ferrous ammonium sulphate was used to initiate the polymerisation reactions. Using the same reaction conditions that were used to obtain graft copolymers, crosslinked networks of all three acrylamides and starch were also synthesised in the presence of various concentrations of N,N-methylene bisacrylamide as crosslinker, and also at two different temperatures. The hydrogels were characterised by FTIR and thermal studies to identify some structural aspects and to obtain evidence of network formation. Water uptake by the hydrogels was studied as a function of time, temperature and pH level. Some of the hydrogels were found to be good absorbers of water and it was observed that the synthetic conditions affected their structure, which in turn affected their water uptake. The hydrogels produced were found to be environment-sensitive and showed significant volume transitions when small changes were made in their environment. These responses of the hydrogels to the changes in their environment can be effectively used in environmental management technologies for the remediation of pollutants and in drug delivery devices. 16 refs.

Title: POLYACRYLATE/(CHITOSAN MODIFIED MONTMORILLONITE) NANOCOMPOSITE: WATER ABSORPTION AND PHOTOSTABILITY
Page Range: p.167-172
Author(s): Haixia Qiu; Jiungao Yu; Junli Zhu
File size: 117K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 2

Abstract
It is known that the water absorption of polyacrylate (PAA)-based superabsorbent polymers decreases in sunlight after a long time. To reduce this, polymer/montmorillonite (MMT) nanocomposites have been developed with photostability. However, the preparation of PPA/MMT nanocomposites is reported to be difficult because it is not easy for PAA to intercalate into MMT sheets. The modification of MMT with hydrophilic molecules is therefore necessary. Montmorillonite was modified with chitosan to facilitate intercalation. It was found that the water absorption of the PAA/modified MMT composite increased by 91 g/g. FTIR analysis identified that the drive for intercalation could arise from the strong interaction between chitosan and MMT. 20 refs.

Title: POLYPROPYLENE/ETHYLENE-OCTENE COPOLYMER/ORGANIC-MONTMORILLONITE NANOCOMPOSITES
Page Range: p.173-180
Author(s): Minyan Guo; Xiaodong Zhou, Gance Dai; Fuzeng Hu
File size: 238K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 2

Abstract
Propylene (PP)/ethylene-octene copolymer(POE)/organic montmorillonite (OMMT) nanocomposites were prepared by melt compounding. PP grafted with maleic anhydride (MPP) was added as the compatibilising agent. Analyses were carried out by wide-angle X-ray diffraction, TEM and SEM, which indicated that polymer chains had intercalated into OMMT, and that some of the OMMT had delaminated into nanolayers dispersed in the PP matrix. Mechanical tests showed that the addition of POE had increased the toughness of PP, but decreased its stiffness, but that when OMMT and MPP were added, the toughness of PP increased greatly, with no profound change in the stiffness. DSC was used to study the melt and crystallisation behaviour of the composites. Results indicated that OMMT and MPP had acted as effective nucleating agents. 14 refs.

Title: PREPARATION AND PROPERTIES OF A WATER-SWELLING RUBBER BY IN SITU FORMED LITHIUM ACRYLATE IN NITRILE RUBBER
Page Range: p.181-190
Author(s): Wentan Ren; Zonglin Peng; Yong Zhang; Yinxi Zhang
File size: 188K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 2

Abstract
Lithium acrylate (LiAA) was in situ prepared in nitrile rubber (NBR) through neutralisation of lithium hydroxide (LiOH) and acrylic acid (AA) during mixing. The NBR/LiAA compounds were vulcanised with dicumyl peroxide (DCP). The in-situ preparation and polymerisation of LiAA were characterised using FTIR spectrometry. The micrographs of the compounds and vulcanisates were explored using SEM. The effects of DCP and LiAA contents on the water-swelling and mechanical properties of the vulcanisates were studied, and the relationship between the LiOH/AA molar ratio and the properties of the vulcanisates was investigated. Results showed that the in situ formed LiAA could improve the mechanical and water-swelling properties of the NBR/LiAA vulcanisates. Properly compounded vulcanisates were found to have high water-swelling ratios over 800%, and tensile strength of ore than 12MPa. DSC measurements indicated that he water absorbed in the vulcanisate existed in PLiAA and NBR networks in three different physical states, namely: free water, freezable bound water and non-freezable bound water. 36 refs.

Title: SYNTHESIS OF MULTIBLOCK COPOLYMERS OF POLY(2-VINYLPYRIDINE) AND POLYOXYETHYLENE AND THEIR APPLICATION AS COMPATIBILIZERS FOR EPICHLOROHYDRIN RUBBER/POLY(VINYL CHLORIDE) BLENDS
Page Range: p.191-198
Author(s): Chaoyang Wang
File size: 169K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 2

Abstract
Multiblock copolymers of poly(2-vinylpyridine) and polyoxymethylene were synthesised by condensing telechelic dihydroxy poly(2-vinylpyridine) and polyoxymethylene with dichloromethane in the presence of potassium hydroxide. The block copolymers behaved as good compatibilisers for the blending of epichlorohydrin rubber with polyvinyl chloride.. It was found that by adding approximately 2-3% block copolymer to the blends improved the mechanical properties. 20 refs.

Title: SYNTHESIS, CHARACTERIZATION AND PROPERTIES OF SILICON DIOXIDE-POLYAMIDE HYBRID FILM
Page Range: p.199-207
Author(s): Zhang C H; Zhang Z Q; Li Q Y; Cao H L
File size: 175K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 13
Issue No: No. 2

Abstract
This study reports on the preparation of silicon dioxide-polyimide hybrid films, from polyamic acid solution and a nano-silicon dioxide precursor. The process for making the polyimide was characterised by FTIR spectra. FT-IR XPS, SEM were used to characterise the silicon dioxide-polyimide hybrid film. Nanoindentation properties and the thermal stability of the polyimide film and the silicon dioxide-polyimide films were investigated by means of a Nano indenter XP and a ZRY-2P thermoanalysis instrument respectively. TGA evidence suggested that the thermal stability of the silicon dioxide-polyimide hybrid film was better than that of the polyimide film and that the thermal decomposition temperature was increased from 547.8 degrees C to 567.5 degrees C. 18 refs.

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