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Polymers and Polymer Composites

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Title: NON-LINEAR VISCOELASTIC AND PHYSICAL AGEING CHARACTERISATION OF THERMOSET PR-500 EPOXY RESIN
Page Range: p.351-371
Author(s): Gupta V; Roy S; Dharani L R
File size: 241K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 12
Issue No: No. 5

Abstract
Because of their polymeric matrices and sometimes viscoelastic fibres, structural polymer composites can exhibit creep or stress relaxation behaviour, and a delayed failure following initial design and fabrication is possible. In order to deal with this problem, methods are needed which will enable long-term failures to be anticipated and thus avoided. To this end, a methodology is described which can be used to model the long-term interlaminar properties in polymer matrix woven composites. The model takes into account the weave architecture, fibre volume fraction, packing density, elastic moduli of the fibres, and the viscoelastic properties of the polymer matrix. This was then applied to predict the critical regions where failure is most likely to occur. This paper summaries the non-linear viscoelastic and physical ageing characterisation data for epoxy resin PR500. The properties summarised were successfully used in a multi-scale micro-mechanical methodology to study the AS4/PR500 five-harness satin woven-fibre composite laminate. 7 refs.

Title: WELDLINES IN INJECTION-MOULDED REINFORCED THERMOPLASTICS: MECHANICAL PERFORMANCE IMPROVEMENT THROUGH INTRUSION INDUCED FIBRE REORIENTATION
Page Range: p.373-381
Author(s): Debondue E; Fournier J-E; Lacrampe M F; Krawczak
File size: 245K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 12
Issue No: No. 5

Abstract
This paper investigates the effect of processing conditions on the mechanical properties of a weldline in short glass fibre reinforced polypropylene. The presence of a weldline is shown to have a deleterious effect on the tensile properties with a serious loss of strength and rigidity. The aim of this study was to improve the mechanical performance of the weldline through a better understanding of its morphology and a subsequent optimisation of the processing conditions. A method of intrusion based on differential gate solidification was used to produce some reorientation of the fibres. 19 refs.

Title: CRYSTALLINITY OF POLYPROPYLENE-SILICA ASH COMPOSITES AFFECTED BY THE MIXING CONDITIONS - DSC STUDIES
Page Range: p.383-398
Author(s): Chaudhary D S; Jollands M C; Cser F
File size: 227K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 12
Issue No: No. 5

Abstract
This article describes a study of the mixing of two incompatible components - polypropylene and rice husk ash, by means of statistical analysis of the composite tensile data, and the respective mixing conditions employed. The state of the filler dispersion and distribution, known to be proportional to the composite modulus, was represented by the quality of mixing and the influence of mixing conditions on the composite's crystallinity. An analysis of the composite mechanical performance indicated that the state of mixing influenced the filler-matrix interaction and the composite tensile modulus. Results showed that an increase on composite crystallinity was related to the increase in tensile modulus. It was also found that reducing the particle size of the filler had a positive effect on the tensile modulus and the strength of the samples. Models proposed from the statistical analysis were used to predict the composite tensile data for the original particle size within the system parameters boundaries. 25 refs.

Title: THERMAL PROPERTIES OF NOVEL PMR POLYIMIDES PREPARED BY COPOLYMERISATION
Page Range: p.399-408
Author(s): Zuo Guang Zhang; Min Li; Yi Shan Pan; Zhi Jie Sun
File size: 297K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 12
Issue No: No. 5

Abstract
In order to address the problems of poor thermooxidative stability of PMR addition curing polyimides, research was carried out to determine the effect of replacing the benzophenone tetracarboxylic acid (BTDE) an, methylenedianiline (MDA), and nadic ester (NE) with new dianhydride, diamine or other endcap reactants. Oligomers with various molecular weights and components were synthesised in order to compare the influence of the chemical structure and the crosslink density of polyimides on the final properties, including thermal properties. Results showed that the incorporation of pyromellitic dianhydride or phenylenediamine into the oxydiphthalic dianhydride-methylenedianiline homopolyimide, could greatly enhance the Tg while retaining comparable thermo-oxidative stability and reasonable processing properties. 20 refs.

Title: RELATIONSHIP BETWEEN FILLER LOADING AND MORPHOLOGY OF THE INTERPHASE IN POLYETHYLENE-CHALK COMPOSITES
Page Range: p.409-416
Author(s): Kozak M; Danch A; Osoba W; Domka L; Stelzer F; Jurga S
File size: 137K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 12
Issue No: No. 5

Abstract
This paper reports on a study of LDPE filled with a natural chalk content of up to 40% wt. The chalk filler is introduced to improve the mechanical properties of LDPE and to reduce the cost of the raw materials. However, the hydrophilic surface of the filler hinders its introduction into the polymer matrix. Tests were carried out to determine the relationship between filler loading ad morphology of the interphase in polyethylene-chalk composites using scanning electron microscopy to investigate the morphology of the filler molecules and the microstructure of the composites, and light scattering to estimate the distribution of the filler molecules. Results are discussed, and indicate that the filler in PE acts as a stretching agent for the chains located in the interphase region, reducing molecular fluidity and increasing free volume depending on the amounts of filler used. 34 refs.

Title: EFFECT OF BETA-CYCLODEXTRIN ON THE DISPERSION SYNTHESIS OF PMMA PARTICLES
Page Range: p.417-421
Author(s): Li Songjun; Hu Jie; Liu Bailing
File size: 85K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 12
Issue No: No. 5

Abstract
A preliminary investigation into the effect of beta-cyclodextrin on the dispersion polymerisation of PMMA particles is presented. The experimental results show that the addition of cyclodextrin to the reaction system increases the conversion of MMA and decreases the average diameter of the PMMA particles. A tentative explanation is offered that the unique structure of cyclodextrin helps to assemble MMA monomer and increase its concentration in the polymerisation loci. Other factors such as the interaction between cyclodextrin and the polyvinylpyrrolidone used as stabiliser, also appeared to be an important influence on the polymerisation. 10 refs.

Title: EFFECT OF INJECTION SPEED ON INTERNAL STRUCTURE AND MECHANICAL PROPERTIES IN SHORT GLASS FIBRE REINFORCED POLYAMIDE INJECTION MOULDINGS
Page Range: p.423-431
Author(s): Kuriyama T; Mizoguchi M; Ogawa T
File size: 663K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 12
Issue No: No. 5

Abstract
The internal structure of injection mouldings was investigated under various processing conditions and the effects of internal structure on the mechanical properties and fatigue life were discussed, with reference to short glass fibre-reinforced nylon 6,6 mouldings. The effect of the injection speed, in particular, is examined, and results are discussed on the basis of acoustic emission and fractographic observations associated with static and fatigue testing. It was shown that both the heterogeneous structures, identified by variations in fibre distribution and the mechanical properties and fatigue life, were affected by the injection speed. The latter was said to be due to the strong relationship between the internal structure and the fracture behaviour. In particular, the existence of resin rich regions dominated the fracture behaviour in both tensile and fatigue testing, leading to a short fatigue life. 13 refs.

Title: RHEOLOGICAL BEHAVIOUR OF PP/PET AND MODIFIED PP/PET BLENDS. II. DYNAMIC VISCOELASTIC PROPERTIES
Page Range: p.433-447
Author(s): Zdrazilova N; Hausnerova B; Kitano T; Saha P
File size: 219K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 12
Issue No: No. 5

Abstract
This study addresses the problem of recycling immiscible blends of modified and unmodified blends of post-consumer PP/PETP with reference to dynamic viscoelastic properties. Compatibilisation of such blends represents one approach to recycling significant amounts of scrap materials without the need for separation steps. In order to study the effect of the matrix, three polypropylenes differing in flow properties were chosen, and the compatibilisation was carried out by both one- or two-step reactive in-situ techniques. In the former case, the addition of 1 wt. % of maleic anhydride, and in the latter, polypropylene already modified by the supplier were used. The positive effect of compatibilisation was shown, not only from the results of the morphological study (dispersed phase size reduction, strengthened interfacial adhesion), but also through increased values of the viscous and elastic characteristics, which suggested enhanced interactions between the blend components. 35 refs.

Title: EFFECT OF COUPLING AGENTS ON MECHANICAL PROPERTIES OF HDPE/WHEAT STRAW COMPOSITES
Page Range: p.449-452
Author(s): Shakeri A R; Hashemi S A
File size: 53K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 12
Issue No: No. 5

Abstract
Results are discussed of the use of various coupling agents used to improve the mechanical properties of wheat straw reinforced HDPE. In particular, the effect of the coupling agents on the tensile, impact, and flexural properties was investigated using integrated processing and extrusion technology, i.e. a single step process. It was found that composites prepared from 1% of silane treated straw and/or 1% maleic anhydride with 0.5% peroxide treated polymer showed an increase in tensile and impact strength, compared with the other composites. 5 refs.

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