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Polymers and Polymer Composites

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Title: TENSILE PROPERTIES OF POLYMERIZATION-FILLED KEVLAR PULP/POLYETHYLENE COMPOSITES
Page Range: p.1-15
Author(s): Zhang Y; Rodrigue D; Ait-Kadi A
File size: 244K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 12
Issue No: No. 1

Abstract
Polymeric-filled composites and melt blended composites of Kevlar pulp/HDPE composites were prepared to compare their mechanical properties. It was found that breaking strains of polymerisation filled composites were higher than those for melt blended composites for a similar fibre concentration. Tensile data were then used to compare several models of short fibre polymer composites. Melt blended composites were found to have higher fibre aspect ratio than polymerisation filled composites due to the original treatment of the fibre with aqueous NaOH solution for polymerised-filled process. The higher breaking strain is attributed to factors such as better fibre dispersion and improved fibre-polymer interfacial adhesion. Results of calculations involving Berlin's model in combination with that of Rosen for critical aspect ratio were found to give reasonable prediction of tensile properties. In addition, it was concluded that fibre aspect ratio in composites is strongly related to the processing technique employed. 59 refs.

Title: EFFECT OF PROCESSING ON DUCTILITY AND STRENGTH OF KEVLAR/POLYETHYLENE COMPOSITES
Page Range: p.17-27
Author(s): Zhang Y; R; Rodrigue D; Ait-Kadi A
File size: 107K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 12
Issue No: No. 1

Abstract
In this study of the effect of processing on the ductility and strength of Kevlar/PE composites, attention is given to ductility and tensile strength as a function of strain rate to compare composites prepared by melt blending and polymerisation filling. Improved ductility was obtained for polymerisation filled composites, as a result of better fibre-polymer interfacial adhesion, whilst ductility decreased upon increasing fibre content and strain rate. Several models for short fibre composites are compared in their prediction of tensile strength for these composites, to include the effect of critical fibre aspect ratio. Results show that the preparation technique has an effect on tensile strength of composites in relation with fibre distribution and interfacial adhesion. 37 refs.

Title: DYNAMICALLY CURED PP/EPOXY BLENDS COMPATIBILISED WITH MAH-g-PP
Page Range: p.29-42
Author(s): Jiang X; Huang H; Zhang Y; Zhang Y
File size: 195K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 12
Issue No: No. 1

Abstract
The dynamic vulcanisation process, usually used to prepare thermoplastic elastomers, was used to prepare PP/epoxy blends compatibilised with maleic anhydride-grafted PP. An investigation was undertaken into the influence of dynamic cure, MAH-g-PP content, curing agents, and epoxy equivalent weight on the mechanical properties of the blend. Dynamic mechanical thermal analysis results indicate that the compatibility between the PP and epoxy resin was improved by the addition of MAH-g-PP, and that the storage modulus increased with increasing epoxy resin content. Thermogravimetric analysis results indicate that the incorporation of epoxy resin into PP could improve the thermal stability of PP, and that the dynamically cured PP/MAH-g-PP/epoxy blends had better thermal stability than the PP/epoxy and PP/MAH-g-PP/epoxy blends. 42 refs.

Title: DUAL-CURE PROPARGYL NOVOLAC-EPOXY RESINS: SYNTHESIS AND PROPERTIES
Page Range: p.43-53
Author(s): Nair C P R; Vijayan D; Gouri C
File size: 132K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 12
Issue No: No. 1

Abstract
Co-reaction of epoxy resin with a partially propargylated novolac resulted in a dual cure resin system with improved processability. The resin system showed moderately good adhesion strength, which was optimised for a phenol/epoxy equivalent ratio of 2:1. Good retention of properties was observed for the dual-cure system at 100 degrees C. Replacement of the novolac epoxy with diglycidyl ether of bisphenol-A resulted in enhanced adhesion. Co-curing with epoxy led to ease of processing without affecting the mechanical characteristics of the resultant glass composites. Minimisation of the epoxy content was needed in order to avoid sacrificing the thermal characteristics and Tg of the system. 17 refs.

Title: PHOSPHAZENE-TRIAZINE POLYMERS BY ALDER-ENE REACTION
Page Range: p.55-62
Author(s): Nair C P R; Ninan K N
File size: 110K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 12
Issue No: No. 1

Abstract
With a view to developing a phosphazene-triazine cyclomatrix polymer with enhanced shelf life for the pre-polymer, the possibility is explored of using Alder-ene cure chemistry for the design of a novel thermoset. The protocol was to effect the cure of a mixture of allylphenoxy trazine and allyl phenoxy cyclotriphosphazenes using a bismaleimide. Tough thermoset polymer can be obtained by co-reaction of maleimide and allyl groups, where the maleimide reacts with allyl phenols through the Alder-ene reaction via an intermediate Wagner-Jauregg reaction. This paper examines the physical, mechanical and thermal properties of the system, as functions of the reactant stoichiometry. It was found that the temperature of onset of thermal degradation and Tg of the cured polymers increased in proportion to the maleimide content. Phosphazine and triazine were found beneficial in reducing the rate of thermal erosion at high temperatures. The flame resistance and atomic oxygen resistance of the polymers are stated to be expected to be good and are currently under evaluation. 23 refs.

Title: STRUCTURE AND PROPERTIES OF BIODEGRADABLE POLYMERS: ROLLING EFFECT IN POLY(BUTYLENE SUCCINATE) SHEETS
Page Range: p.63-73
Author(s): Vega-Baudrit J; Pereira R, Nakayama K; Masuda T; Cao A
File size: 164K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 12
Issue No: No. 1

Abstract
This study addresses the improvement of the properties of biodegradable aliphatic polyester films by altering the molecular chain orientation. The sheets are prepared by extrusion, and are studied under uniaxial drawing as a function of the draw condition. Changes in the molecular orientation of the films and their crystallinity as a result of stretching are investigated using differential scanning calorimetry, dynamic mechanical analysis, tensile testing, sonic modulus, X-ray diffraction, density, birefringence, and measurements of % haze. It was concluded that rolling can be used to improve and control the physical properties of extruded polybutylene succinate sheets. 8 refs.

Title: IDENTIFYING DELAMINATION IN CROSS-PLY AND QUASI-ISOTROPIC BEAMS OF CFRP BY A STANDARDIZED ELECTRICAL RESISTANCE METHOD
Page Range: p.75-85
Author(s): Todoroki A; Tanaka Y; Shimamura Y
File size: 156K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 12
Issue No: No. 1

Abstract
This paper describes the use of an electrical resistance change method for the identification of damage in electrically conductive composites. The method involves the standardisation of measured electrical resistance changes in order to identify the delamination location more precisely. The method was applied to cross-ply and quasi-isotropic laminated beams, and the effectiveness of the method was confirmed experimentally. In addition, the effect of the stacking sequence was investigated experimentally. It is confirmed that, although the standardised electrical resistance changes of the two stacking sequences resembled each other when the delamination location and length were similar, response surfaces to estimate delamination location must be made individually to obtain reliable results. 21 refs.

Title: LINEAR TEMPERATURE PROGRAMMING RHEOMETERS FOR THE CURE OF RUBBERS. EFFECT OF THE VARIOUS PARAMETERS
Page Range: p.87-98
Author(s): Rosca I D; Granger R; Vergnaud J M
File size: 123K
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Journal: Polymers and Polymer Composites
Issue Year: ppc
Volume: 12
Issue No: No. 1

Abstract
Advantages are discussed of the use of rheometers in scanning mode in order to determine the kinetic parameters of the cure of rubbers. In this method, the heating rate is crucial. The rubber used in this study was EPDM, and the state of cure versus temperature curves obtained in scanning mode were calculated using a numerical model that takes into account the heat transfer by conduction through the rubber, the coefficient of heat transfer at the die-rubber interface, and the kinetics of the heat generated by the cure reaction. The kinetic parameters were determined mathematically from these state-of-cure versus temperature curves. The kinetic parameters calculated in these ways were found to be similar to those introduced by obtaining the state-of-cure versus temperatures curves using the numerical model. Whatever the heating rate, ranging from 2 to 10 K/min, and whatever the coefficient of heat transfer at the die-rubber interface which expresses the quality of the contact, satisfactory use of the moving die rheometer was demonstrated in scanning mode in order to determine the kinetics of the cure of rubbers, even when the enthalpy of cure is high. 22 refs.

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