Polymers and Polymer Composites

Blends of poly(ethylene naphthalate) (PEN) and a liquid crystalline copolymer based on p-hydroxybenzoate and ethylene terephthalate, known as Novaccurate E310 (E310), were studied. The effect of compatibilizers on the mechanical properties and morphologies has been investigated. The mechanical properties of the PEN/E310 (weight ratio 80/20) blend were considerably improved on the addition of 4,4′-dihydroxy-3,3',5,5′-tetramethyldiphenyl ether (TM-DPE), in agreement with the improvement in compatibility shown by the SEM analysis. The gel permeation chromatography analysis showed that most of the TM-DPE in the PEN/E310/TM-DPE blend does not react. The IR spectral analysis suggested that the hydrogen bonding between the hydroxyl group of TM-DPE and the ester group of PEN and/or E310 acts beneficially for compatibilization.

Blends of poly(ethylene naphthalate) (PEN) and a liquid crystalline copolymer based on p-hydroxybenzoate and ethylene terephthalate, known as Novaccurate E310 (E310), were studied. The effect of compatibilizers on the mechanical properties and morphologies has been investigated. The mechanical properties of the PEN/E310 (weight ratio 80/20) blend were considerably improved on the addition of 4,4′-dihydroxy-3,3',5,5′-tetramethyldiphenyl ether (TM-DPE), in agreement with the improvement in compatibility shown by the SEM analysis. The gel permeation chromatography analysis showed that most of the TM-DPE in the PEN/E310/TM-DPE blend does not react. The IR spectral analysis suggested that the hydrogen bonding between the hydroxyl group of TM-DPE and the ester group of PEN and/or E310 acts beneficially for compatibilization.

Fracture analysis of delamination type cracks in angle-ply elastomeric laminates was carried out using three-dimensional finite element analysis. The fracture parameter, tearing energy/J-integral that characterizes delamination failure in elastomer composites was computed from the finite element results of stresses and strains, and compared with existing analytical results using three different methods. The results obtained were validated with existing analytical methods in the literature. Numerical results of stress distributions and J-integral values are presented for various cord orientations and crack sizes. The results presented illustrate that cord-orientation and crack size have a strong effect on the values of tearing energy/J-integral. The results of the stress distributions and J-integral should help to improve our understanding of delamination type failures in elastomeric composite laminates.

Fracture analysis of delamination type cracks in angle-ply elastomeric laminates was carried out using three-dimensional finite element analysis. The fracture parameter, tearing energy/J-integral that characterizes delamination failure in elastomer composites was computed from the finite element results of stresses and strains, and compared with existing analytical results using three different methods. The results obtained were validated with existing analytical methods in the literature. Numerical results of stress distributions and J-integral values are presented for various cord orientations and crack sizes. The results presented illustrate that cord-orientation and crack size have a strong effect on the values of tearing energy/J-integral. The results of the stress distributions and J-integral should help to improve our understanding of delamination type failures in elastomeric composite laminates.

A detailed study of the morphological features of polyaniline-poly(ethylene-co-vinyl acetate) (PANI-EVA) composites is presented. It is shown that their microstructure consists of highly ordered electrically conductive PANI paths embedded in the insulating EVA matrix. Long fibrils of PANI and interconnected fractal-like networks were also observed. It was found that the size of the primary PANI particles was ca. 5–10 nm. A spontaneous flocculation of these particles contributed to the formation of conductive pathways at extremely low percolation thresholds (Φ_c) (loading level ca. 0.005 wt. fraction). The sizes of the PANI domains varied during storage of the films and a key property of the conductive constituent (the PANI phase) was observed, namely a tendency for its solid state rearrangement. This PANI self-organization has been interpreted according to the new interfacial model of polymer composites.

A detailed study of the morphological features of polyaniline-poly(ethylene-co-vinyl acetate) (PANI-EVA) composites is presented. It is shown that their microstructure consists of highly ordered electrically conductive PANI paths embedded in the insulating EVA matrix. Long fibrils of PANI and interconnected fractal-like networks were also observed. It was found that the size of the primary PANI particles was ca. 5–10 nm. A spontaneous flocculation of these particles contributed to the formation of conductive pathways at extremely low percolation thresholds (Φ_c) (loading level ca. 0.005 wt. fraction). The sizes of the PANI domains varied during storage of the films and a key property of the conductive constituent (the PANI phase) was observed, namely a tendency for its solid state rearrangement. This PANI self-organization has been interpreted according to the new interfacial model of polymer composites.

Various resin gating methods commonly used for the Resin Transfer Moulding (RTM) method of composite manufacture are discussed, with their associated advantages and disadvantages. Peripheral gating combined with vacuum impregnation was identified from previous studies as being particularly beneficial in achieving complete wet-out and fast injection times. Reported design rules for gating and venting arrangements are also discussed. This investigation has attempted to assess the capabilities of peripheral gating, initially for simple geometrical shapes which then increased in complexity. Existing design guidelines were confirmed and new concepts proposed. RTM processing of the final shape to be considered was finally assessed by comparison of peripheral with rectilinear gating. This process also identified the importance of component design for manufacture and the benefits of peripheral gating. It is hoped that this experimental investigation will not only be useful to RTM mould designers but also to those involved in resin flow modelling of such processes for composite components

Various resin gating methods commonly used for the Resin Transfer Moulding (RTM) method of composite manufacture are discussed, with their associated advantages and disadvantages. Peripheral gating combined with vacuum impregnation was identified from previous studies as being particularly beneficial in achieving complete wet-out and fast injection times. Reported design rules for gating and venting arrangements are also discussed. This investigation has attempted to assess the capabilities of peripheral gating, initially for simple geometrical shapes which then increased in complexity. Existing design guidelines were confirmed and new concepts proposed. RTM processing of the final shape to be considered was finally assessed by comparison of peripheral with rectilinear gating. This process also identified the importance of component design for manufacture and the benefits of peripheral gating. It is hoped that this experimental investigation will not only be useful to RTM mould designers but also to those involved in resin flow modelling of such processes for composite components

Graft copolymerization onto polyamide-6,6 film has been studied by grafting a binary mixture of methyl acrylate and acrylamide using gamma rays from a ⁶⁰Co source as initiator by the mutual method in an aqueous medium. The effect of total dose, concentration of monomer, and amount of water on the percentage grafting (Pg) has been determined. The effect of alcohols of varying chain length on the Pg of the binary mixture has been studied. They all decreased it. However, the mixed solvent system (H₂O + alcohol) at certain compositions was found to enhance it. A plausible mechanism for the graft copolymerization of the binary mixture (methyl acrylate + acrylamide) onto polyamide film by the mutual method has been proposed.

Graft copolymerization onto polyamide-6,6 film has been studied by grafting a binary mixture of methyl acrylate and acrylamide using gamma rays from a ⁶⁰Co source as initiator by the mutual method in an aqueous medium. The effect of total dose, concentration of monomer, and amount of water on the percentage grafting (Pg) has been determined. The effect of alcohols of varying chain length on the Pg of the binary mixture has been studied. They all decreased it. However, the mixed solvent system (H₂O + alcohol) at certain compositions was found to enhance it. A plausible mechanism for the graft copolymerization of the binary mixture (methyl acrylate + acrylamide) onto polyamide film by the mutual method has been proposed.

Initially amorphous PET sheets were prepared from recycled flake made from post-consumer PET bottles. Drawing and/or rolling of the sheets were performed at 80°C using a draw ratio up to 4.2. The influence of draw ratio on the structure, molecular orientation, and mechanical properties of drawn sheet was investigated. Not only was the tensile strength at yield stronger, but the modulus of the deformed sheets was much higher than that of as- extruded sheets. This was attributed to the enhanced chain orientation and crystallinity of PET with increasing draw ratio. In this work, no particular inferiority in the mechanical properties of PET sheets recycled from used PET bottles (compared with the fresh virgin bottle grade resin) could be seen.

Initially amorphous PET sheets were prepared from recycled flake made from post-consumer PET bottles. Drawing and/or rolling of the sheets were performed at 80°C using a draw ratio up to 4.2. The influence of draw ratio on the structure, molecular orientation, and mechanical properties of drawn sheet was investigated. Not only was the tensile strength at yield stronger, but the modulus of the deformed sheets was much higher than that of as- extruded sheets. This was attributed to the enhanced chain orientation and crystallinity of PET with increasing draw ratio. In this work, no particular inferiority in the mechanical properties of PET sheets recycled from used PET bottles (compared with the fresh virgin bottle grade resin) could be seen.

The effect of radiation on the properties of glass fibre reinforced epoxies was investigated. Radiation treatment with a maximum dose of 30 MGy was performed for virgin samples and after 0.5, 1, 2, and 5 years of exposure in cold, moderate and warm damp climates. Evaluation of climatic and radiation resistance was by the change in bending strength, interlaminar shear strength, and Young's modulus. Dynamic mechanical analysis and linear dilatometry were employed to investigate the epoxy matrix during ageing. It has been established that radiation treatment of both virgin and climatically aged samples causes the destruction of the interfacial bond. The large increase in mechanical properties observed is explained by the competing effects of two processes. There is little indication of the occurrence of additional crosslinking of the epoxy binder during irradiation. It is shown that ageing in the reverse order (radiation treatment with subsequent exposure to the climate) is more severe, and intensifies the changes in the properties of the material.

The effect of radiation on the properties of glass fibre reinforced epoxies was investigated. Radiation treatment with a maximum dose of 30 MGy was performed for virgin samples and after 0.5, 1, 2, and 5 years of exposure in cold, moderate and warm damp climates. Evaluation of climatic and radiation resistance was by the change in bending strength, interlaminar shear strength, and Young's modulus. Dynamic mechanical analysis and linear dilatometry were employed to investigate the epoxy matrix during ageing. It has been established that radiation treatment of both virgin and climatically aged samples causes the destruction of the interfacial bond. The large increase in mechanical properties observed is explained by the competing effects of two processes. There is little indication of the occurrence of additional crosslinking of the epoxy binder during irradiation. It is shown that ageing in the reverse order (radiation treatment with subsequent exposure to the climate) is more severe, and intensifies the changes in the properties of the material.