Plasticised polyvinyl chloride (PPVC) compounds were biaxially stretched,
annealed in the drawn state and subsequently exposed to electron beam irradiation.
During sample irradiation the crosslinking reaction was promoted by a radiation
sensitising monomer, trimethylolpropanetrimethacrylate (TMPTMA), included in the
PVC compound formulations. The influence of stabiliser type and level, TMPTMA
level and irradiation dose on the network structure produced was investigated. A tin
stabiliser, Stanclere TL, was selected for this study as it promoted the crosslinking
reaction and it showed no interfering peaks in the wide angle x-ray diffraction
(WAXD) traces which were used to follow the development of structural order. The
appearance of gel, the material insoluble in THF, in irradiated oriented samples proved
that a crosslinked structure was created. The gel formation increased with TMPTMA
level and irradiation dose. The gel content was found to affect mechanical properties at
elevated temperatures and produced an increase in the area shrinkage temperature.
Sample thickness and the plasticiser content were found to have a major effect upon
gel formation. The thicker the sample was, the smaller the quantity of gel that was
formed. Samples containing 46.5phr plasticiser showed greater gel content than
samples containing 25phr plasticiser as a result of the higher molecular mobility in the
more plasticised samples. It was also found that the orientation of the film decreased
the efficiency of network formation in PVC formulations with a 46.5phr plasticiser
content but no significant change in gel content could be detected in those containing
Tensile properties and impact strength at room temperature were slightly
improved in irradiated samples. The modified structure resulted in an improvement in
tensile strength and penetration resistance at higher temperatures and an increased area
shrinkage temperature. Crosslinking did not affect room temperature recovery or
crystalline orientation; however irradiation crosslinking reduced crystallinity.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.