Radiation effects on structure and properties of poly(ε-caprolactone)

Poly (epsilon-caprolactone)s ( PCLs) with different molecular weight were cross-linked by gamma-radiation. The radiation crosslinking feature was examined by Soxhlet extractor with toluene and analyzed by using the Charlesby-Pinner equation. The crosslinking degree is related to molecular weight and radiation dose,and the relation between the sol fraction and the radiation dose follows the Charlesby-Pinner equation. Radiation may cause a drop of tensile strength and elongation for all the samples d. The DSC diagrams demonstrated that radiation caused an increase of crystallinity and a decrease of melting temperature of PCL crystals. The DMA analysis indicated that radiation crosslinking raised heat deformation temperature of PCL and caused a rubbery state after the melting of PCL crystals. The shape memory results indicated that only those specimens that had a sufficiently high cross-linking degree (gel content is higher than about 15%) were able to show the typical shape memory effect, a large recoverable strain and a high final recovery rate. The response temperature of the recovery effect (about 55degreesC) was related to the melting point of the samples. The PCL shape memory polymer was characterized by its low recovery temperature and large recovery deformation.