Preparation and properties of elastomers based on a cycloaliphatic diepoxide and poly(tetrahydrofuran)

A cycloaliphatic diepoxide is polymerised in the presence of poly(tetrahydrofuran) with hydroxy end-groups (PTHF). The cationic polymerisation is induced with an iodonium salt as initiator. The shear modulus as well as the glass transition temperature decreases with increasing amount of PTHF. Samples with 25 mol% PTHF of a Mn between 650 and 2900 show a rubber-like behaviour at room temperature. The maximum strain increases and the modulus of elasticity decreases with increasing Mn of the PTHF. During the polymerisation the samples shrink and the shrinkage increases with increasing Mn of the PTHF. The shrinkage is caused by the decomposition of the PTHF. After a long term thermal treatment the PTHF of the samples prepared with PTHF of high Mn had––in contrast to the samples prepared with PTHF of low Mn––nearly completely escaped out of the samples. This indicates that the ether bonds between the cyclohexane ring of the epoxy resin and the PTHF are much more stable than the ether bonds within the PTHF chains.