Effect of 5-ethylidene-2-norbomene or cyclopentene comonomers on the micro-structures, mechanical and dynamic mechanical properties of polydicyclopentadiene

A copolymerization reaction was carried out by adding different contents of 5-ethylidene-2-norbomene or cyclopentene to dicyclopentadiene (DCPD) using an optimized polymerization process. The effects of different amounts of the comonomers on the conversion, mechanical properties and thermal stability of the polymer products were investigated and compared. The results showed that the addition of 5-ethylidene-2-norbomene accelerated the reaction rate and had little effect on the overall conversion rate of the reaction, while the addition of cyclopentene decreased the reaction rate and conversion rate. The tensile modulus, tensile strength, flexural modulus and flexural strength of the copolymer showed a trend of increasing and then decreasing with the increase of the comonomers content, reaching a peak at 5wt% of 5-ethylidene-2-norbomene or 3wt% of cyclopentene. At this peak condition, its impact strength could be improved by 50% compared to DCPD homopolymer. Below this peak condition, the Tg and  thermal stability of the copolymer did not change significantly.