Dramatically enhanced tensile strength and impact toughness of polydicyclopentadiene composites by covalent bond formation between phenyl-functionalized silica and dicyclopentadiene

Abstract

Enhanced tensile strength and impact toughness of polymers are desirable for their engineering applications through introduction of low loading fine fillers. In this work, dramatically enhanced tensile strength and impact toughness of polydicyclopentadiene (PDCPD) composites are simultaneously achieved by addition of phenyl-functionalized silica (P–SiO2) at low loadings. First, P–SiO2 particles with a uniform size of ca. 600 nm were prepared via a one-step sol-gel process, leading to covalent bond formation between phenyl-functionalized silica and dicyclopentadiene. Then, P–SiO2/PDCPD composites were fabricated by in-situ polymerization, and their tensile and impact properties were investigated. Interestingly, it is observed that the yield strength of the P–SiO2/PDCPD composites was dramatically enhanced by 63% and the notched Izod impact strength (impact toughness) was improved by 217% via addition of 0.3 wt% P–SiO2. Besides these enhancements, the storage modulus and glass transition temperature of PDCPD were also increased by the introduction of silica particles at low loadings. Consequently, it is clear that silica particles with rigid phenyl groups are promising for enhanced strength and toughness of silica/PDCPD composites. Compatibility between PDCPD and P–SiO2 as well as strong covalent bonding between phenyl groups and DCPD are responsible for the dramatic reinforcements of the composite tensile strength and impact toughness, etc.