Promotion on the thermal and mechanical behaviors of epoxy resin using phthalonitrile and functionalized‐SiO2

The phenolic‐type phthalonitrile (PN) was added to EP/DDM system in order to enhance the thermal and mechanical performance at high temperature. The influence of the added PN on the curing process of EP/DDM was studied via DSC and the activating energy (Eα) was calculated based on iso‐conversional method. The Eα values corresponding to EP/DDM crosslink reaction remained at about 60 kJ mol−1 while it dramatically increased to 68.2 kJ mol−1 when PN content reached 50 wt% (EP‐PN50). The Tg and char yield at 700°C in N2 increased from141°C, 25.7%, for the neat EP/DDM to 226°C, 68.7% for the EP‐PN50. The measured char yields of the cured blend were higher than the calculated values which implies the interaction between EP/DDM and polyphthalonitrile network. The tensile and bending tests were carried out at 413 K and the modulus of EP‐PN50 remains 2.3 Gpa. On the meantime, the cyano‐functionalized SiO2 (CNSiO2) was prepared to further promote the mechanical behaviors of this resin blend in high temperature. The contact angles of raw SiO2, KH560SiO2, CNSiO2 with EP‐PN50 are 59.3, 52.6, 49.7°, respectively, which confirms the better wettability of CNSiO2 to the EP/PN blend. Furthermore, the tensile and bending tests conducted at 413 K confirmed that the CNSiO2 was more efficient on enhancing the mechanical performance of this EP/DDM/PN system at high temperature.