Hybrid cationic ring-opening polymerization of epoxy resin/glycidyloxypropyl-polyhedral oligomeric silsesquioxane nanocomposites and dynamic mechanical properties

摘要

Glycidyloxypropyl-polyhedral oligomeric silsesquioxanes (G-POSS) were prepared from 3-glycidyloxypropyl-trimethoxysilane (GTMS) by hydrolytic condensation. The hybrid cationic thermal polymerization of G-POSS with bisphenol A epoxy resin (E-51) using diphenyliodonium fluoride borate (DPI center dot BF4) as a cationic initiator and benzoyl peroxide (BPO) as a co-initiator was investigated by DSC and FTIR. The structure of G-POSS was characterized by liquid chromatography-mass spectrometry (LC/MSD), FTIR and NMR. The effect of BPO content on reaction system, the distribution of G-POSS in the curing system, curing reaction activation energy E-a and dynamic mechanical properties of the E51/G-POSS nanocomposites were characterized. The results showed that octa(3-glycidyloxypropyl)-POSS (G-POSS) had been synthesized and displayed uniform dispersion in E51/G-POSS curing system. The DPI center dot BF4, which was capable to initiate the thermal ring-opening curing of epoxy resin, showed an initial curing temperature of epoxy resin decreased by 54.7 degrees C when the added amount of BPO was 2 wt%. The reaction process was well accorded with Kissinger's kinetics model, and the average curing reaction activation energy E-a was increased as the content of G-POSS increased. The T-g and storage modulus of the E-51/G-POSS nanocomposites reached its optimum when the content of G-POSS was 2 wt%. The T-g of nanocomposite was 8.3 degrees C higher than that of the pure epoxy resin. The T-g and storage modulus decreased with the further increasing of G-POSS content.