Effect of phenyl-functional structured silanol on the network formation of epoxy-amine systems

The type of R-group on trisilanol polyhedral oligomeric silsesquioxane (POSS) (R₇Si₇O₉(OH)₃) can affect the acidity of the −OH group present. Trisilanol phenyl POSS was found to be more acidic since the phenyl group on the silicon atom increased the acidity of the silanol group. Based on the fact that acidic alcohol systems like phenol accelerate the epoxy amine curing reaction, the effect of trisilanol phenyl POSS on the curing kinetics of the epoxy amine reaction was studied on commercially available epoxy resins like diglycidyl ether of bisphenolA, DGEBA and tetraglycidyl diamino diphenyl methane, TGDDM with diamine terminated polypropylene oxide, Jeffamine D-230 and 2, methyl 1,5 pentadiamine, DytecA as curing agents. We observed a significant increase in the glass transition temperatures T_g for TGDDM amine systems containing trisilanol phenyl POSS under low temperature curing conditions. Dynamic Mechanical Analysis (DMA) was performed on cured epoxy amine samples containing trisilanol phenyl POSS, varying from 0 to 1.0% and the glass transition temperature was determined from the tanδ peak. Fourier Transform Infrared Spectroscopy (FTIR) experiments was used to study the curing kinetics in epoxy amine systems with and without trisilanol phenyl POSS. It was observed that the trisilanol phenyl POSS initially improves the rate of the secondary amine reaction with the epoxy leading to increased consumption of amine and epoxy, thereby forming a network having higher glass transition temperatures.