Abstract
Epoxy resins were synthesized using phenyl silsesquioxanes with three kinds of structures, double-decker (DDEP), cage (DDQEP) and ladder-like (PGSQ). The epoxy resins were thermally hardened by heat using tetraethylenepentamin as a curing agent. Thermal properties were measured by thermal gravimetric analysis and dynamic mechanical analysis. Mechanical properties were measured by tensile test. In these studies, we confirmed following points. (1) The thermal decomposition proceeded in two steps under an air atmosphere; the primary decomposition temperatures for all three samples were found at 270°C and the secondary decomposition temperatures were observed at 600°C. (2) The glass transition temperature (Tg) was determined by dynamic mechanical analysis as follows; DDQEP had the highest Tg (86°C), while PGSQ had the lowest Tg (67°C). The storage modulus was barely changed below and above Tg. (3) The order of fractural energy was DDEP>DDQEP>PGSQ, and DDEP gave 18 times larger energy than that of the PGSQ. Through these studies, correlations between silsesquioxanes structures and some properties (fractural strength, fractural energy and Tg) was found, although the decomposition temperature was independent of the structures.
