The compound of octa-(3-glycidoxypropyl) silsesquioxane (POSS) was prepared in higher yield by the hydrolysis and condensation of 3-glycidoxypropyl trimethoxysilane (KH560) in the solvent of methanol with hydrochloric acid as the catalyst. The effects of reaction conditions, such as monomer concentration, the contents of water and catalyst were investigated. The results showed that the better values of these reactive factors were KH560/H₂ O/HCl=1.5/1/0.02(molar ratio), 55~60°C of reaction temperature, respectively. The FTIR, GC-MS and ¹³C NMR spectrum showed the structure of POSS was incompletely condensed. The thermogravimeric analysis (TGA) shows POSS had good thermal stability.

The E-51 epoxy resin modified by adding 3-glycidoxypropyl polyhedral silsesquioxane cage and the use of equivalent of 4,4'-diaminodiphenyl sulfone (DDS) as the curing agent has been discussed. The FTIR spectrum, gelation characteristics and differential scanning calorimetry (DSC) was used to study the curing behavior and kinetics of the composites. The mechanical properties of the systems were also considered. The results show that the cured reaction has the lower activation energy Ea = 48.7KJ/mol. The heat deformation temperature (HDT), thermal decomposition temperature and glass transition temperature (Tg) of the composite is 200, 442 and 245°C, 31, 58 and 20°C higher than that of E-51/DDS system prepared under the same curing condition. This composite has higher thermal residue, which can be as high as 25% near 800°C. The flexural and impact strength remains almost unchanged at the same time. We also discussed the modification of TDE-85/MNA system by POSS, and found that the Tg of TDE-85/POSS/MNA system is 35°C higher than that of TDE-85/MNA system from TGA.