The role of γ-aminopropyltriethoxysilane (γ-APS) on thermal stability of TEOS-PDMS Ormosils

The degradation process of TEOS-PDMS Ormosils containing different amounts of gamma-APS has been studied by means of DTA, TG, FTIR and Si-29-NMR measurements. It has been found that the amount of gamma-APS improved the thermal properties of Ormosil materials. The increase in gamma-APS content causes the increment on the decomposition temperatures and activation energies of the studied Ormosils. These results have been attributed to the favourable effect of gamma-APS in the copolymerisation re:action between TEOS and PDMS molecules. Si-29-NMR analyses have shown that the incorporation of gamma-APS increases the concentration of D(Q) units in the Ormosil structure, i.e., increases the number of TEOS molecules bonded to PDMS ones. Initial decomposition temperature (IDT), temperature of maximum weight loss rate (T-max), integral procedure decomposition temperature (IPDT) and activation energy values (E) were calculated from different equations which described the degradation of these materials. Addition of 10 wt% gamma-APS produced an increase of 63 degrees C in the IDT and of 115 and 110 degrees C, respectively, for T-max and IPDT (up to 478 and 610 degrees C) compared to the free gamma-APS Ormosil. Activation energy values also rise up to 69.4 kJ(.)mol(-1) by introducing 10 wt% of gamma-APS.