Effects of nanosilica filler on the thermal and mechanical properties of an epoxy/amine resin system

Abstract

The cure kinetics of an epoxy resin with surface modified silica filler (Nanopox F 400 resin) and without silica filler (DGEBA resin), cured with an amine curing agent, DDS at an N-H/epoxy molar ratio of 1.1:1 was studied by Dynamic Scanning Calorimetry in two basic modes; Dynamic temperature scanning and Isothermal temperature scanning. Dynamic temperature scanning analysis suggests that the addition of surface modified silica nanoparticles in the epoxy resin increases the rate of reaction by acting as a catalyst. The hydroxyl groups in silica nanoparticles catalyze the cure reaction by shifting the exothermic peak towards the lower temperature. Under dynamic temperature scanning, the glass transition temperature (Tg) was lower for the Nanopox F 400 system than the unfilled control system. The glass transition temperature and changes in the Tg found in DSC analysis were in line with TMA analysis and DMA analysis. Isothermal scanning analysis shows that the control system follows the Kamal autocatalytic model whereas Nanopox F 400 system follows the modified Kamal autocatalytic model. The model parameters were determined by a nonlinear multiple regression method. The mechanical properties of Nanopox F 400 resin and control resin both cured with DDS at an N-H/epoxy molar ratio of 1.1:1 were examined by tensile testing. The tensile results showed increase in modulus and decrease in tensile strength for 40 wt. % surface modified Nanopox F 400 system compared to the control system. The effect of processing technique and silica content on the tensile properties of silica reinforced epoxy resin was further analyzed. The structure of Nanopox F 400 resin was characterized by FT-IR spectroscopy and 1H NMR spectroscopy.