Synthesis of highly grafted MWCNTs with epoxy silane to improve curing, thermal and mechanical performances of epoxy nanocomposites

Abstract

Hydrophobic CNTs have weak interfacial interactions to epoxy matrix which causes their agglomeration and significant decline in the thermal/electrical/mechanical of epoxy nanocomposites. In this research, multi walled carbon nanotubes (MWCNTs) were acid treated at three different times to prepare nanotubes with the highest functional groups on surface. Thereafter, the best functionalized nanotubes were surface modified using 3-glycidyloxypropyltriethoxysilane (GPTES) at different concentrations to prepare GPTES@MWCNTs nanoparticles with the highest silane grafting content. The unmodified, acid treated and GPTES@MWCNTs were characterized carefully. The pure, functionalized and silane modified nanotubes were then applied to epoxy resin at 0.5 to 2 wt% and the mechanical, curing, thermo-mechanical and morphological features of the nanocomposites were assessed. It was declared that the unmodified MWCNTs (at 0.5 wt%) caused about 35 % decline in enthalpy of curing and 24 °C decrement in decomposition temperature of the epoxy polymer. However, the modified nanotubes enhanced the curing enthalpy and decomposition temperature of the polymer by 95 % and 31 °C compared to the unmodified nanocomposites, respectively. It was also found that the GPTES@MWCNT containing nanocomposite (at 0.5 wt%) showed enhanced tensile, flexural and compressive strengths by 69, 106 and 34 % compared to the pristine epoxy sample and 47, 73 and 25 % compared to the unmodified nanocomposite, respectively. It also caused 54 % and 13 °C improvement in the storage modulus and Tg compared to the unmodified nanocomposite.