Palygorskite as an epoxy polymer reinforcement agent

Palygorskite, a silicate clay with a pleated 2:1 layered structure, has a lath-like particle morphology that makes it an attractive candidate for the formation of polymer nanocomposites. Here, we report the properties of palygorskite in pristine and silylated forms for the reinforcement of rubbery and glassy epoxy matrices. Three silylation reagents were used for surface modification of the mineral, namely, gamma-aminopropyltrimethoxysilane (APTMS), N-dodecyltriethoxysilane (DTES), and 1,1,1,3,3,3-hexamethyidisilazane (HMSZ). The silylated palygorskite derivatives provided better dispersions in rubbery epoxy matrices than the pristine mineral, affording improvements in mechanical properties at low loadings levels of 2 and 5% (w/w). But at higher loadings where increases in the viscosity of the pre-polymer helps to stabilizes the mineral dispersion, little or no differences were observed for the reinforcement benefits provided by the pristine and silylated forms of palygorskite. Glassy epoxy nanocomposites formed from both pristine and silylated palygorskite exhibited marginal improvements in tensile properties regardless of the mineral loading level, suggesting that the tensile strength of the pleated sheet silicate may be approaching that of the polymer matrix. (c) 2006 Elsevier Ltd. All rights reserved.