Moisture sorption by epoxy resin filled with MWCNT of different thickness

The aim of this work was to determine the effect of environmental ageing on sorption and thermophysical characteristics of epoxy and epoxy-based nanocomposites (NC) filled with multiwall carbon nanotubes (MWCNT) with different thicknesses. Two types of MWCNT with average diameter of 140 (aspect ratio - 50) and 9.5 (aspect ratio - 150) nm, respectively, were used. The considered filler content was within the range 0.005-0.1 wt. % for thin and 0.5-2 wt. % for thick MWCNT. For epoxy and NC specimens the moisture absorption and resorption after desorption in silica gel were performed in atmospheres with 47, 73, and 91% RH at room temperature. Dynamic thermal mechanical analysis was employed to evaluate hygrothermal ageing effects in as-produced and "aged" NC samples after moisture ab/de-sorption. It was experimentally confirmed that the equilibrium moisture content of the NC decreased with filler content for both MWCNT if compared to the neat epoxy resin. The diffusion coefficients for NC filled with 0.1 and 2 wt. % of MWCNT were reduced by 17 and 20%, accordingly. The improved environmental stability of the NC was explained by the reduction of free volume and restriction of polymer chain mobility due to addition of MWCNT to epoxy resin.