Using Molecular Simulation to Explore Unusually Low Moisture Uptake in Amine-Cured Epoxy Carbon Fiber Reinforced Nanocomposites

Reinforced nanocomposites based on a diamine-cured diglycidylether of bisphenol A are reported containing a mono-amino POSS reagent and polyacrylonitrile fibres. Covalent incorporation of mono-amino POSS at 2 wt % leads to especially attractive properties, including an increase (20 K) in glass transition temperature (Tg) and thermal stability (increase in char yield of up to 5%). The addition of POSS (2 wt %) in DGEBA leads to a reduction in moisture uptake of less than 0.30-0.91wt %, depending on relative humidity (after 6000 hours), with little effect on Tg (reduction of 9-11 K compared with 11-22 K in the unmodified DGEBA). Molecular dynamics simulation is used to visualise the cured network structure of these nanocomposites, relating free volume to water uptake. Translation of the properties from neat resin to CFRP is very encouraging with a reduction in the equilibrium moisture absorption of up to 29 % in the latter.