Water uptake of epoxy composites reinforced with carbon nanofillers

The water absorption behaviour of neat epoxy resin and reinforced with different contents of carbon nanotubes (CNTs) and nanofibres (CNFs) is reported. The water absorption was monitored gravimetrically and its effect on the thermal and mechanical properties was studied. The maximum water content absorbed significantly decreases with the addition of nanofillers, especially in epoxy/CNT composites. This decrease is higher than the behaviour predicted from ideal mixing law. The evolution of glass transition temperature during ageing confirms that water uptake causes several phenomena, such as plasticization and postcuring matrix processes. The effect of water absorption on mechanical properties changes during hygrothermal ageing. At the beginning, the mechanical strength decreases but then it is recovered. This is justified by the presence of different mechanisms of water absorption and interaction with the epoxy matrix.