Factors Affecting Moisture Absorption in Polymer Composites Part II: Influence of External Factors

Abstract

The influence of external factors like relative humidity (0) and ambient temperature (T) on the moisture absorption behaviour of permeable (Jute-Epoxy) and impermeable (Glass-Epoxy and Graphite-Epoxy) types of composites were reported. The respective equilibrium moisture contents (Mm and Mm) increased exponentially with relative humidity. The diffusion coefficients of both type of composites (D~'and D,) increased with ambient temperature and could be represented by an Arrhenius relationship. The permeable composite showed a higher exponential power on the relative humidity term than the impermeable composite (2.64 for Jute composite as compared to 2.0 reported by Shen and Springer for a graphite composite) and a lower activation energy for diffusion (0.9 x 101 cal. mole-' for the jute composite as compared to 4.429 x 103 cal. mole-1 obtained for a glass composite). These trends were attributed to the fibre permeability leading to different diffusion barriers in such composites.