Moisture Absorption and its Influence on the Tensile Properties of Glass-Fibre Reinforced Polyamide 6,6

The equilibrium amounts of moisture absorbed by a range of grades of glass fibre reinforced polyamide 6,6 were approximately proportional to the weight fraction of the polymer. However, the moisture diffusivity was found to be also a function of variations in specimen preparation and microstructure. The diffusivities of the moulded composite specimens indicated a law of mixtures relationship; whereas those with machined edges differed significantly. Moisture-induced deterioration of tensile strength was most severe up to 1.5% and 3% by weight moisture contents for the glass-fibre containing and unfilled polyamide 6,6, respectively. Moisture ingress, as would be expected, resulted in increased elongations to failure for the unfilled polymer but caused almost no variation in the elongation behaviour of the reinforced polymer.