Solvent Uptake and Accelerated Solar Aging Studies of Cotton – Polypropylene Commingled Composite Systems

Natural fibre-reinforced thermoplastic composites have a significant role in non-structural applications. Natural fibres are biodegradable, renewable and of low cost, high toughness and possess good thermal properties. This work involved the study of solvent absorption of cotton/polypropylene (PP) side-by-side commingled composites in different solvents, its variation by chemical treatments, temperature, fibre content etc., the extent of tensile property deterioration by solar radiation in a solar light concentrator and by water diffusion. It was observed that though cotton is highly hydrophilic, the diffusion was a matrix-dominated phenomenon. The extent of moisture absorption increased with the fibre content but decreased on treatment with maleic anhydride-modified PP. The former added a greater number of hydrophilic hydroxyl groups while the latter consumed them and enhanced the fibre–matrix interfacial adhesion. Increase in temperature accelerated the rate of moisture absorption and reduced the time required for equilibrium swelling. Exposure to sunlight in solar concentrator deteriorated mechanical properties such as tensile strength and tensile modulus by weakening the fibre–matrix interfacial adhesion and by chain scission.