Effects of Two Pre-Treatment Methods on Water Absorption Property of Polyester-Fibre Composites

The use of plant fibres as reinforcement in composite materials is finding increasing interest in the automotive and building industry, and the properties of plant fibre composites have been addressed in numerous research studies. The replacement of synthetic fibres with natural fibres in composites is based on their renewable and environmentally friendly nature. The aim of this work is to investigate the effects of two chemical pre-treatment methods on the water absorption property of polyester-fibre composites. Fully grown kenaf (hibiscus cannabalis) bast fibres were manually retted from the stalk, washed, and cut into short fibre lengths of about 10 cm. One portion of the fibres was pre-treated with 5% pbw NaOH solution before immersing it in glacial acetic acid and then in acetic anhydride. The second portion was pre-treated with 5%pbw of NaOH and 0.125% of KMnO4 in acetone. The third portion of fibres was untreated to serve as control. The ground fibre was incorporated into ortho unsaturated polyester and cast with Teflon square shaped mould. The cured samples were weighed and immersed in water at room temperature until no further gain in weight was observed. The SEM of the fibres and the composites was taken. The results showed that the acetylation pre-treatment method reduced the water absorption property of the composites by a minimum of 46.0% across all fibre volume fractions while the permanganate pre-treatment reduced it by at least 25.5%. Chemical pre-treatment of fibres can therefore