5. Treatment of sugar palm fibre
In order to enhance interfacial properties of natural fibre composites, surface treatment on natural fibres is needed. Bachtiar (2008), Bachtiar, Sapuan, and Hamdan (2008b), Bachtiar et al. (2008c), Bachtiar, Sapuan, and Hamdan (2009a) studied the effects of alkaline treatment of sugar palm fibre by sodium hydroxide (NaOH) on mechanical properties of sugar palm fibre used to reinforce epoxy composites. The results (Table 5) verified that mechanical properties (tensile, flexural and impact) of the composites increased particularly for tensile modulus. This is due to the reduction of hydrophilic property of sugar palm fibre after the treatment which had increased the interfacial bonding between sugar palm fibre and epoxy matrix. This is achieved after treating the fibre with NaOH to react with hydrophilic hydroxyl groups of the fibre and improves hydrophobic characteristics and facilitates good interfacial bonding with matrix materials. Apart from that, the same study reported that higher concentration of alkaline solution and prolonged soaking time resulted in the decrease in mechanical properties of the composites. Even though the surface of sugar palm fibre had been treated, the over treated samples led to the weakening of the fibre cell wall, resulting in inferior fibre mechanical properties. This shows that when stress is transferred to the fibre, the fibre breaks.