The effect of alkalization and fibre alignment on the mechanical and thermal properties of kenaf and hemp bast fibre composites: part 2 – cashew nut shell liquid matrix

Long and random hemp and kenaf fibres were used in as-received condition and alkalized in a 6% NaOH solution. They were combined with cashew nut shell liquid (CNSL) resin and hot-pressed to form natural fibre, natural matrix composites. The mechanical properties of the composites were investigated to observe the effect of fibre alignment and alkalization. A general trend was observed whereby alkalized and long fibre composites gave higher flexural modulus and flexural strength with alkalized long kenaf–CNSL composite giving superior mechanical properties. A general trend was also observed for the overall mechanical test results of the composites whereby high flexural modulus and high flexural strength are associated with a low work of fracture. Wide endothermic peaks present in differential thermal analysis thermograms for all of the composites indicated the presence of moisture which leads to inferior mechanical properties. Dynamic mechanical thermal analysis carried out on the composites showed that the alkalized fibre composites have higher E′ and lower tanδ, corresponding to the trends of higher flexural modulus and lower work of fracture respectively.