Thermal and dynamic mechanical analysis of polystyrene composites reinforced with short sisal fibres

The thermal behaviour of polystyrene composites reinforced with short sisal fibres was studied by means of thermogravimetric and dynamic mechanical thermal analysis. The thermal stability of the composites was found to be higher than that of sisal fibre and the PS matrix. The effects of fibre loading, fibre length, fibre orientation and fibre modification on the dynamic mechanical properties of the composites were evaluated. Fibre modifications were carried out by benzoylation, polystyrene maleic anhydride coating and acetylation of the fibre and the treatments improved the fibre-matrix adhesion. PS/sisal composites are thermally more stable than unreinforced PS and sisal fibre. The addition of 10% fibre considerably increases the modulus but the increase is found to level off at higher fibre loadings. The Tg values of the composites are lower than that of unreinforced PS and may be attributed to the presence of some residual solvents in the composites entrapped during the composite preparation. The treated-fibre composites show better properties than those of untreated-fibre composites. The Arrhenius relationship has been used to calculate the activation energy of the glass transition of the composites. A master curve is constructed based on time-temperature superposition principle.