Effect of Ageing on the Mechanical Properties of Short Sisal Fibre Reinforced Polystyrene Composites

The water absorption behaviour and the effects of ageing on the mechanical properties of short sisal fibre reinforced polystyrene composites have been studied with special reference to fibre loading and fibre-matrix interface modification. The composites were subjected to different ageing conditions viz., immersion in boiling water for 24 h, immersion in cold water for 15 days and exposure to hot air at 80°C for five days. The interface modifications were performed by benzoylation, polystyrene maleic anhydride (PSMA) treatment, toluene diisocyanate treatment and silane treatment. The tensile properties and dimensions of the aged samples were measured and compared with unaged samples. The water uptake was found to increase with fibre loading and decrease with fibre modifications. However, PSMA treatment and silane treatment do not produce much variation in water uptake. The mechanical properties and dimensional stability of the treated fibre composites were found to be superior to those of untreated composites under identical ageing conditions. However, it is interesting to note that on water ageing, untreated fibre composites show minimum decrease in tensile strength compared to treated fibre composites and can be explained based on the thermal shrinkage of the polystyrene matrix. The superior properties of the treated composites were associated with the better interfacial interactions in treated fibre composites.