Effect of ageing on the mechanical properties of short sisal fibre reinforced polystyrene composites

The water absorption behavior and the effects of ageing on the mechanical properties of short sisal fiber reinforced polystyrene composites have been studied with special reference to fiber loading and fiber matrix interface modification. The composites were subjected to different ageing conditions, e.g., 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 fiber loading and decrease with fiber modifications. However, PSMA treatment and silane treatment do not produce much variation in water uptake. The mechanical properties and dimensional stability of the treated fiber 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 fiber composites show minimum decrease in tensile strength compared to treated fiber 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 interracial interactions in treated fiber composites.