The effect of alkali treatment on tensile properties of coir/polypropylene biocomposite

The increase demand for use of natural fiber in biocomposites is due to its inexpensive material, abundantly available and it has reasonable strength. In this study, coir fiber were treated with NaOH solution (3 wt% and 5 wt%) for 2, 4 and 6 hours at room temperature. The treated and untreated coir fiber with size of 160 - 250 mu m were extruded with polypropylene (PP) at fiber content of 10 and 30 wt%. The effect of alkali treatment was analyzed for its chemical composition, thermal stability and morphology. The biocomposites were tested for its tensile properties. Results showed that alkali treatment at 5 wt% for 6 hours had higher cellulose composition which was 29% compared to untreated coir. Thermal stability of treated sample increased and had high percentage of residue which showed the improved hydrophobicity of the sample. The surface of treated sample were rough due to removal of impurities and silica bodies. The tensile properties of biocomposite prepared from 5 wt% NaOH treated fiber/PP were higher by 28% compared to untreated coir/PP. This study shows that alkali treated coir fiber had better characteristics compared to untreated coir fiber and lead to the higher tensile properties of the PP-based biocomposite.