Performance Properties of PP/Sisal Fibre Composites having Near Critical Fibre Length and Prediction of Their Properties

Critical fibre length (L-c) of natural fibre as reinforcement for polymeric composites is an essential parameter for enhancing mechanical properties. In this work, the effect of fibre treatment and addition of polypropylene grafted maleic anhydride (PP-g-MA) on L-c of sisal fibre, and interfacial shear strength (IFSS) of polypropylene (PP) matrix and sisal fibre (SF) were investigated. A single fibre pull-out test was used for the investigation, and the lowest critical fibre length was found to be 8 mm for PP/SF composites with compatibilizer (PP-g-MA). The final fibre length in the composites confirms the presence of near-critical length fibres. The composites prepared using near critical fibre length significantly improve the mechanical properties with increased fibre concentration. Flexural modulus of the composite with the highest amount (40 wt.%) of fibre was enhanced by 294 % compared to neat PP, which is a significance of near-critical fibre length. The prediction of composite properties was made by the inverse rule of mixture and Hirsch theory. It is found that PP/Sisal fibre composites offer properties that can be potentially used to produce high strength-to-weight ratio structural components.

Automated summary

This study investigated the effect of fibre treatment and addition of polypropylene grafted maleic anhydride (PP-g-MA) on the critical fibre length (L-c) of sisal fibre and the interfacial shear strength (IFSS) of polypropylene (PP) matrix and sisal fibre (SF). The results showed that using fibres with a length close to the critical length significantly improved the mechanical properties of the composites.