Poly(lactic acid)/natural rubber/kenaf biocomposites production using poly(methyl methacrylate) and epoxidized natural rubber as co-compatibilizers

Biocomposites have received a great deal of attention in academic research and industry because they are environmentally friendly and produce less carbon footprint, especially with the use of natural fibers. Nevertheless, compatibility issues require complexity to overcome the field of composite materials. Biocomposites based from poly(lactic acid) (PLA), natural rubber (NR) and kenaf were prepared by melt blending in an internal mixer. PLA/NR composition was fixed at 90/10 (wt/wt), while kenaf loading varied from 0 to 20 phr. The aim of this work was to study the effect of epoxidized natural rubber (ENR) and poly(methyl methacrylate) (PMMA) addition as co-compatibilizers in the biocomposites. Rheological behavior during mixing showed higher processing torque and stabilization torque after compatibilization. The mechanical properties deteriorated with increasing kenaf loading in biocomposites. Incorporation of rigid kenaf particles within matrix resulted in poor stress transfer and restricted chain movement. Addition of compatibilizer increased the tensile strength, elongation-at-break, tensile modulus and impact strength. Upon compatibilization, the interfacial interaction between kenaf and matrix is improved, enabling more efficient stress transfer, thus higher mechanical properties. Water absorption of biocomposites was studied by immersion in distilled water for 30 days. At high kenaf loading, water absorption percentage increased due to hydrophilic nature of kenaf. After compatibilization, water absorption decreased due to better interfacial adhesion. Morphological study of tensile fractured and impact fractured surface of biocomposites was investigated using scanning electron microscopy. Less fiber pull-out, more work of fracture and less interfacial gap between fiber and matrix were observed for compatibilized biocomposites, indicating enhanced interfacial adhesion. Addition of ENR and PMMA in PLA/NR/KF biocomposites was able to pare down the compatibility issues, contributing to improvement of overall properties.