Mechanical, thermal and flammability properties of poly (Lactic acid)/banana fibre/graphene nanocomposites toughened by core shell rubber

Abstract

A biocomposite consists of Poly (lactic acid) (PLA) and Banana Fiber (BF) was prepared responding to high demand of biodegradable product. The mechanical as well as the morphological studies were done to find the optimum BF loading for the biocomposite system. Nevertheless, the optimum BF loading could not determine since most of the mechanical properties exhibit a decremental trends and the scanning electron microscope (SEM) analyses revealed that there was an interfacial gap presence between the PLA/BF due to poor compatibility between those two. An epoxy-based compatibilizer (brand name Joncryl) was then incorporated into the biocomposite system to improve the overall mechanical properties of PLA/BF biocomposite. However, addition of Joncryl only gave a slight improvement on impact strength but adversely affected the tensile and flexural strength. Hence, graphene (Gr) was added to improve the properties of the nanocomposite. Sample of PLA/10% BF with 0.5 phr Gr loading recorded the highest tensile and flexural strength compared to other formulations thus was selected as the optimum loading for the PLA/BF/Gr nanocomposite. Thermal gravimetry analysis (TGA) and differential scanning calorimetry tests (DSC) revealed that increased amount of Gr had enhance the thermal stability of the biocomposite. On the contrary, the increase contents of Gr had decreased the nanocomposite toughness, which was shown by the impact test results. In order to overcome the drawback, a core shell rubber (CSR) was introduced to the system as a toughening agent. Based on the overall mechanical properties, 15 phr CSR content showed the highest impact strength and elongation at break while having an acceptable thermal stability. The limiting oxygen index (LOI) for 15 phr CSR content was at 21 volume%, which exceeded the threshold mark of 20.8 volume%. This indicate that the nanocomposite produced at this formulation can be classified as a safe material.