Improvement of mechanical and impact performance of poly(lactic acid) by renewable modified natural rubber

Abstract

© 2020 Elsevier Ltd Enhancement of mechanical properties of biodegradable and compostable poly(lactic acid) is remarkably achieved by melt-blending with particular modified natural rubber. The modified natural rubber is prepared by a two-step process using hydrogenation, followed by an epoxidation reaction, in latex phase, which is sustainably derived from the rubber trees. The as-prepared epoxidized hydrogenated natural rubber is used (10% by weight) for the first time, as a toughening agent, in a mixture with poly(lactic acid). The structure modification of the rubber containing hydrogenated and epoxide moieties provides improved compatibility between rubber and poly(lactic acid). The results demonstrate the maximum increment in impact performance and elongation at break of the modified natural rubber/poly(lactic acid) blend with the values of 32.43 kJ/m2 and 348%, respectively. The results reveal that the impact resistance and elongation at break of PLA blend can increase approximately ninefold and forty-ninefold, respectively, compared to the neat PLA. Meanwhile, there is an improvement in tensile strength (41.79 MPa) and modulus (2.02 GPa) of the blend when compared to the unmodified natural rubber/poly(lactic acid) blend (31.39 MPa tensile strength and 1.57 GPa modulus). Furthermore, the microstructure, evidenced by scanning electron microscopy, reveals the presence of the fine rubber particles and the appearance of some fibrils on the impact-fractured surface of the blends. Therefore, the modification of natural rubber improves its compatibility with poly(lactic acid) and enhances the mechanical and impact properties of poly(lactic acid). The successful preparation of natural rubber-based toughening agent using an environmental-friendly latex system paves the way for broadening and diversifying the use of natural rubber and also poly(lactic acid), in which both derived from renewable resources with the truly-sustainable developments and sustainability.