Abstract:
This study aimed to improve the toughness and thermal stability of poly(lactic acid) (PLA) by incorporating epoxidized natural rubber (ENR) and silica nanoparticles (nSiO2). The ENR was prepared from natural rubber latex via in situ epoxidation using 0.5M formic acid (HCOOH) and 0.75M hydrogen peroxide (H2O2) at 50 ˚C for 4h. Based on FT-IR spectra, epoxide content of ENR was about 30 mol%. The as-prepared ENR was then blended with various loadings of PLA (10, 20, and 30 wt%) in an internal mixer, followed by a compression molding. The results showed that the incorporation of ENR into PLA caused an enhancement in the impact strength and elongation at break, but deteriorated the tensile strength, Youngs modulus and thermal stability. According to the optimum impact strength and elongation at break (16.4 MPa and 7.8%, respectively), the 80/20 PLA/ENR blend was selected for preparing composites with three loadings of nSiO2 (1, 2 and 3 phr). It was found that the impact strength and thermal stability of the composites were improved compared to those of the 80/20 PLA/ENR blend. Among the investigated 80/20/2 PLA/ENR/nSiO2 composites exhibited the highest mechanical and thermal properties. Moreover, the mechanical and thermal properties of the 80/20/2 PLA/ENR/nSiO2 prepared by melt mixing were also compared with those of the composite prepared by mixing ENR and nSiO2 in latex stage in the same content of nSiO2. It was revealed that at the similar nSiO2 content (2 phr), the composite prepared by latex mixing exhibited lower mechanical and thermal properties than the composite prepared by melt mixing.