Utilization of modified epoxidized natural rubber and zinc oxide on properties of polylactic acid/epoxidized natural rubber blends: Mechanical properties, antibacterial efficiency and biodegradability

Abstract

Polylactic acid (PLA) is a biopolymer with brittleness and no antibacterial efficiency, which can be solved by the combination with epoxidized natural rubber (ENR) due to polar-polar interaction and with modified zinc oxide nanoparticles (ZnO) regarding the releasing of zinc ions (Zn2+) and reactive oxygen species (ROS). To minimize self-interaction in each PLA and ENR molecular chain, ENR with different % epoxidation was modified (mENR) by grafting with sebacic acid (SA). The addition of mENR with 50 % mol to PLA significantly improved the properties of pure PLA in terms of mechanical and impact properties, toughness, and also provided disinfectant ability. Regarding antibacterial properties, the efficiency against Staphylococcus aureus and Escherichia coli was significantly improved by adding ZnO to the blends. Combination of mENR to PLA matrix during mixing operation increases improved ZnO dispersion and distribution in PLA/mENR blends. Thus, antibacterial efficiency had been enhanced using proper mENR:ZnO concentration ratios in the PLA matrix, relative to other modified ZnO types. Also, incorporation of mENR:ZnO enhanced impact strength and retarded biodegradability of the blends due to hydrophobicity of ENR in PLA matrix. The findings of the blends' properties suggest potential for new functional applications, especially in disinfectant sheet lamination products where strength and protection against bacterial growth together with proper degradation period are required.