Effect of different plasticizers on the properties of bio-based thermoplastic elastomer containing poly(lactic acid) and natural rubber

Bio-based thermoplastic elastomers (TPE) containing natural rubber and poly(lactic acid) were prepared by melt blending in an internal mixer. The blend ratio was 60% of natural rubber and 40% of poly(lactic acid). Dynamic vulcanization of natural rubber was performed with the sulfur system. The 2 mm -thick sheet samples were prepared by compression molding. The objective of this study was to investigate the effect of plasticization of PLA on the mechanical and physical properties of the derived TPE. Four plasticizers were selected: tributyl acetyl citrate (TBAC), tributyl citrate (TBC), glycerol triacetate (GTA), and triethyl-2-acetyl citrate (TEAC). The investigated properties were the tensile properties, tear strength, thermal ageing and ozone resistance, hardness, resilience, tension set and compression set. All plasticizers increased the strain at break. TBAC and TBC increased the stress at break. All plasticizers decreased the tear strength, hardness and resilience, and slightly changed the tension and compression set. TBAC seemed to be the best plasticizer for the TPE. The presence of 4 pph (parts per hundred resin) of plasticizer provided the highest strength and tensile toughness and the strain at break increased with the increasing plasticizer content. The plasticizers decreased the T-g and T-cc of the PLA and did not affect the degree of crystallinity of PLA in the TPE.