Design of super-tough co-continuous PLA/NR/SiO2 TPVs with balanced stiffness-toughness based on reinforced rubber and interfacial compatibilization

Abstract

Elastomer has been proved to be a prominent toughener for polylactide (PLA), however, the remarkable increase in toughness always accompanies a sharp decrease in tensile strength. In this work, based on rubber reinforcement theory and interfacial compatibilization technique, co-continuous PLA/natural rubber (NR)/silica (SiO2) thermoplastic vulcanizates (TPVs) with balanced stiffness and toughness were designed. By employing thermodynamic and kinetic factors, SiO2 was restricted to distribute in rubber phase or at the interface due to the strong physical entanglements between NR and SiO2, which played a significant role in reinforcing rubber and interfacial compatibilization. As a result, impact strength of the TPVs was greatly improved without decrease in tensile strength. With 12.5 phr SiO2, impact strength increased to 85.1 kJ/m2 (without fracture), which was 8 times of blank sample and 30 times than that of neat PLA, respectively. In addition, the influence of reinforced rubber, superior interfacial adhesion on fracture toughness and deformation mechanism were investigated semi-quantitatively under digital Izod impact tests.