Preparation, stretch‐induced crystallization and thermo‐oxidative aging behavior of poly (lactic acid)/saponite grafted polystyrene nanocomposites films

Abstract

AbstractIn this work, modified saponite (SAP‐g‐PS) was prepared by Pickering emulsion polymerization, and the optimum synthesis conditions of SAP‐g‐PS were investigated. Furthermore, SAP‐g‐PS was used as a reinforcing filler for poly (lactic acid) (PLA) and the mechanical properties results revealed that the elongation at break increased by 81.51% compared to pure PLA when SAP‐g‐PS was added up to 0.5 wt%. Scanning electron microscopy analysis showed that the fracture of PLA based nanocomposite films was ductile. The thermal analysis results showed that the maximum thermal decomposition temperature was increased from 352.19°C (PLA0, pure PLA film) to 361.63°C (PLA3, 0.5 wt% SAP‐g‐PS), and the crystallinity was increased from 18.2% (PLA0) to 31.3% (PLA3) at the traction ratio of 14. The stretch‐induced crystallization behavior of PLA based nanocomposites films was investigated under the conditions of the optimum blow molding process, and it was found that the elongation at break of PLA0 films increased from 25.8% to 37.4% and that of PLA3 was increased from 81.4% to 135.5% with the increase of the traction ratio, the crystallinity of both films showed an increasing trend, which indicated that the presence of the tensile flow field improved the orientation of the PLA, and increased its crystallization and mechanical properties. The thermo‐oxidative aging kinetics of PLA based nanocomposites films with different additions of SAP‐g‐PS were investigated by thermo‐oxidative aging experiments, and the lifetime of the films were predicted by the Arrhenius equation, which showed that the addition of SAP‐g‐PS effectively improved the lifetime of PLA based nanocomposites films.