Property modification and process parameter optimization design of polylactic acid composite materials. Part I: polylactic acid toughening and photo-degradation modification and optimized parameter design

Abstract

The aims of this series of studies were to improve the characteristics of polylactic acid (PLA) composites, including toughness modification and photo-degradability suppression. For toughness modification, polybutylene succinate (PBS) was used to modify the toughness of PLA material, and for photo-degradability suppression, ultraviolet (UV) absorbers and hindered amine light stabilizers (HALS) were used to restrain the photo-degradability of PLA material. The composite granules were produced by twin-screw extrusion followed by film extrusion, and the Taguchi method and principal component analysis are used to optimize processing parameters for toughening modification analysis. Through differential scanning calorimetry testing and melt flow index analysis it was determined that this combination of PLA-based composite material had good compatibility, processing flowability and weather resistance. Compared with pure PLA, it was found that the bending strength was decreased by 27.49%, the tensile strength was increased by 13.47% and impact strength was increased by 22.95%, when the processing parameter of the PBS blending ratio was 10 wt% and the mixing of UV absorbers and HALS blending ratio was 0.5 wt%. The screw speed of the twin-screw mixer extruder was 200 rpm, and the die head temperature was 220℃. After 480 hours of UV accelerated aging testing, the retention rate of tensile strength was 94.86%, which is higher than that of pure PLA by 44%. The retention rate of breaking elongation was 85.17%, which was higher than that of pure PLA by 35.17%.