Effect of D‐lactide content of annealed poly(lactic acid) on its thermal, mechanical, heat deflection temperature, and creep properties

Abstract

AbstractIn our research, the effect of D‐lactide content in injection‐molded and annealed poly(lactic acid) (PLA) was investigated for crystallinity as well as crystalline forms (less‐ordered α′ and more‐ordered α crystalline forms) and thus on the mechanical, heat deflection temperature (HDT), and creep properties. Three different PLA grades 3052D, 3001D, and 3100HP were investigated with D‐lactide contents of 4%, 1.4%, and 0.5%, respectively. The injection‐molded PLA specimens were then postproduction annealed in a heat chamber at 80–140 °C for 1 h to develop various crystallinities and various ratios of α′ and α crystal forms. It was demonstrated that not only annealing but also the D‐lactide content significantly influences the crystallization, crystal structure, and accordingly properties of PLA like notched Charpy impact strength, HDT, and creep characteristics. Higher HDT, impact properties, and creep resistance could be reached by using PLA with lower D‐lactide content with a certain annealing temperature range to develop definite crystal structures. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47103.