The influence of nucleating agents, plasticizers, and molding conditions on the properties of injection molded PLA products

Poly(lactic acid) (PLA) is a “green” alternative to petroleum-based plastics and a desirable choice for many applications. However, low heat deflection temperature and lack of toughness, together with the slow crystallization kinetic of neat PLA hinder its widespread application. The weak properties of PLA can be improved with the improvement of crystallinity, which depends on molecular weight, D-lactide content, the presence of different modifiers and the processing conditions. We aimed to maximize the crystallinity and crystallization rate of PLA to explore the limitations of PLA when it is processed by injection molding. Therefore, we selected PLA with low D-lactide content, the three effective nucleating agents and the two suitable plasticizers. We found that the heat deflection temperature, tensile strength, and Young’s modulus of PLA modified with nucleating agents were considerably better than those of Acrylonitrile Butadiene Styrene (ABS). However, the elongation at break of the annealed and the simultaneously nucleated and plasticized PLA compounds was significantly lower than that of ABS. The addition of nucleating agents and plasticizers and the variation of mold temperature did not improve the brittleness of PLA. The elongation at break of PLA was still very low and stayed in the 1.7–2.5% range.