Rapid Crystallization of Poly(lactic acid) by Using Tailor-Made Oxalamide Derivatives as Novel Soluble-Type Nucleating Agents

The crystallization rate and crystallinity of poly(lactic acid) (PLA) was significantly increased by the incorporation of 0.25–1.0 wt % of tailor-made oxalamide derivatives (NAs). The nucleation effect and nucleation mechanisms of the NAs were studied via diferential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD) techniques. The experimental results convincingly revealed that the NA molecules are soluble in a PLA melt and are capable of self-organizing into fibrils upon cooling. The fibrils as efficient nucleation sites induced rapid growth of α-form PLA crystal along the fibrils, forming shish-kebab-like structures. In isothermal crystallization, very fine PLA sperrulites with high density were obtained in the presence of NAs. The high nucleation efficiency and the simple synthetic routes of the NAs make them promising to be a new generation of nucleating agents for (bio)polymers, e.g., PLA.