Effects of Nucleating Agents with Different Structures on the Crystallization Behaviors of Polylactic Acid
To investigate the effects of different nucleating agents on the crystallization behaviors of polylactic acid(PLA),commercially available nucleating agents with different molecular structures(phosphate nucleating agent,hydrazide nucleating agent and multiamide nucleating agent)were selected.The effects of nucleating agents on the structures and crystallization behaviors of PLA were studied by using instruments such as Fourier transform infrared spectroscopy(FTIR),differential scanning calorimetry(DSC),and polarizing microscopy(POM).The results show that different nucleating agents do not change the molecular structures of PLA during the melt blending process.However,different nucleating agents could eliminate or reduce the cold crystallization induction periods of PLA to varying degrees,refine the spherical crystals of PLA,and increase the crystallization temperatures of PLA.Among them,the zinc phenylphosphate nucleating agent(TMC-200)has the strongest ability to refine PLA spherulites,and no obvious cold crystallization peak is observed on the secondary heating DSC curves of PLA-200 composite at different heating rates.At the same time,TMC-200 nucleating agent could increase the crystallinity of pure PLA from below 3%to above 30%.In addition,the crystallization peak temperatures of PLA-200 composite maintain above 100℃,and the crystallization activation energy of PLA-200 composite is decreased to 119.2 kJ/mol.
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