Cold crystallization and postmelting crystallization of PLA plasticized by compressed carbon dioxide

• Published in: Journal of polymer science. Part B, Polymer physics Vol. 46; no. 23; pp. 2630 - 2636
• Main Authors: Yu, Long, Liu, Hongsheng, Dean, Katherine, Chen, Ling
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.12.2008; Wiley
• Subjects: Applied sciences; biomaterials; carbon dioxide; Crystallization; differential scanning calorimetry (DSC); Exact sciences and technology; glass transition; kinetics (polym.); Organic polymers; Physicochemistry of polymers; PLA; pressure; Properties and characterization; differential scanning calorimetry (DSC); Talc; PLA; Compressed gas; Carbon dioxide; kinetics (polym.); pressure; Experimental study; Transformation temperature; Melt crystallization; Lactic acid polymer; Pressure effect; Plasticizer; crystallization; Kinetics; biomaterials; glass transition; Nucleating agent; Isothermal crystallization
• ISSN: 0887-6266; 1099-0488
• DOI: 10.1002/polb.21599

The cold crystallization at temperature Tcc (melting > Tcc > glass transition) and the postmelting crystallization of polylactic acid plasticized by compressed carbon dioxide (CO₂) were studied using a high-pressure differential scanning calorimeter. The kinetics of the two kinds of crystallization were evaluated by the Avrami equation as a function of pressure at certain temperatures. The effects of using talc as a nucleation agent on the two types of crystallization under pressure were also investigated. The results show that compressed CO₂ increased the mobility of the polymer chains in solid state, resulting in an increased rate of cold crystallization. The decreased rate of postmelting crystallization was mainly in the nucleation-controlled region, which indicates that the number of nuclei was decreased by the compressed CO₂. The growth rate of the two crystallization types followed the Avrami equation, but the kinetics of each depended upon temperature and pressure. The inclusion of talc accelerated postmelting crystallization but had little effect on cold crystallization.