Thermal diffusivity and secondary crystallisation kinetics in poly(lactic acid)

POLYMER

卷:179

Article

Marsh, J. J.¹  Turner, R. P.¹  Carter, J.¹  Jenkins, M. J.¹ 

[1] Univ Birmingham, Sch Met & Mat, Birmingham B15 2TT, W Midlands, England

关键词: Poly (lactic acid);    Laser flash analysis;    Diffusivity;    Secondary crystallisation;   

DOI  :  10.1016/j.polymer.2019.121595

来源: Elsevier

【 摘 要 】

The non-steady state technique of laser flash analysis (LFA) was used to record the variation of thermal diffusivity with time during the cold-crystallisation of poly(lactic acid), a grade that contains 4% D stereoisomer. The measured diffusivity data was analysed in terms of the Avrami and Hoffman-Lauritzen models for polymer crystallization and this yielded kinetic data that was comparable to that which originated from DSC. Within the temperature range 88 to 109 degrees C, mechanistic 'n' values of 2.0 +/- 0.1 were calculated and a nucleation constant of 6.58 x 10(-5) K-2 was determined. Measurements of thermal diffusivity were also recorded over a longer time-scale to determine whether thermal diffusivity was a useful indicator of secondary crystallization and this data was analysed using a modified Avrami equation that includes a root-time dependence of the secondary process. Secondary crystallisation rate constants (k(s)) increased with crystallisation temperature and yielded an activation energy for the secondary crystallisation process of 40 kJ/mol.

【 授权许可】

Free