New non-destructive optical approach to determine the crystallization kinetics of PLA under a CO2 atmosphere with spatial and temporal resolution

Abstract

The kinetics of crystallization of Polylactic Acid (PLA) in the presence of CO2 pressures from 1.5 to 4 MPa, has been studied by measuring the optical absorbance evolution of the material with time. To perform this study, an own-designed pressure vessel provided with windows has been used. The non-destructive approach presented in this paper allows for obtaining very accurate crystallinity data as a function of time for a wide range of pressures. Besides, this new approach allows measuring with spatial resolution, i.e., obtaining the crystallization kinetics' evolution in different areas of the samples, which helps to analyze in detail the crystallization mechanisms by using the Avrami approach. The results obtained have allowed observing an unexpected peak in the absorbance curve connected with the physical phenomena taking place during the CO2 uptake and the associated crystallization of PLA.