Comparative study of physical and chemical properties of PLA-based films obtained by solution casting and flat-slot die melt extrusion

Abstract

In this study the effect of processing methods on physical and chemical properties of polylactide (PLA) (Mn 130 kDa, L-93/ D-7) was investigated. PLA-films were obtained by solution casting and melt extrusion using Bestfiilament extruder equipped with flat-slot die. SEM, AFM, FTIR-spectroscopy and DSC were used for characterization of the films. The films obtained by flat-slot die melt extrusion had a relief surface with prominent strands and inclusions, while the cast films had a smooth surface with pores or gaps ranging in size from 20 to 60 μm. The average roughness (Ra) and root-mean-square roughness (Rq) of the surface of cast films were at the level of 45-48 and 37-39 nm, respectively. Meanwhile, for the melt films these values increased and corresponded to 122 and 65 nm, respectively. According to FTIR, both types of films were characterized by an increase in the absorption peaks at 1800-1700, 1450-1470 and 1350-1320 cm-1, which correspond to stretch vibrations of ester bond and bending vibrations of the C-H bond, respectively. DSC data showed decrease in crystallinity of PLA and change in its internal structure from amorphous-crystalline to amorphous after the processing.