Investigation of the Influence of PLA Molecular Structure on the Crystalline Forms (α’ and α) and Mechanical Properties of Wet Spinning Fibres

In this paper, the influence of the molecular structure of polylactide (PLA)—characterised by its molar mass and content of d-lactide isomer—on the molecular ordering and α’–α form transition during fibre manufacturing by the wet spinning method is described. Fibres were studied by wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). Additionally, the physical and mechanical properties of the fibres were determined. This study also examines the preliminary molecular ordering and crystallisation of PLA fibres at various draw ratios. The performed experiments clearly show the dependence of the molecular ordering of PLA on the molar mass and d-lactide content during the wet spinning process. The fibres manufactured from PLA with the lowest content of d-lactide and the lowest molar mass were characterised by a higher tendency for crystallisation and a higher possibility to undergo the disorder-to-order phase transition (α’ to α form). The structural changes in PLA explain the observed changes in the physical and mechanical properties of the obtained fibres