Melt spinning of poly(l/d)lactide 96/4: Effects of molecular weight and melt processing on hydrolytic degradation

This study focused on determining the effects of molecular weight on the degradation of polylactide 96l/4d in melt spinning and the effects of melt processing on hydrolytic degradation. Three polylactides with different inherent viscosities were melt spun, and the fibres were studied in vitro. Results showed that during melt spinning high-molecular-weight polylactide degraded because polymer chains were subject to high shear stress and high melt temperatures, whereas a low-molecular-weight polylactide with low melt viscosity was not affected by melt processing. Most degradation occurred during the melting phase in the length of the extruder barrel. Lactide monomer, generated as the polymer degraded in the melt, significantly affected in vitro degradation such that the degradation rate was directly proportional to the lactide concentration of the polymer.