Hydrogen Peroxide-Induced Controlled Degradation of Poly(lactic acid) for Melt-Blown Nonwovens

This study aimed to increase the melt flow index (MFI) of poly(lactic acid) (PLA) through aqueous hydrogen peroxide (H2O2)-induced degradation. From this work, the impacts of hydrogen peroxide concentration and processing time were examined with samples that were prepared through reactive melt batch mixing. The hydrogen peroxide treatment and change in processing times were shown to decrease molar mass (MW) to various degrees, up to 70%. Overall crystallinity was only decreased with lower peroxide concentrations, while the glass transition temperature was reduced by 4 to 11% among all treated samples. Results confirm degradation via random chain scission with additional contributions from heat, hydrolysis, and potential alcoholysis. All results concur with the finding that lower peroxide concentrations paired with longer processing times result in the most effective degradation, while higher peroxide concentrations begin to favor cross-linking as processing time continues, resulting in increased MW. Therefore, lower peroxide concentrations are recommended for greater control over the extent of degradation. The resulting high MFI PLA can have applications that require low viscosity, such as melt-blown nonwoven materials where the treated sample was shown to produce finer, more uniform fibers at lower operating temperatures compared to raw PLA.