Role of Hydrolysis on the Biodegradation of PLA Fibers Under Industrial Composting Conditions

Polylactic acid (PLA) is a bio‐based and renewable polymer increasingly used as a sustainable alternative to polypropylene and polyester in nonwoven applications. Although PLA biodegrades under industrial composting conditions, degradation can be slow, with fibers sometimes remaining intact for extended periods. PLA biodegradation occurs in two stages: (i) hydrolytic cleavage of ester bonds generating low‐molecular‐weight oligomers, followed by (ii) microbial assimilation to carbon dioxide and water. This study investigates how hydrolysis prior to composting influences the biodegradation of melt‐spun PLA fibers representative of spunbond nonwovens. Fibers were composted at 58°C ± 2°C using activated vermiculite following ISO 14855. A subset of fibers was pre‐hydrolyzed for 31 days at 58°C and pH 7 to evaluate the effect of abiotic hydrolysis. Hydrolysis induced significant physicochemical changes in the PLA fibers, including reduction in molecular weight (MW) (~190 kDa to < 10 kDa), bimodal molecular weight distributions indicating chain scission, and increased crystallinity (8.6%–70.9%). Under composting conditions, pre‐hydrolyzed fibers degraded substantially faster and exhibited no lag‐phase compared with untreated fibers. After 57 days, biodegradation reached 77.5% ± 5.8% for pre‐hydrolyzed fibers and 50.5% ± 7.2% for untreated fibers, demonstrating that hydrolysis‐induced MW reduction accelerates PLA biodegradation.