Biodegradation Behavior of Neat <scp>PLA</scp> Fibers Under Controlled Industrial Composting Conditions: Fiber Characterization and Physical Changes During the Composting Process

ABSTRACT Poly(lactic) acid (PLA) is an important polymer that can replace some synthetic polymers and its biodegradability in fiber form is relatively unexplored while its biodegradability in various environments is controversial. This study examines the impact of fiber processing (drawing) on the biodegradation behavior of PLA (PLA 6100D, NatureWorks LLC) fibers suitable for nonwoven applications under industrial composting conditions (ISO 14855). PLA fibers were produced via melt spinning and subjected to two processing conditions, undrawn and drawn at a ratio of 4. Fiber characterization, including x‐ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile testing, scanning electron microscopy (SEM), and gel permeation chromatography (GPC), was conducted to assess crystallinity, thermal and mechanical properties, and molecular degradation. The drawn fibers exhibited a significantly higher degree of crystallinity (57.7% ± 5.5%) compared to undrawn fibers (23.0% ± 2.0%) and showed enhanced mechanical strength but reduced ductility and thermal stability. Over a six‐month industrial composting period, undrawn fibers achieved a higher biodegradation extent (64.3% ± 7.8%) than drawn fibers (55.0% ± 8.2%). GPC analysis revealed molecular weight reduction over biodegradation time, with a marked shift toward lower molecular weights by month two. A strong correlation between molecular weight reduction during degradation and melting temperature was observed, indicating progressive molecular degradation. Surface morphology analysis showed peeling in undrawn fibers and crack formation in drawn fibers during biodegradation. These results showcase the influence of molecular orientation and crystallinity on the biodegradation behavior of PLA fibers under industrial composting conditions.