Key determinants of hydrolytic stability of PLA/PBS blend fibers: The role of aromatic sulfonate derivative and carbodiimide

The hydrolytic stability of poly (lactic acid) (PLA)/poly (butylene succinate) (PBS) blend fibers was systematically investigated by incorporating an aromatic sulfonate derivative (nucleating agent, N) and carbodiimide (anti-hydrolysis agent, Anti-H). Neat PLA/PBS blend fibers (3 wt% PBS) retained only ∼53.9% of their initial tensile strength after hydrolysis, whereas fibers containing both the nucleating agent (N) and anti-hydrolysis agent (Anti-H) preserved up to 97.2% of their initial strength. DSC and 2D-WAXD analyses showed that N selectively promoted the development and retention of the PLA (203) crystalline reflection, accompanied by enhanced crystallinity and molecular orientation along the PLA (200)/(110) planes. 1D-WAXD demonstrated that the intensity ratio of PLA (203) to PLA (200)/(110) reflections correlates with hydrolytic retention following a Boltzmann-type sigmoidal relationship, with a critical threshold x 0 ≈ 0.227. Time-dependent FTIR and XPS analyses demonstrated that Anti-H effectively capped the terminal –COOH groups, suppressing autocatalytic chain scission and providing complementary chemical stabilization. Hydrolysis decreased –COOH and –C O functional groups, while the H-bonded –OH increased. Correlation analysis indicated that changes in –C O most strongly influenced tensile retention. SEM observations revealed smooth fiber surfaces with no discernible defects or phase separation, as well as minimal morphological and compositional changes in the optimized fibers after hydrolysis. Collectively, these results demonstrate that the exceptional hydrolytic durability of PLA/PBS blend fibers arises from the synergistic interplay of selective (203) crystalline coherence, preserved molecular orientation, and chemical end-group stabilization.