Appraisal of epsilon-Caprolactam and Trimellitic Anhydride Potential as Novel Chain Extenders for Poly(lactic acid)

The potential of epsilon-caprolactam (CAP) and trimellitic anhydride (TMA) compounds as novel chain extenders for poly(lactic acid) (PLA) has been assessed; the amounts of 0.01, 0.025, and 0.05 wt% each additive have been added. The chain extension was evidenced by the increase in PLA/CAP and PLA/TMA viscosities in mixing torque measurements and by infrared spectroscopy. PLA reaction with CAP and TMA has also been confirmed from contact angle and surface free energy studies, which have shown that the increase in TMA amount decreased the hydrophilicity of PLA due to the decreased concentration of terminal surface hydroxyl groups. However, the addition of CAP accentuated the PLA hydrophilicity as indicated by the increase in the polar component of the surface energy. On the other hand, the glass transition temperature of PLA/TMA and PLA/CAP decreased as a result of a local plasticizing effect, which favored the chain mobility and the crystallization of PLA due to the concomitant nucleating effect of the chain extenders moieties too. Furthermore, the higher molecular weight of PLA/CAP and PLA/TMA was responsible for their increased thermal stability and higher impact strength with respect to PLA. POLYM. ENG. SCI., 2020. (c) 2020 Society of Plastics Engineers