Enhanced thermal stability of poly(lactide)s in the melt by enantiomeric polymer blending

Abstract Poly( l -lactide) (i.e. poly( l -lactic acid) (PLLA)) and poly( d -lactide) (i.e. poly( d -lactic acid) (PDLA)) and their equimolar enantiomeric blend (PLLA/PDLA) films were prepared and the effects of enantiomeric polymer blending on the thermal stability and degradation of the films were investigated isothermally and non-isothermally under nitrogen gas using thermogravimetry (TG). The enantiomeric polymer blending was found to successfully enhance the thermal stability of the PLLA/PDLA film compared with those of the pure PLLA and PDLA films. The activation energies for thermal degradation (Δ E td ) were evaluated at different weight loss values from TG data using the procedure recommended by MacCallum et al. The Δ E td values of the PLLA/PDLA, PLLA, and PDLA films were in the range of 205–297, 77–132, and 155–242 kJ mol −1 when they were evaluated at weight loss values of 25–90% and the Δ E td value of the PLLA/PDLA film was higher by 82–110 kJ mol −1 than the averaged Δ E td value of the PLLA and PDLA films. The mechanism for the enhanced thermal stability of the PLLA/PDLA film is discussed.

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