Sulphonated poly(ethylene terephthalate)/poly(3-hydroxy butyrate) blends: Miscibility, thermal behavior, and specific interactions

Abstract

PETs/PHB blends with different compositions were produced by "casting" method. The blends were investigated by TGA, DSC, 1H and 13C NMR and FTIR. Phase separation occurred during blend preparation. PETs and PHB were present in both formed phases. The phases presented different thermal stabilities unrelated to phase component concentration changes. The miscibility study by DSC showed that PHB-phase rich blends are immiscible, whereas the PETs-rich phase blends are miscible. The 1H NMR spectra of the miscible blends exhibited a peak close to the PHB methylene signal, which is in accordance with the interaction between the PETs SO3- groups and the PHB carbonyl groups. This interaction result in a shift of the PHB carbonyl group absorption band in the FTIR spectra and a variation in the chemical shift of the PHB carbonyl group resonance peak in solid state 13C NMR. No specific interaction was observed for the immiscible blends.