Hydrolytic degradation of poly(ethylene terephthalate) copolymers containing nitrated units

摘要

The hydrolytic degradation at 80℃ of a series of poly(ethylene terephthalate) (PET) copolymers containing 5-nitroisophthalic (PETNI) and nitroterephthalic (PETNT) units is described. The degradation process was followed by weighting, viscometry, differential scanning calorimetry (DSC), and nuclear magnetic resonance (NMR) spectroscopy. The nitrated copolyesters degraded faster than semicrystalline and amorphous PET, and the degradation rate increased with the content of nitrated units. DSC measurements showed that the melting temperature of the semicrystalline samples increased slightly upon hydrolytic degradation, whereas the degree of crystallinity remained essentially unchanged. NMR spectroscopy revealed that hydrolysis occurred preferentially by cleavage of the ester groups of the nitrated units, and that most of the degradation products remained in the degraded polymer samples.