Influence of aging on molecular motion in PBAT-thermoplastic starch blends studied using solid-state NMR

The influence of seven-month aging on molecular motion in blends of biodegradable poly(butylene-adipate-co-terephthalate) (PBAT) and corn starch plasticized with water, urea (U) and/or glycerol (G) was studied using solid-state 1H and 13C NMR spectroscopy. Changes in 1H and 13C NMR spectra due to aging in G-containing blends are explained by starch retrogradation. The increasing number of urea-glycerol interactions in the aged UG-containing blend can be deduced from the 1H NMR spectra. The formation of a crystalline phase was not observed in the U-containing blends. The 13C spin-lattice relaxation times and scanning electron microscopy support this interpretation of the NMR spectra.