Study on the phase separation of plasticised starch/poly(vinyl alcohol) blends

The phase separation and the intermolecular interactions of a series of extruded plasticised starch (PlS)/poly(vinyl alcohol) (PVOH) blends with various starch to PVOH ratios has been studied. Investigation on their thermo-mechanical behaviour indicated the existence of two phases: the low temperature transition was attributed to the PVOH-rich phase and the high temperature transition was assigned to the PlS-rich phase. An increase in the α -relaxation temperature of the PVOH-rich phase with the introduction of starch in the system suggested a small degree of miscibility. The water was also shown to partition unequally between both phases. High resolution solid-state NMR revealed slight variations between the different PlS/PVOH compositions, which could be related to either interactions between PVOH and starch chains or difference in short-range ordering (e.g. single helices). Proton spin-lattice relaxation time measurements confirmed the phase separation within the blend occurring, however, with a small degree of inter-mixing.