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Edible films from the blending hydroxypropyl methylcellulose (HPMC) with hydroxypropyl starch (HPS) have been developed. This work focuses on the relationship between morphologies and mechanical properties of such systems. To aid understanding of blend morphology, a new technique used to identify the two phases through dying of the HPS by iodine has been developed, which provided a simple and convenient way to clearly distinguish between HPMC and HPS phases. It was found that the blend system is immiscible and there is phase transition point depending on blending ratio and solution concentration. The lower transparency point of the blend and phase transition reign of HPMC from continuous phase to separated phase correspond with the variation of tensile modulus. The modulus and elongation decreased with increased solution concentration, which is correlatable with the morphologies present, where it was found that the HPMC gradually changed from a continuous phase to a distinct phase. [ABSTRACT FROM AUTHOR]

Highlights: [•] Hydroxypropylene grafted on both cellulose and starch improved their compatibility. [•] PEG acted as both a plasticizer and a compatibilizer for the blends. [•] Viscosity of starch at lower temperature improved viscosity balance of the system. [ABSTRACT FROM AUTHOR]