Regulation of fine structure of different types of natural waxes by octenyl succinate starch in starch bioplastics

Abstract

This work conducted a comparative study on the ability of octenyl succinate starch to regulate the fine structure and physicochemical properties of starch-based plastics containing different types (beeswax, candelilla wax, carnauba wax) and contents of waxes. All the waxes increased the apparent viscosity and storage modulus of the film-forming solution, and obstructed the establishment of hydrogen bond within the film matrix. The limited emulsifying capacity of octenyl succinate starch resulted in different distributions of the three waxes in the matrices, thereby forming different films' microstructures. Carnauba wax negatively affected the hydrophobicity, barrier and mechanical properties of the films due to its poor compatibility with the starches. In contrast, the addition of beeswax and candelilla wax effectively improved the hydrophobicity and moisture barrier, especially for some appropriate wax heterostructures presented in the matrices. Results suggested that octenyl succinate starch could be well emulsified and compatible with beeswax (5%–15% w/w content) to regulate the fine structure to achieve lower water sensibility of starch bioplastics.