Improved water resistance of starch films

A new work describes the water resistance enhancement of the interface between starch films and acrylated epoxidised soybean oil coating.

Maize is the world's dominant source of starch. Image source: ulleo - Pixabay (symbol image).

Starch-based materials are a promising biobased polymer for packaging applications. To improve the water resistance of starch films, composite systems consisting of hydrophobic acrylated epoxidised soybean oil (AESO) coating and oxidised starch were prepared. To enhance the interfacial bonding between the starch film and AESO coating (AC), surface modification of oxidised starch with polyethyleneimine (PEI) was carried out. PEI modified AC coated oxidised starch films demonstrated significantly reduced water adsorption at the exposed cross-section, while only marginal improvement was observed when unoxidised starch AC coated with PEI treatment was used.

650% improvement of bonding strength

Lap shear experiments demonstrated that the surface treatment of PEI on oxidised starch resulted in more than 650% improvement of bonding strength with AESO coating compared to untreated oxidised starch. This improvement of interface adhesion and water resistance is due to the new interface created through the formation of ionic bonds between PEI and oxidised starch, as well as the chemical bonds between the hydrophobic AESO and PEI molecules.

The study has been published in Progress in Organic Coatings, Volume 163, February 2022.

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