Modified Starches in aqueous and plastisol coating

Abstract: The interest for coatings containing renewable materials has enlarged in the last decade. Materials from the nature are investigated like starch, cellulose derivatives, protein (gelatin), chitosane by many. In this study potato starch has been used.

The objectives of this work were to a) investigate the film properties of modified regular potato starch and modified high amylos potato starch with different small molecules tested as possible plasticizers, b) Investigate whether starch and poly(vinyl alcohol) (PVAL) could be compatible in a powder for plastisol coating and c) investigate plastisol coatings based on starch and PVAL. The main part of the work were addressed to barrier properties such as water vapour permeability, glass transition temperature, swelling properties, mechanical (tensile) properties and preparation of plastisol films.

The water vapour permeance ( ) was significantly lower for modified high amylose potato starch than for the corresponding starches based on regular potato starch, both for free films and for coated paper. The different molecules investigated as plasticizer did not result in any significant change in of the films or coated paper. of free film based of hydrophobically modified starch was higher than for hydroxypropylated starch films.

Spray dried powders made from solutions of starch and PVAL were used for plastisol coatings. It was demonstrated that plastisols based on a mixture of incompatible polymers could be produced, e.g. as a mixture of starch/PVAL powder and poly(alkyl methakrylate) powder dispersed in suitable of liquid plasticizers.

SEM micrographs of the plastisol film reveled that the coating may contain a lot of voids originating from uptake of air during dispersion. Dispersion in vacuum reduced the amount of void in the coating layers.