Effect of crosslinker on thickener properties of acrylic acid-cassava starch graft copolymer for water-based screen print quality on plastic sheets

Abstract

Cassava starch grafted copolymers as a thickener for cast polypropylene film was carried out under a grafting copolymerization of acrylic acid onto cassava starch via a hydrogen peroxide-ascorbic acid initiation method. The effect of crosslinking agent concentration on water absorption capacity and rheological properties of the cassava starch grafted acrylic acid thickener was investigated. The cassava starch graft copolymer thickener was used in the preparation of two water-based screen inks. Non-silicone and silicone defoamers were used as an ingredient in the inks I and II, respectively. The properties of the two ink, namely, rheological properties, dispersion, and surface tension were examined. Cast polypropylene film was treated by corona treatment. The effects of treatment energy and corona ageing of the film on surface energy of the treated plastic films were studied. The two inks were printed on the corona treated pla.stic films by screen printing. The dot gain (or dot loss), tone reproduction, dot characteristics, print contrast, gloss and adhesion of printed plastic films were evaluated. The results obtained were evaluated statistically in order to obtain the optimum ink formulation for toe plastic film printing. The suitable crosslinking concentration used in toe synthesis of toe cassava starch graft copolymer thickener was 0.5 wt% based on toe monomer concentration because of toe product so obtained gave the minimum water absorption capacity and stable ink properties. The concentrations of toe crosslinked thickener governed the viscosity and the rheology of the inks having pseudoplastic behavior. Besides, toe rheological properties, pigment dispersion, and surface tension of toe two inks were insignificantly different. The qualities of toe plastic film printed by toe ink with the non-silicone defoamer slightly better than toe another one. This research elucidates toe relationship of corona treatment level, the surface energy of polypropylene films, and print qualities as well as toe suitability of screen printing ink containing cassava starch-acrylic acid thickener/crosslinking agent for print quality.