Poly(acrylic acid) grafted soy carbohydrate as thickener for waterborne paints

Abstract

Thickeners are widely used to change rheological properties of latex paints. Soy carbohydrate is an abundant, but a rarely utilized agricultural by-product. The grafting of poly(acrylic acid) onto soy carbohydrate particles forms gel particles that can change rheological properties of latex paints. The grafting polymerization of acrylic acid onto carbohydrate particles using ammonium cerium (IV) nitrate as initiator increased the particle size and viscosity of the aqueous particle dispersion. The viscosity increased with the increased amount of grafted poly(acrylic acid). Strain and frequency dependent moduli show a difference in dispersion-properties between the grafted soy carbohydrate and hydroxyl ethyl cellulose. The latex paint with poly(acrylic acid) grafted soy carbohydrate shows similar viscosity at low shear rate region and lower viscosity at higher shear rates when compared to the latex paint with hydroxyl ethyl cellulose. High-shear-recovery measurements of the latex paints predict sagging properties that are consistent with the ASTM sagging tests.