Simplification of interior latex paint using biopolymer to replace rheological additives and calcium carbonate extender

An interior latex paint was simplified by using soy protein (SP) to replace hydroxyl ethyl cellulose (HEC) thickener, rheological modifier, and calcium carbonate. The rheological and solid-state properties of the latex paints were investigated. The SP paint had similar viscosity characteristics as that of the HEC paint for practical applications. Strain sweep experiments show that the SP paint has less antisettling characteristic compared to the HEC paint. The dispersion structure of the SP paint is less flexible than that of the HEC paint, but has similar strength at large strain. The values of storage moduli at very low frequency indicate both the HEC and SP paints have a long-term stability. The SP paint had a slower recovery rate after high shear compared to the HEC paint, indicating that the SP paint will have better leveling, but slightly more sagging during application. The dried SP paint had a greater storage modulus than the HEC paint under ambient temperature. The SP paint also had a higher glass transition temperature, indicating a greater ability of protein to immobilize polymer latex. The magnitude of G′ shows that the SP paint is more rigid than the HEC paint. The hardness test shows that the SP paint had a greater hardness than the HEC paint.