ABSTRACT
Styrene-butadiene (SB) polymers are used in coatings formulations primarily to improve coating strength, printability, gloss, pigment and fiber binding, and substrate bond strength. The styrene-butadiene polymers are produced primarily by emulsion polymerization to form a latex. A latex is a dispersion of finely divided spherical particles of polymer in water. The monomer ratios of styrene and butadiene can be adjusted to give the desired amount of flexibility or stiffness. Polystyrene latex contains hard polymer particles that will not form a continuous film upon drying at room temperature. Polybutadiene latex contains very soft, gummy polymer particles that will produce a weak, sticky film when dried. By copolymerization of styrene and butadiene monomers and adjustment of the monomer ratios, it is possible to obtain a copolymer with a wide range of intermediate properties. Thus, a copolymer latex with a high styrene content will produce a very tough, durable film but will not have the flexibility and adhesive performance of a latex with a high butadiene content.
