Styrene-butadiene (SB) latex is a common type of emulsion polymer used in a number of industrial and commercial applications. Because it’s composed of two different types of monomers, styrene and butadiene, SB latex is classified as a copolymer. Styrene is derived from reacting benzene and ethylene, and butadiene is a byproduct of ethylene production.
Styrene-butadiene latex differs from both of its monomers and from natural latex, which is made from the sap of Hevea brasiliensis trees (aka rubber trees). It also differs from another manufactured compound, styrene-butadiene rubber (SBR), which shares a similar name but offers a different set of properties.
Manufacturing of Styrene-Butadiene Latex
Styrene-butadiene latex is manufactured through the polymer emulsion process. This involves adding the monomers to water along with surfactants, initiators, carboxylic acids and specialty monomers. Initiators trigger the chain-reaction polymerization that joins the styrene monomer to the butadiene monomer. Butadiene itself is the union of two vinyl groups, so it is capable of reacting with four other monomer units. As a result, it can extend the growth of the polymer chain but is also able to link one polymer chain to another. This is called crosslinking, and it’s vitally important to styrene-butadiene chemistry. The crosslinked part of the polymer doesn’t dissolve in suitable solvents but swells to form a gel-like matrix. Most commercial styrene-butadiene polymers are heavily crosslinked, so they have a high gel content, a critical property that has a strong influence on the performance of the latex, allowing for more toughness, strength, and elasticity than other materials. Up next, we’ll explore how these properties can be put to good use across a number of industries and applications.
Commercial Uses
Styrene-butadiene latex offers a number of benefits, including filler acceptance and tensile/elongation balance. The flexibility of this copolymer allows for a near-infinite number of mixtures that result in high water resistance and adhesion to challenging substrates. These qualities of SB latex make this synthetic essential to an ever-widening group of markets. SB latex formulations are commonly used as a coating in paper products, such as magazines, flyers and catalogs, to achieve high gloss, good printability, and resistance to oil and water. SB latex enhances a pigment’s binding power and, in turn, makes paper smoother, stiffer, brighter and more water resistant. As an added bonus, SB latex is much less expensive than alternative coatings. SB latex is a popular choice for adhesives in certain industries like flooring. For example, the polymer is found as the back coating of textiles like tufted carpets. The back coating provides water resistance and holds the tufts in place, which improves stability and reduces fraying at the edge. These are just some of the uses of styrene-butadiene latex. In reality, it provides infinite possibilities, as evidenced by its utility for running tracks, textile coatings, pressure sensitive adhesives, and nonwoven fabrics. Styrene butadiene polymer emulsions are also a key component in liquid-applied membranes, and low MVTR barrier coatings for food packaging.
Post time: Aug-10-2022