It is common in the hygiene industry to make elastic laminates by bonding elastic strands using an adhesive. The laminate comprises a layer of non-woven, elastic strands, and a polypropylene back sheet. These three components are held together using an adhesive. Many kinds of adhesives are viable, but hot-melt adhesives are typically used and those based on styrenic block copolymers are favored. Of the types of block copolymers available, styrene-isoprene-styrene (SIS) block copolymers are preferred.
An elastic strand bonding adhesive is typically formulated with several co-ingredients. Along with the polymer, it’s common to add a resin, an oil, an antioxidant, and optionally a wax. Moreover, the resin portion of the formula may consist of two different types of resin. One resin typically is soluble in mid-block, and the second resin is typically soluble in the end block. The mid-block resin provides tack and adhesion, while the end-block resin raises the modulus of the adhesive to make the bond stronger.