Styrene block copolymers (SBCs) offer cohesion, strength, and heat resistance for both pressures sensitive adhesives (PSAs) and non-pressure sensitive adhesives. The styrene phase forms a physically crosslinked network in the adhesive at room temperature. Crosslinking via UV or EB radiation will provide even greater heat resistance.
Of the SBCs, styrene isoprene styrene (SIS) is most often used in hot melt PSAs. SIS polymers are generally preferred over styrene-butadiene-styrene (SBS) polymers for hot melt adhesives because the SIS polymers provide a higher level of tack and are less likely to form gels during processing.
RESULTING PROPERTIES
A typical general purpose styrene isoprene styrene pressure sensitive hot melt adhesive is provided above. It can be crosslinked by the addition of a multifunctional coupling agent and UV initiator. It can be used for bonding low energy surfaces such as plastic films. It has good tack and peel strength, and good temperature resistance for a styrene isoprene styrene.
