A HOT-MELT PRESSURE-SENSITIVE ADHESIVE BASED ON STYRENE-BUTADIENE-STYRENE RUBBER - THE EFFECT OF ADHESIVE COMPOSITION ON THE PROPERTIES

Hot-melt pressure-sensitive adhesives based on styrene-butadiene block copolymers with aliphatic and aromatic tackifying resins and plastify ing oils have been analyzed. The importance of the resin structure in the compatibility with the block copolymer and the influence of the di fferent paraffinic-naphthenic character of the oil in PSA performance have been shown. Ternary systems with a fixed polymer content (30%) an d with variable resin and oil contents show a good miscibility over th e whole range of compositions, and only one glass transition temperatu re was found in each composition. The relationship between chemical co mposition and bulk performance are expressed in terms of the viscoelas tic behavior of the adhesives, measured by DMTA. It has been shown tha t at a given resin content there is a minimum on tan delta peak vs. te mperature, the melt viscosities present a plateau region and the tack strength shows a maximum. An important conclusion is that phase separa tion is not a requirement for maximum tack; some restricted miscibilit y is enough, present in a few microdomains of the blend. (C) 1996 John Wiley & Sons, Inc.