ABSTRACT
There are several kinds of PSA. such as mbber-based PSA, hot-melt PSA. acrylic PSA. silicone-based PSA. and others. Rubber-based PSA includes natural rubber and synthetic rubber. but the former is much more used than the latter. Because rubber alone is not sticky enough as PSA. we have to blend some tackifier resins with the rubber. II must be pointed out thai solvents must be used in the manufacturing process of the rubberbased PSA. Polymers mostly used in ho!-meli PSA are SIS. SBS (block co-polymers of styrene-isoprene-styrene or styrene-butadiene-styrene) and SEBS (hycliogcnated SBS). Tackifier resins must be blended with these block co-polymers. too. No solvent is needed for these co-polymers either in the blending process or in the coating process. This is why these systems are called hot-melt PSA. and this is a great advantage which this type of PSA has. There are many kinds of acrylic PSA because they are produced by combining various acrylic co-monomers (acrylates and/or methacrylates). some of which are made by solution polymerization and others by emulsion polymerization. Everybody thinks that any industrial products must be environmentally friendly. and therefore in the field of PSA. people have tried to reduce solvent-based materials as much as possible, which is the reason why the production of water-based (emulsion) PSA is gradually increasing. Tackifier resins used not to be blended with acrylic co-polymers because it is quite easy to make polymers with any T~ and modulus hy controlling the kind and composition of co-monomers. Recently. however. there have been many cases where tackifier resins have been introduced in this type of PSA for the purpose of modifying the adhesion properties against polyolefins. Silicone-based PSA is a blend of silicone rubbers and silicone resins. Because surface tension of this series of polymers is low. they easily stick to Teflon. polyimides, silicone mbbers. etc .. which are known to be inert to most adhesives. At the same time. this type of PSA is resistant to heat. chemicals. weathering. etc.
