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Non-Covalent Cross-Linking for High Performance Adhesives

Matthias Gerst Polymers for Adhesives, BASF SE

A classic industrial goal for pressure sensitive adhesives (PSA), which are lightly crosslinked low Tg acrylate polymers, is to replace solvent borne products (where solvent needs to be evaporated to make the adhesive film) with dispersions in water. Although these water based dispersions are attractive alternatives for environmental reasons, the properties of the adhesive films made upon drying emulsions cannot yet fully match the adhesive properties of the films made from drying solutions.

One intrinsic difference between solvent borne and water borne products is the type of cross-linking and its distribution in the polymer film PSA. Solvent-borne adhesives are crosslinked after they are dried and have a very homogeneous distribution of crosslinks, while waterborne products, because of the bulk polymerization method, tend to be more crosslinked inside each particle and less between them.

It was found that using non-covalent cross-linking in aqueous dispersions can significantly improve the adhesive properties of the dry film relative to fully covalent crosslinking. In the current seminar, selected examples using such “dipole-dipole” and “ionic” crosslinking chemistry will be presented.