Design Rules for Microgel-Supported Adhesives

The ability of carboxylated PNIPAM microgels bearing adsorbed PVAm to increase the strength of wet paper and wet cellulose film laminates was measured as a function of the microgel diameter, cross-linking degree, PVAm molecular weight, and roughness of the cellulose substrates. The experimental results and simulations from a model led to the following design rules: (1) For low microgel dosages, small microgels are better because they cover more surface; however, very small gels can get buried in pores. (2) For high microgel dosages, larger gels are better because a saturated monolayer of adsorbed large gels puts more adhesive in the joints. (3) Adhesion increases with decreasing microgel modulus (cross-linking). (4) Adhesion is not sensitive to the molecular weight of the reactive PVAm microgel coating polymer.