Influence of the Chain Extender Nature on Adhesives Properties of Polyurethane Dispersions

Several waterborne polyurethane adhesives containing different chain extenders were prepared by using the acetone process. Concretely, the polyurethane dispersions were synthesized by the prepolymer method based on three chain extenders: two diols and one diamine: 1,4-butanediol, 1,6-hexanediol and hydrazine. The adhesive solutions were characterized by flow rheology, pH measurements, particle size, and solids content. The solid adhesive films were characterized by plate-plate rheology, dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The adhesion properties were measured front T-peel test of leather/polyurethane adhesive/SBR rubber joints. As a result, the chosen chain extender influences significantly the polyurethane synthesized properties, especially determines the crystallinity of the polymer, as well as thermal and adhesive properties. Particularly, the molecular weight of the chain extender determines the structure of the synthesized polyurethanes.