In the application of fabric coatings, waterborne polyurethane not only plays the role of an adhesive but also carries specific functional characteristics. The full play of its performance depends on whether the coating can closely adhere to the substrate. So, where exactly does the adhesion force between the waterborne polyurethane coating and the substrate come from? What methods are there to enhance this adhesive force and make the fabric substrate bond more firmly?

From the perspective of academic theory, the early bonding theory tended to be the mechanical action theory, suggesting that the adhesive force mainly relied on the micro-pore anchoring effect and the physical interlocking caused by surface roughness. Accordingly, the surface characteristics of the adhesive and the substrate have become the key factors determining the adhesion strength. Subsequently, the adsorption theory further deepened our understanding of the bonding mechanism, regarding it as a special interface phenomenon. Various polar groups in the polyurethane molecular chain, such as carbamate bonds, hydroxyl groups, ether-oxygen bonds, etc., constitute the core elements of the cohesive force of the adhesive by forming dispersion forces. In addition, the diffusion theory emphasizes the mutual permeability between the adhesive and the adherend. It vividly depicts the viscous characteristics of polymers with a "crawler" model, indicating that highly branched polymers exhibit more significant advantages in bonding performance compared to linear polymers.

Comprehensive classical theory above, we can extract the following key strategies: improve coating adhesion and fabric of the fabric surface appropriately pretreatment, to increase its wettability; Adjust the polarity of waterborne polyurethane molecules to promote stronger intermolecular interactions; And increase the branching degree of molecules, taking advantage of the spatial structure of polymer chains to further enhance the adhesion effect. These measures together constitute an effective way to optimize the bonding strength between the coating and the fabric.