胶粘剂/胶黏剂为什么能粘接的胶接理论之扩散理论

胶接理论之扩散理论

扩散理论认为，高分子材料之间的粘接是由于胶黏剂与被粘物表面分子或链段彼此之间处于不停的热运动引起的相互扩散作用，使胶黏剂与被粘物之间的界面逐步消失，变成一个过渡区，最后在过渡区形成相互穿透的交织的牢固结合，胶接接头的强度随时间的延长而增至最大胶接强度。如果胶黏剂是以溶剂的形式涂覆到被粘物表面，而被粘物表面又能在此溶剂中溶胀或溶解，则彼此间的扩散作用更为显著，其胶接强度就越高。因为胶黏剂和被粘物间的相互扩散是产生胶接力的主要因素，胶接强度与它们的相容性有关。

因此扩散理论强调两点：一是胶黏剂的大分子与被胶接材料的表面要相容，即溶度参相近；二是强调扩散。这样才能形成良好的过渡区的网络结构，获得更好的胶接强度。

但是，扩散理论对不同聚合物材料之间的粘接作用还不能作完满的解释，对聚合物材料与金属、陶瓷、玻璃等材料之间的粘接几乎无法解释。

Diffusion theory of bonding theory

According to the diffusion theory, the adhesion between polymer materials is due to the mutual diffusion caused by the continuous thermal movement between the surface molecules or chain segments of the adhesive and the adherend, which makes the interface between the adhesive and the adherend disappear gradually and become a transition zone, and finally form a solid and interwoven bond in the transition zone, The strength of the adhesive joint increases to the maximum with time. If the adhesive is coated on the surface of the adherent in the form of solvent, and the surface of the adherent can swell or dissolve in this solvent, the diffusion effect between them is more significant, and the bonding strength is higher. Because the diffusion between the adhesive and the adherent is the main factor of adhesive force, the adhesive strength is related to their compatibility.

Therefore, the diffusion theory emphasizes two points: one is that the macromolecules of the adhesive should be compatible with the surface of the bonded material, that is, the solubility parameters are similar; Second, emphasis on diffusion. Only in this way can a good network structure of transition zone be formed and better bonding strength be obtained.

However, the diffusion theory can not fully explain the adhesion between different polymer materials, and can hardly explain the adhesion between polymer materials and metal, ceramic, glass and other materials.