# 4.1.2 Diffusion Theory

> From: LOCTITE®X Digital Manual for Bonding (https://www.loctitex.com/en/manuals/bonding/4.1.2-diffusion-theory/)

#### 4.1.2 Diffusion Theory

Diffusion theory is applicable for long-chain polymers that are capable of movement. Adhesion is the result of the diffusion of molecules between the adhesive and the surface. Depending on the adhesive’s chemical properties, operational conditions and substrate, the diffusion will vary in depth.

_Figure 75 Diffusion theory of adhesion_

![Figure 75 Diffusion theory of adhesion](/en/manuals/bonding/assets/img/difussion-theory-adhesives-separated-mixed-difused.jpg)