There are several reasons why PTFE is difficult to stick: First, the surface energy is low, and the critical surface tension is generally only 3 1 ~ 34 dynes/cm. Because of the low surface energy and large contact angle, the adhesive can not fully wet PTFE, so it can not bond PTFE well; Secondly, it has high crystallinity and good chemical stability. The swelling and dissolution of PTFE are more difficult than amorphous polymers. When the adhesive is coated on the surface of PTFE, it is difficult for polymer molecular chains to diffuse and entangle with each other in the chain domain, and strong adhesion cannot be formed. Thirdly, PTFE has a highly symmetrical structure and is also a nonpolar polymer. The adsorption of adhesive on PTFE surface is caused by van der Waals force (intermolecular force), which includes orientation force, induction force and dispersion force. For the surface of nonpolar polymer materials, there is no condition for forming orientation force and induction force, but only weak dispersion force, so the adhesion performance is poor.
Based on the above understanding, generally speaking, in order to solve the problem of PTFE adhesion, people mainly start with surface modification and synthesis of new adhesives. Chemical treatment of sodium-naphthalene complex
High temperature melting method
Radiation grafting method
Low temperature plasma technology
Laser treatment method (belonging to additive manufacturing method, the material is modified first, then activated by micro aviation laser, and electroless copper plating)