Analysis of the reason why PTFE is difficult to bond

Polytetrafluoroethylene (PTFE) has excellent chemical stability, electrical insulation, self-lubricating, non-flammability, aging resistance, high and low temperature adaptability and chemical corrosion resistance, and has high mechanical properties. A dual-purpose engineering plastic with excellent comprehensive performance. However, due to the poor wetting properties of the PTFE surface, it cannot be bonded well, thus greatly limiting its range of use. In order to make PTFE more widely used, it is necessary to treat the surface to improve the bonding performance and improve the bonding strength.
The reason why PTFE is difficult to bond is that PTFE is difficult to bond. From the analysis of its physical properties, there are mainly the following reasons:
(1) The surface energy is low, and the critical surface tension is generally only 1.85×10-2N/m. The advancing contact angle (θd) of PTFE is 118°, the receding contact angle (θr) is 91°, and the contact angle (θ) is 104°. , which is large in all materials, and the larger the contact angle, the smaller the degree of wetting, that is, the worse the wettability, the adhesive does not sufficiently wet the PTFE, and thus does not adhere well to the PTFE;
(2) The crystallinity is large and the chemical stability is good. The swelling and dissolution of PTFE are more difficult than the non-crystalline polymer. It is difficult for the adhesive to be coated on the PTFE surface to interdiffusion and entanglement of the polymer molecular chains. Adhesion
(3) PTFE structure is highly symmetrical and belongs to non-polar polymer. The adsorption of adhesive on the surface of PTFE is caused by the interaction between molecules, such as orientation force, inducing force and dispersive force. PTFE non-polar The surface does not have the conditions for forming the orientation force and the inducing force, and can only form a weak dispersion force, and thus the adhesion property is poor;
(4) The solubility parameter of PTFE micropowder is small, so the adhesion to other substances is also small. Therefore, in order to solve the problem that PTFE is difficult to bond, it is generally necessary to start from surface modification to improve its bonding performance and to develop a new adhesive.