In the process of using PTFE Tube, we found that it is difficult to stick polytetrafluoroethylene tube. What are the physical reasons for this phenomenon? Because the surface wettability of PTFE tube is poor and it can not be well bonded, its application range is greatly limited. In order to make the polytetrafluoroethylene pipe more widely used, it is necessary to treat its surface to improve its adhesion and strength.
There are many reasons why PTFE pipes are difficult to bond:
1. The adhesion force on the surface of polytetrafluoroethylene tube is caused by intermolecular forces, including orientation force, induction force and dispersion force. The non-polar surface of polytetrafluoroethylene tube does not have the condition of orientation force and induction force, but can only form weak dispersion force, so its adhesion is very poor.
2. The surface energy of polytetrafluoroethylene tube is low, and the critical surface tension is only 1.85 × 10-2n / m. The forward contact angle (θ d) is 118o, the backward contact angle (θ R) is 91o, and the contact angle (θ) is 104o, which is higher in all materials. The larger the contact angle is, the smaller the wetting degree is. That is to say, the worse the wettability is, the adhesive can not fully wet PTFE, so it can not well adhere to polytetrafluoroethylene pipe.
3. The solubility parameter SP value of polytetrafluoroethylene tube is very small, so the adhesion with other substances is also very small. It can be seen from the above analysis that in order to solve the problem of difficult adhesion of polytetrafluoroethylene pipes, two aspects of surface modification should be generally started to improve their adhesion performance and develop new adhesives.
4. High crystallinity and good chemical stability. The expansion and dissolution of polytetrafluoroethylene tube is more difficult than that of amorphous polymer. When the adhesive is applied on the surface of the PTFE tube, the polymer molecules are difficult to diffuse and entangle with each other, and can not form strong adhesion.
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