Surface activation of polytetrafluoroethylene by bonding of polymeric silicic acid

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Abstract
When porous polytetrafluoroethylene (PTFE) is treated in a silicon tetrahalide atmosphere and then hydrolysed by means of a water jet, it is possible to achieve surface activation of the PTFE with silicic acid. This results in the surface of the PTFE becoming completely wettable, particularly if SiCl4 is used. This paper provides an account of the physical and chemical investigation into the surface of the activated system. Measurement of the contact angles (with water) and determination of the silanol groups provide evidence of the surface activity. ESCA experiments show that concentrations of silicic acid above 14% w/w result in almost complete coverage of the PTFE surface. Using the BET method to measure the specific surface area, it can be seen that this is not simply a result of adding the areas of the two components, PTFE and silicic acid. © 1993 John Wiley & Sons, Inc.