Polytetrafluoroethylene wettability

Allan, A. J. G. Wettability and friction of polytetrafluoroethylene film effect of prebonding treatments- J. Polymer Sci. 24, 461—466 (1957). 

For gas filtration, the membrane should be treated to make it hydrophobic if not already inherently so. Membranes made from polytetrafluoroethylene or polypropylene are already nonwetting, and wettable polymers are treated by the manufacturer to render them hydrophobic. If the gas filter is hydrophilic, water condensing on the filter or entrained by the gas will wet the pores and be retained by capillary action unless the differential pressure across the filter exceeds the "bubble-point" pressure. In this case, the filter is "blinded" by water and the flow is restricted considerably. 

Figure 7, Wettability of copolymers of polytetrafluoroethylene and poly-chlorotrifluoroethylene [47]...

NH3 (ammonia) 1. Wettability enhaneement 2. Suppressing of losses of plastifieator 3. Enhaneement of adhesion Aromatic polyamides, wool, polyether, rough cotton fabric Polyvinylchloride (PVC) Polyoxymethylene (acetal), polytetrafluoroethylene (PTFE), polyearbonate (PC), polyaerylate, polyphenyleneoxide... 

CF4, CF4 h O2 1. Enhancement of wettability of plastic surfaces Polyethylene (PE), polyoxymethylene (aeetal), polystyrene (PS), polypropylene (PP), polytetrafluoroethylene (PTFE), polymethylmethacrylate (PMMA), polyimide (PI)... 

This book presents coverage of the dynamics, preparation, application and physico-chemical properties of polymer solutions and colloids. It also covers the adsorption characteristics at and the adhesion properties of polymer surfaces. It is written by 23 contemporary experts within their field. Main headings include Structural ordering in polymer solutions Influence of surface Structure on polymer surface behaviour Advances in preparations and appUcations of polymeric microspheres Latex particle heterogeneity origins, detection, and consequences Electrokinetic behaviour of polymer colloids Interaction of polymer latices with other inorganic colloids Thermodynamic and kinetic aspects of bridging flocculation Metal complexation in polymer systems Adsorption of quaternary ammonium compounds art polymer surfaces Adsorption onto polytetrafluoroethylene from aqueous solutions Adsorption from polymer mixtures at the interface with solids Polymer adsorption at oxide surface Preparation of oxide-coated cellulose fibre The evaluation of acid-base properties of polymer surfaces by wettability measurements. Each chapter is well referenced. 

Adsorption phenomena may also play an important role in fouling and hence it is important to the select an appropriate membrane material. Hydrophobic materials of the type mentioned above have a larger tendency to foul in general, especially in the case of proteins. Furthermore, such hydrophobic materials (e.g. polytetrafluoroethylene) are not wetted by water and no water will flow through the membrane at normal applied pressures. This non-wettability is another disadvantage and such membranes have to be pretreat, for example with alcohol, prior to use with aqueous solutions. 

Polytetrafluoroethylene would withstand the cell conditions but the porous P.T.F.E. made then failed as a diaphragm because of its non-wettability (19). The breakthrough was to be inspired by fuel cell technologists who were then using P.T.F.E. powder (20) to limit the wettability of fuel cell electrodes. 

Figure 4.1 Wettability envelopes of polytetrafluoroethylene and etched PTFE [24].

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