Polytetrafluoroethylene pore layers

J. Xu et al. [283] have shown that immobilization of enzymes can be done using a specially designed composite membrane with a porous hydrophobic layer and a hydrophilic ultrafiltration layer. A polytetrafluoroethylene (PTFE) membrane with micrometer pores as an excellent hydrophobic support for immobilization was employed for the porous hydrophobic layer, and a biocompatible material of polyvinyl alcohol (PVA) which provided a favourable environment to retain the lipase activity was used to prepare the hydrophilic... 

As illustrated in Figure 1.2, one side of the cathode GDL facing to the catalyst layer is generally provided with a micro-porous layer (MPL) of polytetrafluoroethylene (PTFE) with hydrophobic characteristics. It has much smaller pores and a much smoother surface than the GDL. The MPL plays an important role in the water management of polymer electrolyte fuel cells however, details of the meehanism that works to suppress water flooding are not fully understood. Questions still remain about whether the water transfer in the MPL occurs in the liquid or vapor phase. 

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