Polymer binder polytetrafluoroethylene

In preparing the electrodes for low-temperature fuel cells that use membrane electrolytes, a polymer binder is essential to bind discrete catalyst particles to form a porous catalyst layer that simultaneously facilitates the transfer of ions, electrons, and reactants/products. Firstly, polytetrafluoroethylene (PTFE) was used... 

Semihydrophobic electrodes are made from an active electrode material (- electrocatalyst), a binder (dissolved polymer), and a hydrophobizing agent (e.g., dispersion of polytetrafluoroethylene PTFE). Upon thorough mixing a slurry is obtained, which is spread onto a material serving as mechanical carrier and in most cases also as current collector. After removal of the solvent a porous layer/sheet is obtained. Upon contact with an aqueous electrolyte solution various interactions are possible [ii] ... 

Tapes. A great variety of tapes find application in electrical equipment. Some tapes contain filler materials in macroscopic form such as glass fibers, mica flakes, and cloth others have finely divided filler particles or no fillers at all. In the heavily filled materials the polymeric binders are present in small fractions, and the major emphasis may be on their adhesive capabilities rather than on their properties as dielectric materials. Most of the polymers used in tapes have already been mentioned in connection with other insulation applications, for example, polyesters, aromatic polyamides, polyimides, and polypropylene. Other polymers frequently used for electrical tapes are vinyls, including poly(vinyl fluoride) these are particularly well suited as conformable tapes. Polytetrafluoroethylene (Teflon TFE) has also been fabricated into tape constructions, frequently in combination with adhesives to provide a bondable material. 

As discussed in Chapter 10, there are various F-containing polymers that can be used as binders. For example, polytetrafluoroethylene (Pl FF) can be used as a water-based dispersion, and P F can be used after dissolution in organic electrolytes. However, to make a dispersion of PTFE, some surfactants are needed, which will produce some side reactions with electrode materials of lithium-ion batteries. Unfortunately, the dispersion is not stable at elevated temperature and after long-term storage. As a result, PVDF is preferred instead of PTFE since the electrochemical stable window of PVDF is also broader than that of other F-containing polymers, and it is very stable with many positive and negative electrode materials. Its reaction with li metal only starts above 200°C, which is above the normal temperature scope for lithium-ion batteries. As shown in... 

---