Tetrafluoroethylene polymer dispersions

A coating dispersion which imparts resistance to attack by acidic flue gas to glass fabric coated with said dispersion, consisting essentially of

• (a) water,
• (b) 5-65% by weight tetrafluoroethylene polymer, said weight based on weight of water and polymer, said polymer being of film-forming molecular weight,
• (c) 2-60% by weight of a polyhydrolyzable silane of the formula
• R.sub.1 Si--(OR).sub.3
• wherein R is lower alkyl, preferably alkyl of 1-3 carbon atoms, and R.sub.1 is phenyl or substituted lower alkyl, preferably of 1-3 carbon atoms, in which the substituents are selected from halogen, quaternary ammonium, or --NR'R" in which R' and R" are each H, lower alkyl, lower alkoxyalkyl, amino lower alkyl, hydroxyl lower alkyl, or substituted amino lower alkyl, said weight based on weight of tetrafluoroethylene polymer,
• (d) 1-20% by weight of a hydrocarbyl siloxane, said weight based on weight of tetrafluoroethylene polymer,
• (e) 1-20% by weight of a polymer of a fluorinated ester of an acrylic acid, said weight based on weight of tetrafluoroethylene polymer.