NEW FLUORINATED ACRYLIC POLYMERS FOR IMPROVING WEATHERABILITY OF BUILDING STONE MATERIALS

Acrylic polymers are widely used for their suitability to be shaped in different molecular structures. However, while very appropriate for m any applications, these materials are characterized by a limited outdo or stability. In order to improve this last characteristic while maint aining the simple and flexible synthetic route, a study was performed based on the preparation of fluorinated polymers from acrylic monomers where several I-I-atoms in different positions were replaced with F-a toms. The structure design was aimed to optimize (e.g. minimize) the f luorine content of the final material while obtaining improved chemica l and photochemical stability, good filmability and limited permeabili ty to condensed water. The preparation of polymers of methacrylates de rived from partially fluorinated alcohol by free radical mechanism is described. The fluorine content and distribution in the macromolecules is modulated by selecting different monomers and by copolymerization with nonfluorinated acrylates or vinylethers. The selection of the com onomers and their relative content in the polymer allows to control th e glass transition temperature and the filmability as well as the prot ection efficiency of the coating. Polymers derived from more complex m onomers such as alpha-trifluoromethyl-methylacrylate are also describe d. The suitability of these new materials for protective coating of st ones is tested by evaluating their stability to different chemical and physical agents and their selective permeability to water vapour vs. condensed water. (C) 1997 Elsevier Science S.A.