GAS AND WATER-VAPOR TRANSPORT THROUGH POLYMER-BASED PROTECTIVE MATERIALS FOR STONE MONUMENTS - FLUORINATED POLYURETHANES

Gas and water vapour transport properties are of main concern in evalu ating the suitability of a polymeric material to be used as a protecti ve for monuments. In this work, oxygen, carbon dioxide and water vapou r transport properties have been investigated for a new class of polym ers, fluorinated polyurethanes, which have been recently proposed as a protective material for stone monuments. They consist of block copoly mers made of hydrophilic polyurethane and hydrophobic perfluoropolyeth er blocks. The properties of these copolymers are expected to be stron gly related to the relative amounts of these two blocks. In this inves tigation, three different types of fluorinated polyurethane copolymers were considered in order to assess the effect of chemical composition and physical morphology on mass transport properties. In particular, sorption and permeation experiments were performed at 30 degrees C to evaluate permeabilities, diffusivities and solubilities. In fact, the analysis of the effect of chemical composition on transport properties can give useful selection criteria to tailor the material to be used as a protective.