Unsaturated polyester resins modified with perfluoropolyethers

Telechelic macromers based on hydroxyterminated perfluoropolyethers (HO-R-H-PFPE-R-H-OH) with different molecular weights were used for the preparation of fluorine-containing unsaturated polyester resins (FUPR). The products resulting from the reaction of the monomers usually employed for the preparation of unsaturated polyesters with HO-R-H-PFPE-R-H-OH were in any case milky liquids. The degree of reaction of the hydroxyl terminal groups of HO-R-H-PFPE-R-H-OH was monitored by H-1-NMR analysis on the fractions collected after sedimentation experiments; amount and composition of the sediment and sedimentation rate were found dependent on both the molecular weight of fluorinated macromer and the method used for polyesterification. The molecular weight of HO-R-H-PFPE-R-H-OH and the reaction conditions had also a strong influence on the final morphology of crosslinked polymers. A very poor interphase adhesion was observed when unreacted HO-R-H-PFPE-R-H-OH was blended with the unsaturated polyester. On the contrary, when the fluorinated macromer was allowed to react during polyesterification, the adhesion of the fluorine-rich dispersed phase to the unsaturated polyester matrix was good for low molecular weight HO-R-H-PFPE-R-H-OH and when the fluorinated prepolymer had been modified by a previous reaction with chlorendic anhydride, but it was poor, as for unreacted macromers, for high molecular weight HO-R-H-PFPE-R-H-OHs. FUPRs prepared using a low molecular weight HO-R-H-PFPE-R-H-OH exhibited a significant improvement of the flexural strength even at very low level of addition (3% by wt).