Antigraffiti polyurethane coating containing fluorocarbon side chains grafted polymethylsiloxane

摘要

The novel polymethylsiloxane grafted by fluorocarbon side chains was synthesized via hydrosi-lylation reaction of polymethylhydrosiloxane (PMHS) with 2,2,3,4,4,4-hexafluorobutyl acrylate (HFBA) in the presence of Karstedt's catalyst. The reaction factors of reaction temperature, reaction time, catalyst dosage, solvent dosage, and molar ratio of the reac-tants were investigated through orthogonal experiments. Under optimal conditions, the grafting ratio of HFBA to PMHS reached 91.6%. The structure of the grafted polymer was characterized by FTIR and ~1H NMR spectra. The synthesized polymer was incorporated into two-component polyurethane coating formulations as an additive to prepare antigraffiti coatings. After curing, the contact angle measurement was performed and the results showed that surface free energy of the coating film decreased dramatically from 30.7 to 21.4 mJ/m~2. The inks of permanent markers cannot spread readily on the coating film and can be removed easily, indicating that the incorporation of the synthesized polymer endowed the coating with admirable antigraffiti performance. XPS analysis revealed that atomic concentrations of silicon and fluorine near the surface (about 10 nm) were much higher than deeper within the film (about 100 nm), suggesting that these two elements had a strong migration tendency toward the coating-air interface. AFM measurement showed that the inclusion of synthesized polymer in coating did not affect the surface roughness of the film.