Low surface energy polymeric films from novel fluorinated blocked isocyanates

Abstract

To obtain films with a well-defined F-content, a hydroxyl-functionalized oligoester was treated with with 2 different isocyanates: a novel fluorinated blocked isocyanate (FnB-NCO, F(CF2)n-CH2CH2-O-CO-(CH2)5-NH-CO-NCL, NCL = N-substituted caprolactam, n = 6, 8) and a conventional blocked polyisocyanate (Desmodur BL-3272). The ratio of FB-NCO and BL-3272 was varied to adjust the F-content. The crosslinking reactions were monitored by attenuated total reflectance FTIR. The F-enrichment in the top surface of the films was examd. by contact angle measurements and XPS. Temp. effects on both crosslinking and film wettability were investigated. Polymeric films with surface energies as low as 10 mN/m were prepd. The curing temp. not only demonstrated a dramatic effect on the reaction rate but also showed a significant effect on the wettability of the films. A higher curing temp. led to a less significant surface enrichment of F, due to the fast immobilization of the crosslinked networks. The mixts. had excellent stability below the deblocking temp. (.apprx.140 Deg) of the blocked isocyanates. [on SciFinder (R)