The preparation of surface fluorinated polyethylene films with excellent properties similar to that of fluoropolymers

Abstract

Various surface fluorinated polyethylene films with different fluorination degree have been prepared by direct fluorination. The chemical structure of the resulted fluorinated polyethylene layer has been effectively tuned by direct fluorination, where the fluorination degree and chemical structures are highly dependent on fluorination temperature. Direct fluorination with low temperature mainly results in a formation of CHF groups, whereas CF2 groups are prevailing at high temperature, which plays a major role in the enhancement of weathering-resistant properties. The polyethylene films with highly fluorinated layers show better weathering-resistant property, which are much more stable against UV irradiation compared with the virgin. Moreover, better thermal stability could also been observed in air atmosphere (up to 428.8°C) compared with the virgin (396.6°C) for the fluorinated layer. The increasing fluorination degree also results in lower surface energy (from 34.5 to 14.3mNm−1, 58.6% reduction), and higher contact angle of water (from 98.1° to 117.9°, 20.2% improvement) and diiodomethane (from 53.9° to 98.9°, 84.5% improvement), which contributing to the enhance of barrier properties towards O2 (30% reduction) and water as well as organic solvents. In addition, the corresponding apparent activation energy and pre-exponential factor of the direct fluorination process calculated from Arrhenius equation are 58.86kJmol−1 and 1.53×107min−1, respectively.