Synthesis and characterization of thermally self-curable fluoropolymer triggered by TEMPO in one pot for high performance rubber applications

Abstract

The preparation of functional fluorine materials through chemical modification of commercial fluoropolymers has been recognized as an economic and convenient strategy to expand the application field of fluoropolymers. In this work, a thermally self-curable fluoroelastomer triggered by 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) has been successfully synthesized in one pot and carefully characterized. This strategy involves two competitive processes, including the coupling reaction between macroradicals and TEMPO, and the dehydrochlorination of commercially available poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-co-CTFE)) by a route involving a three-molecule process, together with a small amount of elimination by an E2 mechanism and β-H elimination The structure and properties of the target polymer were demonstrated by nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). The two competitive reaction processes were carefully investigated under various reaction conditions, including different reaction temperatures, reaction times, ligands, solvents, copper salt, and dosage of TEMPO. The resultant polymer is rather stable at ambient temperature and easily cured at high temperature by ‘pulling the trigger’, namely by breaking C–O or O–N bonds, and the free radicals generated in situ are responsible for initiating the crosslinking of double bonds on the polymer main chain. No other additives are required for the crosslinking of the resultant polymer, which provides a facile chemical route to prepare crosslinked fluoropolymers with high purity and excellent mechanical properties. The curing of the resultant polymer could be accomplished in several minutes at 150–160 °C without the need for a post-cure process.