Chemical Devulcanization of Crosslinked Nitrile Rubber Using Tetra-n-Butylammonium Fluoride (TBAF) as a Devulcanization Aid

Utilization of tetra-n-butylammonium fluoride (TBAF) as a new, hitherto unknown devulcanization aid in the chemical devulcanization of sulfur crosslinked diene rubber has been demonstrated. The influences of crosslink structure (the ratio of mono-, di-, and polysulfidic bonds) and carbon black (CB) loading on the efficiency of acrylonitrile-butadiene-rubber (NBR) devulcanization have been studied. The rubber vulcanizates were treated with TBAF solutions under varying conditions (solution concentration, solvent type, temperature, and reaction time). Changes in crosslink density and other relevant network properties of the rubber vulcanizates were measured. Results showed a significant reduction in crosslink density—up to 50% after chemical treatment. The fluoride-based approach, in which fluoride salt is a source of nucleophilic fluoride anions (F−), can cleave the sulfidic crosslinks, demonstrating significant potential for efficient recycling of used rubber vulcanizates by their devulcanization.