Universal Coupling Agent for Carbon Black and Silica

A pyrrole compound such as 2-(2,5-dimethyl-1H-pyrrol-1-yl)-1,3-propanediol (serinol pyrrole, SP) forms stable adducts with carbon black and with silica. Hence, a pyrrole compound such as serinol pyrrole is able to functionalize both carbon black and silica. Preparation of the adducts was performed through a simple and sustainable method: SP and the filler were mixed and heated. A solvent (acetone) was used only to allow an easy mixing at the lab scale. Catalysts were not involved. The synthesis of SP and the functionalization reactions are characterized by high yield and high atom efficiency. The CB-SP adduct was used in a composite based on IR/BR and CB/Silica, in place of a minor amount of CB. It did not have effect on the vulcanization behavior and promoted lower Payne effect, with the crossover of the G’ vs strain curves. The silica-SP adduct was used in a composite based on S-SBR and NR and silica as the only filler: silica, silica-TESPT and silica-SP systems were compared. The silica-SP system gave faster vulcanization and lower hysteresis. The silica-TESPT system gave the best tensile properties. Results here reported, though preliminary, indicate that a pyrrole compound such as serinol pyrrole is able to promote a strong interaction and a chemical linkage between the filler, either carbon black or silica, and the rubber compound. To our knowledge, it is for the first time reported the ability of the same chemical (family of chemicals) to behave as coupling agent with the rubber matrix for both carbon black and silica.