Polybutadiene-g-polypentafluorostyrene as a coupling agent for lignin-filled rubber compounds

Abstract

This study investigated the role of polybutadiene-g-polypentafluorostyrene (PB-g-PPFS) as a coupling agent between lignin and styrene butadiene rubber (SBR) in preparation of compounds with higher mechanical strength and lower viscoelastic loss. Lignins are three-dimensional amorphous polymers consisting of benzene rings carrying alkyl, alkoxy, and hydroxyl groups as substituents. These substituents render lignin electron-rich. The PPFS domains in PB-g-PPFS provide an electron-deficient π-ring system that can couple lignin with rubber via arene–perfluoroarene interactions. PB-g-PPFS molecules were synthesized with 2:1 molar ratio of pentafluorostyrene and polybutadiene, respectively. The arene–perfluoroarene interactions were confirmed by UV–vis spectroscopy and the morphology was examined by scanning electron microscopy. The tensile strength improved by 20% and 10% for compounds of lignin and lignin–carbon black hybrid fillers, respectively. The loss tangent value reduced due to improved filler–rubber interactions promoted by PB-g-PPFS compounds.