Non-covalent chemical functionalization of micron-sized styrene-butadiene rubber with silica particles via solid-state cryogenic mixing process

Abstract

The effective, high-value reutilization of reclaimed rubber, obtained from end-of-life tires, in the production of new high-performance tires remains an environmental and technological challenge. Cryogenically ground micron-sized rubber particles demonstrate a significant promise to realize satisfactory physical performance measures in reclaimed rubber-based tires. However, the maximum useable content of the cryogenically ground micron-sized rubber particles to be incorporated into tires is strictly limited by their ineffective interfacial chemical interactions with the host pristine rubber matrix during the post-polymerization process. Here, this work presents the non-covalent chemical functionalization of the cryogenically ground micron-sized styrene-butadiene rubber particles with reactive silica particles via a solid-state cryogenic mixing process. The highly-scalable solid-state mixing process enables the sufficiently uniform and near-homogenous distribution of the silica particles on the micron-sized rubber particles. Scanning electron microscope images highlight the micron-sized rubber particles decorated with individual silica particles. Fourier transform infrared and solid-state nuclear magnetic resonance spectra of the functionalized micron-sized rubber particles demonstrate a non-covalent conjugation mechanism between the silica and rubber particles in which the chemical fingerprint of the prime rubber backbone chains remains chemically intact. The chemically functionalized cryogenically ground micron-sized rubber particles possess reactive silica particle sites that are ultimately designed to facilitate the participation of the recycled rubber particles in post-polymerization processes with host matrix which shall allow higher loading levels than the state-of-the-art configurations.