Natural rubber degradation products: Fine chemicals and reuse of rubber waste
Franciela Arenhart Soares, Alexander Steinbüchel
Abstract
Natural rubber (NR)1 is a biopolymer mainly composed of isoprene units linked to form double bonds with cis configuration. After the vulcanization process, NR is widely employed not only into fabrication of tyres, but also for many other products. Due to the forthcoming depletion of fossil fuel sources and to the growing tyre waste issue, NR is considered as a potential source of fine chemicals. Isoprene oligomers can be obtained either through bio- or chemical fragmentation processes. Although several microorganisms are able to fragment the rubber chains were isolated, the use of isolated enzymes proved to be more efficient regarding the number of compounds produced. Among the chemical methodologies for NR depolymerization, oxidative cleavages and cross metathesis are the most commonly used procedures to obtain isoprene oligomers. After enzymatically catalyzed fragmentations through oxidative cleavage possesses, the obtained oligomers have aldehyde and ketone end chain groups. A wide range of terminal groups can be obtained with metathesis reactions. We also point to the main procedures to recover isoprene oligomers and highlight some applications and perspectives.