NUREMBERG, Germany — Add lignin — a byproduct of the pulping process in the paper industry — to the list of bio-based materials being considered as alternatives to petrochemical-derived
Pirelli & C. S.p.A. is planning to roll out later this year passenger tires incorporating wood-derived lignin fillers produced via an innovative process technology as a sustainable alternative to carbon black.
Using lignin in the rubber mixing process helps enhance the mechanical strength of the rubber, Pirelli said in explaining its use in bicycle tires. According to Merriam-Webster, lignin is an "amorphous polymer related to cellulose that provides rigidity and together with cellulose forms the woody cell walls of plants and the cementing material between them."
Employing novel chemical treatment and co-precipitation techniques, Pirelli's development follows years of research and development to overcome the challenges of mixing lignin successfully into rubber compounds, according to Luciano Tadielli, innovative materials researcher for Pirelli, who presented the concept during the recent combined Deutsche Kautchuk Tagung/International Rubber Conference held in Nuremberg.
The industrial process has been optimized for "scale-up and utilization in car tire products," Tadielli said. Pirelli has used lignin in bicycle tires — especially for electric-assist "e-bikes" — since 2020. Pirelli has dubbed that technology "SmartGrip+" compounding.
Pirelli expects to market passenger tires incorporating lignin in Europe late this year, but Tadielli did not say which line. Pirelli will start with one application in one tire size, as the lignin-based compounds for each application can be very different, he added.
"It is not like [adding] a new grade of carbon black, which is already a norm and can be swapped in one-to-one in different tire compounds," he told European Rubber Journal in an interview during the DKT/IRC event.
The tire compound being developed will have a lignin filler content of around 15%, which means substituting half of the carbon black, he said.
The first lignin-filled tire likely will be for the replacement segment, he said, "to see what happens from a market point-of-view."
Automotive companies, Tadielli said, are focused on incorporating renewables from the perspective of the entire vehicle.
"So, if they want to make an action only about recyclable materials... then lignin is off the table because it is not in that area.
"But," he concluded, "if they ask for sustainable, bio-sourced materials, then here we are."