PhD Defence Priyanka Sekar | Sustainable Reinforcing Filler for Eco-friendly Tires - A step towards understanding the reinforcing potential of hydrothermally treated lignin

Sustainable Reinforcing Filler for Eco-friendly Tires - A step towards understanding the reinforcing potential of hydrothermally treated lignin

Priyanka Sekar is a PhD student in the Department of Elastomer Technology and Engineering. (Co)Promotors are prof.dr. A. Blume and dr. A.G. Talma from the Faculty of Engineering Technology.

The environmental impact of tires, including greenhouse gas emissions and dependence on fossil-based materials, has driven the tire industry toward sustainability and a circular economy. This shift involves using bio-based and recycled materials to develop more sustainable tires to reduce carbon footprints. Lignin, a byproduct of the paper and bio-refinery industries, shows promise as a sustainable reinforcing filler for rubber compounds due to its renewable nature and unique characteristics, such as high carbon content, good antioxidant properties, lightweight, biodegradability, and thermal stability. However, certain limitations exist in the practical application of conventional lignin, primarily stemming from its limited compatibility with non-polar rubber.

In the present thesis, the use of a hydrothermal treatment (HTT) technique has been recommended to improve the reinforcing effects of conventional lignin in a styrene-butadiene/butadiene rubber blend (SSBR/BR). Various surface modifiers, including silane, thiol, and epoxide, were investigated to enhance the performance of hydrothermally treated Kraft lignin in the selected non-polar rubber. Among them, silane-based modifiers, especially bis(triethoxypropyl)tetrasulfide (TESPT), exhibited significant potential in improving the reinforcing effect of HTT lignin in SSBR/BR compounds. Besides, it was also found that the interaction mechanism between HTT lignin and sulfur silanes is different from that of silica/silane. It was revealed through model studies that the coupling between HTT lignin and silane does not occur via the ethoxy groups of silane but instead via the thiol group of the silane.  Thus, the existing knowledge gap in the modification of HTT lignin is emphasized.

In conclusion, the present study highlights the importance of understanding the interactions between HTT lignin, modifier, and functionalized or non-functionalized rubber to fully envisage the potential of HTT lignin as a reinforcing filler.