The automotive industry is on the cusp of a major shift, with groundbreaking research promising to transform tire manufacturing and recycling. Researchers at the University of Twente, Netherlands have unveiled a novel approach using "dynamic imine bonds" in tire tread compounds, potentially paving the way for a circular economy and drastically reducing the environmental impact of end-of-life tires (ELTs).

For decades, the tire industry has relied on a silica/silane coupling system, predominantly using agents like TESPD, to bond silica fillers to the rubber matrix. This system, while ensuring high performance, creates strong, irreversible covalent bonds that make recycling a formidable challenge. The consequence? Mountains of ELTs piling up in landfills or being incinerated, contributing significantly to environmental pollution.

However, a recent study has introduced a game-changing alternative: dynamic imine bonds. These bonds, formed through a reversible reaction between amines and aldehydes, offer a unique advantage—they can be broken and reformed under controlled conditions, making them ideal for enhancing recyclability.

The researchers successfully implemented this concept by modifying silica surfaces with 3-aminopropyltriethoxysilane, followed by the introduction of various aromatic aldehydes. This in-situ process, conducted during the rubber compound mixing, created a new silica-rubber coupling system with dynamic imine bonds.

The results were remarkable. Rubber compounds incorporating these dynamic bonds exhibited improved mechanical properties compared to traditional compounds. They demonstrated higher tensile strength and elongation at break, indicating greater durability and longevity. Furthermore, they showed superior fatigue behavior, suggesting enhanced resistance to wear and tear.

Perhaps the most significant breakthrough is the enhanced recyclability potential. The dynamic nature of imine bonds facilitates easier devulcanization, a critical step in rubber recycling. This innovation could significantly reduce the vast quantities of ELTs that accumulate annually, moving the industry closer to a sustainable, closed-loop system.

While the new compounds showed a slight decrease in wet grip, the improved mechanical performance and reduced rolling resistance, which translates to better fuel efficiency, present a compelling trade-off. The potential for reduced fuel consumption and lower carbon emissions is a significant win for both the industry and the environment.

The implications of this research extend beyond tires. The successful implementation of dynamic imine bonds in rubber compounds opens doors for their application in other rubber-based products, such as seals, hoses, and damping systems. This could revolutionize various industries, making them more sustainable and environmentally friendly.

The research was carried out by Pilar Bernal-Ortega, Faculty of Engineering Technology, Department of Mechanics of Solids, Surfaces and Systems (MS3), Chair of Elastomer Technology and Engineering, University of Twente, Netherlands; Anke Blume, Faculty of Engineering Technology, Department of Mechanics of Solids, Surfaces and Systems (MS3), Chair of Elastomer Technology and Engineering, University of Twente, Netherlands. It was authored by Rafal Anyszka, Faculty of Engineering Technology, Department of Mechanics of Solids, Surfaces and Systems (MS3), Chair of Elastomer Technology and Engineering, University of Twente, Netherlands; Raffaele di Ronza, Bridgestone EU NV/SA, Italy and Claudia Aurisicchio, Bridgestone EU NV/SA, Italy Branch.