Yokohama develops additive-free crack-resistant rubber

Hiratsuka, Japan – Yokohama Rubber Co. (YRC) has developed a “highly crack-resistant" rubber material, made from nanoparticle-based polymers, which does not require additives such as organic solvents and reinforcing agents.

Developed in collaboration with a research group from the Shinshu University’s school of textile science and technology and RISM (research initiative for supra-materials) the rubber material can be “can be easily recycled without deterioration”, said YRC 23 June.

The project used nanoparticle-based polymers synthesised via "mini-emulsion polymerisation", a process which involves the polymerisation of monomers and initiators after micronising them in water by using ultrasonic irradiation.

The nanoparticles were then combined with a “nanoparticle dispersed aqueous solution” to create a nanoparticle film (rubber material) through evaporating the water from the dispersed aqueous solution.

The team inserted rotaxane molecules, also known as supramolecular compounds, into the nanoparticles as a crosslinking agent to enhance resistance to crack propagation.

By introducing rotaxane, YRC said, the team avoided the use of other additives, such as reinforcing agents, while enhancing the elasticity of materials.

The nanoparticle films can be decomposed by immersing them in a water-ethanol solution, which YRC said is a “a low environmental-impact process”.

Here, by evaporating the highly volatile ethanol, the water-ethanol solution can be converted back into the dispersed aqueous solution containing nanoparticles and water.

This, said YRC, enables the regeneration of the nanoparticle film without any deterioration.

YRC expects further research based on knowledge gained to lead to the development of safer and more durable tires and rubber products.

The research results were published in Langmuir, an American Chemical Society journal, on 17 June.