Sumitomo Rubber advances visualisation of tire rubber reinforcement

Kobe, Japan – Sumitomo Rubber Industries (SRI) has developed a new method to visualise reinforcement mechanisms in tire rubber, through a collaboration with Tohoku University.

The project combined two advanced techniques to map the distribution of strain-induced crystallisation within polyisoprene rubber at the nanometre scale, SRI announced 3 Sept.

The methods included “in-situ transmission electron microscopy (TEM) observation while stretching the specimen” and “obtaining multiple electron diffraction patterns by scanning an electron beam with a nanometre-sized spot.”

Explaining the process, SRI said that when rubber undergoes large deformation, polyisoprene molecular chains are stretched, leading to strain-induced crystallisation.

This crystallisation has long been thought to contribute to rubber reinforcement, but until now there was no way to directly observe its spatial distribution.

This, said SRI, made it difficult to identify how reinforcement could be controlled and improved.

In its joint study with Tohoku University, SRI examined polyisoprene rubber – which has the same chemical structure as natural rubber – and silica-filled polyisoprene rubber.

Using TEM, researchers visualised crystallisation in both materials.

In silica-filled polyisoprene rubber, SRI noted, aggregates of silica particles exist inside the rubber.

Observations showed that when stretched, these aggregates aligned in the stretching direction, with crystallisation occurring along the aligned structure.

SRI said it will apply these findings to improve the wear resistance and crack resistance of its tire rubber.

A paper based on the research, Self-reinforcement in filled rubber via strain induced crystallisation, was published 2 Sept in Nature.

Read the research paper.