Sumitomo reports 'world-first' in atomic-scale analysis of rubber

Tokyo – Sumitomo Rubber Industries (SRI) has reported an advance in the evaluation of tire-rubber deterioration: simultaneously observing movement of structures and ingredients on a molecular scale.

For the research, an SRI-led research team* used an 'x-ray free electron laser' to observe the movement of carbon particles and polybutadiene macromolecules in tire rubber at a time resolution of 890 nanoseconds.

Claimed to be “the fastest in the world”, the monitoring technique brings SRI closer to realising “highly accurate evaluation of tire-rubber deterioration,” said its 5 Sept Japanese-language statement.

“For the first time in the world, this research group has succeeded in measuring molecular motion with high precision at the atomic scale at the nanosecond level,” said the SRI announcement.

Understanding the movement of fine particles and polymers near the interface between different components is important in evaluating tire-performance, the group pointed out.

For the new development, auto-correlation analysis was performed for each pixel in a diffraction image containing a 'halo' obtained by a two-dimensional X-ray detector.

The SRI-led team focused on carbon black (50 to 80 nanometres in diameter) and polybutadiene, which are key components of tire rubber.

Time-division measurement of X-ray diffraction was performed using two types of samples with different rubber compounding states, with imaging confirming the diffraction rings of carbon and the X-ray 'halo' from the polymer.

Autocorrelation analysis was then performed on the diffraction regions to extract the 'attenuation coefficients' for the motion of microparticles and macromolecular structures.

The coefficients obtained showed that the movement of the fine particles and polymer structure differed greatly between carbon and polymer.

This, explained SRI, is due to differences in the 'restraint environment' and friction conditions of the molecular interface of each sample.

Furthermore, the study demonstrated that each component behaves differently near the interface between heterogeneous components, according to the statement.

*The research was carried out by prof Yuji Sasaki, department of materials Science, University of Tokyo; Dr Masahiro Kuramochi, assistant professor in the department of materials science and engineering, Ibaraki University, and Hiromichi Kishimoto, director of the analysis center, at SRI's R&D headquarters.