Scientists observe world’s fastest molecular motion of tire rubber components

Researchers have achieved an unprecedented level of insight into the intricate molecular dance of common automobile tire components, polybutadiene, and carbon black, utilizing the world’s most rapid time-resolution techniques.

The findings, unveiled in the pages of Applied Physics Letters, unveil a striking atomic-level interplay between these two ingredients, potentially opening doors to more precise diagnostics for tire rubber wear and the creation of longer-lasting materials.

Automobile tire rubber is a blend of synthetic rubber, such as polybutadiene, and nanoparticles, like carbon black, which augment its physical attributes. While in motion, tires endure formidable forces that cause these components to interact, leading to wear and deterioration.

Evaluating tire performance necessitates delving into not only the static structure of the complex particle network created by the polymer and nanoparticles but also understanding their interplay and respective movements. These dynamics have a direct impact on material qualities like wear resistance. Some of these molecular motions occur incredibly swiftly, making atomic-scale time-resolved measurements indispensable for developing and verifying dynamic models of such materials.

An international research team led by scientists from the University of Tokyo, Ibaraki University, and European XFEL has achieved an astounding time resolution of 890 nanoseconds (that’s billionths of a second) in observing the molecular motions within polybutadiene and carbon black samples, which naturally occur due to the material’s structure. This groundbreaking achievement was made possible at the European XFEL’s SPB/SFX instrument.

Tokushi Sato from European XFEL, one of the corresponding authors of the publication, elaborated on the methodology used, stating, “Using the recently developed method of diffracted X-ray blinking, we simultaneously detected fast changes in the polymer chains and in the additive nanoparticles on the atomic scale. We observed a clear interaction between polybutadiene and carbon black, indicating that the mobility of polybutadiene differed significantly depending on the type of carbon black added.”

Each sample featured a distinct type of carbon black. The experiment disclosed that, in one sample, polybutadiene exhibited considerably swifter movement on the surface of the carbon black particles, resulting in inferior automotive tire performance compared to the sample where the two components were more tightly bonded. These findings hold promise for advancing methods to examine tire rubber deterioration in the lab during development, potentially leading to materials with enhanced longevity.

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