Tire Innerliner Analysis for NHTSA Tire Aging Test Development Project

A project to develop an accelerated aged endurance test for tires is being conducted by the United States Department of Transportation - National Highway Traffic Safety Administration. Six models of tires were collected from service in Phoenix Arizona, USA

and a wide assortment of material tests were conducted on various rubber compounds in the tires to track the evolution of properties during on-vehicle service. Scientific literature attributes the evolution of changes in properties of the rubber compounds and

their interfaces to thermal-oxidation. A key tire component affecting thermal-oxidation in tires is the tire innerliner because it slows the diffusion of oxygen from the tire cavity to tire compounds. An understanding of the tire innerliners was desired including

innerliner composition. The innerliner composition of the six NHTSA tire brands from the NHTSA tire data set (NHTSA tire types B, C, D, E, H, and L) were analyzed for composition. In addition, the compositions of innerliners from another 37 tire types were

analyzed. The analytical techniques used to determine the liner compositions included X-ray fluorescence spectroscopy, energy dispersive X-ray spectroscopy, pyrolysis-gas chromatography /flame ionization detector, and pyrolysis-gas chromatography /mass

spectroscopy. The innerliner composition correlated with liner permeability. Innerliner permeability was measure on extracted liner slices. The permeability results were correlated with the compositional results, for which butyl content was a major factor

affecting permeability rates.