Direct Characterization of Tire Materials by Photoacoustical Infrared and Proton Induced X-Ray Emission Spectroscopy

Abstract

Abstract In an effort to find out if compound composition could help explain the observed differences in “chip/chunk tearing” on worn off-the-road tires from two manufacturers, direct characterizations were made on tread lugs from the two tires. Two nondestructive direct analytical methods were used. They are photoacoustical Fourier transform infrared spectroscopy (PA-FTIR) and proton induced x-ray emission spectroscopy (PIXE). These techniques were also used to examine a variety of rubber compounding ingredients, such as polymers and fillers, and model tire compounds containing different levels of these ingredients. PA-FTIR requires essentially no sample preparation. It was successfully used to determine the polymer structure and to suggest the nonblack filler type in highly loaded carbon-black filled, sulfur-cured compounds and in tire sections. The characterization was based upon structural information derived from vibrational band frequencies. Elemental information was obtained by using direct PIXE spectral analysis of polymers, fillers, and two worn off-the-road tire tread lugs. Again, no sample preparation was needed and quantitative information was obtained on the elements present. Results show that the tire that did not display a tear problem was manufactured with a cushion (tread base) and a tread (cap), both containing silica at the 12–15 phr levels. The tire that had a visible chip/chunk problem was constructed with two layers of a very similar stock, but neither layer contains silica.