Carbon black effect on the pyrolysis behavior of natural rubber in tire wear particles

Abstract

Natural rubber (NR) is major rubber component of tire tread compounds. Tire wear particles (TWPs) are found in the environment, and their quantification has been performed using a pyrolysis technique. Isoprene and dipentene are principal pyrolysis products of NR. In the present work, model TWPs with different sizes and carbon black contents were prepared using tire tread compounds made of NR and an abrasion tester. The carbon black contents were 35, 55, and 75 phr (sample codes: C33, C55, and C75, respectively). The TWPs of 1.0 × 104–4.0 × 106 μm [2], corresponding to the NR weight of 1–1094 μg, were pyrolyzed, and influence of the particle size and carbon black content on the pyrolysis behavior of NR was investigated. The abundances of isoprene and dipentene produced by the TWPs were lower than those produced by the pure NR sample of the same weight. The production rate of dipentene in the C35 sample was lower than those in the other samples. The isoprene/dipentene ratios of the TWPs were lower than those of the pure NR with the same weight. By decreasing the TWP size, the isoprene/dipentene ratios slightly increased until the TWP size was approximately 1.0 × 105 μm [2] and then exponentially increased. The factors influencing the pyrolysis behavior of the TWPs were the adsorption of the pyrolysis products by carbon black, the relatively more significant production rate of isoprene in the sulfur-crosslinked region, and the pyrolysis behavior in the bound rubber region similar to that of pure NR. Because the pyrolysis behaviors of the TWPs differed depending on the size and carbon black content, it should be considered to quantify the TWP content in environmental samples.