Microcharacterization of Heterogeneous Specimens Containing Tire Dust
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GAI
M CORBETTA*,
TIGRAN DOLUKHANYAN§, GIAMPAOLO
¶ § *
GIovANIm F CROSTA**,
GIUIAmI, CHANGMO SUNG§
of Environmental Sciences, University of Milano - Bicocca, I - 20126 Milano, IT Pirelli Pneumatici, I - 20126 Milano, IT Center for Advanced Materials, Dept. of Chemical Engineering, University of Massachusetts, Lowell, MA 01854 Center for Electromagnetic Materials and Optical Systems, Dept. of Electrical and Computer Engineering, University of Massachusetts, Lowell, MA 01854
ABSTRACT This work is focused on dust or debris produced by the wear of tire tread. Two problems are addressed, which are solved by analytical electron microscopy (AEM): characterization of tire debris and identification of tire debris particles in a heterogeneous specimen. The characteristic morphology, microstructure and elemental composition of tire debris can all be determined by AEM. The scanning electron microscope (SEM) shows that the surface of a tire debris particle has a typical, warped structure with pores. The characteristic elements of tire rubber are S and Zn, which are detected by energy dispersive X ray (EDX) spectroscopy. The identification of rubber particles in heterogeneous debris containing talc and produced by a laboratory abrader is possible by the analytical SEM. Transmission electron microscope images, EDX spectra and selected area electron diffraction patterns characterize tire debris at the sub-micron scale, where the material can no longer be treated as homogeneous. INTRODUCTION AND MOTIVATION Particulate matter produced by motor vehicles mainly originates from the combustion of hydrocarbons and from the wear of tires, brakes and the road surface. This work is focused on the particles from the wear of tires, also known as tire debris or tire dust. Detailed knowledge about the size, shape, microstructure and constituents of tire debris serves a dual purpose: * to model and estimate the impact of particles on human health and on the environment; * to diagnose and control the tire manufacturing process. This work provides preliminary characterization and identification results about tire debris particles. Materials come from laboratory wear tests; specimens are suitably prepared and are examined by analytical electron microscopes (AEMs). The characteristic morphology, microstructure and elemental composition of tire debris are determined and described. The identification of tire debris by AEM alone is shown to be feasible at least in some types of specimens. 147
Mat. Res. Soc. Symp. Proc. Vol. 589 ©2001 Materials Research Society
Tire Rubber and Debris The amount of debris lost by (passenger and truck) vehicle tires per year has been known for a long time. An estimate for the USA provided by the EPA [1] was 6.108 kg in the 1970s. More recent (1990s) figures are 534106 kg for Great Britain [2] and at least 47.106 kg for Italy (assumed to be 1/7 of the total weight of worn tires) [3]. The main ingredients of tread rubber are: elastomers, fillers and additives. The approximate ranges of values are shown in TABLE I.
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