Document xdk5EbwGogGy4zpjLnENxMX6G

v$- (Durwol), 1957). For example, the effects of abrasive wear and macro- shear hove been investigated. When monitored by x-ray diffraction, chrysotile in brake materials displays structural strain and substructure fragmentation, caused by shear during braking processes (Muxutanl ct al., 1973). Tins shear strain produces material fotigue which, with binder pyrolysis, can cause brake lining disintegration at temperatures far below those required for chrysotile dehvdroxvlotion. Therefore, brake lining disintegration may liberate partially altered, or unaltered, chrysotile fibers. Thermal decomposition of chrysotile Differential thermal analysis indicates that chrysotile undergoes oe- DO hydroxyletion at C50 C to 680 C and recrysta11izcs (anhydrous magnesium Silicate to forsteritc) (Kg^SiO^) at about S30PC to 820C (c.p., Martino?, 1966, Daykin, 1971, Derry, 1971; Monkman, 1971). Those tempciature ranges arc subject to great variation as a function of the chemistry of the fiber, particle sir.c, instrumental variations, sample packing, etc. Also, forstente has been noted to form, during prolonged static heating, at con siderably lower temperatures (Bates and Comer, 1957; Martinez, 1966, Brindley and llaynmi, 1965; Baumann and Dresher, 3966). In genera), temperatures in excess of 570C are required for dehydroxy)ation and in cipient forsteritc formation in chrysotile. Fxtensive study of both the thermal behavior of chrysotile and brake lining composition and design indicates that chrysotile fiber may survive in the decomposed lining dust. Analysis of brake drum dust (decomposed lining) Ten samples of automobile brake drum dusts were collected and examined by optical microscopy, x-rBy diffraction, transmission electron microscop) 8005 1872 PRODUCED BY FORD