TG/DSC study of the thermal behaviour of hazardous mineral fibres

This paper reports a systematic and comparative study of the thermal behaviour of fibres of social, health, economic and industrial relevance using thermogravimetric and differential scanning calorimetry (TG/DSC). The mineral fibres selected for the study are: three chrysotile samples, crocidolite, tremolite asbestos, amosite, anthophyllite asbestos and asbestiform erionite. Powder X-ray diffraction and scanning electron microscopy were used for the characterization of the mineral fibres before and after heating at 1000 or 1100 A degrees C to identify the products of the thermal decomposition at a microscopic and structural scale and characterize their thermal behaviour. TG/DSC data allowed the determination of the structural water content and temperature stability. Furthermore, thermal analysis provided a sensitive and reliable technique for the detection of small quantities of different mineral phases occurring as impurities. After thermal treatment, fibrous samples were completely transformed into various iron oxide, cristobalite and other silicate phases which preserved the original overall fibrous morphology (as pseudomorphosis). Only crocidolite at 1100 A degrees C was partially melted, and an amorphous surface was observed.