AN IN VITRO STUDY OF THE CHEMICAL DURABILITY OF SILICEOUS FIBRES

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Abstract
A comparative in vitro study of the chemical durability of industrial man-made and natural mineral fibres was performed in a simulated extracellular fluid under flow conditions. Seven vitreous, three refractory and three natural fibres were involved. Samples of the leachate were analysed and the silicon concentrations (referred to the initial fibre weights and to the weight fraction of silicon in the fibres) were used to roughly classify the fibres according to their chemical durability in terms of glass network dissolution. In some cases, the effect of selective leaching was demonstrated by potassium or boron analysis. In order to establish a final classification, the effects of the fibre material and of the fibre geometry had to be separated by an appropriate mathematical procedure. Thus, a durability ‘ranking’ of fibre materials was achieved and expressed in terms of a characteristic time required for the complete dissolution of single fibres of given diameter. Man-made mineral fibres exhibited relatively poor durability (with network dissolution velocities ranging from 3.5 to 0.2 nm per day for a glass wool and an E glass fibre, respectively) whereas natural fibres were very persistent against the attack of the biological fluid (e.g. less than 0.01 nm per day for crocidolite).

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