Asbestos fibres production processes

Among several production methods the most commonly used were the so-called Hatschek, Magnani and Manville processes. The asbestos fibre cement elements were also produced by shotcreting. More details on the production methods may be found, among other sources, in Hannant (1978) and in Bentur and Mindess (1990). 

Other types of production processes are also dependent on the special nature of the fresh mix, which is controlled by the special properties of the asbestos fibres. The Magnani process is based on direct deposition of slurry on a porous former, followed by dewatering and consolidation by vacuuming and pressure. The product can be produced by the build-up of several layers. 

When considering the properties of asbestos-cement composites in relation to the production processes, the orientation effect must also be taken into account. The data reported by Allen indicate that the strength in the transverse direction is only about 60-85% of that in the longitudinal direction, with similar ratios reported for the ultimate elongation. Zevin and Zevin [9,10] determined the orientation of the fibres by X-ray methods. They then calculated the strength ratio between the longitudinal and transverse directions, which was found to compare favourably with... 

Some asbestos fibres, when inhaled, can constitute a health hazard leading to lung cancer. The health risks are greatest during the production process, but may be... 

Phenolic plastics. Collective designation for phenolic resin-based plastics. Phenolic resins are produced by condensation of phenol and/or its homologues, such as cresol, with an aldehyde, such as formaldehyde or with an aldehyde-releasing material such as hexamethylenetetramine. Phenol/formaldehyde and/or cresol/formaldehyde resins are used as binding materials in fibre board, laminated paper and fabrics. In phenolic moulding compounds, the proportion of filler (such as wood flour, rock flour, asbestos, stone powder, mica, glass fibre) can be equal to that of the resin. These thermosets can be processed by compression or injection moulding into black or dark-coloured products mainly for the electric industry. 

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