Cellulose fibres, including wood pulp, cotton linters; cotton libres, coconut fibre and sisal, have been used as asbestos substitutes in fibre-cement sheet products, in papers, in filters and in felts. Some corrugated fibre-cement sheeting has been produced with sisal in Kenya.
For the replacement of chrysotile asbestos in filters, since the cellulose does not have the natural positive charge of chrysotile, it must therefore be chemically treated to produce a positive charge.
Cellulose is used alone or in combination with other fibres in rooting felts, but these products do not approach the durability of asbestos roofing felt.
The cellulose fibres that have been use most extensively as asbestos substitutes are softwood pulps (frequently unbleached spruce pulp) for fibre-cement reinforcement. The strength imparted to fibre-cement and the product durability produced is not comparable to what can be obtained with ehrysotile asbestos. Cellulose fibres are hygroscopic and swell when in contact with humid conditions. Cellulose-cement sheet products may be used indoors but cannot be exposed to freezing and thawing and to severe weather conditions. Cellulose-cement pipes cannot be produced.
The cost of cellulose fibres ranges between 3 and 10 times that of chrysotile. Prices ranging from 0.56 to 0.86 $/kg have been reported.
The following properties are assigned to cellulose fibers:
|Tensile strength||300-860 MPa|
|Young’s modulus||10 GPa|
|Temperature limits||120 đến 2320C|
|Specific gravity||1.261,45 g/cm3|
Compared against chrysotile asbestos, cellulose fibres are adequate with regard to availability, cost and reinforcing strength. They are inferior concerning heat and moisture resistance, resistance to weathering and product durability.
Substitutes for asbestos – Marcel Cossette