The Performance Fibre
Saffil Fibres contain 95 to 97 percent alumina, produced by a novel solution
spinning process from the highest purity raw materials and an aqueous medium. In
the design phase of the Saffil project, the team took the advice of expert
toxicologists to develop the fibre diameter and chemical composition
specifications.
The chemistry was determined to avoid the presence of free
silica, which might transform to cristobalite at high temperatures. The
dimensions were specified to avoid fibres of diameter less than one micron, to
minimise biological activity, and to minimise the level of fibres greater than 6
microns, which can cause skin irritation. To meet the thermal and mechanical
performance targets required the development of a unique spinning process to
achieve a narrow diameter distribution around a median value of about 3.5
microns. The fibre design principle was tested and confirmed in a comprehensive
toxicological package. A feature of the process is the ability to restrict the
level of non-fibrous particles (shot) to extremely low levels treatment of fine
porcelain and highest quality steels. This is in marked contrast to processes
used for making vitreous ceramic fibres.