| Description |
In clay bodies, substitution of part or all of the silica will decrease thermal expansion (see also kyanite, mullite) while maintaining the level of maturity (although some adjustment in the feldspar will likely be needed). Pyrophyllite normally increases firing range and therefore decreases firing shrinkage. Thus if a body is too vitreous pyrophyllite can be substituted for feldspar to reduce expansion and maturity at the same time. It has the additional effect of increasing the strength of fired bodies if particles remain intact.
Pyrophyllite is also used as an ingredient in wall tile bodies since it has the effect of reducing moisture expansion.
Pyrophyllite is ideal for certain types of refractories because no calcining is needed. Its physical nature also helps to reduce wear and tear on molds and machinery that handle wet and dry product. |