Versatility in a bright hydrous aluminum silicate
Our Altifil™ and Altiplus™ products are hydrated aluminum silicate minerals produced from Newfoundland deposits of the mineral pyrophyllite with Al2O3 grades ranging from 18% to 28%. It imparts strength to fired ceramic products and can be used in refractory, ceramics, dinnerware and sanitaryware applications. As a valuable refractory raw material we have the following properties:
- Permanent expansion
- Excellent reheat stability
- Low hot load deformation
- Low reversible thermal expansion
- Low thermal conductivity
- High resistance to molten ingress
The permanent expansion is resulted from dehydration between 650◦ C and 870◦ C which corresponds generally to the greatest weight loss and the percentage of expansion on the particle size. When exposed to temperatures above 1050◦ C, a transformation to mullite corresponds to significant increases all aspects of mechanical properties – compression strength, flexural strength and hardness.
Altifil™ and Altiplus™ have less than 0.20% iron oxide which imparts exceptionally white characteristics both in raw form and as a fired ceramic product. While similar chemical structure to talc (a magnesium silicate) Altifil™ and Altiplus™ are non-plastic, yet clay-like, and often used in ceramic bodies to decrease thermal expansion and moisture expansion during service.
Because it expands when heated, pyrophyllite counters the shrinkage of the plastic components in a mix. Pyrophyllite-refractory clay combinations have excellent volume stability and resistance to deformation at high temperatures.
In clay bodies, substitution of part or all of the silica will decrease thermal expansion while maintaining the level of maturity (although some adjustments 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.
In refractory bricks and monolithics Altifil™ has several advantageous properties. At high temperature it swells and melts to form a glassy surficial coating on the brick, which helps prevent ingress of molten metal to the interior.
In electrical porcelain, large amounts (up to 90%) may be used in bodies for optimal electrical properties and high frequency characteristics (where zero porosity is not critical).
In wall tiles, pyrophyllite can be used as an ingredient since it has the effect of reducing the moisture expansion.
Because of its stable nature and physical properties, pyrophyllite is employed in mold release and parting agents in foundry and structural clay.
Pyrophyllite is ideal for certain types of refractories because of its basic properties – pyrophyllite is refractory and no calcining is needed prior to use. Its physical nature (lubricity) is also an advantage with reduced wear on molds and machinery that handle wet and dry product.
In summary, our Altifil™ and Altiplus™ products have versatile applications and can assist in replacing kaolin, silica, talc and feldspar in your application process with price stability.
Products are available in a variety of formats ranging from 1-3mm pebbles down to 2 micron powders.