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Specific
gravity 4.4, Moh hardness 3.0 - 3.5. A popular low cost filler, although
its high specific gravity means a lot of barytes is required to fill a little
space. Increases density - some customers still think a heavier block is
superior to a lightweight block! Relatively inert - high heat
stability. Improves wear, lowers friction level a little.
Many
of the best formulas on the market are heavily loaded with barytes. Yet
some manufacturers have difficulty making products with more than 5%. The
secret is in the process. Barytes is normally a fine powder (2%<200
mesh, 98%<325 mesh) and large quantities produce a dense product impervious
to the diffusion of gases during baking. Those manufacturers using copious
amounts of barytes rarely open bake above 345°F otherwise blistering would
occur. To bake at higher temperatures requires the extra expense of
confined baking on baking forms.
Beware,
barytes can be contaminated with metal oxides like silicon and iron
oxides. The more silica in the barytes the higher the friction level of
the finished product. Barytes with silica content at. say, 10% is not
necessarily bad. Just recognize it is there and it is affecting friction
level. Make sure your supplier sells a consistent product.
In
some places what is sold as barytes is, in fact, a mixture of barium and
strontium sulphates. This does no have to be bad either. Just don't
switch back and forth from one 'barytes' to another.
PHYSICAL
PROPERTIES OF BARYTES
Highest Density of any Extender
- Contributes
to particle packing density
- Improves
holdout
- Noise
absorption
- Contributes
to improved adhesion
Extremely
Low Solubility
- Chemically
inert
- Not affected
by acids or alkalis
- Insoluble in
water
- Low
reactivity with binders (extremely low MgO and CaO content)
Low
Oil Absorption
Low resin
demand/reduction in needed binder
Low
Moh's Hardness
Grinds
easily
Excellent
Dispersibility
Wets easily
in all systems
Neutral
pH
Thermal
Stability
Thermal
degradation does not occur until 1580 centigrade