Acti-gel® is a self dispersing Thixotrope having rod-shaped particles that average 2 microns in length by 30 Angstrom in diameter. The particles are highly charged along the axis which enables Acti-Gel 208 to bind with the other particles present. Acti-Gel does not absorb moisture and this allows it to dry very quickly during the drying and firing processes.
Fritted Glazes: Both mineral particles & soluble ions are needed to "activate" Acti-Gel 208. Since frit is a glassy material and therefore has no charges present, a small amount of epsom salts (MgSO4) can be added to the suspension (2% to 3% based on the weight of Acti-Gel. Dosage rates for Acti-Gel 208 are in the 0.25% to 0.50% range (based on formula weight) for glaze slurries in the 50% solids and higher range. Glaze slurries in the 30% to 40% solids range require 0.5% to 1.0% Acti-Gel 208 .
Natural Glazes: These generally have enough soluble ions present. To gain additional gel strength with Acti-Gel, add Epsom Salts as above. Dosage levels are similar to Fritted Glazes.
Advantages: In both kinds of glazes, we find that many customers use HEC, CMC or HPMC to stabilize the glaze along with Laponite, Bentonite (Bentone EW, LT, etc.). When Acti-Gel is used, we can reduce Cellulose to 0.05% or 0.1% and, at the same time, eliminate the Bentonite or Laponite. Acti-Gel dries very quickly. This can be a big advantage to many glaze formulas. For those that require a little longer dry time, we found that by adding about 0.05% Cellulose, customers can "dial-in" dry times. Acti-Gel enables the glaze to SPRAY much better than other systems, Acti-Gel glazes have HIGHER ADHESION STRENGTHS and can be applied thicker without running, sagging, settling.
Dry Press Tile
2-5% Acti-Gel (based on dry solids weight of the formula) has been used successfully in tile making formulas that include extrusion & pressing followed by flash calcining. Acti-Gel enables the formulator to use less ball clay and add more feldspar, calcined talc and kaolin. This decreases formula variations as a result of clay inconsistencies, reduces warpage and cracking and improves forming properties.
For Low Shear Mixing applications, we recommend that you first make a predispersion of Acti-GelÂ® 208 in water. The pre-dispersion must be made in a high shear mixer. Solids levels can range from 15-25% solids dispersion of Acti-GelÂ® in water. In High Shear Mixing, add Acti-GelÂ® 208 as a dry powder to the mix. Either way, after adding Acti-GelÂ® 208 to the formula, remember to mix very well.
After mixing, test in the pressing and extrusion processes to see how it performs and to establish optimum dosage levels.
Most customers see a huge difference in the behavior of the mix containing Acti-GelÂ® 208. The mix is more consistent, flow properties are improved, extrusion pressures are lowered and tooling and mold release properties are better. Tiles are easier to form, very manageable - having very good plastic characteristics, delamination is dramatically reduced. Some customers have seen their production recovery rates increase from just 65% to over 90%.
|Glaze Suspender||An attapulgite clay.|
By Tony Hansen
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