Filler Facts

Company produces South Carolina kaolin clays for the adhesive industry.

Hard clay, crude from mine / Finished clay
The kaolin clay products produced by Kentucky-Tennessee Clay (K-T Clay) Co.'s Langley, SC, facility are drawn from naturally occurring deposits that are processed by selective mining, crude blending, flash drying, roller milling, air classification and packaging/shipping. Air-classified, also known as air-floated, clays are the most widely used and cost-effective non-carbon-black performance minerals used in the elastomeric industry. Roller milling deagglomerates the flash-dried crude clay into its very fine (micron down to submicron), ultimate particle size. The air classification process removes the major contaminates found in the clay - primarily finely divided muscovite mica and quartz, with minor amounts of pyrite, hematite, and siderite - therefore carefully controlling the small amount of +325 mesh (>44 um) residue. Kaolins are essential as effective fillers and performance enhancers in a variety of industrial applications, including the following.
  • Adhesives
  • Soft and hard rubber compounds
  • Plastics
  • Protective coatings
  • Traffic paints
  • Joint compounds
  • Fiberglass
  • Refractories

The special use of South Carolina air-floated kaolin, as it is being marketed today, is as a reinforcing agent. K-T Clay is mining one of the few clay deposits of commercial quality and extent in the United States and the world, which is found in a narrow 50-80-kilometer-wide belt stretching from near Columbia, SC, to Macon, GA.

There are two general classifications of kaolin clays. Based on their effects on a compound imparted stiffness, these clays are designated as hard and soft kaolin clays.

Hard Kaolin Clays

Hard kaolin clays have lower median particle size distribution and higher surface area. Industrial applications include hard rubber compounds, plastics, adhesives and a variety of protective coatings. Hard kaolin clays offered by K-T Clay include Barden LGB-1, Suprex and Barden R.

Soft Kaolin Clays

These clays have higher median particle size distribution and lower surface area. The lower uncured viscosity permits significantly higher loadings of filler, which result in additional cost savings. Soft kaolin clays offered include Paragon and Alumex.

Both hard and soft clay types are commonly used where economical processing and compound reinforcement are required.

Selecting a Kaolin Filler

The selection of a particular kaolin filler for an adhesive compound depends on the processing characteristics and physical properties desired, the cost, and the final performance of the finished product. For example, many fillers may reduce cost and have good properties, but the performance given may not match that of a higher cost, quality-controlled filler. The compounder has to start with the best possible raw materials and then adjust the compound to meet product specifications and cost.

The use of the above forms of South Carolina air-floated kaolin clay gives the adhesive producer the opportunity to significantly improve the performance characteristics of finished products. Through careful selection and experimentation, kaolin can further reinforce and enhance adhesive properties that few mineral fillers can match.

For more information on kaolin clays, contact Kentucky-Tennessee Clay (K-T Clay) Co., phone (800) 472-2529; fax (803) 593-4144; e-mail; or visit


1. Kentucky-Tennessee Clay Co., "Kaolin Filler Extenders" Brochure, July 1997.

2. Sutton, D. "Air-floated Kaolin- Not Just Another Filler," Rubber Division, American Chemical Society (Nashville), September 29-October 2, 1998.

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