A glidant is a substance that is added to a powder

Powder (substance)

A powder is a dry,thick bulk solid composed of a large number of very fine particles that may flow freely when shaken or tilted. Powders are a special sub-class of granular materials, although the terms powder and granular are sometimes used to distinguish separate classes of material...

 to improve its flowability. A glidant will only work at a certain range of concentration

Concentration

In chemistry, concentration is defined as the abundance of a constituent divided by the total volume of a mixture. Four types can be distinguished: mass concentration, molar concentration, number concentration, and volume concentration...

s. Above a certain concentration, the glidant will in fact function to inhibit flowability (Which means that there's a critical concentration to be used if increasing powder's flowability is intended with respect to the glidant and the powder properties). In tablet

Tablet

A tablet is a pharmaceutical dosage form. It comprises a mixture of active substances and excipients, usually in powder form, pressed or compacted from a powder into a solid dose...

 manufacture, glidants are usually added just prior to compression.

Examples

Examples of glidants include magnesium stearate

Magnesium stearate

Magnesium stearate, also called octadecanoic acid, magnesium salt, is a white substance which is solid at room temperature. It has the chemical formula . It is a salt containing two equivalents of stearate and one magnesium cation...

, Aerosil

Aerosil

Aerosil is a registered trademark for fumed silica product developed in 1942 by Degussa AG in Germany.- Properties :...

 (colloidal silicon dioxide), starch

Starch

Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...

 and talc

Talc

Talc is a mineral composed of hydrated magnesium silicate with the chemical formula H2Mg34 or Mg3Si4O102. In loose form, it is the widely-used substance known as talcum powder. It occurs as foliated to fibrous masses, its crystals being so rare as to be almost unknown...

.

Mechanism Of Action

A Glidant's effect is due to a counter-action to factors resulting in poor flowability of powders. For instance, correcting surface irregularity, reducing interparticular friction & decreasing surface charge. The result is a decrease in the angle of repose

Angle of repose

The angle of repose or, more precisely, the critical angle of repose, of a granular material is the steepest angle of descent or dip of the slope relative to the horizontal plane when material on the slope face is on the verge of sliding. This angle is in the range 0°–90°.When bulk granular...

which is an indication of an enhanced powder's flowability.