Water Dispersible Granules
Water-dispersible granules, also known as dry flowables, are like wettable powders except instead of being dustlike, they are formulated as small, easily measured granules. Water-dispersible granules must be mixed with water to be applied. Once in water, the granules break apart into fine particles similar to wettable powders. The formulation requires constant agitation to keep them suspended in water. The percentage of active ingredient can be high, sometimes as much as 90 percent by weight. Water-dispersible granules share many of the same advantages and disadvantages of wettable powders except:
- They are more easily measured and mixed
- Because of low dust, they cause less inhalation hazard to the applicator during handling
Water dispersible granules can be made by several techniques. The most common ones include:
- Extrusion – to produce cylindrical pellets
- Pan granulation (tumbling in a pan) to produce spherical balls – this is done by spraying a liquid, usually water, onto the tumbling powder to cause agglomeration by the “snow-ball effect”.
- Compaction – in this process a powder with an included binder is compressed into a small sphere, disc or obloid. Tablets may be considered to be a form of disc shaped compacted granule.