WG Encapsulation: Formulation Engineering Applied to Water-Dispersible Granules
The WG (Water-Dispersible Granule) formulation is a solid system designed to disintegrate and disperse rapidly upon contact with water, producing a homogeneous suspension of the active ingredient in the spray solution.
Its development requires control of both the physicochemical properties of the components and the critical parameters of the granulation process, as the final structure of the granule determines its stability, mechanical strength, wettability and dispersibility.
At AFEPASA, WG formulations are manufactured using fluid-bed technology, based on the dynamic suspension of particles by an upward flow of air. The active ingredients and formulation components are atomised in a controlled manner onto this fluidised bed. The combination of fluidisation, spraying and drying enables precise control of heat and mass transfer phenomena and the progressive build-up of the granule structure.
Granule Formation and Encapsulation
The process begins with the selection of a solid carrier, whose characteristics are defined according to the properties of the active ingredient and the requirements of the final formulation. Once introduced into the equipment, the airflow keeps the particles in continuous motion, creating a homogeneous bed onto which atomisation takes place.
The suspension containing the active ingredient is sprayed in droplets of controlled size. When they come into contact with the fluidised particles, the liquid spreads over their surface while the solvent evaporates. Repetition of this phenomenon results in the progressive deposition of material in successive layers, increasing the granule size in a controlled manner.
When required by the characteristics of the product, an additional coating stage can be incorporated. This outer layer can modify specific properties of the granule, such as its behaviour in the presence of moisture, protection of the active ingredient, or its performance when introduced into water.
The result is a particle whose architecture and physical characteristics can be engineered by controlling variables such as spray flow rate, temperature, airflow, humidity and process time.
Technological Advantages of WG Formulations
Compared with powder formulations such as DP (Dustable Powders), WG formulations significantly reduce dust generation during handling, facilitate dosing and provide improved flow properties. At the same time, their structure must combine sufficient mechanical strength to withstand storage and transport with rapid wetting and disintegration in the spray tank.
Compared with certain liquid formulations, WG technology enables products with a high concentration of active ingredient to be obtained without transporting large quantities of water while avoiding phenomena associated with liquid systems, such as sedimentation during storage.
A Technology Adaptable to Different Active Ingredients
WG technology can be applied to fungicides, insecticides, herbicides, fertilisers, micronutrients and other active ingredients, adapting both the formulation components and the process conditions accordingly.
At AFEPASA, this development covers everything from formulation and granulation parameter optimisation through to industrial scale-up, with the aim of producing granules that remain stable and mechanically resistant during handling while providing homogeneous dispersion under real application conditions.
