SilMaterials in Agriculture

Silicon Materials in Agriculture and Agrochemicals

Agriculture's silicon-material consumption is split across two main categories: precipitated silica as a powder carrier for liquid pesticide active ingredients, and silicone-based superwetters and adjuvants that improve pesticide spray performance.

Precipitated Silica Carrier for Liquid Active Ingredients

Many agrochemical actives (insecticides, herbicides, fungicides) are liquids at processing temperatures but need to be sold and applied as powders or dispersible granules for end-user convenience. Precipitated silica's high pore volume (DBP absorption 200-300 mL/100g) enables conversion of liquid actives to free-flowing powders by absorbing 100-200% of the silica's weight in liquid.

Typical processing:

1. Liquid pesticide active is sprayed onto fluidized precipitated silica in a mixer
2. Silica absorbs the liquid by capillary action into its pore structure
3. Resulting powder is granulated with binders to produce wettable powder (WP), water-dispersible granule (WG), or dust formulation

The agrochemical industry consumes 100,000+ tonnes/year of precipitated silica globally for this carrier function. Specifications: BET surface area 100-200 m²/g, DBP 200-280 mL/100g, low heavy-metal content (FAO/EU agrochemical standards).

Silicone Superwetters as Spray Adjuvants

Conventional pesticide sprays bead up and run off waxy leaf surfaces (Brassica crops, citrus, conifer needles). Silicone-based superwetters reduce spray droplet contact angle from 70-80° to below 10°, allowing the spray to spread completely across the leaf and penetrate into stomata.

The dominant chemistry is polyether-modified trisiloxane (Silwet L-77, Break-Thru S 240, Penetrator 90, etc.). At 0.025-0.1 vol% in spray water, these adjuvants:

• Reduce surface tension to 20-22 mN/m (vs 72 mN/m for plain water)
• Eliminate need for higher pesticide doses on hard-to-wet crops
• Improve early-rain-fast performance (active is internalized before rain washes it off)
• Allow reduced spray volumes (lower water and pesticide use per hectare)

Major brands: Momentive Silwet (the original brand), Evonik Break-Thru, AgroSpray, Chinese-supplied trisiloxane equivalents.

Silicone Defoamers in Fermentation

Industrial fermentation for antibiotics, enzymes, organic acids (citric, lactic), and amino acids uses silicone defoamers (50-500 ppm dose) to control foam in the bioreactor. Without defoamers, foam can overflow the reactor or block sterile-air filters. Silicone defoamers are preferred over hydrocarbon-based alternatives because they don't add carbon load to fermentation media.

For pharmaceutical fermentation, defoamers must be sterile-filterable and free of compounds that would interfere with downstream extraction.

Silicone-Modified Slow-Release Coatings

Controlled-release fertilizers and pesticides use polymer coatings around urea or pesticide cores to release the active over weeks or months. Silicone-modified coating polymers (silicone-modified polyurethane or epoxy) provide:

• Tunable permeability (silicone fraction controls release rate)
• Weather resistance (silicone-modified coatings survive multiple rain events)
• Cost balance (silicone is more expensive than the underlying polyolefin coating but extends service life)

Specifications and Sourcing

Agricultural silicon materials face less-stringent specifications than electronics or medical applications, but still require:

• Heavy metal limits per FAO/EU agrochemical standards
• Surfactant safety for direct-spray applications
• Storage stability in agrochemical formulations (12+ month shelf life)

China is a major producer of both agrochemical precipitated silica and trisiloxane superwetters. Western brand-name products carry premium pricing for documented EU/EPA registration; Chinese alternatives offer 30-50% cost savings for emerging-market and commodity applications.

Related Reading

Agrochemical carrier silica, Polyether silicone oil, Defoaming application, Silicone emulsion category.