How to Ensure Formulation Stability — Shelf Life Engineering

The Four Standard Stability Classes

SC — Suspension Concentrate

• Most complex stability management — suspended solids must resist sedimentation
• Requires dispersant optimization and particle size < 3 µm D50
• Viscosity must balance pourability with anti-settling yield stress
• Premium specification: ≥ 95 % suspensibility, no sediment after 14 d at 54 °C
• Best for: Herbicides, fungicides, high-value foliar applications

EC — Emulsifiable Concentrate

• Simpler physical stability — homogeneous solution, no suspended solids
• Emulsion stability on dilution is the critical parameter
• Solvent migration and container compatibility must be controlled
• Best for: Insecticides with systemic action, fast crop uptake

WDG — Water-Dispersible Granule

• Longest shelf life — low water activity prevents hydrolysis
• Granule integrity and rapid disintegration must be maintained
• Moisture uptake during storage is the primary risk
• Best for: Premium fungicides and herbicides, dust-free handling

FS — Flowable Seed Treatment

• Film-forming polymer stability is critical — must adhere to seed without flaking
• Colourant and active ingredient must remain homogeneously distributed
• Low-temperature storage stability required (5 °C testing)
• Best for: Cereal and vegetable seed treatment programmes

Stability Analysis

The shelf stability of an agrochemical formulation is governed by its physical-chemical properties and the interaction between active ingredient, co-formulants, and packaging. At 54 °C accelerated storage, an SC with D50 < 3 µm and a well-optimized dispersant package shows approximately 30 % less sedimentation than an SC with D50 > 5 µm. Active content retention is primarily determined by pH and hydrolytic stability; secondary stability is influenced by container compatibility and headspace oxygen.

Stability by Formulation Type and Storage Condition

Storage Condition	SC	EC	WDG	FS
54 °C / 14 d (accelerated)	≥ 95 % a.i., ≥ 90 % susp.	≥ 97 % a.i., emulsion pass	≥ 97 % a.i., disint. < 60 s	≥ 95 % a.i., no flaking
40 °C / 75 % RH / 28 d	≥ 97 % a.i., ≥ 92 % susp.	≥ 98 % a.i., emulsion pass	≥ 98 % a.i., moisture < 2 %	≥ 97 % a.i., film intact
25 °C / 60 % RH / 24 mo	≥ 97 % a.i., no sediment	≥ 98 % a.i., emulsion pass	≥ 98 % a.i., free-flowing	≥ 97 % a.i., uniform film
5 °C / 7 d (cold test)	No crystallisation	No phase separation	N/A	No gelling, pourable

Accelerated Testing vs. Real-World Shelf Life

A common misconception is that passing 14 days at 54 °C guarantees 2 years of shelf stability. In reality, 54 °C testing primarily predicts hydrolytic degradation and physical instability at elevated temperatures; real-world shelf life depends on container type, headspace, and storage temperature distribution. For robust shelf life claims, we recommend 54 °C (14 d), 40 °C/75 % RH (28 d), and 25 °C/60 % RH (12–24 mo) data, plus a cold test at 5 °C for liquid formulations.

Agrospear Stability Standards

• SC products: Agrospear SC series — D50 < 3 µm, ≥ 95 % suspensibility after 14 d at 54 °C, active content retention ≥ 97 %
• EC products: Agrospear EC series — emulsion stability pass (0 mL cream, 0 mL sediment) in CIPAC C and D waters, active content retention ≥ 98 %
• WDG products: Agrospear WDG series — disintegration < 60 s, free-flowing after 24 mo at 25 °C, moisture uptake < 1 %

All formulations utilise co-formulant packages validated by accelerated and long-term stability testing per CIPAC methods.

Stability parameters, co-formulant selection, and packaging are all configurable for custom lines — see how we engineer formulations for OEM and private-label brands and walk through our stability testing at the factory floor.