Mixing Disodium EDTA with Aristoflex and HEC: Solving Gel Formation Issues

The issue of the gel not forming when mixing Disodium EDTA with Aristoflex AVC and Hydroxyethyl Cellulose (HEC) is primarily caused by the chemical properties of these ingredients, particularly their sensitivity to electrolytes.

1. Cause of the Problem

• Aristoflex AVC (Ammonium Acryloyldimethyltaurate/VP Copolymer): This is a synthetic polymer that is extremely sensitive to electrolytes (salts). Disodium EDTA is an electrolyte. Even a small amount (0.1-0.2%) can cause Aristoflex AVC to lose its viscosity or prevent it from forming a gel entirely.
• Hydroxyethyl Cellulose (HEC): This is a non-ionic thickener and is resistant to electrolytes. However, HEC usually requires specific conditions to hydrate. If you are mixing it in cold water without heating, it will not thicken.

2. Recommended Mixing Procedure

To achieve the best results with these ingredients, follow this order:

1. Dissolve Disodium EDTA: Dissolve the Disodium EDTA in the water phase first. Ensure it is completely clear.
2. Hydrate HEC:
   • Hydroxyethyl Cellulose (HEC) typically requires heat to hydrate. Heat the water (containing EDTA) to approximately 70°C.
   • Slowly sprinkle the HEC powder into the hot water while stirring or blending continuously until the solution is clear and thickened.
3. Add Aristoflex AVC:
   • Wait for the HEC gel to cool down to room temperature or below 40°C.
   • Slowly add Aristoflex AVC and blend.
   • Note: Because of the EDTA, you will likely need to use more Aristoflex AVC than usual to reach your desired viscosity, or accept a thinner texture.

3. Suggestions for Improvement

• Reduce EDTA: Use the minimum effective amount of Disodium EDTA (0.1%) to minimize the impact on Aristoflex AVC.
• Switch Thickener: If your formula contains many electrolytes (such as high amounts of EDTA, Sodium Lactate, or certain extracts), Aristoflex AVC may not be the suitable choice. Consider using an electrolyte-resistant synthetic thickener like Pro Polymer (which can handle electrolytes better while providing a similar feel) or rely solely on HEC for viscosity.
• Check pH: Ensure the final pH of the formula is within the stable range for all ingredients (typically pH 4.0–7.0 for this combination).