Aircraft de-icing fluids come in four main types (I, II, III, IV), with Type I being the most common for initial de-icing.
Core composition:
- Propylene glycol (main antifreeze base, 50-100% concentration) or sometimes ethylene glycol (less common due to toxicity).
- Water (diluted to 25-100% fluid, depending on strength).
- Surfactants, dyes, and corrosion inhibitors (small percentages for better adhesion, visibility, and metal protection).
- Thickeners (in Types II-IV): Polymers like xanthan gum to increase viscosity for anti-icing holdover.
Types II-IV add these for longer protection but require higher shear-off speeds.
From NASA aviation resources on aircraft icing fluids.