Type IV anti-icing solution is typically composed of which components?

• A. Propylene glycol thickened with a salt
• B. Ethylene glycol thickened with a polymer
• C. Water and sugar
• D. Ethanol and acetone

Answer: (B)

Type IV anti-icing solution is defined by a high-viscosity film formed from an ethylene glycol base that is thickened with a polymer. Ethylene glycol provides the low-temperature performance needed, while the polymer thickener raises viscosity to create a durable, extended-holdover layer on aircraft surfaces. This combination is what gives Type IV its longer protection time compared with other types. Other mixtures fail to meet that high-viscosity, long-holdover requirement, because they involve different bases or low-viscosity solvents that don’t form the same protective film. So the correct composition is ethylene glycol thickened with a polymer.