Octacosenoic acid (C28:1, n-9) is a monounsaturated fatty acid with 28 carbon atoms in the chain with a a double bond at the ninth carbon from the end. Its molecular formula is C28H54O2. It weighs 424.74 grams per mole. It’s considered a very long fatty chain fatty acid.
The melting point is 90.9˚C, which is very high, so any oil that contains this fatty acid will have increased viscosity at room temperature as it’s solid.
This works as an occlusive ingredient to trap in water and reduce transepidermal water loss (TEWL). It can work as a film former for hair and skin to increase friction and lubricity and reduce drag or friction.