Hairspray is a solution of long, chainlike molecules (called polymers) in a very volatile solvent.
Spraying deposits a stiff layer of the polymer on your hair after the solvent evaporates.
The solvent used was once a compound of carbon, fluorine, and chlorine (a chlorofluorocarbon, or CFC).
CFCs are nontoxic, nonflammable, and make almost ideal aerosol propellants.
But when it was learned that they cause destruction of stratospheric ozone, they were replaced with other solvents, like alcohols and hydrocarbons. Unfortunately, these are flammable.
One of the polymers used is polyvinylpyrrolidine, which is also used to glue the layers of wood in plywood together. An non-water soluble polymer called polydimethylsiloxane is added
to make the hold last a bit longer (the polyvinylpyrrolidine is water soluble).
Other polymers used in plastic-based hairsprays are
copolymers with vinyl acetate
copolymers with maleic anhydride
Some hairsprays use natural polymers and solvents
like vegetable gums dissolved in alcohol. One popular ingredient is gum arabic is made from the sap of certain trees that
grow in the Sudan.
Gum tragacanth is another herbal gum that is used to stiffen calico and crepe, as well as hair.
- Ben Selinger, Chemistry in the Marketplace, 4th ed. (Harcourt Brace, 1994).
Author: Fred Senese firstname.lastname@example.org