Aerosols are substances stored under pressure and then released as a suspension of particles in air. Aerosol formulations consists of: –

  1. The Product: which boils at a high temperature. This is the substance we actually use, e.g. hair spray or insect repellent, deodorants.
  2. The Propellant: which boils below room temperature. This is the stimulant which gets the product out of the can.

Propellants are the heartbeat of aerosol industry. There are two types of propellants:

  1. Compressed Gas (e.g. nitrogen or carbon dioxide): These gases are used to dispense the aerosol as a wet spray or solid stream as they are inert. The propellants occupy the head space above the liquid in the can. When the valve is opened the gas pushes the liquid out. These are used in the products like ointments, aqueous antiseptic and germicidal aerosols, contact lens cleaner saline solution etc.
  2. Liquefied Gas (e.g. butane, isobutane, propane): These gases are very effective in dispersing the active ingredients in to a fine mist or foam. These are relatively inert and non-toxic and keep the pressure in the can constant. In earlier days, a lot of liquefied-gas aerosol cans used chlorofluorocarbons (CFCs) as a propellant which were harmful to the ozone layer. However, on 16 September 1987, the Montreal Protocol, an agreement to phase out CFC use was singed. Today, almost all aerosol cans contain liquefied petroleum gas as a propellent, which do not pose as serious a threat to the environment.

Aerosol propellants are used by manufacturers of pesticides, air-fresheners, perfumes, cosmetics, spray paint and food grade packaging material.

Benefits:

  • Economical when compared to other propellants such as Dimethyl ether (DME).
  • Stable propellant compound.
  • Odourless, non-corrosive and non-toxic gas.
  • Offers a wide range of applicable vapour pressures and boiling points.
  • Versatile and efficient propellant.