Sample essay topic, essay writing: Aerosol Spray Cans - 565 words
Aerosol Spray Cans Spray cans produce an aerosol, the technical term for a very fine spray. They do this by means of a pressurized propellant, which is a liquid that boilsat everyday temperatures. Inside the can, a layer of gaseous pressure increased, and eventually it becomes so high that boiling stops. when the nozzle is pressed, the gas pressure forces the product up the tube in the can and out of the nozzlein a spray or foam. The propellant may emerge as well but, now under lesspressure, it immediately evaporates. First patented in the US in 1941, aerosol spray cans have been used asconvenient packages for an ever increasing range of products including paints, insecticides, and shaving cream to name a few. The can is filled with theproduct to be sprayed and the propellant, a compressed gas such as butane orFreon.
The gas is partly liquefied by the pressure in the can, but there is alayer of free gas above the liquid. As the can empties liquefied gas vaporizesto fill the space. The valve is normal held shut by the pressure in the can, and by thecoil spring directly below the valve stem. When the push button is pressed, itforces the valve stem down in its housing, uncovering a small a small hole whichleads up through the stem to the nozzle in the button. This allows the productto be forced up the dip tube by the gas pressure in the can
The nozzle isshaped to give a spray or a continuous stream. To produce a fine mist, a propellant is used which mixes with theproduct. The two leave the nozzle together and the propellant evaporates a soonas it reaches the air, breaking the product in to tiny droplets. The sametechnique used with a more viscous liquid and a wider nozzle results in a foam. For a continuous stream of liquid or more viscous material, a nonmixingpropellant is used, and the dip tube reaches into the product. The widespread use of aerosol cans using Freon as the propellant ledscientists to believe by the late 1970s that the ozone layer in the upperatmosphere, which filters out harmful Ultraviolet radiation from the sun, couldbe destroyed by the large quantities of fluorocarbons in the gas being releaseinto the air.
Federal controls were introduced to ban the use of Freon, andother propellants are now employed, notably butane which, however is dangerouslyflammable. Among young people in United States, conventional drug or alcohol abusehas given away-for an increasing number of teen-agers-to a practice called'huffing', inhaling chemicals found in aerosol sprays and other common householditems such as cigarette lighters, paint thinner, gasoline. Inhalant abuse isbecoming increasingly common among young middle-class teenagers. It is a cheap, and sometimes deadly, thrill. Bibliography:Aylesworth, T. G. It Works Like This.
Garden City: Doubleday & Company, 1968.Casey, Maura. 'When a quick high may be quick death.' The New York Times 30 July 1995 sec:cn p:4 col:5Flexner, Bob. 'Finishes for small projects.' Workbench March 1994Kaplan, Justine. 'Continuum: Are the Ninja Turtles misinformed?' Omni June 1993: p27Macaulay, David. The Way Things Work. Boston: Houghton Mifflin Company, 1988.Pierson, John.
'Form plus function: .. The battle between pumps and aerosols.' The Wall Street Journal 28 Feb. 1994 sec:B P:1 col:1Stepp, Laura Sessions. 'Ringing the alarm on aerosols: Inhalants & Poisons. Awareness Week.' The Washington Post 21 March 1994 sec:C p:5 col:5 Trebilcock, Bob. 'The new high kids crave.' Redbook March 1993.
Research paper and essay writing, free essay topics, sample works Aerosol Spray Cans