What is a Plastic?
Definition of Plastic from www.dictionary.com
- any of a group of synthetic or natural organic materials
that may be shaped when soft and then hardened, including
many types of resins, resinoids, polymers, cellulose
derivatives, casein materials, and proteins: used in place of
other materials, as glass, wood, and metals, in construction
and decoration, for making many articles, as coatings, and,
drawn into filaments, for weaving.
History of Plastics
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References of plastic as far back as the Old Testament
1846 in Europe, Charles Schönbein accidentally discovered nitrocellulose
1851 Ebonite (hard rubber) discovered, was the first thermosetting material to be
prepared
1870 John W. Hyatt reacts nitrocellulose with camphor to make celluloid
1890s – 1907 Formaldehyde Resins very important alternative to celluloid
particularly casein.
1909 Leo Baekeland synthesized bakelite. Led to a class of plastics known as
phenolic resins.
1930’s Wallace Carruthers, a Dupont Chemist, invents plastic polymer known as
nylon.
1930-1940 initial commercial development of today’s major thermoplastics, PVC,
LDPE, PS. The advent of WW II in 1939 brought plastics into great demand.
1945-1955 First Decade after WW II saw the development of PP, HDPE, and the
growth of new plastic in many applications
1978 Linear low density polyethylene introduced (Density of 0.90 – 0.96) reduced
the cost of their production drastically
Plastics Today
• Society of the Plastics Industry (SPI) founded in 1937.
Developed a Resin Identification Code (RIC) in 1988 to
help with the recycling of the different plastics
available.
• There are 7 categories within the RIC.
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1 – PET (polyethylene terephthalate)
2 – HDPE (high density polyethylene)
3 – V or PVC (Vinyl or Poly (vinyl chloride))
4 – LDPE (low density polyethylene)
5 – PP (polypropylene)
6 – PS (polystyrene)
7 – Other (mixed plastics)
1 – PET (polyethylene terephthalate)
(-CO-C6H4-CO-O-CH2-CH2-O-)n
• Packaging applications: Soft drink bottles, water bottles, beer bottles,
mouthwash bottles, peanut butter containers, salad dressing containers,
juice bottles, vegetable oil bottles
• Recycled products: Fiber, tote bags, new PETE containers for both food
and non-food products, fabric for clothing, athletic shoes, luggage,
upholstery, furniture, carpet, fiberfill for sleeping bags and winter coats,
industrial strapping, sheet, and film, and automotive parts, such as luggage
racks, headliners, fuse boxes, bumpers, grilles and door panels
Note: the C6H4 highlighted in the molecular formula above represents a
benzene ring. Benzene is generally considered a carcinogenic substance.
2 – HDPE (high density polyethylene)
(-CH2-CH2-)n
• Packaging applications: Milk containers, juice bottles,
water bottles, bleach, detergent, and shampoo bottles,
trash bags, grocery and retail carrying bags, motor oil
bottles, butter and margarine tubs, household cleaner
bottles, yogurt containers, and cereal box liners
• Recycled products: Drainage pipe, liquid laundry
detergent bottles, oil bottles, pens, benches, doghouses,
recycling containers, floor tile, picnic tables, fencing,
lumber, and mailbox posts
3 - Vinyl or PVC (polyvinyl chloride)
(-CH2-CHCl-)n
• Packaging applications: Window cleaner bottles, cooking oil bottles,
detergent bottles, shampoo bottles, clear food packaging, wire and cable
jacketing, medical tubing, with additional significant usage in household
products and building materials, particularly siding, piping, and windows
• Recycled products: Binders, decking, paneling, mud flaps, roadway
gutters, flooring, cables, speed bumps, and mats
Note: The Cl (chlorine atom) in the molecular formula renders PVC a
potentially toxic material when it is burned. The burning of PVC can result in
the creation of dioxins, a material that is considered highly carcinogenic.
4 – LDPE (low density polyethylene)
( - CH2 - CH2 - )n
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Packaging applications: Squeezable bottles, bread bags, frozen food bags, tote
bags, clothing, furniture, dry cleaning bags, and carpet
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Recycled products: Film and sheet, floor tile, garbage can liners, shipping
envelopes, furniture, compost bins, paneling, trash cans, lumber, landscaping ties
Note: The molecular formulas for LDPE and HDPE are the same. The difference in the
plastics is the density of the molecular chains. The density varies in the manner in
which the polymeric chains form. In HDPE the chain is essentially one long continuous
chain, allowing the strands to fold back upon one another and densely occupy space. In
LDPE the chains have multiple branches, which interfere with a neatly organized
packing of chains. Instead the packing is more disorganized, occupying more space and
thus resulting in a lower density.)
5 – PP( polypropylene)
(-CHCH3-CH2-)n
• Packaging applications: Yogurt containers,
syrup bottles, ketchup bottles, caps, straws,
medicine bottles
• Recycled products: Signal lights, battery cables,
brooms, brushes, auto battery cases, ice scrapers,
landscape borders, bicycle racks, rakes, bins,
pallets, and trays
6 – PS (polystyrene)
(-CHC6H5-CH2-)n
• Packaging applications: Plates, cups, cutlery, meat trays,
egg cartons, carry-out containers, aspirin bottles, compact
disc jackets
• Recycled products: Thermal insulation, light switch plates,
egg cartons, vents, rulers, foam packing, carry-out
containers
Note: C6H5 in the molecular formula comprises a benzene
ring. Benzene is generally considered a carcinogenic
substance.
7 – Other (misc. plastics)
Properties: varies according to constituent resins
Statistic: In 1999 there was minimal usage of resins in the 'other'
category in plastic bottles.
Description: The category of "Other" includes any resin not specifically
numbered 1, 2, 3, 4, 5, or 6, or combinations of one or more of these
resins.
Packaging applications: Three and five gallon water bottles, certain
food product bottles
Recycled products: Plastic lumber, custom-made products
Videos
1944 Plastic Science and Chemistry video:
http://www.youtube.com/watch?v=MKKFe4Y9EA
References
SPI http://www.plasticsindustry.org/AboutPlastics/content.cfm?ItemNumbe
r=670
SPI http://www.plasticsindustry.org/AboutPlastics/content.cfm?ItemNumbe
r=823&navItemNumber=2144
How stuff works - http://science.howstuffworks.com/plastic1.htm
EPA - http://www.epa.gov/osw/conserve/materials/plastics.htm
Earth Odyssey - http://www.earthodyssey.com/symbols.html