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Properties of Plastics
Introduction:
Plastics come in all shapes and sizes. The size and structure of the polymers
that compose different plastics contribute to the plastics’ properties.
Some plastics can be recycled – their properties can be chemically
manipulated to create a new plastic object that may serve a different
function than that of the original object. For example, polyethylene
terephthalate (PET) bottles can be recycled into insulation for winter jackets.
In this activity you will investigate and compare the properties of various
recyclable plastics.
Purpose:
1. Identify some of common plastics and their uses
2. Compare and contrast the properties of different plastics and make
inferences from those comparisons
3. Identify products that different plastics can become through recycling
Procedure
1. Review the table titled Common Plastics and Their Uses. Recyclers use
the code numbers, listed in the first column, to identify different plastics.
2. Collect eight plastic items, which are listed in the table. Choose at least
one product from every row in the table.
3. Use the table titled Properties of Plastics to record your observations.
4. Describe the sample type. (e.g., shampoo bottle, milk carton, etc.)
5. Record the full sample name as well as the abbreviated name, if one
exists.
6. Record the color of the sample.
7. Try to bend the sample. Does it bend or break? Record your observations.
8. Try to stretch the sample. Record your observations.
9. Cut a small piece, about 1 cm by 1 cm, of each sample and place each into
a small container of tap water. Note which samples float (F) and which sink
(S).
10. Add salt to the water until the solution is saturated (some solid salt
remains undissolved on the bottom.) Record whether each sample sinks or
floats.
11. Boil a small amount of water. Remove the water from the heat. Once the
bubbling stops, place the pieces of plastic in the water. Note whether each
sinks or floats. Also note if the heat deforms any of the samples.
12. Answer the questions.
Common Plastics and Their Uses
Code
Name
Uses
Plastic soft drink bottles,
Polyethylene
mouthwash bottles,
Terephthalate
peanut butter and salad
(PET or PETE)
dressing containers
Recycled Products
Liquid soap bottles,
strapping, fiberfill for
winter coats, surfboards,
paint brushes, fuzz on
tennis balls, soft drink
bottles, film, egg cartons,
skis, carpets, boats
High Density
Polyethylene
(HDPE)
Milk, water and juice
containers, grocery bags,
toys, liquid detergent
bottles
Flower pots, drain pipes,
signs, stadium seats, trash
cans, recycling bins, trafficbarrier cones, golf bag
liners, detergent bottles,
toys
Polyvinyl
Chloride
(PVC)
Clear food packaging,
shampoo bottles
Floor mats, pipes, hose,
mud flaps
Low Density
Polyethylene
(LDPE)
Bread bags, frozen food
bags, grocery bags
Garbage can liners, grocery
bags, multipurpose bags
Ketchup bottles, yogurt
Polypropylene
containers and margarine
(PP)
tubs, medicine bottles
Polystyrene
(PS)
Videocassette cases,
compact disc jackets,
coffee cups, knives,
spoons, and forks,
cafeteria trays, grocery
store meat trays and fastfood sandwich containers
Manhole steps, paint
buckets, videocassette
storage cases, ice scrapers,
fast-food trays, lawn
mower wheels, automobile
battery parts
License plate holders, golf
course and septic tank
drainage systems, desk top
accessories, hanging files,
food service trays, flower
pots, trash cans,
videocassettes
Properties of Plastics
Sample
type
Sample
name
Color
Bend
Stretch?
or
break?
Float?
H20
salt H20 hot H20
Deform in
hot H2O?
Questions:
1. Why would it be difficult to recycle polyvinyl chloride into plastic bags?
2. Why is HDPE a good material for boats?
3. Which plastic do you think could best contain extremely corrosive
material? Why?
4. List two uses of high density polyethylene other than those listed in the
table.
5. Two plastics that are targeted for recycling from household waste are
polyethylene terephthalate (PETE) and high density polyethylene (HDPE).
One of the problems of recycling such materials is separating them. Suppose
you have been hired to set up a process for separating large quantities of
waste plastic that is a mixture of PETE and HDPE. Describe how you might
perform this separation.