Properties of Plastics
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.
- Identify some of common plastics and their uses
- Compare and contrast the properties of different plastics and make inferences from those comparisons
- Identify products that different plastics can become through recycling
- Review the table titled Common Plastics and Their Uses. Recyclers use the code numbers, listed in the first column, to identify different plastics.
- Collect eight plastic items, which are listed in the table. Choose at least one product from every row in the table.
- Use the table titled Properties of Plastics to record your observations.
- Describe the sample type. (e.g., shampoo bottle, milk carton, etc.)
- Record the full sample name as well as the abbreviated name, if one exists.
- Record the color of the sample.
- Try to bend the sample. Does it bend or break? Record your observations.
- Try to stretch the sample. Record your observations.
- Cut a small piece, about 1 cm by 1 cm, of each sample and place each intoa small container of tap water. Note which samples float (F) and which sink (S).
- 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.
- 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.
- Answer the questions.
Common Plastics and Their Uses
(PET or PETE)
Plastic soft drink bottles, mouthwash bottles, peanut butter and salad dressing containers
Liquid soap bottles, strapping, fiberfill for winter coats, surfboards, paint brushes, fuzz on tennis balls, soft drink bottles, film, egg cartons, skis, carpets, boats
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
Clear food packaging, shampoo bottles
Floor mats, pipes, hose, mud flaps
Bread bags, frozen food bags, grocery bags
Garbage can liners, grocery bags, multipurpose bags
Ketchup bottles, yogurt containers and margarine tubs, medicine bottles
Manhole steps, paint buckets, videocassette storage cases, ice scrapers, fast-food trays, lawn mower wheels, automobile battery parts
Videocassette cases, compact disc jackets, coffee cups, knives, spoons, and forks, cafeteria trays, grocery store meat trays and fastfood sandwich containers
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
Bend or break?
Float? H20 salt H20 hot H20
Deform in hot H2O?
- Why would it be difficult to recycle polyvinyl chloride into plastic bags?
- Why is HDPE a good material for boats?
- Which plastic do you think could best contain extremely corrosive material? Why?
- List two uses of high density polyethylene other than those listed in thetable.
- 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.