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Plastic: Types & Uses

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  • 0:04 Plastics
  • 0:31 Two Basic Classes
  • 1:30 Plastic Numbers & Uses
  • 4:54 Recyclability
  • 5:27 Lesson Summary
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Lesson Transcript
Instructor: Yuanxin (Amy) Yang Alcocer

Amy has a master's degree in secondary education and has taught math at a public charter high school.

While there are only two classes of plastics, there are actually many different types of plastics. When it comes to the plastics you use every day, they are separated into seven different categories as you'll see in this lesson.

Plastics

Plastics are everywhere. You use them every day. Plastics are used in car parts and for all kinds of storage. Most stores also bag your items in plastic bags. Some plastics are soft while others are hard, almost like glass. If you drink water from a bottle, that bottle is most likely plastic. Plastic is relatively inexpensive so it is used in many applications. There are two basic classes of plastics along with seven popular types of plastics.

Two Basic Classes

According to the American Chemistry Council, Inc., there are literally thousands of different plastics. This is because plastics can be made to suit almost any application. Scientists can make plastics that are see-through, plastics that block oxygen, and even plastics that stretch and then return to their original shape. Plastics can also be made to stop bullets!

Even though there's all this variety, plastic manufacturers still group plastics into two basic classes.

  • Thermoplastics are plastics made to be melted again, placed in a mold to make something, and melted again if needed to make something else. Polyethylene, polypropylene, nylon, and polycarbonate are examples of thermoplastics.
  • Thermosets are plastics that are made into products right away and cannot be melted to make something else again. Much like a clay pot is baked to set it, thermosets are plastics that are heated to set them. Once set, thermosets cannot be turned into something else like thermoplastics can. Epoxies and silicone are thermosets.

Plastic Number & Uses

Within these two basic classes, there are different types of plastics. The plastics have a number identification associated with them. These numbers were introduced by the Society of the Plastics Industry in 1988 to help people know which plastics are recyclable and how to properly dispose of the others. These numbers identify the seven most popular types of plastics.

#1: Polyethylene terephthalate (PETE or PET)

Plastics marked with a 1 are made from polyethylene terephthalate, PETE or PET for short. The #1 plastics are used to make disposable bottles, such as water bottles and soda bottles. Bean bags and rope can be made from this plastic. Some of these plastics may absorb odors and such from the items stored inside. These plastics are known to leach chemicals over time. PET plastics are safe to use under 140° F.

#2: High-density polyethylene (HDPE)

The #2 plastics are made from high-density polyethylene or HDPE. Unlike #1 plastics, HDPE plastics do not leach chemicals. But, this doesn't mean that you can or should reuse these bottles due to the risk of contamination if the bottle previously held a toxic chemical. Milk bottles, shampoos, soap bottles, detergents, and motor oil bottles are made from this plastic. It's also used to make that clear hard-to-open plastic packaging you see on some products. HDPE plastics are safe to use anywhere from -148 to 176° F, so they are dishwasher-safe.

#3: Polyvinyl chloride (PVC)

PVC is plastic #3 and is used for plumbing pipes and outdoor furniture. It can also be used as flooring. It is not food safe. These plastics are usually not recycled.

#4: Low-density polyethylene (LDPE)

LDPE plastics are used in grocery bags, plastic cling wrap, sandwich bags, and squeeze bottles. It is food safe. This type of plastic is often not recycled.

#5: Polypropylene (PP)

Polypropylene plastics are used to make diapers, Tupperware, and other rigid containers, such as medicine bottles. Rakes and ice scrapers are made from this type of plastic as well.

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