Maya Ellison
Plastics are labelled with numbers 1-7 to help recycling plants identify the type of plastic and how it should be processed. Plastics #1 and #2 are the most common types of plastic containers and the most easily recyclable. Plastic #1, also known as PET or PETE, is found in most water and soda bottles and some packaging. It is relatively safe, but it should be kept out of the heat and not reused. Plastic #2, also known as HDPE, is used to make milk jugs, detergent and oil bottles, toys, and some plastic bags. It is the most commonly recycled plastic and is considered one of the safest forms of plastic.
| Characteristics | Values |
|---|---|
| Plastic Number | 1, 2 |
| Common Name | PET, HDPE |
| Float or Sink | Sinks |
| Odor | Burnt Sugar |
| Safety | Safe but avoid heat |
| Recyclability | Recyclable |
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What You'll Learn
Check the recycling symbol for numbers 1 or 2
Plastics are labelled with numbers 1 to 7 to help recycling plants identify the type of plastic and how it should be processed. These numbers are also valuable consumer information, indicating the likelihood of your recycling ending up in a landfill.
Plastics labelled with a 1 or 2 are the most common types of plastic containers and the most easily recyclable. They are also the most likely to have a California Redemption Value (CRV) associated with them. Number 1 plastic, also known as PET or PETE, is found in most water and soda bottles, microwavable food trays, salad dressing bottles, peanut butter jars, and disposable food and beverage containers. It is recyclable but not reusable. Number 2 plastic, or HDPE, is the stiff plastic used to make milk jugs, detergent and oil bottles, toys, and some plastic bags. It is the most commonly recycled plastic and is considered one of the safest forms of plastic.
To identify the number associated with a plastic product, look for the recycling symbol, usually located on the bottom, side, or top of the package. The number is typically found within the chasing arrows triangle and may be tiny, but it is important for identifying the type of plastic and how it should be recycled.
In addition to checking the recycling symbol, you can also identify plastics by their physical characteristics. For example, number 1 plastic is usually clear in colour, while number 2 plastic is typically opaque. You can also try the float test, as polyolefins, which include numbers 2, 4, and 5, generally float in water, while the rest generally sink.
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Identify by floating test—polyolefins float, the rest sink
The float test is a simple way to help identify different types of plastics. This test is based on the density of the plastic—if the plastic is less dense than water, it will float, and if it's more dense, it will sink. Polyethylenes and polypropylenes are examples of plastics that float in water, as they have a density of 1 g/mL. Specifically, the plastics that float in water are HDPE, LDPE, and PP. On the other hand, higher-density plastics such as PET (or PETE), PVC, and PS sink in water.
It's important to note that the float test is not always definitive in identifying a specific type of plastic. While it can help rule out certain plastics, it may not provide a positive identification. For example, while we know that HDPE floats, this test alone cannot distinguish it from LDPE or PP, which also float.
Additionally, the density of plastics can vary depending on their manufacturing process, resulting in a range of density values for each type of plastic. This variability underscores the importance of using the float test in conjunction with other identification methods to more accurately determine the specific type of plastic.
To perform the float test, you would need to prepare a container of water and simply place the plastic item in the water to observe whether it floats or sinks. This test is straightforward and safe, making it a convenient initial step in plastic identification. However, for a more comprehensive understanding, it is recommended to complement this test with other identification techniques, such as the burn test, the Beilstein copper wire test, or susceptibility to acetone.
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Identify by smell—PET smells like burnt sugar, PVC like chlorine
Smell is a key identifier of plastics, and it can be used to distinguish between different types. However, caution should be exercised when smelling burning plastic, as some fumes can be harmful. When identifying plastics by smell, it is helpful to have a known sample for comparison.
Polyethylene terephthalate (PET), a type 1 plastic, has a distinct smell of burnt sugar when ignited, which some liken to the smell of candy floss or sugar candy. It is typically clear, strong, and lightweight, and is often used for beverage bottles, food containers, clothing fibres, and carpets. Conversely, polyvinyl chloride (PVC), a type 2 plastic, has an acrid smell akin to chlorine when burnt. PVC is commonly found in garden hosepipes and certain household plumbing pipes.
The Museum of Design in Plastics (MoDiP) at the Arts University Bournemouth (AUB) has developed a flowchart to aid in the identification of plastics, which includes smell as one of the first three determining factors. This method is particularly useful for quickly identifying the plastics that are easiest to recognise.
In addition to smell, other tests can be performed to identify plastics, including float tests, burn tests, and scratch tests. These tests, in conjunction with smell, can help tentatively identify a plastic before conducting more rigorous and technical analyses for unambiguous identification.
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Check the colour—PET is usually clear, HDPE is usually opaque
Colour can be a useful indicator when trying to identify whether a plastic is PET or HDPE. PET, or polyethylene terephthalate, is usually clear, although it can become opaque when exposed to heat. For example, a PET bottle heated by a candle will become opaque. As one of the most commonly used plastics, PET is found in most water and soda bottles, as well as some packaging.
On the other hand, HDPE, or high-density polyethylene, is usually opaque. HDPE is the stiff plastic used to make milk jugs, detergent and oil bottles, toys, and some plastic bags. It is the most commonly recycled plastic and is considered one of the safest forms of plastic.
While colour can be a helpful indicator, it is not always a reliable method for identifying plastics. For example, HDPE sheets are often white or black, but they can also be found in a variety of colours, especially in manufactured products. Similarly, PET is typically clear, but it can become opaque under certain conditions, as previously mentioned.
Therefore, when trying to identify the type of plastic, it is essential to consider other factors as well. One common method is to look for the recycling symbol on the plastic, which will have a number inside it, indicating the type of plastic. For instance, PET is usually labelled with a "1" inside the recycling symbol, while HDPE is labelled with a "2". Additionally, density tests can be performed to distinguish between different types of plastics, including HDPE and LDPE.
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Check the product—PET is used for water bottles, HDPE for milk jugs
When it comes to identifying plastics, checking the product itself can be a helpful strategy. Two commonly used plastics are PET, which is often used for water bottles, and HDPE, which is typically used for milk jugs.
PET, or Polyethylene terephthalate, is a well-known plastic that is strong, lightweight, and versatile. It is commonly used for water bottles, carbonated soft drink bottles, and food packaging. PET is recyclable and can be turned into new bottles, textiles, and other products. Its strong gas barrier properties make it a preferred choice for manufacturers, allowing them to utilize plastic waste in their products.
On the other hand, HDPE, or High-Density Polyethylene, is a durable and chemically resistant plastic. It is often used for milk jugs, detergent and oil bottles, toys, plastic bags, and industrial applications like chemical tanks and machined parts. HDPE is the most commonly recycled plastic and is considered safe. Its chemical resistance makes it suitable for laundry, shampoo, and cleaning product containers.
By checking the product type, you can often identify whether it is made of PET or HDPE. Water bottles are typically made of PET, while milk jugs and similar containers are often made of HDPE. This knowledge can help you make informed choices about plastic usage and recycling.
Additionally, you can look for recycling symbols on the products. PET is usually identified as #1 plastic, while HDPE is often labelled as #2. These recycling labels provide important information about the type of plastic used, helping consumers make informed choices about their plastic usage and proper waste disposal.
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Frequently asked questions
Plastic type 1, or PET, is usually clear in colour and is used for disposable beverage and food containers and bottles. It is also used in household cleaning product containers.
Plastic type 2, or HDPE, is usually opaque in colour and is used for milk jugs, detergent and juice bottles, butter tubs, motor oil bottles, and some shopping bags.
Plastic type 1 is considered relatively safe, but it should be kept out of the heat as it could cause carcinogens to leach into liquids. It should not be reused.
Plastic type 2 is considered one of the safest forms of plastic. However, it should still be avoided as much as possible, and food or drink should not be microwaved in it.
