Maya Ellison
Plastic is everywhere, from paper clips to spacecraft. It's cheap, versatile, and easy to manufacture, but it also comes with health and environmental risks. Learning how to identify different types of plastic can help you make informed decisions about the products you use and consume. Plastic types are often indicated by a number, known as a resin identification code, which is surrounded by a chasing arrows symbol. However, these codes do not indicate toxicity or safety, and only six plastic types are explicitly identified by numbers (1 to 6), with code 7 being a catch-all category. To identify a plastic type, you can observe its appearance, feel, and even smell. For example, LDPE and HDPE smell like candle wax, while Polypropylene has a paraffin element to it. Knowing the differences between plastic types can help you understand the potential risks and make more sustainable choices.
| Characteristics | Values |
|---|---|
| Identification | Many plastic products have a number, the "resin identification code", surrounded by a chasing arrows symbol. |
| The resin identification code does not indicate toxicity or safety. | |
| The code is not a guarantee of recyclability. | |
| Common Types | Polyester and PET plastics (symbol 1) |
| High-Density Polyethylene (HDPE) (symbol 2) | |
| PVC (symbol 3) | |
| Low-Density Polyethylene (LDPE) (symbol 4) | |
| Polypropylene (PP) (symbol 5) | |
| Polycarbonate (PC) (symbol 7) | |
| Uses | Plastic bottles, clothing, insulation, food packaging, containers, toys, blood bags, detergent bottles, grocery bags, juice containers, milk cartons, fuel tanks, storage containers for motor oil, door and window frames, sporting balls, water pipes, electrical wire insulation. |
| Hazards | Toxic chemicals leach out of plastic and can cause cancer, birth defects, impaired immunity, and endocrine disruption. |
| PVC is one of the most hazardous plastics due to the formation of dioxins when burned. | |
| Polycarbonate with Bisphenol A (found in symbol 7 plastics) is linked to cancers, impaired immune function, early onset of puberty, obesity, diabetes, and hyperactivity. | |
| Identification by Other Methods | Plastic types can be distinguished by appearance, feel, and sound. |
| LDPE and HDPE feel and sound different, LDPE being soft and swishing, and HDPE being crisper and crinklier. | |
| PP feels much firmer and stiffer and does not stretch. | |
| Plastic types can also be distinguished by the smell of the smoke when a flame is applied to them. |
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What You'll Learn
- Look for the resin identification code, usually surrounded by a triangle of arrows
- Identify by appearance and feel: Polyethylene is flexible, LDPE crumbles, and HDPE is tougher
- Burning plastic is hazardous but produces distinct flame colours
- Float test and burn test: While not always accurate, these tests can rule out certain plastics
- Check the label: Most products will have the information listed
Look for the resin identification code, usually surrounded by a triangle of arrows
To identify the type of plastic, look for the Resin Identification Code (RIC), which is usually surrounded by a triangle of arrows. This symbol, known as the "chasing arrows", was originally designed in 1970 to indicate that a product was recyclable. However, in 2013, the ASTM revised the RIC symbol to a solid equilateral triangle to address consumer confusion about recyclability. The presence of a RIC on a product does not necessarily indicate that it is recyclable, nor does the absence of a RIC mean that an object is unrecyclable. The RIC is part of a broader set of recycling codes and helps identify the type of resin used in the plastic product.
The RIC system was developed in 1988 by the Society of the Plastics Industry (SPI), now known as the Plastics Industry Association (PLASTICS). The RICs are used to identify the primary type of resin used in plastic products and facilitate the collection, disposal, and recycling of these products. The use of RICs is mandatory in most US states, with at least 36 states requiring them in some form. However, the specific codes and containers that must be labelled vary between states.
The RICs range from 1 to 7, with each number indicating a specific type of plastic:
- 1: Polyethylene Terephthalate (PET) - Widely recycled and used in soft drink bottles and clear plastic bottles.
- 2: High-Density Polyethylene (HDPE) - Widely recycled and used in milk bottles and some cleaning or personal care products.
- 3: Polyvinyl Chloride (PVC) - Tough and durable plastic often used in building materials, medical devices, and cable insulation. Not easily recyclable.
- 4: Low-Density Polyethylene (LDPE) - Flexible plastic often used in thin packaging, squeezable bottles, and shopping bags. Not easily recyclable in curbside collections.
- 5: Polypropylene (PP) - Has a wide range of chemical compatibility and is used in packing tape, plastic straws, ketchup bottles, and microwavable meal trays. Widely recyclable.
- 6: Polystyrene (PS) - Commonly known as Styrofoam, it is hard to recycle and has been known to leach chemicals when heated.
- 7: Other Plastics - This category includes plastics that cannot be grouped with the previous six, such as bioplastics, composite plastics, plastic-coated paper, and polycarbonate. Products with this label are usually not recycled.
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Identify by appearance and feel: Polyethylene is flexible, LDPE crumbles, and HDPE is tougher
Polyethylene is a flexible plastic with a smooth texture. It can leave marks and has a flammable nature. Polyethylene products can continue to burn even after the fire is out. Over time, the material starts melting and releases the smell of burning wax. LDPE or Low-Density Polyethylene is a type of polyethylene that is flexible and can change its shape without damage. LDPE is used in products like grocery bags, shrink wrap, and juice and milk cartons. LDPE is thin enough to crumble in the palm of your hands. If it crackles and makes a loud noise, that’s a clear sign that the plastic is LDPE. LDPE has higher transparency than other plastics and often appears yellowish. LDPE has a glossy texture and feels soft, tough, and sometimes sticky. LDPE's durability is less than that of PP products but more than that of polyvinyl.
HDPE or High-Density Polyethylene is another type of polyethylene. It is tougher to deform than LDPE. Most HDPE products have a translucent and milky white coating, but uncolored HDPE is waxier in appearance. HDPE is used in containers of juice or shampoo.
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Burning plastic is hazardous but produces distinct flame colours
Burning plastic is dangerous and can have severe health and environmental consequences. When plastic is burned, hazardous chemicals are released, including dioxins and mercury, which have been linked to various health issues such as cancer, birth defects, hormonal changes, declining sperm counts, infertility, and immune system impairment. Additionally, the burning of plastic contributes to air pollution and can have detrimental effects on the environment, including the release of microplastics, which can contaminate soil and water sources.
However, it is important to note that different types of plastics, when burned, produce distinct flame colours. For example, Polyethylene Terephthalate (PET), a common type of plastic used in bottles and clothing, burns with a bright orange flame. On the other hand, Polyvinyl Chloride (PVC), which is used in construction and toy manufacturing, produces a yellow flame when burned.
The colour of the flame can provide a visual clue to help identify the type of plastic that is burning. For instance, the bright orange flame of burning PET plastic can be distinguished from the yellow flame of burning PVC. This identification can be crucial, especially in fire investigation and forensic analysis, as it helps determine the source and cause of the fire.
Additionally, the burning of plastic can also emit distinct odours that can aid in identification. For example, PET plastic has a sweet smell similar to burnt sugar or candy floss, while PVC produces an acrid, chlorine-like odour. These odours can be used as additional indicators to help identify the type of plastic that is burning, especially when combined with visual observations of the flame colour.
While the distinct flame colours and odours produced by burning plastic can provide clues for identification, it is essential to prioritise safety and avoid intentionally burning plastic due to its hazardous nature. The release of toxic chemicals during combustion poses significant risks to both human health and the environment. Instead, proper waste management practices, recycling, and the adoption of environmentally friendly alternatives should be encouraged to minimise the negative impact of plastic on our planet.
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Float test and burn test: While not always accurate, these tests can rule out certain plastics
The float test and burn test are simple methods to rule out certain plastics, although they are not always accurate for specific identification. The float test involves checking the density of the plastic by dropping it into a small vial of liquid of known density. If the plastic floats, it is less dense than the liquid, and if it sinks, it is more dense. For example, polyethylenes and polypropylenes float in water (density = 1 g/mL), while most other plastics sink. Among heavier-than-water plastics, ABS and PS will float in glycerin (density = 1.26 g/mL), but PETE and PVC will not.
The burn test, or Beilstein test, involves using a copper wire to detect the presence of chlorine in the plastic, which is indicative of PVC. Other tests for specific plastics include susceptibility to acetone, which will make most plastics (except polyethylene and polypropylene) become tacky, and whether the plastic turns white under stress, such as bending, which will make PVC whiten but not PET.
While these tests can provide some indication of the type of plastic, they are not definitive and are limited in their accuracy. For more precise identification, other methods or technologies may be required.
It is important to note that performing any kind of burn test or exposing plastics to open flames can be dangerous and should be done with caution and proper safety measures in place.
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Check the label: Most products will have the information listed
Checking the label is the easiest way to identify the type of plastic. Most plastic products will have a label or a recycling symbol that indicates the type of plastic. These symbols are usually found at the bottom of containers or packaging, and they provide information about the chemical composition and recyclability of the plastic.
The most common plastic identification symbols and their meanings are as follows:
- Symbol 1 – Polyester and PET plastics. This includes plastic bottles, insulation materials, and clothing fibres.
- Symbol 2 – High-Density Polyethylene (HDPE), known for its strength and resistance to acidic chemicals. HDPE is commonly used for bleach bottles, fuel tanks, and motor oil containers.
- Symbol 3 – PVC, which can be rigid or flexible. PVC is used in a variety of applications, including pipes, electrical wire insulation, door and window frames, and sporting equipment.
- Symbol 4 – Low-Density Polyethylene (LDPE), which is flexible and can be reshaped without damage. LDPE is often used for grocery bags, shrink wrap, and milk cartons.
- Symbol 7 – Miscellaneous plastics, including acrylic, nylon, and polycarbonate. These plastics are often combined with other polymers and are not always recyclable.
In addition to these standard symbols, some products may have additional markings or labels that indicate specific plastic types or resins used. For example, you may see abbreviations like "PP" for polypropylene, "PS" for polystyrene, or "PC" for polycarbonate.
While checking the label is a straightforward method, it's important to note that not all plastic items will have clear or accurate labelling. Some products may have worn-off markings, lack standard symbols, or be made of plastic blends that are challenging to identify. In such cases, other identification methods, such as density tests, burn tests, or examining the appearance and texture, may be necessary to determine the specific type of plastic.
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Frequently asked questions
The easiest way to identify the type of plastic is by locating three arrows forming a triangle with a specific number in the middle. Symbol 1, for instance, pertains to polyester and PET plastics, while Symbol 2 covers High-Density Polyethylene (HDPE).
Another method to identify plastics is through their appearance and texture. LDPE, for instance, is thin enough to crumble in your hands, and will make a loud, crackling noise. HDPE, on the other hand, is tougher to deform and has a more waxy appearance.
You can also identify plastics by burning them and observing the smoke and ignition. However, this method is not recommended due to the negative health and environmental impacts of burning plastic. LDPE and HDPE, for example, smell like candle wax when burned, while PVC has an acrid smell like chlorine.
Some common plastic symbols include "ABS", "PC", "PA6", and "PP". ABS does not have a symbol but is often marked as ">ABS." It is a tough, rigid, and hard material that is not easy to break. PC stands for polycarbonate, PA6 stands for nylon, and PP stands for polypropylene.
The number 7 on plastic packaging means "other" and includes plastic types that are not specifically categorized under symbols 1-6. This includes mixes of the first six categories as well as other types such as acrylic and polycarbonate.
