Alexei Volkov
Plastic is everywhere, and it's important to know what type you're dealing with. Some plastics are safe for food, others are durable enough to handle harmful chemicals, and some contain toxic chemicals and need careful handling. There are several ways to identify plastic types by sight. The most common is the Resin Identification Code (RIC), a number from 1 to 7 surrounded by a triangle of arrows, which indicates the type of plastic resin. Another way is to look at the density of the plastic, which can be tested using the float test. The burn test can also be used, but this is less safe and convenient.
| Characteristics | Values |
|---|---|
| International codes | Three arrows forming a triangle with a specific number in the middle |
| Symbol 1 | Polyester and PET plastics |
| Symbol 2 | High-Density Polyethylene |
| Symbol 3 | PVC items that can be both rigid and flexible |
| Burn test | A blue flame with yellow tips indicates Polyethylene burning, while yellow flames with green tips point toward PVC plastic |
| Density | Low-density polyethylene can remain above water, as well as polystyrene products |
| Resin Identification Code (RIC) | A chasing arrow around a number that can range from one to seven |
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What You'll Learn
Look for the Resin Identification Code (RIC)
The Resin Identification Code (RIC) is a system that helps identify the type of resin used in a plastic product. It was developed by the Society of the Plastics Industry, Inc. (SPI), now known as the Plastics Industry Association (PLASTICS), in 1988. The RIC was initially created for those working in the recycling and plastic industries, so it is not easily decipherable by consumers. However, it provides valuable information for waste operators and consumers to distinguish one material from another and sort products more efficiently.
The RIC typically appears as a set of three arrows forming a triangle around a number, with each of the seven numbers representing a different type of resin. For example, Symbol 1 represents polyester and PET plastics, commonly found in clothing, plastic bottles, and insulation. Symbol 2 stands for High-Density Polyethylene, used in bleach bottles, fuel tanks, and motor oil storage containers. Symbol 3 denotes PVC items, which can be both rigid and flexible, such as door and window frames, sporting balls, and electrical wire insulation.
While the RIC does not indicate the recyclability of a product, it aids in identifying the resin content, which is crucial for proper waste management and recycling. It is important to note that the RIC only identifies the primary resin used and does not account for other materials or additives that may be present in the plastic product.
Currently, there is a push for a more consumer-friendly plastic recycling code system, such as the How2Recycle system, which provides clear instructions on how to recycle specific items and information about their recyclability. This move towards simpler codes makes sense, considering the high percentage of plastic products that are not recycled.
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Identify by density using the float test
One way to identify plastic type is by performing the float test, which involves observing the buoyancy of a plastic item when placed in water. This test is based on the principle that different types of plastics have varying densities, which affect whether they will float or sink in water.
To perform the float test, simply fill a container with water and place the plastic item in it. If the plastic floats, it is likely one of the three types of plastics that are less dense than water: HDPE, LDPE, or PP. High-density polyethylene (HDPE) is commonly used for milk jugs, laundry soap containers, and fuel tanks, while low-density polyethylene (LDPE) is often used for trash bags. Polypropylene (PP) is another type of plastic that floats in water.
On the other hand, if the plastic item sinks in the water, it has a higher density than water. This density test can help rule out certain types of plastics and narrow down the possibilities. However, it may not always provide a definitive identification, as plastics can vary in density during manufacturing.
It is important to note that the float test is just one method of plastic identification and may not always be completely accurate. Other tests, such as observing international recycling codes or performing a burn test, can also be used in conjunction with the float test for more accurate identification. Additionally, the shape and intended use of the plastic item can provide clues about its type, as certain plastics are favoured for specific applications due to their unique properties.
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Recognise common plastic items like bleach bottles
Bleach bottles are typically made of low-density polyethylene (LDPE). LDPE is a type of plastic with superior quality and strength. It is known for its durability and ability to withstand harsh chemicals like bleach without cracking, fading, or peeling. LDPE is also buoyant, which means it will float if placed in water.
To identify LDPE plastic by sight, look for the recycling symbol on the product. LDPE products will have a triangle with three arrows forming a circle and the number "4" in the centre. This is the universal recycling symbol for low-density polyethylene.
Another way to identify LDPE is by its appearance and texture. LDPE has a smooth, slightly waxy feel to it. It is often used for products that require flexibility and impact resistance, such as plastic bags, squeeze bottles, and some plastic tubing.
While it is not advisable to burn plastic as an identification method due to health and environmental concerns, the colour of the flame produced by burning LDPE is blue with yellow tips.
Recognising common plastic items like bleach bottles can be useful for understanding their intended use and proper handling. Bleach bottles are typically made of LDPE because of its resistance to chemicals, ensuring that the bottle can safely contain the corrosive liquid.
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Observe the colour of the flame when burning
Observing the colour of the flame when burning plastic is a common method used in recycling companies to identify different types of polymers. This process, known as the burn test, can help distinguish between various plastic types by exposing the plastic to a flame and observing the colour, behaviour, and odour of the resulting flame. It is important to exercise caution when performing the burn test due to the potential toxicity of plastic combustion products.
When identifying plastics through the burn test, it is important to pay attention to the colour of the flame. Different plastics produce distinct flame colours, which can be used as an indicator of the plastic type. For example, polypropylene (PP) burns with a yellow flame at the upper end and blue flame in the middle, while SAN exhibits a yellow flame with black smoke. The flame colour of methacrylate plastic is also yellow at the top and blue at the bottom, but it is distinguished by a slight tail of carbon.
The burn test can also reveal the presence of chlorine in the plastic. By heating a copper wire to a colourless red-hot state and placing a small amount of plastic on it, the presence of chlorine will be indicated by a blue-green flame (CuCl2). This test is known as the Beilstein copper wire test.
Additionally, the behaviour of the flame can provide clues about the type of plastic being burned. For example, some plastics, like PP, exhibit dripping during combustion. Others, like PA, may self-extinguish when removed from the fire source.
While the burn test can provide valuable information about the type of plastic, it is important to consider other factors as well. The odour of the burning plastic, for example, can be indicative of certain plastic types. However, it is crucial to prioritise safety and avoid inhaling toxic fumes.
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Identify by sight: PET plastics are often clear
PET plastics, or polyethylene terephthalate, are one of the most widely used packaging resins. They are commonly found in plastic bottles, packaging, and textiles. Due to their clarity and natural CO2 barrier properties, they are often used for carbonated soft drink bottling. This makes them easily identifiable by sight, as they are clear.
However, PET plastics are not always clear. They can also be white or opaque, usually due to the addition of a titanium dioxide pigment. This pigment creates an undesirable haze in the plastic. Other colourants can also be added to PET plastics, such as dark or black colourants, which have become more sortable in recent years due to innovations in sortation technology.
It is important to be able to identify PET plastics for recycling purposes. The recycling of PET plastics is more practical than many other plastic applications because of the high value of the resin and its widespread use in water and soft drink bottling. The recycled material is known as rPET and is used in various consumer goods, such as household items, furniture, and electronic accessories.
There are other methods to identify PET plastics besides visual identification. One method is to look for the international recycling symbol. Symbol 1 pertains to polyester and PET plastics and can be found on many household items, including clothing, plastic bottles, and insulation materials. Another method is to test the density of the plastic, as PET plastics have a density of 1.38 g/cm^3 and will sink in water.
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