How to Identify Different Types of Plastic

Plastic is material consisting of any of a wide range of synthetic or semi-synthetic organic compounds that are malleable and can be molded into solid objects. Due to their low cost, ease of manufacture, versatility, and imperviousness to water, plastics are used in a multitude of products of different scale, including paper clips and spacecraft. Plastic is truly a remarkable material to work with, but it comes with its downsides as well. This article will cover all your major questions about plastic.

Questions This Article Will Answer

1. What are the different types of plastic?
2. How do I distinguish between different plastics?
3. What are the pros and cons of using plastic?
4. What does plastic do to the environment?
5. Can plastic harm human health?
6. What is plastic and how is it made?

Plastic is an essential component used in making many kinds of products. Some items made using plastics include: water bottles, combs, and beverage containers. When it comes to using plastics, knowing the differences between the types of plastic, as well as their SPI codes, will help you make more informed decisions.

1. Polyethylene Terephthalate (PETE or PET)
2. High-Density Polyethylene (HDPE)
3. Polyvinyl Chloride (PVC)
4. Low-Density Polyethylene (LDPE)
5. Polypropylene (PP)
6. Polystyrene or Styrofoam (PS)
7. Miscellaneous plastics (includes: polycarbonate, polylactide, acrylic, acrylonitrile butadiene, styrene, fiberglass, and nylon)

Plastic types are distinguished and separated based on the chemical makeup and codes allocated to them by international agreement. Below is a table explaining each type of plastic.

Flame: A blue flame with a yellow tip would be indicative of the polyolefins and nylon. You might think, well how would you separate these two if their flame is the same? Remember from above, the polyolefins would float and nylon (PA) would sink.

A yellow flame with a green tip on contact shows PVC (Polyvinyl Choride), yellow with dark smoke could be PET or Polycarbonate, and yellow with sooty, dark, smoke could be polystyrene or ABS (the plastic housing of your computer monitor).

Burn: The polyolefins ignite quite readily. Be very careful if you are testing this type of plastic because molten plastic can drip and will leave an ugly burn if you make contact with it.

PVC (many garden hosepipes and certain piping for household plumbing, but it is becoming an unpopular plastic in modern times) and ABS will only ignite with moderate enthusiasm and will soften, but not release dripping "firebombs" of plastic; while PET also ignites moderately, but bubbles as it melts.

Smell: After you have applied a flame to the plastic piece to test it, and carefully observed the smoke and ignition potential, you can carefully waft some of the smoke towards your nose. WARNING: if you have already identified the plastic from other methods and particularly in where you suspect the plastic is PVC, do not smell the smoke.

If you must, and we advise against it where possible, a small whiff of the smoke will give you further clues as to the plastic identification code under which your suspect can be classified.

PET smells similar to burnt sugar (the odour reminds the author of eating candy-floss or sugar-candy in his childhood). PVC has an acrid smell like chlorine, so stay away from the smoke and gas given off by PVC. LDPE and HDPE smell like candle wax, while Polypropylene smells similar to candle wax, but with an element of paraffin to it. ABS and polystyrene both smell like styrene, but the ABS also has a faint rubbery smell to it.

Touch and Sound: The polyolefins are a rather tricky bunch of characters. They generally all float, have the same flame and dripping "firebomb" effect and even smell the same! This makes them rather tricky to tell apart, particularly when they are in the form of film. In other words, when they are packaging like packets or film wrapping.

Plastic packets can be made from LDPE, HDPE or PP. Now your senses of touch and hearing are drafted into play.

LDPE feels soft and smooth, like the bag Mom packs your sandwich into. Additionally, if you rub it together, it will make a soft swishing sound, as opposed to a crinkling, harsher sound.

HDPE feels harder and essentially, more crinkly. Many plastic shopping bags are manufactured from HDPE and the easiest way to distinguish them from LDPE bags is from the sound the make when you crinkle them in your hands. If the sound is soft and swishing (think of green leaves blowing in the trees), then you have identified LDPE; if the sound is crisper and crinkly (think of dry leaves being squished together), then you have HDPE. The two sounds are quite distinct.

Our final campaigner in this section is PP, also known as polyprop or polypropylene. Packets made of this plastic sound similar to HDPE and are crinkly. PP is generally used for packaging food, such as chocolate and chips wrappers, or the clear packets you might buy a gentleman's shirt in. It feels much firmer and stiffer, but the most important trick here, is that it does not stretch. It simply rips and tears without stretching at all.

The huge floating island of plastic in the Pacific ocean comprises only the plastics that float. What about all those that sink? Where are they?

The easiest way to identify between broad groups of plastic is by establishing whether they float or sink. While there are exceptions, the polyolefins generally float in water and the rest, generally sink. The polyolefins include numbers 2, 4 and 5 from above (High Density Polyethylene (2), Low Density Polyethylene (4) and Polypropylene (5)). So as a rule of thumb, if a piece of the plastic floats, it will be one of these and otherwise, it will something else.

This sounds astonishing, but try this and you will see. Chop a manageable piece (possibly thumbnail-sized) off a milk bottle (HDPE) and it will float; conversely, a piece from a cool drink bottle (PET) will sink!

The frightening part of this, is that the massive floating island of plastic in the ocean, comprises primarily plastics that float and, as you can see from those the sink vs those that float, there are many types of plastic that sink and that we must presume are all lying on the bottom of our oceans.

There are many misconceptions about the floating "island of garbage" and the reality is very different from the public image of a giant pile of trash floating in the ocean.

Plastic can have negative affects on human health. Toxic chemicals leach out of plastic and are found in the blood and tissue of nearly all people on earth. Over exposure to plastic is linked to certain cancers, birth defects, impaired immunity, endocrine disruption, and other ailments.

Negative Health Effects Linked to Plastics

Phthalates (DEHP): Phthalates cause endocrine disruption, linked to asthma, developmental and reproductive effects. Medical waste with PVC and pthalates is regularly incinerated, causing public health effects from the release of dioxins and mercury, including cancer, birth defects, hormonal changes, declining sperm counts, infertility, endometriosis, and immune system impairment.

Polycarbonate with Bisphenol A (#7): Scientists have linked very low doses of bisphenol A exposure to cancers, impaired immune function, early onset of puberty, obesity, diabetes, and hyperactivity, among other problems (Environment California).

Polyvinylchloride (#3 PVC): Polyvinylchloride Can cause cancer, birth defects, genetic changes, chronic bronchitis, ulcers, skin diseases, deafness, vision failure, indigestion, and liver dysfunction.

Plastic Can Also Affect Air Quality

Burning of plastic in the open air can lead to environmental pollution because of the release of poisonous chemicals. Polluted air, when inhaled by humans and animals, can affect their health and cause respiratory problems.

How to Avoid Using Plastic Products

• Buy food in glass or metal containers and avoid polycarbonate drinking bottles with Bisphenol A.
• Avoid heating food in plastic containers, or storing fatty foods in plastic containers or plastic wrap.
• Do not give young children plastic teethers or toys.
• Use natural fiber clothing, bedding, and furniture.
• Avoid all PVC and Styrene products.
• Buy food in glass or metal containers.
• Avoid heating food in plastic containers, or storing fatty foods in plastic containers or plastic wrap

Plastics are derived from natural and organic materials. These materials include cellulose, coal, natural gas and salt. They are, of course, also derived from crude oil. Crude oil is a complex mixture of thousands of compounds and needs to be processed before it can be used.

How Is Plastic Made?

The production of plastics begins with the distillation of crude oil in a refinery. This step separates the heavy crude into groups of lighter components, called fractions. Each fraction is a mixture of different hydrocarbon chains, which differ in terms of the size and structure of their molecules. One of these fractions that is created, naphtha, is the crucial compound for the production of plastics.

Processes for Producing Plastics

Two main processes are used to produce plastics. One process is called polymerisation and the other is called polycondensation. They both require specific catalysts. In a polymerisation reactor, monomers (ethylene and propylene) are linked together to form long polymer chains. Each polymer chain has its own properties, structure, and size. It all depends on the various types of basic monomers used.

The two main polymer families are:

• Thermoplastics (which soften on heating and then harden again on cooling).

• Thermosets (which never soften once they have been moulded).

• Ecowatch, "10 Ways to Use Less Plastic Every Day"
• Ocean Society, "7 Ways To Reduce Ocean Plastic Pollution Today"
• Scientific American, "Plastic Not-So-Fantastic: How the Versatile Material Harms the Environment and Human Health"