What is PET – 7 Grades of Plastic

This post is also available in: हिन्दी (Hindi) العربية (Arabic)

Most of us are aware of PET or PETE (Polyethylene Terephthalate). Have you ever noticed a triangular mark at the bottom of a plastic container? What does it mean?

What is PET

It looks like a recycling symbol (three bent arrows forming a triangle) with a number inside. This symbol does not depict the number of times that the plastic has been recycled, as is commonly believed. Instead, the symbol is used to tell recyclers and waste management handlers what the plastic is made from.

What is PET – Types of Plastics

Having knowledge of the different types of plastic is critical to understanding the complexity of recycling, upcycling and the health factors associated with plastic. The first step is to simply know the core basics for the types of plastic that we most encounter, numbered according to their recycling codes.

What is PET

Let’s decode the symbols in the chart above.

To summarize, there are 7 types of plastic exist in our current modern days:

1. Polyethylene Terephthalate (PET or PETE or Polyester)

PET is also known as a wrinkle-free fiber. It’s different from the plastic bag that we commonly see at the supermarket. PET is mostly used for food and drink packaging purposes due to its strong ability to prevent oxygen from getting in and spoiling the product inside. It also helps to keep the carbon dioxide in carbonated drinks from getting out.

Although PET is most likely to be picked up by recycling programs, this type of plastic contains antimony trioxide—a matter that is considered as a carcinogen—capable of causing cancer in a living tissue.

What is PET
Polyethylene Terephthalate (PET or PETE)

The longer a liquid is left in a PET container the greater the potential for the release of the antimony. Warm temperatures inside cars, garages, and enclosed storage could also increase the release of the hazardous matter. For that reason it’s called ‘Use and Trash Plastic’. It is meant for one time use only!

2. High-Density Polyethylene (HDPE)

HDPE has long virtually unbranched polymer chains which makes them really dense and thus, stronger and thicker from PET. HDPE is commonly used as the grocery bag, opaque milk, juice container, shampoo bottles, and medicine bottle.

What is PET
High-Density Polyethylene (HDPE)

Not only recyclable, HDPE is relatively more stable than PET. It is considered as a safer option for food and drinks use, although some studies have shown that it can leach estrogen-mimicking additive chemicals that could disrupt a human’s hormonal system when exposed to ultraviolet light.

3. Polyvinyl Chloride (PVC)

PVC is typically used in toys, blister wrap, cling wrap, detergent bottles, loose-leaf binders, blood bags and medical tubing. PVC or vinyl used to be the second most widely used plastic resin in the world (after polyethylene), before the manufacture and disposal process of PVC has been declared as the cause of serious health risks and environmental pollution issues.

What is PET
Polyvinyl Chloride (PVC)

In terms of toxicity, PVC is considered as the most hazardous plastic. The use of it may leach a variety of toxic chemicals such as bisphenol A (BPA), phthalates, lead, dioxins, mercury, and cadmium.

Several of the chemicals mentioned may cause cancer; it could also cause allergic symptoms in children and disrupt the human’s hormonal system. PVC is also rarely accepted by recycling programs. This is why PVC is best to be avoided at all cost.

4. Low-Density Polyethylene (LDPE)

Polyethylenes are the most used family of plastics in the world. This type of plastic has the simplest plastic polymer chemical structure, making it very easy and very cheap to process.

LDPE polymers have significant chain branching including long side chains making it less dense and less crystalline (structurally ordered) and thus a generally thinner and more flexible form of polyethylene.

What is PET
Low-Density Polyethylene (LDPE)

LDPE is mostly used for bags (grocery, dry cleaning, bread, frozen food bags, newspapers, garbage), plastic wraps; coatings for paper milk cartons and hot & cold beverage cups; some squeezable bottles (honey, mustard), food storage containers, container lids. Also used for wire and cable covering.

Although some studies have shown that LDPE could also cause unhealthy hormonal effects in humans, LDPE is considered as a safer plastic option for food and drink use. Unfortunately, this type of plastic is quite difficult to recycle.

5. Polypropylene (PP)

Stiffer and more resistant to heat, PP is widely used for hot food containers. Its strength quality is somewhere between LDPE and HDPE. Besides in thermal vests, and car parts, PP is also included in the disposable diaper and sanitary pad liners.

What is PET
Polypropylene (PP)

Same as LDPE, PP is considered a safer plastic option for food and drink use. And although it bears all those amazing qualities, PP isn’t quite recyclable and could also cause asthma and hormone disruption in humans.

6. Polystyrene (PS)

Polystyrene (PS) is the styrofoam we all commonly use for food containers, egg cartons, disposable cups and bowls, packaging, and also bike helmets.

What is PET
Polystyrene (PS)

When exposed with hot and oily food, PS could leach styrene that is considered as brain and nervous system toxicant. It could also affect genes, lungs, liver, and immune system. On top of all of those risks, PS has a low recycling rate.

7. Other

Number 7 is for all plastics other than those identified by number 1-6 and also plastics that may be layered or mixed with other types of plastics, such as bioplastics.

What is PET
Other Types

The best-known plastics of this group are polycarbonates (PC) used to build strong, tough products. Polycarbonates are commonly used for eye protection in the creation of lenses for sunglasses, sport and safety goggles. But they can also be found on mobile phones and, more frequently, in compact-discs (CD).

Harmful Effects of Plastics

Following table shows the harmful effects of various types of plastics:

PlasticCommon UsesAdverse Health Effects
Polyvinyl Chloride (#3PVC)Food packaging, plastic wrap, containers for toiletries, cosmetics, crib bumpers, floor tiles, pacifiers, shower curtains, toys, water pipes, garden hoses, auto upholstery, inflatable swimming poolsCan cause cancer, birth defects, genetic changes, chronic bronchitis, ulcers, skin diseases, deafness, vision failure, indigestion, and liver dysfunction
Phthalates (DEHP, DINP, and others)Softened vinyl products manufactured with phthalates include vinyl clothing, emulsion paint, footwear, printing inks, non-mouthing toys and children’s products, product packaging and food wrap, vinyl flooring, blood bags and tubing, IV containers and components, surgical gloves, breathing tubes, general purpose labware, inhalation masks, many other medical devicesEndocrine disruption, linked to asthma, developmental and reproductive effects. Medical waste with PVC and phthalates 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)Water bottlesScientists  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.
PolystyreneMany food containers for meats, fish, cheeses, yogurt, foam and clear clamshell containers, foam and rigid plates, clear bakery containers, packaging “peanuts”, foam packaging, audio cassette housings, CD cases, disposable cutlery, building insulation, flotation devices, ice buckets, wall tile, paints, serving trays, throw-away hot drink cups, toysCan irritate eyes, nose and throat and can cause dizziness and unconsciousness. Migrates into food and stores in body fat. Elevated rates of lymphatic and hematopoietic cancers for workers.
Polyethylene (#1 PET)Water and soda bottles, carpet fiber, chewing gum, coffee stirrers, drinking glasses, food containers and wrappers, heat-sealed plastic packaging, kitchenware, plastic bags, squeeze bottles, toysSuspected human carcinogen
PolyesterBedding, clothing, disposable diapers, food packaging, tampons, upholsteryCan cause eye and respiratory-tract irritation and acute skin rashes
Urea-formaldehydeParticle board, plywood, building insulation, fabric finishesFormaldehyde is a suspected carcinogen and has been shown to cause birth defects and genetic changes. Inhaling formaldehyde can cause cough, swelling of the throat, watery eyes, breathing problems, headaches, rashes, tiredness
Polyurethane FoamCushions, mattresses, pillowsBronchitis, coughing, skin and eye problems. Can release toluene diisocyanate which can produce severe lung problems
AcrylicClothing, blankets, carpets made from acrylic fibers, adhesives, contact lenses, dentures, floor waxes, food preparation equipment, disposable diapers, sanitary napkins, paintsCan cause breathing difficulties, vomiting, diarrhea, nausea, weakness, headache and fatigue
Tetrafluoro-ethelyneNon-stick coating on cookware, clothes irons, ironing board covers, plumbing and toolsCan irritate eyes, nose and throat and can cause breathing difficulties
Source: Center of Disease Control Report, Fourth National Report on Human Exposure to Environmental Chemicals Updated Tables, March 2021

Key Takeaways:

  • Though it varies between types, every single category of plastic could leach hazardous materials if put in an extreme situation such as extreme heat.
  • 3 types of plastic that are considered as safer options among the others are Polyethylene Terephthalate (PET), High-Density Polyethylene (2-HDPE), and Polypropylene (5-PP).
  • Although the experts are currently working on inventing the best method and strategy to recycle all of those types of plastic, the 2 types of plastic that are mostly picked up by the recycling programs are Polyethylene Terephthalate (1-PET) and High-Density Polyethylene (2-HDPE).

Image Credit: Litter vector created by pch.vector – www.freepik.com

Leave a Comment