TYPES OF PLASTIC
"Plastic" can mean many different things - learn more about the different shapes, sizes and varieties of plastic that end up in our lakes and rivers.
Large plastic litter that enters aquatic environments like the Great Lakes and surrounding waterways gradually breaks down into smaller and smaller pieces. Plastic pieces that are smaller than 5mm (approximately the size of a grain of rice) are known as microplastics. Some are so small that they can only be detected under a microscope.
Research has shown that sources of microplastic pollution include:
Microbeads from toiletries and personal care products. These were banned in Canada in 2018, but microbeads from products being used before then are still present in our waterways.
Broken down fragments of single-use plastic items like pens, straws, coffee cup lids, cigarette lighters and plastic bags
Plastic microfibres shed from textiles during the laundering process
Cigarette butts, which contain the microplastic cellulose acetate
Just as microplastics are defined as plastic particles or fragments that are smaller than 5 mm, macroplastics can be broadly defined as plastics that are larger than 5mm in diameter. It should be noted, though, that these classifications are not internationally standardised. Some definitions of macroplastics categorize them as plastics larger than 20mm, while others define them as items larger than 25 mm. The term mesoplastic is also often used to define plastic between 5 and 25 mm in diameter.
Macroplastics are very often easier to locate in the environment because of their size, and also easier to trace. Macroplastic pollution in the Great Lakes region often takes the form of fully intact or only partly broken down items like plastic bottles and bags. Foam (like Polystyrene, more commonly known in Canada as Styrofoam™) is also common, as are large fragments of plastic sheeting and films.
Types of Plastic
There are thousands of different types of plastic, and each has its own characteristics. This versatility is part of what makes plastic so valuable. Here are some of the more common kinds in use today:
Polyethylene is the most common plastic on earth. Low-Density Polyethylene (LDPE) is ductile and used to make products like plastic bags (e.g., grocery bags), clear food containers and disposable packaging. It is not commonly recycled. Medium-Density Polyethylene (MDPE) can be found in gas pipes, shrink film and screw closures. High-Density Polyethylene (HDPE) is more rigid than both LDPE and MDPE, and is used for plastic bottles, water and sewer piping, toys, boats, and folding chairs. It is commonly recycled and does not easily break down when exposed to sunlight, heating or freezing. Ultra High Molecular Weight Polyethylene (UHMWPE) has low friction properties, making it more abrasion-resistant than HDPE. It is found in military body armour, hydraulic seals and bearings, biomaterial for hip, knee, and spine implants, and artificial ice skating rinks. Polyethylene pellets are also used in the plastic industry for the manufacture of plastic products.
Polyethylene Terephthalate (PETE or PET)
PET is the most common thermoplastic resin of the polyester family. It has excellent chemical resistance to organic materials and water, is easily recyclable, and possesses a high strength-to-weight ratio. PET is used in fibers for clothing, containers for foods, water and soda bottles and many other products that we use every day. Fibers that shed from clothing, upholstery, or carpet are a common type of microplastic pollution found in our lakes.
Polyvinyl Chloride (PVC)
This plastic polymer can be manufactured to possess rigid or flexible properties. It is well-known for its ability to blend with other materials. The rigid form of PVC is commonly used in construction materials, doors, windows, bottles, non-food packaging and more. When plasticizers such as phthalates are added, it creates a softer and more flexible form of PVC, typically found in plumbing products, clear food wrappers, toys, blister packaging, clothing, medical tubing, and similar products. While some PVC can be repurposed, it is considered hard to recycle.
This plastic material is one of the most flexible thermoplastics on the planet, contributing to its widespread use. Stronger than plastics like polyethylene, it retains flexibility and will not crack under repeated stress. It is durable, flexible, heat and acid resistant and affordable, with sheets used to make laboratory equipment, automotive parts, medical devices, and food containers. Polypropylene pellets are also used in the plastic industry as a feedstock for the manufacture of plastic products.
This plastic is lightweight, easily-formed and inexpensive, with a wide variety of uses including disposable foam drinking cups, take-out “clamshell” food containers, egg cartons, picnic cutlery, foam packaging, floating docks and “peanut” foam chips used to fill shipping boxes. Polystyrene is also widely used to make rigid foam insulation and underlay sheeting for laminate flooring used in home construction. Polystyrene breaks down easily and is dispersed quickly throughout the natural environment. While the technology for recycling polystyrene exists, the end market is small.
This is a naturally transparent thermoplastic polymer, often used in place of glass or acrylic - it is, in fact, many times stronger and more resilient than glass despite being lighter, and much less prone to damage or degradation in harsh conditions. It has the ability to filter out UV rays, which makes it an ideal material for eyewear. Polycarbonate is used for many things, including cell phones, countertops, spectacle lenses, protective visors and shields, greenhouses, office dividers, plant nurseries, vehicle headlights, small vehicle windshields, bullet-resistant “glass” and more.
A thermoplastic polyamide, nylon is an extremely popular and versatile form of plastic, commonly used to make thread, ropes, fabric for clothes and a wide range of consumer products. It is strong, elastic and durable, relatively resistant to abrasion and chemicals, and water-resistant (thought not fully waterproof), as well as being easy to maintain. Its strength, low-friction properties and chemical resistance, as well as the fact that it has a very high melting point, makes it the material of choice for reinforcement in rubber material like car tires and in injection molded parts for vehicles and mechanical equipment.