Maya Ellison
Plastic is everywhere, from our computers and televisions to our cars and houses. However, not all plastics are created equal. There are hundreds of types of plastic, but only a handful that we interact with regularly. These include polyethylene, the most common plastic on Earth, and polyvinyl chloride (PVC), used in construction and pipes. Plastic types are differentiated by their unique properties, such as durability, heat resistance, and flexibility. Some plastics are easily recyclable, while others are dangerous and harmful to the environment. Knowing the different types of plastics is critical to understanding the complexities of recycling and upcycling, as well as the potential health hazards associated with plastic.
| Characteristics | Values |
|---|---|
| Number of types | 7 |
| Naming convention | Abbreviations or trade names, e.g. PET, PVC, Styrofoam, Plexiglas (Perspex), Nylon |
| Identification | Resin Identification Code (RIC) system, standardised numbering system developed by ASTM International |
| Common types | Polyethylene, Polypropylene, Polyvinyl chloride, Polystyrene, Polycarbonate, Polyethylene Terephthalate (PET), Polyurethane, Polyamide (Nylon), Polyphthalamide, Acrylic, ABS |
| Additives | Plasticizers, flame retardants, fillers, colourants, heat stabilizers |
| Manufacturing | Large companies may do their own compounding prior to production, but some use third parties (compounders) |
| Production | Petroleum-based, some from renewable resources like polylactic acid |
| Amount produced | 9.2 billion metric tons between 1950 and 2017, with more than half produced since 2004 |
| Uses | Packaging, food containers, household products, optical devices, automotive parts, toys, clothing, plumbing, electrical cable insulation, medical devices, agricultural products |
| Recyclability | PET is the most widely recycled plastic, LDPE is not often recycled, PVC is hardly recyclable, HDPE is one of the easiest to recycle |
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What You'll Learn
Polyethylene Terephthalate (PET)
PET is a thermoplastic polymer resin from the polyester family. It is produced through the polymerization of ethylene glycol and terephthalic acid, and it can be processed using common moulding methods like injection moulding, blown moulding, and extrusion. Depending on its processing and thermal history, PET may exist as an amorphous (transparent) or semi-crystalline polymer. It is strong, tough, abrasion-resistant, and has excellent dimensional stability.
PET is commonly used in packaging and textile production. Its durability, mechanical strength, and transparency make it ideal for disposable carbonated beverage bottles. PET is also used in artificial fibres for textiles, providing outstanding wear resistance, low moisture absorption, and durability. These textile applications include blankets, bed sheets, comforters, carpets, and clothing.
PET is further used in 3D printing, with PETG (polyethylene terephthalate glycol) being a popular material for high-end applications. PETG can be modified for self-cleaning properties, making it suitable for traffic signs and LED spotlights. PET is also one of three layers used in the creation of glitter, although many companies are phasing out its use in favour of bio-friendly alternatives.
While PET is widely recycled, it contains antimony trioxide, a carcinogen. The release of hazardous matter increases with the length of time a liquid is left in a PET container and when exposed to warm temperatures. As a result, single-use PET bottles have become problematic for the environment, contributing significantly to plastic pollution.
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Polyvinyl Chloride (PVC)
History
PVC was first synthesized in 1872 by German chemist Eugen Baumann. However, early attempts to use PVC in commercial products by Russian chemist Ivan Ostromislensky and German chemist Fritz Klatte in the early 20th century were thwarted by difficulties in processing the rigid and sometimes brittle polymer. Waldo Semon and the B.F. Goodrich Company later developed a method to plasticize PVC by blending it with additives, including dibutyl phthalate.
Uses
PVC is widely used in the building and construction industry, replacing traditional materials such as wood, metal, concrete, rubber, and ceramics. It is used in pipes, siding, fascia, gutters, windows, roofing, fencing, decking, wall coverings, and flooring. PVC is also used in the healthcare industry for blood bags, medical tubing, and packaging for medicines and personal care products. In the automotive industry, PVC is used for wire and cable insulation.
Properties
PVC is known for its strong resistance to chemicals, sunlight, oxidation, impact, water, weather, and corrosive environments. It can be modified by chlorination, increasing its chlorine content to enhance durability, chemical stability, and flame retardancy. However, lead compounds previously added to PVC to improve workability and stability have been shown to leach into drinking water, leading to their discontinuation in Europe.
Environmental Impact
PVC is challenging to recycle and should be avoided when possible. However, life-cycle studies suggest that PVC can be effective in protecting the environment due to its low greenhouse gas emissions and conservation of resources and energy.
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Polypropylene (PP)
Polypropylene, also known as polypropene or PP, is a thermoplastic polymer with a wide variety of applications. It is the second-most widely produced commodity plastic, after polyethylene. PP is tough, flexible, and has a high chemical resistance. Its properties are similar to polyethylene, but it is harder and more heat-resistant.
Phillips Petroleum chemists J. Paul Hogan and Robert Banks first demonstrated the polymerization of propylene in 1951. The stereoselective polymerization to the isotactic form was discovered by Giulio Natta and Karl Rehn in 1954, leading to large-scale commercial production by the Italian firm Montecatini from 1957 onwards.
PP is produced via chain-growth polymerization from the monomer propylene. It belongs to the group of polyolefins and is partially crystalline and non-polar. The methyl group in its structure improves mechanical properties and thermal resistance, although chemical resistance decreases. The density of PP is between 0.895 and 0.93 g/cm3, making it the commodity plastic with the lowest density.
PP has a slippery, tactile surface and is used in plastic packaging, plastic parts for machinery, fibres, textiles, and electrical goods. It is also used in the automotive industry for battery casings, trays, and bumpers, and in the medical field due to its waterproof properties, flexibility, and resistance to mould, bacteria, and chemical corrosion.
The versatility of PP has sustained its growth, enabling it to challenge the market share of alternative materials. Its ability to adapt to a wide range of fabrication methods and applications has led to its popularity in various industries.
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Polycarbonate (PC)
In the automotive industry, PC is used to create lighter, stronger, and more durable components. This includes headlight lenses, interior parts, and sunroofs, where its impact resistance and lightweight properties are advantageous. PC is also used in safety equipment within the automotive sector, such as safety goggles, face shields, and helmets.
In the E&E market, PC is widely used in optical media, such as computer and audio compact discs. It is also utilized in sheeting and glazing applications, as well as in electrical and electronic devices like business machines and telecommunications equipment. The high-temperature resistance of PC makes it well-suited for internal components and current-carrying devices.
PC is a popular choice for general industries and packaging due to its durability, cost-effectiveness, and appearance. It is used in a variety of applications, including appliances, transportation, and miscellaneous uses. The largest UK application outside of E&E is in the optical media market.
PC is available in multiple grades, such as film, flame retardant, reinforced, and stress crack resistant, allowing for customization based on specific needs. It is often blended with other polymers like ABS or polyesters, enhancing its impact properties and improving fuel and weather resistance.
While PC offers many advantages, there have been concerns about the use of bisphenol A (BPA) in its production. Studies indicate that BPA is a potential environmental hazard, especially during decomposition in landfills, contributing to aquatic pollution. Additionally, there are concerns about the potential leaching of BPA into foods and beverages when used in food contact applications, although regulatory authorities have recognized the safe use of PC in such cases.
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Polystyrene (PS)
Polystyrene, abbreviated as PS, is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. It is one of the most widely used plastics, with several million tonnes produced annually. PS is naturally transparent, lightweight, and inexpensive, making it a popular choice across industries.
PS has two main forms: foam, also known as expanded or extruded polystyrene, and rigid, solid plastic. The foam variant is soft, white, and insulating, while the solid plastic is naturally clear, hard, and brittle. The foam variant is often used for packaging, while the solid plastic is used for items such as protective packaging, containers, lids, bottles, trays, tumblers, and disposable cutlery.
PS is also used in biomedical research and science, with Petri dishes, test tubes, and microplates being made from this material. It is FDA-compliant, meaning it is certified safe for use with food and beverages. Additionally, PS is used in automotive and electrical components, electronics, and optics applications like lighting fixtures.
Despite its versatility, PS has some disadvantages. It has poor chemical resistance, is non-biodegradable, and is not widely recycled. Its disposable nature and visibility as litter have made its use in packaging controversial. However, PS manufacturers often produce their own styrene, and the wide variety of styrene uses makes it a good proxy for industrial production.
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Frequently asked questions
The 7 types of plastic are LDPE, PE, Polyester, HDPE, PVC, LDE, PP, PS, and PC. LDPE is a low-density plastic that is durable and flexible and used in shopping bags, cling wraps, and more. Polyethylene (PE) is the most common plastic on earth and is used in a wide variety of products. Polyester is the fourth-most produced synthetic plastic and is used in clothing, food containers, and glass fiber. HDPE is used in containers for milk, shampoo, and toiletries. PVC is used in construction materials, bottles, and toys. PP is the second-most widely produced commodity plastic and is used in laboratory equipment, automotive parts, and food containers. PS is a transparent thermoplastic used in food packaging, takeaway containers, and laboratory ware. PC is an engineering plastic that is strong and flexible and used in sunglasses, DVDs, and police riot gear.
Biodegradable plastics are designed to biodegrade much faster than traditional plastics. While some biodegradable plastics are made from bioplastics, others are made from fossil fuels and petroleum, which are not sustainable. Biodegradable plastics are typically not compostable, but bioplastics may be compostable if they are made from plant-based materials.
Plastic additives are chemical additives that give plastic polymers additional properties, such as flexibility. Common plastic additives include plasticizers, flame retardants, fillers, colorants, and heat stabilizers. Plasticizers are used to make plastic softer and more flexible, such as in squeezable shampoo bottles. Colorants are used to add color to plastics, such as in toys or appliances.
Some plastics may contain toxic pollutants such as bisphenol A (BPA), phthalates, lead, dioxins, mercury, and cadmium. Polycarbonate plastic, which is used in baby bottles, compact discs, and medical storage containers, has been associated with toxic BPA. PVC plastic has also been described as toxic by the World Health Organization due to its vinyl chloride content. Polyethylene terephthalate (PET), a common plastic used in food and drink packaging, contains antimony trioxide, which is considered a carcinogen.
