Main Uses and Attributes

Two main groups of plastics can be distinguished by their reaction to heat. Thermoplastics soften and melt when heated and harden when cooled again. Thermosets, on the contrary, become rigid when heated and stay rigid after cooling, which makes recycling more complex.[1] The development of plastics has resulted in a wide array of different polymers with specific properties for a multitude of applications in nearly every sector in the modern world.

Polyethylene Terephthalate (PET) is one of the most widely produced synthetic plastics in the world. Because of its outstanding chemical resistance to water and organic materials, PET is easily recyclable. PET is suitable for products with complex parts, surface quality, and dimensional accuracy. It is commonly used in fibers for clothing, containers for foods and liquids, cosmetic containers, and chemical containers like bottles of household cleaners.[2]

Polyamide (PA), or nylon, is often used to replace low-strength metals in industrial applications like car engines, industrial valves, and automotive parts because of its high strength, chemical compatibility, and high-temperature resistance.[3] Polyamide is also oil-resistant and has an outstanding wear resistance. Aside from its contribution to the automotive industry, nylon can also be formed into fibers, where it is found in textiles of all sorts, toothbrushes, cookware, and other consumer goods ranging from guitar strings to and tents.[4]

Acrylonitrile Butadiene Styrene (ABS) plastic is inexpensive and strongly resistant to physical impact and corrosive chemicals. It is an amorphous polymer comprised of three monomers: acrylonitrile, butadiene, and styrene. Varying quantities of each monomer can be added to the formula to alter the finished product. ABS plastic is commonly used in many everyday items including 3D printing, injection molding, refrigerators, computers, televisions, air conditioners, and washing machines. [5]

Polyvinyl Chloride (PVC) is widely used in commercial and residential property construction applications because of its ability to blend with other materials. PVC can be adapted to be either flexible or rigid, and can be produced variously as a film, fiber, or foam. The rigid form of PVC is often found in doors, window frames, bottles, and non-food packaging.[6] Examples of flexible forms of PVC include shoe soles, electrical cables, toys, and fire protective clothing.[7]

Polycarbonate is as clear as glass with a high-impact strength that is 200 times stronger than glass. It is also easily molded and formed and can be cut on-site without fabrication or pre-forming.[8] PC is commonly used in various products like CDs/DVDs, car headlamp lenses, sunglasses, baby feeding bottles, roofing and glazing, and greenhouses. It’s also the kind of plastic the police use for riot gear.

Polyether ether ketone (PEEK) is a high-performance engineering plastic with outstanding resistance to harsh chemicals, excellent mechanical strength, and dimension stability. PEEK is an organic thermoplastic polymer, comprised of a semi-crystalline structure which gives it a strong chemical structure. PEEK is widely used in industrial applications such as semiconductors, automobiles, aerospace, oil and gas, mining, heavy equipment, and renewable energy as it is able to endure harsh environmental conditions. [9]

Organic and inorganic compounds – additives – are added to nearly every plastic to optimise it for the intended use. The most common additive in plastic are plasticisers, which are typically liquid, non-volatile organic substances that improve flexibility, particularly when thermoforming, shaping, and molding.

“Filler” minerals such as calcium carbonate, silica, clay, kaolin and carbon are also often added to polymers, both increasing bulk at lower cost while making the plastic easier to mold and shape. Mineral fillers can increase heat-deflection and reduce thermal expansion. Carbon fibers are frequently added to polymers because they increase the tensile strength without adding weight, improving heat deflection and electrical conductivity.

Polymer stabilisers are chemical additives that mitigate degradation caused by oxidation, UV exposure, and heat. Stabilisers also minimise reactions with catalysts that could break down the plastic at the chemical structural level.

Most thermoplastics are flammable and will bend and melt when introduced to a high temperature. Adding flame retardants delays ignition and minimises burning, but also offers long-term benefits by reducing free radicals. Aluminum hydroxide, phosphorus compounds, and brominated compounds are the most common types of flame retardants, which are regulated in most jurisdictions.[10]