The properties of a plastic make it suitable for a certain use. Some of these properties are transparency, density, thermal behaviour, flammability, strength, corrosion resistance, and heat conductivity.
For example, some plastics are good for making bottles because they are impact resistant, while others are more useful in carpet fibres as a result of their durability. The weight of a plastic is also important as it impacts on the production and shipping costs of products.
There are six main resins used to produce nearly all of the plastics used in packaging. Check out their properties below.
Polyethylene Terephthalate (PET/PETE)
PET is clear and tough, with good gas and moisture barrier properties. This plastic is commonly used in soft drink bottles and many other injection-moulded consumer product containers. Other applications include strapping, moulding compounds, and containers. Cleaned, recycled PET flakes and pellets are in great demand for spinning fibre for carpet yarns and producing fibrefill and geotextiles. Polyester is its nickname.
High-Density Polyethylene (HDPE)
Unpigmented HDPE bottles are translucent and stiff , with good barrier properties. Pigmented HDPE bottles generally have better stress, crack, and chemical resistance. They are well suited for the packaging of products with short shelf lives. HDPE is used to make bottles for juice, pop, water, and laundry products. Because HDPE has good chemical resistance, it is also used in packaging many household and industrial chemicals such as detergents and bleach.
Polyvinyl chloride (PVC) – Vinyl
In addition to stable physical and electrical properties, PVC has excellent chemical resistance, good weatherability, and puncture resistance. The diverse range of vinyl products can be broadly divided into rigid and flexible materials. Bottles and sheets are major rigid markets, along with construction applications such as pipes, fittings, siding, carpet backing, and windows. Flexible vinyl is used in wire and cable insulation, film and sheet, floor coverings, synthetic leather products, coatings, medical tubing , and many other applications.
Low-Density Polyethylene (LDPE)
A plastic used predominately in film applications due to its toughness, flexibility and relative transparency. It is popular in applications where heat sealing is necessary. LDPE is also used to manufacture some flexible lids and bottles, along with grocery and garbage bags, and coating for milk cartons. It is also widely used in wire and cable applications for its properties and processing characteristics.
Polypropylene has excellent chemical resistance, is strong, and has the lowest density of the plastics used in packaging. It has a high melting point, making it ideal for hot-fill liquids like ketchup. PP is found in everything from flexible and rigid packaging to fibres and large moulded parts for automotive and consumer products.
Polystyrene is a very versatile plastic that can be rigid or foamed. General-purpose polystyrene is clear, hard , and brittle, with a relatively low melting point. Typical applications include protective packaging, containers, lids, cups, bottles, and trays.
There are hundreds of plastics in existence. The plastics below are made with a resin other than the 6 main resins listed above, or they consist of a combination of resins.
A two-phase thermoplastic material combining styrene-acrylonitrile copolymer and acrylic rubber. It can be co-extruded over acrylonitrile-butadiene-styrene for weatherability of window frames.
These are thermoplastic resins made of acrylic esters or methacrylic. The most typical applications are lighting fixtures and glazing.
- Acrylonitrile-butadiene-styrene (ABS)
A thermoplastic derived from acrylonitrile, butadiene, and styrene. ABS pipe, when properly installed, can withstand heavy loads of soil, slab foundations , and high surface loads without collapse, cracking or denting. It is resistant to any solution of ammonium chloride, calcium chloride or sodium hydroxide, all of which are corrosive to many metals. It is also used to a limited extent in window frames.
- Chlorinated polyvinyl chloride
A thermoplastic produced by the post chlorination of polyvinyl chloride resin. Its uses include hot and cold water pipe and industrial liquid handling.
- Ethylene-vinyl acetate
A thermoplastic co-polymer of ethylene and vinyl acetate used in wire and cable insulation and sewer pipe repair.
- Melamine and urea formaldehyde
These are thermosetting resins formed by the condensation reaction of formaldehyde with melamine or urea whose applications include laminating resin for countertops and adhesives for wood, particle board, and plywood.
A heat-cured thermoset, formed by the reaction of phenol and formaldehyde, used in electrical devices and as a plywood adhesive.
A semi-crystalline thermoplastic formed by polymerization of 1-butene used in residential hot and cold water pipe and sub-floor hydronic heating systems.
- Polybutylene terephthalate
Polybutylene terephthalate (PBT) is a plastic that is used as an insulator in the electrical and electronics industries. It is a thermoplastic crystalline polymer, and a type of polyester. PBT is resistant to solvents, shrinks very little during forming, is mechanically strong, heat-resistant up to 150°C (or 200°C with glass-fibre reinforcement)
An engineering thermoplastic usually based on Bisphenol A reacted with carbonyl chloride with applications including window and skylight glazing.
- Polyphenylene oxide
A thermoplastic produced through the oxidative coupling polymerization of 2,6-dimethylphenol used to make roofing panels.