Copper, silver and aluminum are all metals, yet each has unique properties. We do not make a car out of silver or a beer can out of copper because the properties of these metals are not the best choice for final product. Likewise, while plastics are all related, each resin has attributes that make it best suited to a particular application. Plastics make this possible because as a material family they are so versatile.
For instance, six resins account for most of the plastics used in packaging:
- PET (polyethylene terephthalate) is a clear, tough polymer with exceptional gas and moisture barrier properties. PET’s ability to contain carbon dioxide (carbonation) makes it ideal for use in carbonated soft drink bottles.
- HDPE (high density polyethylene) is used in milk, juice and water containers in order to take advantage of its excellent protective water retention properties. Its chemical resistance properties also make it well suited for items such as containers for household chemicals and detergents. And HDPE is used for the secondary packaging, such as reusable pallets, that helps deliver products safely and efficiently in the product distribution system.
- Vinyl (polyvinyl chloride, or PVC) provides excellent clarity, puncture resistance, and cling. As a film, vinyl can breathe just the right amount, making it ideal for packaging fresh meats that require oxygen to ensure a bright red surface while maintaining an acceptable shelf life.
- LDPE (low density polyethylene) offers clarity and flexibility. It is used to make bottles that require extra flexibility. To take advantage of its strength and toughness in film form, it is used to produce grocery bags and garbage bags, shrink and stretch film, and coating for milk cartons.
- PP (polypropylene) has high tensile strength, making it ideal for use in caps and lids that have to hold tightly on to threaded openings. Because of its high melting point, polypropylene can be hot-filled with products designed to cool in bottles, including ketchup and syrup. It is also used for products that need to be incubated, such as yogurt.
- PS (polystyrene), in its crystalline form, is a colorless plastic that can be clear and hard. It can also be foamed to provide exceptional insulation properties. Foamed or expanded polystyrene (EPS) is used for products such as meat trays, egg cartons and coffee cups. EPS is also used for secondary packaging to protect appliances, electronics and other sensitive products during transport.
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