Plastic is not one material--it is a family of related materials with varying properties that can be engineered to meet the requirements of a broad range of uses, including packaging. Below is a list of six types of plastic (or resin) that are commonly used to make packaging for properties for the product they are making.
Many plastic containers display a resin identification code on the bottom to indicate what type of plastic the container is made from. This code does not mean the container is made from recycled plastic, nor does it mean the plastic is recyclable. It only indicates the type of plastic resin used, to help in the sorting of items to be recycled.
Recyclers want to sort plastic containers by the type of resin so that the properties of the individual resin can be maintained and then manufacturers can reuse the material in the highest value end-use possible. The more uniform the postuse plastics going in to the recycling process, the more predictable the properties of the recycled plastic coming out.
California law (Public Resources Code section 18000 et seq) requires that rigid plastic containers sold in California be labeled with a code to identify the resin used.
PET or PETE
Most commonly recycled plastic, is used to make two-liter soda bottles and plastic liquor bottles. Recycled into many products such as bottles for cleaning products and non-food items, egg cartons, and fibers (carpet, t-shirts, fleece, etc.).
(high density polyethylene)
Also a commonly recycled plastic, used to make milk and juice bottles. Recycled into many products such as lumber substitutes, base cups for soft drink bottles, flower pots, toys, pails and drums, traffic barrier cones, bottle carriers, and trashcans.
V or PVC
Used to make flooring, shower curtains, house siding, garden hoses, and many other products. Not commonly recycled.
(low density polyethylene)
Used to make cellophane wrap, disposable diaper liners and squeeze bottles. Not commonly recycled.
Used to make packaging pipes, tubes, long underwear. Not commonly recycled.
You may know this as "Styrofoam." Used to make coffee cups, take-out food packaging, egg cartons, and packaging "peanuts." Recycled in some areas and made into the same type of products, insulation, plastic "wood," and hard plastic pens.
All other plastic resins or a mixture of resins. Not commonly recycled. More detailed information about these plastics (and some others) their properties, and recycled products that can be made from them is available on the Definitions and Specifications page