The well-recognized “chasing arrows” symbol we see on plastic containers and products does not mean the product is recyclable. The little number inside the triangle tells the real story.
Within each chasing arrows triangle, there is a number which ranges from one to seven. The purpose of the number is to identify the type of plastic used for the product, and not all plastics are recyclable or even reusable. There are numerous plastic-based products that cannot break down and cannot be recycled.
Understanding the seven plastic codes will make it easier to choose plastics and to know which plastics to recycle. For example, water bottles that display a three or a five cannot be recycled in most jurisdictions in the US. A three indicates that the water bottle has been made from polyvinyl chloride, a five means that it’s been made of polypropylene, two materials that are not accepted by most public recycling centers.
1 – PET (Polyethylene Terephthalate)
One of the most commonly used plastics in consumer products, and is found in most water and pop bottles, and some packaging.
2 – HDPE (High-Density Polyethylene)
Used to make milk jugs, detergent and oil bottles, toys, and some plastic bags. HDPE is the most commonly recycled plastic and is considered one of the safest forms of plastic.
3 – PVC (Polyvinyl Chloride)
sed to make clear plastic food wrapping, cooking oil bottles, teething rings, children’s and pets’ toys, and blister packaging for myriad consumer products.
4 – LDPE (Low-Density Polyethylene)
Often found in shrink wraps, dry cleaner garment bags, squeezable bottles, and the type of plastic bags used to package bread.
5 – PP (Polypropylene)
When you try to open the thin plastic liner in a cereal box, it is polypropylene. This keeps your cereal dry and fresh. PP is also commonly used for disposable diapers, pails, plastic bottle tops, margarine and yogurt containers, potato chip bags, straws.
6 – PS (Polystyrene)
Most often used to make disposable styrofoam drinking cups, take-out “clamshell” food containers, egg cartons, plastic picnic cutlery.
7 – Other (BPA, Polycarbonate and LEXAN)
The "#7" category was designed as a catch-all for polycarbonate (PC) and “other” plastics.
Used to make baby bottles, sippy cups, water cooler bottles and car parts. BPA is found in polycarbonate plastic food containers.
http://learn.eartheasy.com/2012/05/plastics-by-the-numbers/