【英语时差8,16】回收塑料（在线收听）

Recycling Plastics When plastic containers are recycled, they are first cleaned, then ground into tiny pellets and put into a flotation tank. This separates out the various plastic resins from other waste material. Once they are separated out, the plastic resins are ready for reuse. They are melted down, then molded into new plastic products. Plastics are made mostly of polymers, large molecules of carbon and hydrogen and oxygen. These polymers can be mixed with a number of other ingredients, including stabilizers, fillers, and coloring agents. This makes for a wide variety of types of plastic, having many different useful properties. Unfortunately, this variety also makes plastic one of the most difficult things to recycle. The biggest problem for plastic recyclers is that plastics come in many different types, and it’s impossible to tell some of these apart just by looking at them. For example, two liter soda bottles are made of a plastic called polyethylene terephthalate, or P.E.T.. Another type of plastic, polyvinyl chloride, can look just like P.E.T., but if a small amount of it is present with the soda bottles you are recycling, it can ruin the entire batch. To help prevent this problem, manufacturers stamp all plastic products with a recycling code number. Plastics are grouped into seven categories. P.E.T. plastic is number one, while polyvinyl chloride is number three. Milk jugs and plastic grocery bags are both number two. It’s important to separate your plastics very carefully before you recycle them. And remember: carrying your bottles to a recycling center is just the first step. It’s just as important to BUY items made from recycled material as it is to recycle them.