Translations:Adventist Youth Honors Answer Book/Nature/Recycling/19/en
PP
Refrigerated containers, some bags, most bottle tops, some carpets, some food wrap. Polypropylene is often used for food containers, particularly those that need to be dishwasher safe. The melting point of polypropylene is very high compared to many other plastics, at 320°F (160°C), which means that the hot water used when washing dishes will not cause polypropylene dishware to warp. This contrasts with polyethylene, another popular plastic for containers, which has a much lower melting point. Polypropylene is also very easy to add dyes to, and is often used as a fiber in carpeting which needs to be rugged and durable, such as the carpet one finds around swimming pools or paving miniature golf courses. Unlike nylon, which is also often used as a fiber for rugged carpeting, polypropylene doesn't soak up water, making it ideal for uses where it will be constantly subject to moisture. Research is ongoing with polypropylene, as makers experiment with different methods for synthesizing it. Some of these experiments yield the promise of exciting new types of polypropylene, with new consistencies and a different feel from the fairly rigid version we are all used to. These new elastic versions of polypropylene are very rubbery, making them even more resistant to shattering and opening up many different uses for an already pervasive plastic. Polypropylene is not as sturdy as polyethylene, but it has benefits that make it the better choice in some situations. One of these situations is creating hinges from a plastic, such as a plastic lid on a travel mug. Over time, plastics fatigue from the repetitive stress of being opened and shut, and eventually will break. Polypropylene is very resistant to this sort of stress, and is the plastic most often used for lids and caps which require a hinging mechanism. Like many plastics, polypropylene has virtually endless uses, and its development has not slowed since its discovery. Whether used for industrial molds, rugged currency, car parts, or Tupperware, polypropylene is one of a handful of materials the world is literally built around.
