polypropylene (pŏlˌēprōˈpəlēn) [key], plastic noted for its light weight, being less dense than water; it is a polymer of propylene. It resists moisture, oils, and solvents. Since its melting point is 121°C (250°F), it is used in the manufacture of objects that are sterilized in the course of their use. Polypropylene is also used to make textiles, ropes that float, packaging material, and luggage.
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