Polypropylene is used for similar purposes as polyethylene, but is generally harder and more heat resistant. It's typically used in containers filled with hot food, and has a simple chemical structure (many CH3 methyl groups - one carbon and three hydrogen molecules) that make it very soft.
Food containers for ketchup, yogurt, cheese, margarine, syrup, takeout, medicine containers, straws, bottle caps, Rubbermaid products and other opaque plastic containers (including baby bottles) are all made from polypropylene (PP). This plastic is also used for a variety of purposes such as disposable diapers and panty liners, thermal vests, appliance parts, and many automotive parts (bumpers, carpets, fixtures).
PP is considered one of the safer plastics, but make sure to recycle as much as possible. It is relatively stable, although leachable plastic additives such as the stabilizer oleamide have been shown to work. When PP labware is used for scientific experiments (PP1), it is generally considered a safe plastic for use in food and beverages, and an earlier study suggested that heated PP may be associated with worker exposure in PP factories, associated with occupational asthma (PP2). This type of plastic is microwave safe and dishwasher safe, another better option is to use glass containers to heat food and wash the plastic by hand instead of using a dishwasher.
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