Made of polypropylene (PP), it is the only plastic box that can be put into the microwave oven (it should be noted that lunch boxes are usually marked whether they are suitable for use in the microwave oven, and the cover material of some lunch boxes is not PP, so they cannot be put into the microwave oven for heating. It's best not to bring a lid when heating meals. )。 The polypropylene lunch box is thick and strong. When used at the temperature of 140℃- MINUS 30℃, it can be cooked in a high-temperature microwave oven and refrigerated in a low-temperature freezer. Not brittle and aging, non-toxic and tasteless.
Extended information: Polypropylene is a thermoplastic resin polymerized from propylene. According to the arrangement position of methyl groups, they can be divided into isotactic polypropylene, atactic polypropylene and syndiotactic polypropylene.
When methyl groups are arranged on the same side of the molecular backbone, it is called isotactic polypropylene; If methyl groups are arranged on both sides of the molecular main chain in disorder, it is called random polypropylene; If methyl groups are alternately arranged on both sides of the molecular main chain, it is called syndiotactic polypropylene. In general industrial polypropylene resin, the isotactic structure content is about 95%, and the rest is random or syndiotactic polypropylene.
Industrial products are mainly composed of isotactic substances. Polypropylene also includes a copolymer of propylene and a small amount of ethylene. Usually a translucent colorless solid, tasteless and nontoxic. Because of its regular structure and high crystallinity, its melting point can reach 167℃. Its outstanding advantages are heat resistance and corrosion resistance, and the product can be sterilized by steam. Low density, it is the lightest general plastic. The disadvantages are poor impact resistance at low temperature and easy aging, but they can be overcome by modification respectively.
* * * Polymer-based PP material has low thermal deformation temperature (100℃), low transparency, low gloss and low rigidity, but it has strong impact strength, and the impact strength of PP increases with the increase of ethylene content. The Vicat softening temperature of polypropylene is 65438 050℃. Because of its high crystallinity, this material has good surface hardness and scratch resistance. There is no environmental stress cracking problem in PP.
The melt mass flow rate (MFR) of PP is usually 1~ 100. PP with low MFR has better impact resistance, but lower tensile strength. For materials with the same MFR, the impact strength of poly type is higher than that of homopolymer type. Due to crystallization, the shrinkage of PP is quite high, generally 1.6~2.0%.
2065438+07101The list of carcinogens published by the International Agency for Research on Cancer of the World Health Organization was preliminarily sorted out for reference. Polypropylene is in the list of three types of carcinogens.
Reference: Baidu encyclopedia polypropylene