The label of the plastic lunch box says pp material, but there is no sign of serial number 5 on the lunch box. Can you guarantee that it is really PP material?

Polypropylene (PP) is a semi-crystalline thermoplastic. High impact resistance, strong mechanical properties, resistance to various organic solvents and acid and alkali corrosion. It is widely used in industry and is one of the common polymer materials.

Pp material

Specific gravity: 0.9-0.9 1g/cm3 molding shrinkage: 1.0-2.5% molding temperature: 160-220.

PP is a crystalline polymer. Among the commonly used plastics, PP is the lightest, with a density of only 0.9 1g/cm3 (smaller than water). Among general plastics, PP has the best heat resistance, its thermal deformation temperature is 80- 100℃, and it can be boiled in boiling water. PP has good stress cracking resistance and long bending fatigue life, commonly known as "hundred-fold adhesive". The comprehensive performance of PP is better than that of PE. PP products are light in weight, good in toughness and chemical resistance. Disadvantages of PP: low dimensional accuracy, insufficient rigidity and poor weather resistance. It is prone to aging, brittleness and deformation after demoulding.

In daily life, the commonly used crisper is made of PP.

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.