The sign on the bottom of the plastic beverage bottle has a triangle consisting of three arrows, and the number is 1 ~ 7. Some signs also have the word "pet" under them. The triangle formed by these three arrows means "recyclable", and the numbers inside represent different materials. "1" refers to the PET polyester beverage bottle, which can be filled with normal temperature water in a short time, but it cannot be filled with high temperature water or acid-base beverages. It is recommended not to reuse it, and the mineral water bottle should not be exposed to the sun in the car. "2" refers to the plastic container made of HDPE, which is often used for medicine bottles, cleaning supplies and bathing supplies. This kind of product is not easy to clean thoroughly, and it is not suitable for water cups and the like, and it is not suitable for recycling. "3" means that it is made of PVC and polyvinyl chloride, and it is resistant to heat at 60℃. If it exceeds 60℃, vinyl chloride monomer may be released, and long-term contact may cause hepatobiliary tumors. "4" means products made of LDPE and low density polyethylene, which are often used in raincoats, building materials, plastic films, plastic boxes and so on. These two materials are widely used because of their excellent plasticity and low price. However, they have low heat resistance and may release harmful substances when decomposed at high temperature, so they are rarely used in food packaging. "5" means made of PP and polypropylene, which is the only plastic box that can be put into the microwave oven and can be reused. "6" means that plastic products made of PS polystyrene cannot be used in high temperature, strong acid and strong alkali environment. "7" stands for acrylonitrile-styrene resin. This material has been used in the mass production of kettles, cups and baby bottles for many years before 10, with high safety, but try not to use it for filling boiling water. The cup made of this material has high transparency and resistance to falling, but its durability is poor.