Hello, landlord! Daily plastic bags are roughly divided into six categories! 1. Short for polyethylene. It is a high molecular organic compound formed by addition polymerization of ethylene. Polyethylene is recognized as the best material in contact with food in the world. Non-toxic, tasteless, odorless, in line with food packaging hygiene standards. Polyethylene film is light and transparent, with moisture resistance, oxygen resistance, acid resistance, alkali resistance, general air tightness and excellent heat sealing performance. Known as the "flower of plastic". It is the most commonly used and important material for plastic packaging and printing. 2. Short for PVC-PVC, the molecular formula is (CH2-CH2) N, which is the most important kind of vinyl polymer and the second largest plastic variety in the world after polyethylene. In China, the output ranks first among plastics. In the printing industry, PVC color calendering film and transparent glazing film are often used to make packaging and decoration of books, folders, tickets and other covers. 3. Shrinkfilm Shrinkfilm is a kind of thermoplastic film, which is stretched and oriented in the production process and will shrink when it is treated with hot air or irradiated with infrared rays during use. After heat treatment, the film is tightly wrapped on the package, and the shrinkage force reaches the maximum in the cooling stage, which can be stored for a long time. 4.LDPE- low density polyethylene (LDPE) is the most widely used variety in plastic packaging and printing industry in various countries. The specific gravity is 0.92 ~ 0.93, and it can float in water. The crystallinity is low (60%), and bulk polymerization is carried out under the pressure of 1000 ~ 3000 kg/cm ㎡, so it is also called high pressure polyethylene. At 23℃, the density is about 0.92. The calendering formability is poor, and it is suitable to be processed into tubular films by blow molding. Suitable for food packaging, fiber products packaging and daily chemical products packaging. 5.HDPE- high density polyethylene, abbreviated as HDPE. The density is 0.941~ 0.965g/cm3. It is made by low-pressure polymerization, so it is also called low-pressure polyethylene. It is milky white, indicating poor gloss. The film can be processed by blow molding and T-die extrusion process. Heat and cooking resistance, cold and frost resistance, moisture-proof, gas-proof, good isolation performance, not easy to break, and its strength is twice that of LDPE. It is easy for people to talk about strong paper, which is called "paper-like plastic film". 6.BOPP- biaxially oriented polypropylene biaxially oriented polypropylene, also known as biaxially oriented polypropylene, is characterized by tensile molecular orientation, and its mechanical strength, folding strength, air density and moisture-proof barrier are superior to ordinary plastic films. Compared with cellophane per unit area, the unit price is lower than cellophane. Because this film has excellent transparency, the reproduced color after internal printing is particularly bright and beautiful, and it is an important base material of plastic composite soft packaging. Attachment: Toxicity Identification of Plastic Bags Most commonly used food plastic bags are polyethylene films, which are non-toxic and can be used to hold food. There is also a membrane made of PVC, which is not toxic in itself, but the additives added according to the purpose of the membrane are often harmful to the human body and have certain toxicity. Therefore, this film and plastic bags made of this film are not suitable for holding food. If you want to identify PVC plastic bags and polyethylene plastic bags, you can use the following simple methods to identify them. Polyethylene film (non-toxic) is milky white, translucent (especially obvious when stacked several times), smooth to the touch, as if the surface is coated with a layer of wax, hard to shake, brittle in sound, flammable in case of fire, yellow in flame, dripping with mucus when burning, and scented with candles when burning. PVC film (generally toxic) is transparent and pigment-free, and its surface feels sticky, shaking badly and its sound is low. It is not easy to burn in case of fire, and it goes out immediately after leaving the flame, and the flame is green.