According to materials: polyethylene is divided into low density polyethylene, LLDPE and high density polyethylene. According to the production process, it is divided into pe flat pocket, self-sealing bag, chain clip bag, envelope bag, punching bag, handbag, zipper bag and PE film. 1, PE flat pocket is the simplest manufacturing process. After the film is blown by the machine, it is cut into bags on the bag-making machine and sealed at the bottom. 2. The self-sealing bag is a bone strip when the machine blows the film, which can be sealed by hand. With chain Bao Butong, these two kinds of bags are generally easily confused. 3. The chain clip bag is a bag made of PE film and two clips (this clip chain comes out separately). Generally, there are relatively wide indentations on both sides of the bag, but the self-sealing bag does not. The self-sealing bag has few printing colors, and the chain-clamping bag can print complex patterns. The envelope bag has a tongue like an envelope. Stick a piece of tape on your tongue and fold it to seal the bag. Generally, clothes are used more. The courier bag is actually a kind of envelope bag. Punching a handbag is to punch a hole at the top of a flat pocket to facilitate the handbag. 6. Holding a handbag is to add a plastic film strip to the top of the bag to facilitate the bag. This process is labor-intensive and costly. 7. Zipper bag is to install a zipper belt and a zipper cap at the seal of the bag. 8.PE film is a film that is not made into a bag after being blown out by the machine. Also divided into winding film and shrink film. Individual calculation and length calculation (volume) are commonly used in the market. Small bags are mainly used for packaging small accessories. Most accessory packages of electronic products have anti-static effect. The bag mouth is divided into flat mouth and self-sealing structure, the latter is also called bone bag (PE bone bag) or dense bag. The (roll) bag needs to be cut (material packaging) and printed (for supermarket use) by itself. In addition, PE plastic wrap can also be called PE bag. Note that the plastic wrap that comes into direct contact with food must use PE material (the other is generally PVC), which is safer for human body. Solution: PVC cling film is more transparent, malleable and sticky than PE cling film. When PVC cling film is on fire, the flame is black, smoky and pungent, and will not drip oil, and will automatically go out after leaving the fire source. When PE cling film burns, the flame is yellow, tasteless and dripping with oil, and it can continue to burn after leaving the fire source.