Is a kind of plastic bag, used for packaging, its raw materials are generally polyethylene, polypropylene and other chemical plastic raw materials. Braiding density refers to the number of warp and weft yarn roots in the woven fabric of 100mm×100mm. The main raw material for foreign production is polyethylene (PE), and the main material for domestic production is polypropylene (PP), which is a thermoplastic resin made of ethylene by polymerization. In industry, the copolymer of ethylene with a small amount of alpha-olefin is also included. Polyethylene is odorless, non-toxic, feel like wax, has excellent low temperature resistance (low use temperature up to -70 ~ -100℃), good chemical stability, resistance to most acid and base erosion (not resistant to acid with oxidation properties), insoluble in general solvent at room temperature, small water absorption, good electrical insulation performance; However, polyethylene is very sensitive to environmental stress (chemical and mechanical action) and has poor heat resistance and aging. The properties of polyethylene vary from variety to variety, mainly depending on the molecular structure and density. Products with different densities (0.91 ~ 0.96g/cm3) can be obtained by different production methods.