What is polyethylene?
The PE film has moisture resistance and low moisture permeability. Polyethylene film (PE) can produce low-density, medium-density, high-density polyethylene and cross-linked polyethylene with different properties depending on the manufacturing method and control method.
Its density is about 0.92 g/cm3. Low-density polyethylene film has good transparency and heat-sealing property, can be waterproof and moisture-proof; low tensile strength, large tensile elongation, easy to wrinkle, film below 0.03mm, tension control should be small, and tension everywhere It should be constant, especially when heated, it is more easily deformed, which makes it difficult to color. Therefore, when drying, the surface temperature of the film should not be too high (within 55 degrees). According to different film forming processes, it can be divided into blown film (IPE), cast film (CPE), low foaming film and so on. The tensile strength and opening of the IPE film are better than that of the CPE film. It can be used as a food bag or a garment bag for front printing. The thickness of the CPE film is uniform, the surface gloss, transparency and heat sealability are better than PE, and can be printed on the front and back. However, the production cost is high. CPE film is mainly used as the inner layer of composite bag and packaging of cosmetics, pickles and cakes; low foaming film has good decorative property, thick texture, not easy to stretch and deform, and is printed on the front side, used for new year painting, trademark and hand bag.
Medium density polyethylene
Its density is between 0.93 and 0.94 g/cm3 and its performance is between high density and low density polyethylene.
The density is between 0.94 and 0.965 g/cm3. The high-density polyethylene film has better heat resistance and mechanical strength than the low-density polyethylene film, and has a small tensile elongation, and the film thickness is generally 0.03 mm or more, but the transparency is poor. It is printed on the front side and is mainly used as a vest bag, a garbage bag and a liner bag.
Because it has higher heat resistance, tensile strength, heat shrinkage and barrier properties than other polyethylene products, its use is further expanded. In 2014, it was mostly used as a heat shrinkable packaging film.
In general, as the density increases, the mechanical properties and barrier properties increase correspondingly, and the heat resistance is also good. Polyethylenes of the same density have different properties due to the different film forming processes. This is because the rotting method can be rapidly cooled, the crystallinity is low, the transparency is high, the turbidity is small, but the molecular arrangement is more irregular, so the barrier property is small, that is, the transmittance is large, the elongation is low, and the tear resistance is Poor cracking.