- Nov 22, 2017 -
The air permeability of PE packaging film is large, and its permeability is decreased with the increase of density. PE packing film has moisture resistance and little moisture permeability. According to the different manufacturing methods and control methods, polyethylene film (PE) can produce low density polyethylene packaging film, medium density polyethylene packaging film, high-density polyethylene packaging film and cross-linked polyethylene packaging film and other products with different properties. 
Low density polyethylene packaging film
The density is about 0.92g/cm3. Low density polyethylene film transparency and good sealing performance, waterproof, moisture-proof; low tensile strength, tensile elongation, easy wrinkled, thin film below 0.03mm, tension control should be small, and all the tension to a constant, especially easy to deform when heated, causing difficulties in color. Therefore, when drying, the film surface temperature should not be too high (within 550C). According to the film forming process, can be divided into blown film, cast film (IPE) (CPE), several low foaming film etc.. The tensile strength and opening property of IPE film is better than that of CPE film. It can be used as food bag and clothing bag by positive printing. The CPE film has uniform thickness, good surface gloss, transparency and heat sealing property than PE. It can be printed on the positive and negative sides, but the production cost is high. CPE film is mainly used as the inner layer of composite bags and packaging of cosmetics, pickles and pastries; low foaming film has good decoration, thick texture, and is not easy to stretch deformation. It is used for front printing, and is used as New Year pictures, trademarks and hand carrying bags.
Medium density polyethylene
Its density is about 0.93 ~ 0.94g/cm3, and the performance is between high density and low density polyethylene.
High density polyethylene
The density is 0.94 - 0.965g/cm3. The heat resistance and mechanical strength of HDPE film are better than LDPE film, the elongation at break is small, the film thickness is more than 0.03mm, but the transparency is poor. It is mainly used as vest bag, garbage bag and lining bag.
Because of its higher heat resistance, tensile strength, heat shrinkage and barrier properties than other polyethylene products, its use is further expanded, and most of them are used as heat shrinkable packaging films.
Generally speaking, with the increase of density, mechanical properties and barrier properties will be increased accordingly, heat resistance, and life is good. Polyethylene with the same density has different properties because of the different film forming process. This is because the salivation method can fast cooling, low crystallinity, high transparency, turbidity is small, but more irregular arrangement of molecules, so the barrier is small, the transmittance of larger, lower elongation, tear resistance difference.