Classification of polyethylene film

Low density polyethylene film is generally made by blow molding and tape casting.

The thickness of cast polyethylene film is uniform, but it is rarely used because of its high price. Blown polyethylene film is made of blow molded PE particles by blow molding machine, with low cost, so it is widely used. Low density polyethylene (LDPE) film is a translucent, shiny, soft film with excellent chemical stability, heat sealing, water resistance, moisture resistance, freezing resistance and boiling. It can be used for food preservation film.

The density of low-density polyethylene film is about 0.92g/cm3. The transparency of low density polyethylene film is good, which can prevent water and moisture; The tensile strength is low, the tensile elongation is large, and it is easy to wrinkle. For films below 0.03mm, the tension control should be small, and the tension should be constant everywhere, especially when heated, it is easier to deform, causing difficulty in color matching. Therefore, when drying, the film surface temperature should not be too high (within 55 degrees).

According to different film forming processes, the tensile strength and opening property of IPE film are better than those of CPE film. It can be used as food bags, clothing bags, etc. by positive printing; CPE film has uniform thickness, better surface gloss, transparency and heat sealing than PE, and can be printed on both sides, but the production cost is high. CPE film is mainly used as the inner layer of composite bags and the packaging of cosmetics, pickles and cakes; Low foaming film has good decorative property, thick texture, and is not easy to stretch and deform. It is printed on the front and used as New Year pictures, trademarks, handbags, etc.

Functional features

The main disadvantage of LDPE is its poor barrier to oxygen. It is commonly used as the inner film of composite flexible packaging materials, and it is also the most widely used and most widely used plastic packaging film, accounting for more than 40% of the consumption of plastic packaging film.

Because polyethylene molecule does not contain polar groups, and has high crystallinity and low surface free energy, the printing performance of the film is poor, and the adhesion to ink and adhesive is poor, so surface treatment is required before printing and composite.