Low density polyethylene film and polyester film
LDPE film is usually made by blow molding and tape casting. Tape cast polyethylene film has uniform thickness, but it is rarely used because of its high price. Blown polyethylene film is made of blown grade PE particles by blow molding machine with low cost, so it is widely used. Low density polyethylene (LDPE) film is a kind of translucent, glossy and soft film with excellent chemical stability, heat sealing, water resistance and moisture resistance, freezing resistance and boiling. Its main disadvantage is that it has poor resistance to oxygen. It is often used as the inner film of composite flexible packaging materials. 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.
Due to the fact that there are no polar groups in polyethylene molecules, high crystallinity and low surface free energy, the film has poor printing performance and poor adhesion to ink and adhesive, so surface treatment is needed before printing and compounding. Polyester film is a kind of film material made from polyethylene terephthalate (PET) by extrusion and biaxial tension. It is a colorless, transparent and glossy film with excellent mechanical properties, high rigidity, hardness and toughness, puncture resistance, friction resistance, high temperature and low temperature resistance, chemical resistance, oil resistance, air tightness and fragrance retention. It is one of the commonly used composite film substrates with permeability resistance. However, the price of polyester film is higher, and the thickness is generally 12mm. It is commonly used as the outer layer material of cooking and packaging, with good printability.