Biaxially stretched polypropylene film (BOPP) is generally a multi-layer co-extruded film, which is made of polypropylene particles formed by co-extrusion sheet, and then stretched in both vertical and horizontal directions. Due to the tensile molecular orientation, this film has good physical stability, mechanical strength, air tightness, high transparency and gloss, toughness and wear resistance, and is a widely used printed film, generally using a thickness of 20 ~ 40 μm, the most widely used is 20 μm. The main disadvantage of biaxial tensile polypropylene film is poor heat sealing, so it is generally used as the outer film of composite film, such as moisture resistance, transparency, strength, stiffness and printability after composite with polyethylene film are ideal, suitable for holding dry food. Because the surface of the biaxial polypropylene film is non-polar, high crystallinity and low surface free energy, its printing performance is poor, and the adhesion to the ink and adhesive is poor, and surface treatment is required before printing and composite.

Features: BOPP has the advantages of light weight, non-toxic, odorless, moisture-proof, high mechanical strength, good dimensional stability, good printing performance, and good transparency. It has the advantages of high transparency, good gloss, good barrier property, high impact strength and low temperature resistance. Its disadvantage is that it is easy to shrink the film when it is hot closed (except for the heat shrink smoke film using its heat shrink performance).

Bidirectional stretch polyester film BOPET film, as the outer material of the cooking bag. The usual thickness is 12 μm

BOPET film has the following advantages:

① Good mechanical properties, and good rigidity, high strength.

② Excellent cold resistance and heat resistance. The suitable temperature range is -70 ~ 150℃.

③ Good water resistance, air resistance and fragrance preservation.④ It has good antistatic property, easy to vacuum aluminum plating, and can be coated with PVDC, thereby improving its heat sealing, barrier property and printing adhesion.

⑤ Resistant to grease and most solvents, weak acid and alkaline liquids. The disadvantage of BOPET film is poor puncture resistance.

In addition, there are many varieties of film, as well as polyethylene film, nylon film and so on.