1. From a conceptual point of view:

　　PC (polycarbonate): It is a colorless, transparent, bright and beautiful plastic. Because PC is non-toxic and odorless, it has good ultraviolet transmission resistance, moisture-proof and fragrance-preserving performance, wide temperature resistance range, no brittleness at -180℃, and long-term use at 130℃, so it is an ideal food Packaging Materials.

　　PET: A material with good crystallinity, colorless and transparent, and extremely tough. It has the appearance of glass, is odorless, tasteless, non-toxic, flammable, has a yellow flame with a blue edge when burning, and has good air tightness.

　　2. From the characteristics and usefulness:

　　PC: It has the characteristics of good impact resistance and easy forming. It can be manufactured into bottles, cans and various forms of containers for packaging fluid substances such as beverages, alcohol, and milk. The disadvantage of PC is stress cracking. In addition to the selection of high-purity raw materials and strict control of various processing conditions in the production, the modification of resins with low internal stress, such as a small amount of polyolefin, nylon, polyester, etc., can be melt blended, which can significantly improve stress crack resistance and water resistance .

　　PET: Small expansion coefficient, low molding shrinkage, only 0.2%, which is one tenth of polyolefin, smaller than PVC and nylon, so the product has stable dimensions. The mechanical strength is high-quality, and its expansion is similar to aluminum. The film strength is 9 times that of polyethylene, 3 times that of polycarbonate and nylon, and the impact strength is 3 to 5 times that of ordinary films. The film also has moisture-proof and fragrance-preserving properties. Although polyester has the above advantages, its film is more expensive, difficult to heat seal, and easy to be charged with static electricity, so it is rarely used alone. Most of them are coated with a resin with better heat sealability to make a composite film.