1. Conceptually

PC (polycarbonate): it is colorless, transparent, smooth and beautiful plastic. PC is an ideal food packaging material because it is non-toxic and odorless, has good UV resistance, moisture resistance and fragrance retention, has a wide temperature resistance range, is not brittle at – 180 ℃ and can be used for a long time at 130 ℃.

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

2. In terms of characteristics and usefulness

PC: it has the characteristics of good impact resistance and easy molding. It can be made into bottles, cans and containers in various forms for packaging fluid substances such as beverages, wines and milk. The biggest disadvantage of PC is stress cracking. In addition to selecting high-purity raw materials and strictly controlling various processing conditions, resin modification with low internal stress, such as melt blending of a small amount of polyolefin, nylon and polyester, can significantly improve the stress cracking resistance and water resistance.

PET: small expansion coefficient, low molding shrinkage, only 0.2%, one tenth of polyolefin, smaller than PVC and nylon, so the size of the product is stable. The mechanical strength is the best, and its expansion degree is similar to that of aluminum. The film strength is 9 times that of polyethylene, 3 times that of polycarbonate and nylon, and the impact strength is 3 ~ 5 times that of general films. The film has moisture-proof and fragrance retention properties. Although polyester has the above advantages, its film is expensive, difficult to heat seal and easy to carry static electricity, so it is rarely used alone. Most of them are coated with resin with good heat sealing property to make composite films.

Therefore, the PET bottle with biaxial extension blow molding method can give full play to the characteristics of PET, that is, it has good transparency, high surface gloss and glassy appearance. It is the most suitable plastic bottle to replace the glass bottle.