The bottle cap is an important part of food and beverage packaging, and it is also the first place where we come into contact with the product. It does not look so conspicuous, but it has the function of keeping the contents of the product airtight, and also has the functions of anti-theft opening and safety. 1. Classification and molding method of plastic anti-theft bottle caps
1. According to the raw materials of bottle caps: it can be divided into PE caps and PP caps. PE (polyethylene): The density is 0.94-0.96g/cm3, and the processing temperature is about 220°C; it is softer than PP, and the single-piece cover is more commonly used. PE is basically divided into three categories, namely high-pressure low-density polyethylene (LDPE), high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE). General bottle cap materials usually use high-density polyethylene (HDPE). PP (polypropylene): the density is 0.9-0.91 g/cm3, the processing temperature is about 220 ℃; comparison: (1) PP density is smaller than PE, and the strength, stiffness, hardness and heat resistance of PP are better than PE, and can be used in Use at around 100 degrees Celsius; (2) PE is softer than PP, so the single-piece cover is usually made of PE material; (3) PE and PP materials are similar in price and can be used for food packaging.
2. According to the form: it can be divided into single-piece cover and double-piece cover. Single-piece cap: There is no gasket inside the bottle cap, and the entire cap is made of the same material, and it is sealed by folding or inner plug; Double-piece cap: There is a gasket inside the bottle cap, and the gasket material is soft, and it is maintained by the rebound force of the compressed gasket. Sealing; At present, the plastic bottle cap lining material suitable for beverage filling process generally adopts thermoplastic elastomer added to polyolefin.
Comparison:
(1) The single-piece cover is not cushioned and does not need a cushioning machine, so the investment in equipment is less than that of the two-piece cover. And the price of the gasket material is more than twice that of the cover material, and the cost of the single-piece cover is lower than that of the double-piece cover;
(2) The single-piece cover has high requirements on the size and shape of the bottle mouth; The deformed rebound force presses the outer edge and end face of the bottle mouth to seal; the inner plug single-piece cap is sealed by the interference fit between the outer diameter of the inner plug and the inner diameter of the bottle mouth. The gasket of the double-piece cap is soft and has a greater tolerance for bottle mouth defects.
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