Why does PET blowing need to use medium and high pressure air compressor
Time:2020-09-22 12:10:18 Source: 优尼捷 View: 735
- The function of the medium and high pressure air compressor is to fully stretch the melt, close to the mold wall, so that the bottle is fully formed, and at the same time, it is stretched laterally to improve its lateral strength. The main influencing factors are location and pressure.
- The pressure of the medium and high pressure air compressor is generally 3.7-4MPa, which is determined by its molding characteristics and the nature of the filled beverage (carbon dioxide). There are two positions, namely, the position of high pressure gas and the position of exhaust. The time between the two is the pressure holding time in molding. The length of this time has a great influence on the stability of the bottle volume. Insufficient high-pressure air may cause improper bottle molding and insufficient foot blowing.
Plastic hollow containers are widely used in beverage, medicine, cosmetics, food and chemical industries due to their light weight, low price, and high safety. They have attracted more manufacturers to choose plastic containers instead of glass containers. Nowadays, the environmentally friendly plastic made of PET is generally used. The tubular plastic parison obtained by extrusion or injection molding of the thermoplastic resin is placed in a split mold while it is hot (or heated to a softened state). After the mold is closed, compressed air is injected into the parison to blow the plastic parison It expands and clings to the inner wall of the mold, and after cooling and demolding, various hollow products are obtained.
The working pressure of compressed air used for blow molding generally reaches 3-4 MPa. In the compressed air under this pressure, gaseous water and oil pollutants will be more concentrated into liquid pollutants. This is true for both oil-free compressors and screw air compressors. The following are the defects of blow molded products due to different reasons of compressed air:
1. Due to insufficient compressed air pressure, orange peel-like patterns appear on the surface of blow molded products, or the outline or graphics are not clear, and the volume of blow molded products may not meet the standard due to insufficient air pressure.
2. There are pits on the surface of the blow molded product due to impurities in the compressed air
3. The parison is blown out when the product is formed due to the high pressure of the compressed air
4. The product is dirty due to water and oil contaminants in the compressed air.
Therefore, it is particularly important to select the appropriate compressed air post-processing equipment.
Compressed air post-processing equipment generally includes dust removal equipment (precision filter), water removal equipment (refrigeration dryer, adsorption dryer, gas-water separator, etc.), degreasing equipment (professional compressed air degreasing equipment, activated carbon filter.). Configure the corresponding purification facilities for different purposes.
Nanjing Hante provides customers with oil-free compressors, nitrogen compressors, sulfur hexafluoride (sf6) compressors, helium compressors, medium and high pressure air compressors and other industrial equipment. We not only provide customers with air compressors, but also Customers provide oil-free compressed gas system solutions.
