Why do we need to use a medium and high pressure air compressor for PET bottle blowing
The function of the medium and high pressure air compressor is to fully extend the molten material, tightly adhere to the mold wall, and fully shape the bottle. At the same time, it performs lateral stretching to improve its lateral strength. The main influencing factors include location and pressure。
The pressure of a high-pressure air compressor in use is generally 3.7-4MPa, which is determined by its molding characteristics and the properties of the filled beverage (carbon dioxide). There are two positions, namely the position of high pressure gas and the position of exhaust gas. The time between the two is the holding time during molding, and the length of this time has a significant impact on the stability of the bottle capacity. Insufficient high-pressure air can lead to improper bottle formation and insufficient foot blowing.
Plastic hollow containers are widely used in the beverage, pharmaceutical, cosmetics, food, and chemical industries due to their lightweight, cost-effective, and high safety characteristics. They have also attracted more manufacturers to choose plastic containers instead of traditional glass containers. The commonly used eco-friendly plastic nowadays is PET material. The tubular plastic parison obtained by extrusion or injection molding of 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 immediately introduced into the parison, causing the plastic parison to expand and tightly adhere to the inner wall of the mold. After cooling and demolding, various hollow products are obtained.
The working pressure of compressed air used for blow molding generally reaches 3-4 MPa. Compressed air under this pressure state, where gaseous water and oil pollutants accumulate more into liquid pollutants. This is true for both oil-free compressors and screw air compressors. The following are the defects of blow molded products caused by different reasons of compressed air:
1. Due to insufficient compressed air pressure, orange peel like patterns appear on the surface of blown products, or the contours or graphics are unclear. At the same time, insufficient air pressure can also cause the volume of blown products to not meet the standard
2. Due to impurities in compressed air, the surface of blow molded products may show pitting
3. Due to high compressed air pressure, the shape of the product is blown out during molding
4. Due to the water and oil contamination inside the compressed air, the product is dirty.
So, selecting appropriate compressed air post-treatment equipment is particularly important. The post-processing equipment for compressed air generally includes dust removal equipment (precision filters), water removal equipment (refrigeration dryers, adsorption dryers, gas water separators, etc.), and oil removal equipment (professional compressed air oil removal equipment, activated carbon filters, etc.). Configure corresponding purification facilities for gases of different uses.
