OIL FREE SCREW & SCROLL AIR COMPRESSOR SOLUTIONS FOR PET BLOWING
OIL FREE SCREW & SCROLL AIR COMPRESSOR SOLUTIONS FOR PET BLOWING
The raw materials of plastic bottles must meet relevant national standards, especially medicinal bottles must meet medical and health requirements. There are four common raw materials for plastic bottles, polypropylene (PP), polyester (PET), polystyrene (PS), polyethylene (PE), etc.
1. Polypropylene (PP)
It has low density, and its strength, hardness and heat resistance are better than those of high-density polyethylene. However, it becomes brittle at low temperatures, is not wear-resistant, and is prone to aging. However, corresponding additives can be added for modification, and the performance level of HDPE can be achieved after modification.
2. Polyester (PET)
PET has many advantages as a packaging container for pharmaceuticals such as eye drop bottles. PET bottles are light and strong, with significantly higher strength and elasticity than plastic bottles made of other plastic materials. Among commonly used plastics, they have better performance in blocking water vapor and oxygen. PET bottles have good chemical resistance and can be used for packaging all items except strong alkalis and some organic solvents. They are suitable for making thin-walled, light-weight, and high-strength pharmaceutical packaging bottles. Therefore, PET bottles have gradually replaced traditional glass bottles.
3. Polystyrene (PS)
Colorless and transparent, its light transmittance is second only to organic glass, and it has good colorability, water resistance and chemical stability. However, PS raw materials are brittle, have average strength, are prone to stress brittle cracking, and are not resistant to organic solvents such as benzene and gasoline, so they are rarely used in the field of pharmaceutical packaging. However, after modification, the impact resistance of the material can be greatly improved.
4. Polyethylene (PE)
It is corrosion-resistant and can be chlorinated. Polyethylene is divided into high density (HDPE), low density (LDPE) and linear low density (LLDPE). HDPE has high melting point, hardness and strength, low water absorption, good processability and radiation resistance, and is often used to produce plastic bottles for tablets. LDPE has good softness, elongation and impact strength and can be used in plastic bottles for eye drops. LLDPE has high impact strength, fatigue resistance and wear resistance, and is rarely used in pharmaceutical packaging such as eye drop bottles.
PET is the most widely used beverage packaging material today. PET bottles originated in the early 1980s. Due to their light weight, easy forming, low price, and easy mass production, they have developed rapidly and with unstoppable momentum since their inception. In just about 20 years, it has developed into the most important form of beverage packaging in the world. PET is not only widely used in the packaging of medicines, carbonated drinks, bottled water, condiments, cosmetics, liquor, dried fruit candies, edible oils, pesticides and detergents, but also specially treated special filling bottles can also be used for juice and tea beverage packaging.
How is PET material made into plastic bottles?
There are usually three ways:
In blow molding, the tubular plastic parison obtained by extruding the raw material is placed in a split mold while it is hot. Immediately after the mold is closed, pet compressed air is compressed in the parison to inflate the plastic parison and stick to the inner wall of the mold. After cooling, the parison is removed. mold to obtain various hollow products. The main products are: beverage bottles, jars, cosmetic containers, medicine bottles, etc.
Injection molding uses pressure to inject molten plastic into plastic product molds, and then cools and molds it to obtain various plastic parts. There are specialized machines and molds for injection molding, with large output and low prices. Injection molding has the widest range of products. As long as there is a mold, products can be made, and it is very convenient.
In blister molding, a flat hard plastic sheet is heated and softened, then vacuum adsorbed to the mold surface, and then cooled and formed. It saves raw and auxiliary materials, is light in weight and easy to transport. The products are generally relatively shallow, such as basins, flat plates and other products with large and relatively shallow diameters.
How to choose the right air compressor?
For application of blowing molding, pressure of 20~40bar compressed air is required. If the plastic container is used for food, beverage or pharmaceutical products, oil free compressed air is required.
For application of injection molding, pressure of 6~10bar compressed air is required.
Model selection is important as it can reduced the energy consumption and prolong machine’s life. Capacity of the compressor, whether vsd or not, air cooled or water cooled shall be taken serious consideration before purchasing.
