The rheological properties of pet plastic in the molten state are better, and the influence of pressure on viscosity is greater than that of temperature. Therefore, the flow properties of pet plastics are mainly affected by pressure. The processing method of Plastic Cosmetic Bottles is as follows:
- Plastic processing
Because the pet macromolecule contains aliphatic groups and has a certain degree of hydrophilicity, it is more sensitive to water at high temperatures. When the water content exceeds the limit, the molecular weight of the pet decreases during processing, and the product appears brittle. Therefore, the material must be dried after processing. The drying temperature is 150°C, more than 4 hours, generally 170°C, 3-4 hours. Air jet method can be used to check whether the material is completely dry.
- Due to the short stabilization time after the melting point of PET and the high melting point, an injection system with more temperature control sections and less self-friction and heat generation during the plasticization process should be used. The actual weight of the product should not be less than 23% of the injection volume of the machine. Based on these requirements, Ramada has developed a series of pet-specific plasticizing systems in recent years. The clamping force is greater than 6300tm2.
three. Mold and gate design
PET preforms are generally formed by hot runner molds. It is better to have a heat insulation board between the mold and the injection molding machine template, the thickness is about 12mm, and the heat insulation board must be able to withstand high pressure. The exhaust must be sufficient to avoid local overheating or chipping, but the depth of the exhaust port is generally not more than 0.03mm, otherwise it is easy to produce flashing.
four. Melt temperature
It can be measured by air jet method. 270-295℃, enhanced gf-pet can be set at 290-315℃.
5 injection speed
Generally, the injection speed should be fast to prevent premature solidification during the injection process. But the speed is too fast and the shear rate is high, making the material fragile. The injection is usually completed within 4 seconds.
- Retention time
Do not use too long a retention time to prevent molecular weight reduction. Try to avoid temperatures exceeding 300°C. If the shutdown time is less than 15 minutes. Only air jet treatment is required; if it exceeds 15 minutes, clean with viscous polyethylene and lower the temperature of the barrel to polyethylene until the machine starts again.
- Matters needing attention
If the mold temperature is not properly controlled or the material temperature is not properly controlled, "white fog" and opacity are likely to occur. The mold temperature is low and uniform, the cooling rate is fast, and the crystallized product has poor transparency.
Taizhou jinfu Packaging Technology Co.,Ltd is a manufacturer of plastic bottles, plastic thick-walled bottles, cosmetic bottles, Beverage Bottle, various spray bottles.