1. Treatment of plastics: because PET macromolecules contain lipids and are hydrophilic to a certain extent, the granules are sensitive to water at high temperature. When the moisture content exceeds the limit, the molecular weight of PET will decrease in processing and the products will be colored and brittle.Trapped here, in front of the processing must be carried out on the material drying, the drying temperature is 150 ℃, more than 4 hours, generally is 170 ℃, 3-4 hours.The material can be examined by air - shooting to see if it is completely dry.
The proportion of recycled materials should not exceed 25%, and the recycled materials should be thoroughly dried.
2. Injection molding machine selection: PET is required to use an injection system with more temperature control sections and less self-friction heat generation during plasticization due to its short stability time after melting point and high melting point, and the actual weight of the product (water-bearing material) should not be less than 2/3 of the injection amount of the machine.Based on these requirements, ramada has developed a small series of PET specific plasticizing system in recent years.The clamping force shall be selected as greater than 6300t/m2.
3. Mold and gate design: PET bottle blank is generally formed by hot runner mold. There should be heat insulation board between the mold and the mold template of the injection molding machine.Exhaust must be sufficient to avoid local overheating or fragmentation, but the exhaust depth should not exceed 0.03mm, otherwise it is easy to produce flash.
4. Glue temperature: it can be measured by air shooting.270-295 ℃, enhance the level of GF - PET can be set to two hundred and ninety - 315 ℃, etc.
5. Injection speed: generally, the injection speed should be fast to prevent premature solidification.But too fast, high shear rate makes the material fragile.The shot is usually completed in 4 seconds.