The rheological properties of PET in the molten state, stress on the influence of the viscosity is bigger than the temperature, therefore, guangzhou hongyuan plastic packaging of PET materials mainly from the pressure to change the melt flow rate.
1, plastic processing because of PET macromolecular contains aliphatic, has certain hydrophilicity, aggregate at high temperature is more sensitive to water, when the moisture content is more than the limit, in the processing of PET molecular weight drops, products with color, crisp. Therefore, must be to dry the material before processing, the drying temperature is 150 ℃, more than 4 hours, generally is 170 ℃, 3-4 hours. Can be used to test whether the material is completely dry. The proportion of recycled materials should not exceed 25%, and the recovery material should be thoroughly dry.
2, selection of injection molding machine PET since the stable time is short, after melting point and melting point is high, so need more temperature control section and plasticizing the friction heat generating less injection system, and products (water cut materials) actual weight not less than two-thirds of injection machine.
3, mould and PET bottle embryo gate design general use molding mould of hot flow path, between the mold and injection molding machine template must have the best insulation board, its thickness is about 12 mm, and heat insulation board must be able to bear high pressure. Exhaust must be sufficient in order to avoid local overheating or rupture, but the vent depth is generally not more than 0.03mm, otherwise it is easy to produce a flying edge.
4. The melt temperature can be measured by air injection. 270-270 ℃, enhance the level of GF - PET can be set to 290-315 ℃, etc.
5. The injection speed is generally fast, which can prevent premature coagulation during injection. But too fast, high shear rate makes the material fragile. The shot is usually finished in 4 seconds.
6. The lower back pressure is better, so as not to wear out. Usually no more than 100bar. Usually not used.
7. Do not use long detention time to prevent the decrease of molecular weight. As far as possible avoid temperature above 300 ℃. Stop for less than 15 minutes. It is only required for air shooting; If it is more than 15 minutes, clean with the viscosity PE and reduce the cylinder temperature to PE temperature until the machine is turned on again.
There is a high demand for the production of plastic bottles made of PET. Therefore, the company is highly selective in the selection of equipment and employees' assessment.