1. Plastic treatment
Because PET macromolecules contain lipid groups and have certain hydrophilic properties, the grain is sensitive to water at high temperature. When the water content exceeds the limit, the PET molecular weight decreases in processing, and the products become color and brittle.
Therefore, before processing, the material must be dried, with the drying temperature of 150℃, more than 4 hours; generally 170℃, 3-4 hours. Air method can be used to test for complete drying. The proportion of PET bottle billet recycling materials should generally not exceed 25%, and the recycled materials should be thoroughly dried.
2. Selection of injection molding machine
Because PET has a short stable time after the melting point and a high melting point, it is necessary to choose the injection system with more temperature control sections and less self-friction and heat generation during plasticizing, and the actual weight of the product (including water intake material) should not be less than 2 / 3 of the injection amount of the machine.
3. Mold and pouring gate design
PET bottle embryo, generally formed with heat flow channel mold, mold and injection molding machine template between the better to have a heat insulation plate, its thickness is about 12mm, and the heat insulation plate must be able to withstand high pressure. Exhaust must be sufficient to avoid local overheating or fragmentation, but the depth of the exhaust port generally does not exceed 0.03mm, otherwise it is easy to produce flying side.
4. Melt temperature
Available air-emission method measurement, 270-295℃ range, enhanced grade GF-PET can be set to 290-315℃, etc.
5. Speed of injection
The general injection speed should be fast to prevent premature coagulation during the injection. But too fast, the shear rate is high, make the material fragile. The shooting is usually completed in 4 seconds.
6. Back pressure
The lower the better, to avoid wear. Generally not exceeding 100bar, usually not used.
7. Time to stay
Do not use too long retention time to prevent the molecular weight drop, and try to avoid the temperature above 300℃. If the shutdown is less than 15 minutes, only do air shooting treatment; if more than 15 minutes, then clean with the viscosity PE, and drop the cylinder temperature to the PE temperature, until the restart.
8. Precautions
Recycling material can not be too large, otherwise, easy to produce in the material “bridge” and affect plasticizing;
If the mold temperature control is not good, or the material temperature control is not appropriate, easy to produce “white fog” and opaque; the mold temperature is low and uniform, fast cooling speed, less crystallization, then the product is transparent.
Huangyan Leiao Molding Co. , Ltd. is located in Huangyan District mould city, Taizhou, Taizhou province, which is “The hometown of Chinese mould”. The company is mainly engaged in the injection mold manufacturing, has many years of mold experience, mainly manufacturing and processing of bottle embryo mold, PET commodity mold, bottle cap mold, car interior and exterior decoration mold… … In the needle valve hot runner injection mold system has its own unique design and processing technology, based on the concept of “Integrity management”, with domestic and foreign customers to establish a long-term good relations of cooperation, I believe that Leiao will be your worthy of confidence in the cooperative enterprise.
Post time: Nov-03-2022