1. Plastics treatment
Because PET bottle macromolecule contains lipid group and has certain hydrophilicity, the pellet is more sensitive to water at high temperature. When the water content exceeds the limit, the molecular weight of PET decreases, and the product becomes colored and brittle. In this case, the material must be dried before processing, the drying temperature is 150 C, more than 4 hours, generally 170 C, 3 - 4 hours. The air can be used to check whether the material is completely dry.
The proportion of recycled materials should not exceed 25%, and the recycled materials must be thoroughly dried.
2. Injection molding machine selection
Because PET has a short stabilization time and a high melting point after melting point, it is necessary to choose an injection system with more temperature control sections and less heat generated by self-friction during plasticization, and the actual weight of the product (water-containing material) can not be less than 2/3 of the machine injection quantity. Based on these requirements, Ramada has developed a series of special plasticizing systems for PET in recent years. Clamping force is chosen according to greater than 6300t/m2.
3. Mold and gate design
PET bottle embryo is generally molded by hot runner mold. It is better to have a heat insulation plate between the mold and the mold of injection molding machine. Its thickness is about 12 mm, and the heat insulation plate must be able to withstand high pressure. Exhaust must be sufficient to avoid local overheating or fragmentation, but its exhaust port depth should not exceed 0.03 mm, otherwise it is easy to produce flying edge.
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