Some Considerations Of The PET Mould
PET Mould which is a rather special mold, mold design, processing, transfer process has a lot of precautions, explain to you today under the PET material properties and some precautions.
As the PET macromolecule contains a lipid, has a certain hydrophilicity, pellets at high temperature water is more sensitive, when the moisture content exceeds the limit, the processing of PET molecular weight decreased, the product color, brittle. Therefore, before processing, the material must be dried, the drying temperature is 150 ℃, 4 hours or more; usually 170 ℃, 3-4 hours. Available air method to test whether the material is completely dry. PET preform recycled material ratio generally not more than 25%, and the recovery of the material should be thoroughly dried.
PET mould because of the melting point after a short time of stability, and the melting point and high, so the need to use more temperature control section, plastics from the friction heat less injection system, and the product (moisture content) actual weight can not be less than the machine injection Two thirds of the volume. PET preform, generally with hot runner mold molding, mold and injection molding machine template is best to have insulation board, the thickness of about 12mm, and the insulation board will be able to withstand high pressure. Exhaust must be sufficient to avoid local overheating or fragmentation, but the exhaust depth is generally not more than 0.03mm, otherwise easy to produce flash.
General injection speed faster, to prevent premature injection of solidification. But too fast, high shear rate, the material fragile. The shot is usually completed in 4 seconds. Do not allow the residence time is too long, to prevent the molecular weight down, try to avoid the temperature above 300 ℃. If the downtime is less than 15 minutes, just air-jet treatment; if more than 15 minutes, then use the viscosity of PE cleaning, and the barrel temperature dropped to PE temperature until it is switched on. Seconds to complete.