Pet Preform Injection Precautions

 From the scientific name, you don't necessarily know what a pet preform is. In fact, the chances of seeing Pet Preform in life are still quite large. Let's take a look at PET plastic preforms. PET plastic preforms are typical injection molding products, easy to transport, mostly plastic materials, uniform texture, good insulation, is the intermediate product of plastic bottles, oil barrels. In general, pet plastic preform injection needs to pay attention to the following aspects:        1. Plastic treatment: Since PET macromolecules contain a lipid group and have certain hydrophilicity, the pellets are sensitive to water at high temperatures. When the moisture content exceeds the limit, the molecular weight of PET decreases during processing, and the product is colored. Become brittle. In this case, the material must be dried before processing, and the drying temperature is 150 ° C, more than 4 hours, generally 170 ° C, 3-4 hours. Airborne methods can be used to verify that the material is completely dry. The proportion of recycled materials should not exceed 25%, and the recycled materials should be thoroughly dried.       2. Selection of injection molding machine: Since PET has a stable time after melting point and a high melting point, it is necessary to select an injection system with more temperature control sections and less self-friction heat during plasticization, and the product (water-containing material) The actual weight cannot be less than 2/3 of the machine's injection volume.       3, mold and gate design: PET preforms are generally formed by hot runner mold, between the mold and the injection molding machine template, there should be a heat insulation board, the thickness of which is about 12mm, and the insulation board must be able to withstand high pressure. Exhaust gas must be sufficient to avoid local overheating or chipping, but the depth of the exhaust port should not exceed 0.03mm, otherwise it will easily produce flash.       4, melting temperature: can be measured by air-to-air method. Between 270 and 295 ° C, the enhanced grade GF-PET can be set to 290-315 ° C and the like.       5, injection speed: the general injection speed is fast, can prevent premature coagulation during injection. But too fast, the high shear rate makes the material brittle. The shot is usually completed in 4 seconds.       6, back pressure: the lower the better, so as not to wear. Generally no more than 100bar. Usually no need to use.       7. Residence time: Do not use excessive residence time to prevent molecular weight from falling. Try to avoid temperatures above 300 °C. If the shutdown is less than 15 minutes. Only need to be air-blasted; if it is more than 15 minutes, clean it with viscosity PE and reduce the temperature of the barrel to PE temperature until it is turned on again. Although the pet plastic preform injection process is not complicated, the quality of pet plastic preforms is closely related to the injection molding process. If you happen to want to choose a reliable China Pet Bottle manufacturer, I believe that we will provide you with better PET preforms, and we welcome your comments.