Home Product / Techniques PET Preform Injection Molding

What are the characteristics of PET material? What should be noted during injection molding? PET is polyethylene terephthalate, a saturated polyester co-polymerized with terephthalate and Ethylene Glycol. It is good in transparency, gloss and airtight, and it meets the Food Safety Standard, and it can be recycled for re-use. The glass transfer temperature (Tg) of PET is between 75 - 80°C, and injection molding temperature is between 270 - 310°C, the mold temperature is 130 - 150°C. Since PET is high in water absorption, humidity prevention is specially required in storage, and before processing, it has to be dehumidified and dried under 150 - 180°C for 4 hours normally. And, in order to prevent the resin to re-absorb moisture, it shall be kept at temperature above 140°C. When operation is stopped, to prevent the resin turning yellowish, the dehumidifier / dryer temperature needs be drop to 100°C, only maintaining the temperature but not humidity. At the injection molding, if the material temperature is too high, screw shearing force is too high or revolving too fast, it is likely to generate acetaldehyde and leading to caudation. Normally, the molded PET bottle shall contain less than 3ppm of acetaldehyde.

What are the types of PET preform molding? In general, PET preform molding methods are in two types: direct blowing molding and extended blowing molding. Direct blowing molding: This is to inject molten PET bottle on same machine (normally referred to as Injection Stretch Blow Molding, then in the hollow mold blow and stretch to molded product. Since the PET bottle is molded and stretch blown on same unit, so it is also called one step method, and before the bottle cooling off, the bottle is blown with the remaining heat, so it is also called Hot Bottle Blank method. Stretch blowing molding: In this method, injection machine is employed to produce the bottle, then the cooled bottle is heated on stretch blown unit, and stretch and blow in hollow bottle to mold. Since this method is processing on injection and stretch blow machine, it is also called 2-Step method. Also, this method heats cooled bottle to blow and stretch, it is also called Cold bottle method. The process flow is as the following: dehumidify and dry PET materialèinjection machine melt material and inject into moldècool PET bottle to moldèdual axis stretch blow molding by Stretch Blow Molding. Note: The dual-axis stretch is stretch longitudinally with stretching rod and high- pressure air for laterally extension. The application: Generally, one-step method is better suitable for small volume production for large number of specifications. 2-step method is suitable for mass production of limited type. Our FT-P series—PET preform injection molding special unit is of 2-step method.

What equipment is included in a complete PET preform system? PET perform injection molding machine. Dehumidifiers Hopper Dryer Auto Loaders Mold Temperature Controllers Chiller Robot Conveyor

What products are allowed to be packed in PET containers? PET material has been widely used in the packing container for the following products: water bottle, juice bottle, edible oil bottle, cosmetics bottle, drug bottle, bear bottle, wide neck bottle, detergent bottle.

Do you provide molds for PET preform too? Except offering PET preform special injection machine, we also supply PET preform molds, including ordinary mineral water bottle, 5 gal. bottle, hot filling bottle and wide neck bottle. For details please refer to "PET Preform Mold" in the Products section of this website. We also supply PET preform molding system, as well as Turn-Key Project, which include PET preform injection machine, stretch blowing machine, preform mold, stretch blowing mold, peripheral equipment for dehumidifier / drying/ feeding systems.

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