What should be paid attention to in the temperature of hollow blow molding production?


Author: MULAN -Plastic Molding Manufacturer

The hollow blow molding process is to place the semi-molten tube blank (parison) obtained by extrusion or injection molding into molds of various shapes, and blow compressed air into the tube blank to make it close to the mold. On the wall of the cavity, the molding method of hollow products is obtained by cooling and demoulding. Its molding process includes the manufacture of plastic parisons and the blow molding of parisons. This molding method can produce various packaging containers such as bottles, pots, barrels, daily necessities and children's toys with different calibers and capacities. When operating the hollow blow molding machine for processing, some temperature control must be paid attention to to ensure that suitable plastic bottles are produced. 1. Melting temperature TM: For crystalline polymers, it refers to the temperature at which the three-dimensional long-range ordered state of the macromolecular chain structure transforms into a disordered viscous fluid state, also known as the melting point. It is the lower limit of the molding processing temperature of the crystalline polymer. 2. Glass transition temperature TG: refers to the transition temperature of an amorphous polymer (including the non-crystalline part of a crystalline polymer) from a glass state to a high elastic state or from the latter to the former. It is the lowest temperature at which the macromolecular chain segments of amorphous polymers can move freely, and it is also the upper limit of the working temperature of the product. 3. No-flow temperature: the highest temperature at which no flow occurs under a certain pressure. Hollow blow molding is to add a certain amount of plastic into the barrel at the upper end of the die of the capillary rheometer, heat it to a certain temperature, and then apply a constant pressure of 50MPA after constant temperature for 10 minutes. If the material does not flow out of the die, after pressure relief Raise the temperature of the material by 10 degrees, keep it warm for 10 minutes, and then apply the same constant pressure until the melt flows out of the die. Subtract 10 degrees from this temperature to get the non-flow temperature of the material. 4. Flow temperature TF: refers to the temperature at which the amorphous polymer changes from a highly elastic state to a viscous fluid state. It is the lower limit of the processing temperature of amorphous plastics. 5. Decomposition temperature TD: Hollow blow molding refers to the polymer in a viscous fluid state. When the temperature further increases, the degradation of the molecular chain will be intensified, and the temperature at which the polymer molecular chain is significantly degraded is the decomposition temperature.

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