Perfect molding for making PET plastic preforms

Information summary

As the global demand for PET plastic bottles continues to grow, the preforms used to manufacture PET plastic bottles have also become the focus of attention. In order to ensure the perfect forming of PET preforms, many issues need to be paid attention to, and from the temperature...

As the global demand for PET plastic bottles continues to grow, the preforms used to manufacture PET plastic bottles have also become the focus of attention. In order to ensure the perfect forming of PET preforms, many issues need to be paid attention to, and every link from temperature to raw materials needs to be strictly controlled. PET is a hygroscopic material. If the water content is too high, hydrolysis will occur under high temperature treatment, and the PET molecular chain will be broken and thermally decomposed to produce acetaldehyde. The physical and mechanical properties are reduced, and the crystallization rate is reduced. Increase the speed. When the preform is injected, part of the preform will crystallize and turn white, which will affect the quality of the product. Before injection molding of the preform, the PET pellets must be dried to a moisture content of .% or less, which can produce a good non-crystalline transparent preform.

After the preform mold dryer is dehumidified, high-temperature air is used to circulate the dried PET particles in the hopper. For dry air, the dew point temperature must be between °C and °C. Set the temperature between °C to °C and dry for about minutes. In the first step of injection-extended air molding, the preform is injection molded to produce the preform. The preform is injected into the cavity with molten glue, and then the preform is quickly cooled to below the crystallization temperature The temperature is formed to form a transparent preform. The second step is to heat the preform to a temperature higher than the glass transition point, and then stretch it to blow and cool the molded body. The processing method is divided into one stage and two stages. The first stage is to complete the injection and blow molding in the same machine, and then cool the preformed preform to a temperature lower than the crystallization temperature, but still maintain the thermoelastic state, and finally blow into the bottle. The two-stage type is completed by two machines, an injection molding machine and a hollow molding machine. First, after the preform is manufactured by the injection molding machine, the preform is cooled to the solidification temperature, taken out and cooled to room temperature. When the bottle is blown, it is sent to the hollow molding machine to heat the preform to the blowing temperature, and then blow molding and cold molding. In addition to the extrusion molding process, most of the injection molding process conditions for PET preform molding use injection molding to make preforms.

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