Process control and characteristics of blow-plastic processing products

Process control and characteristics of blow-plastic processing products

Because the performance of blowing plastic film has a great relationship with the consumer process parameters, so in the process of blowing film, it is necessary to enhance the control of process parameters, standard process operation, to ensure the smooth stop of consumption, and obtain high quality film products. In the consumption process of polyethylene blowing film, mainly control the following process parameters:

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1. Extruder temperature

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When blowing low density polyethylene (LDPE) film, the extrusion temperature is generally controlled between 160℃ ~170℃, and the average nose temperature is guaranteed, the extrusion temperature is high, the resin is easily synthesized, and the film is brittle, especially the longitudinal tensile strength is significantly reduced; when the temperature is low, the resin plasticizing is poor, the tensile strength of the film is low, and the luster and transparency is poor, so that the pattern like wood growth rings and uncondensed crystal core (fish eye).

2. Blow ratio

The blowing ratio of the factory is one of the control points of the consumption process of blowing plastic film after blowing, which refers to the ratio between the diameter of the membrane bubble and the diameter of the unblown pipe ring. The swelling ratio is the lateral contraction multiple of the film. In practice, the film stops the lateral stretching. The stretching will have a certain level of orientation effect on the plastic molecules, and the swelling ratio increases, so that the lateral strength of the film advances. However, the blowing ratio can not be too large, otherwise it is easy to form membrane bubble instability, and the film is easy to wrinkle. Therefore, the blowing ratio should be suitable with the traction ratio. Generally speaking, the blowing ratio of low density polyethylene (LDPE) film should be controlled at 2.5~3.0.

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The conditions of the blowing plastic factory home needs to pay attention to what problems

The conditions of the blowing plastic factory home needs to pay attention to what problems

The purpose of process condition adjustment is to meet the minimum wall thickness as uniform as possible and the weight of the product parts as small as the other (reduce the cost of materials). A reasonable way to set the process parameters is to combine experience with numerical analysis skills. The foundation process is,

① The use of the established computer model, imitating the blowing mold, feeding type billet, sandwich board and other conditions;

② Input parameters on wall thickness distribution of each stage;

③ Analysis of the obtained imitation results, through the computer imitation to show which parts of the wall thickness can not meet the requirements, and which parts of the wall thickness is super thick;

④ Use artificial experience, adjust the input parameters, repeat the process of ① ~ ③, ensure that the parts of the product reaches the minimum wall thickness, minimize the wall thickness of the product.

⑤ Analyze and compare the results of multiple process plans, and finally determine the optimized process parameters. Tensile blow molding, also known as biaxial orientation blow molding, is a method of forming packaging containers by mechanical method of axial stretching billet and radial blowing (tensile) type billet with compressed air under the condition of high elastic force of polymer. Stretch blowing molding has one step method, two step method.