Anping County Wennian Wire Mesh Products Co., Ltd. offers a wide range of plastic netting and solutions across multiple industries and detailed applications.
High polymer plastic support net for underground coal mine belongs to the bi-directional stretching and overall shape. Therefore, its requirement for the manufacturing process are different from those of injection molding and thermoset products, being more complex and having more stringent requirements. It is not only related to the selection of equipment, but also depends on how to produce qualified products adequately, reasonably, efficiently, with low consumption, quality and quantity. Through the selection of equipment analysis and raw material characteristics analysis and so forth, the process route is as shown in figure 1.
HPP-01: The production process of high polymer plastic support net for underground coal mine is complex and has many stringent requirements.
Key design parameters in technological process
The reasonable technological conditions have great influence on the tensile strength, flame retardance and anti-static properties of the products, especially the time and temperature.
HPP-02: In order to produce high-quality plastic support net, professional production machines should be adopted.
In terms of tensile strength, the tensile temperature, tensile ratio and tensile speed (the time taken at a certain stretch) are considered. The highly oriented tensile orientation properties of PP can greatly improve its mechanical strength. Through the experiment, the tensile strength is maximum when the tensile ratio of the mesh is 1:8–1:9. That is, when the punching diameter is 4 mm and the tensile length is 30–36 mm, the strength is maximum which can reach 7 times when it is not stretched, and no stress whitening phenomenon. Tensile temperature and tensile speed also have some influence on strength, and generally follow the principle of low temperature and high speed tensile.
The control of time and temperature is important in flame retardancy and anti-static, especially for anti-static properties of products. Electrical properties and mixing time have optimum values. At the beginning of mixing, the dispersion of shear force is dominant, so the electrical conductivity increases with time. When the optimum value is reached, shear failure plays a dominant role in structural damage, so the longer the time, the worse the conductivity. When molding temperature is high, the surface resistance of the material is lowered. At the same time, the flame resistance and mechanical properties are also unfavorable when the temperature is too high.
The key design parameters in technological process are shown in table 1.
|Low speed 5 min, 460 rpm; High speed 5 min, 900 rpm.
|Add anti-static agent at the end of low speed mixing
|Extruder mixing extrusion
|Machine barrel (from charging hole to nose neck 1-6 zone): 160, 170, 185, 195, 210, 190 °C; Extrusion die 5 zones: 205, 200, 190, 200, 205 °C
|Three roller cooling through water, outlet water temperature 35–50 °C
|After the plate is made, the sink is cooled at 40 degrees.
|Once stretching 10 mm, twice stretching 20–26 mm
|Natural cooling after stretching
|Preheat 170 °C, stretch 148 °C, finalize the design 140 °C
|Natural cooling after a short period of water cooling
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