Foam sheet operation process
DATE：2021/12/2 8:49:52 / READ： / SOURCE：This station
Foam sheet operation process
① Ingredients. Weigh the materials separately according to the formula and add the materials in order.② Mixing. The polyethylene resin is mixed in a plastic mixing machine for 3 to 5 minutes, and the temperature is controlled at about 110 to 120°C. After mixing the polyethylene resin into flakes, add azodicarbonamide and tribasic lead sulfate. At this time, the temperature drops to 70～100℃, then mix for 10 minutes, and then add dicumyl peroxide at the same temperature. Mix for 5 minutes to form flakes
③Slicing. According to the shape of the product to be processed, die cut into the required size of the sheet
④ Compression molding. Put the flakes into the mold, heat the mold to 160°C, pressurize it to 0.6MPa, and press for 12-15 minutes.
⑤Open mold foaming. There are two mold opening methods as follows.
a. Hot mold opening method After the foaming agent is completely decomposed, the pressure of the hydraulic press is released, the hot melt sheet is expanded and ejected, and the foaming is completed within 2 to 3 minutes. The rapid expansion and foaming of the molten material is conducive to the formation of small cells, but it cannot achieve too high a foaming ratio. It is difficult to achieve a balance between the gas pressure generated by the decomposition of the foaming agent and the viscosity and elasticity of the material. The slight resistance during foaming will cause the foam to crack. Therefore, special attention must be paid to controlling the elasticity of the melt to ensure normal production. conduct.
b. The cold mold opening method cools the cross-linked and foamed mold to about 65°C, opens the mold to take out the foam block, and immediately sends it to a 120-170 oven for heating for secondary foaming; the hot-pressed foam block can also be placed It is heated and expanded for a second time in a mold with a larger volume, and the mold is opened after cooling to obtain a polyethylene foamed plastic product with a closed-cell structure, fine and uniform cells and excellent mechanical strength. The foam sheet with high expansion ratio can be obtained by heating for secondary foaming under normal pressure.
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