In special cases, determine the molding temperature should consider the rolling pattern will be at what temperature, the adhesive will be coated on the back of the sheet at what temperature. The entire surface with uniform heating forming sheet, such as striated or high thickness difference, which would impede uniform heating. In order to realize the uniform heating, the radiation heater is required to be irradiated evenly, especially in the side part. A method of using a mirror or an auxiliary heater to prevent heat loss. Vacuum forming method for hard and soft polyvinyl chloride sheet. Air pressure and can achieve the vacuum degree (about 0.05 cm Hg) between the difference that the forming force, the maximum value of 0.95 atmospheric pressure. Many kinds of vacuum forming method, in the pre stretching way and uses the different mold (die or mold) and distinguish.
The thin slices cut from the sheet are fed into the vacuum forming machine, which is heated in a tight pressing frame at each side of the film. Heating using infrared light irradiation device. Generally only one side of the hot side of the heat, if the thickness of the sheet, you can take both sides of the heating or heating furnace in the method of preheating. Infrared radiator used more, and the thermal efficiency of the utility model is basically not subject to the influence of reflection, namely the sheet color will not too drastically affects the heating time. Hot strength of radiant heaters shall guarantee more than 2.5 w / cm 2 radiator from the sheet surface distance is determined according to the sheet surface. The preheating temperature of the hard and soft polyvinyl chloride sheet is 90~130. Determination of the surface temperature of the sheet by using a molten body temperature measuring device or a temperature measuring pen.
Molding temperature is generally determined by the following factors:
Film quality: containing plasticizing agent less slices can bear high temperature and not to tear the continous, emulsion polymerization and suspension polymerization of vinyl chloride sheet temperature.
Sheet thickness: the thickness of the sheet, the more heat the heat required, the molding temperature is higher.
Forming depth: the deeper the forming, the lower the temperature should be, this is to ensure that the sheet can have enough strength.
The thermal stability of the required: the forming temperature is higher, the higher thermal stability.
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