Polystyrene foam molding
DATE：2022/6/21 8:35:32 / READ： / SOURCE：This station
Polystyrene foam molding
The raw material for one-step molding of polystyrene foam is lotion polymerized powdered polystyrene resin, and its process flow is shown in the figure. After mixing polystyrene powder resin with foaming agent, the mixture is heated and pressurized to form a blank, and then heated and foamed to form a foamed plastic. The foam has a closed cell structure, uniform cell and good dielectric properties, and is widely used in the radio industry. Lotion polymerized powdered polystyrene -- drying -- ball milling and mixing -- sieving -- weighing and pre pressing into a blockFoaming agent - molding fusion - Blank - placing (7~11 days) - steam foaming - shaping all edges - polystyrene one-step molding process. Hollow plate production line www.handern com
1. raw materials and formula
See table 4-5 for main raw material specifications and formulas of polystyrene foam. When azodiisobutyronitrile is used as blowing agent, the residue of decomposition is toxic substance tetramethylbutyronitrile, which has plasticizing effect on polystyrene. Therefore, with the increase of the amount of azodiisobutyronitrile, the plasticizing effect will increase, and the unit weight of the foam will be affected to a certain extent. Therefore, the production density is 100kg/m ³ Azodiisobutyronitrile shall be used in combination with ammonium bicarbonate for the following foamed plastics. If only ammonium bicarbonate is used as blowing agent, the structure of the foamed plastic is very poor, resulting in uneven coarse and pore size. The density of this foamed plastic and the use ratio of two foaming agents: main original specifications and formulas hollow board production line www.handern com
Original lotion polymerized polyethylene glycol smoke specification 1% benzene solution relative viscosity / (PA ·) passing 80 days /in spicy residue /%55
0.045 material specification industrial volume note: 1in=25.4mm. Industrial grade table 4-6 raw material ratio and product density raw material ratio / portion
Howe styrene resin ADI! Foamed plastic meal size
2. mixed hollow plate production line www.handern com
The lotion polymerization of powdered polystyrene and powdered blowing agent azodiisobutyronitrile need to be mixed with ammonium bicarbonate, which can usually be completed by ball mill. The mixing effect of ball mill can be judged by the ball milling fineness and mixing uniformity of polystyrene resin and foaming agent. These two indexes directly affect the forming quality of foamed plastics. The mixed materials can only be used after being decorated with sieves of required specifications.
3. moulded parison
The mixed material shall be measured according to the size of the product. When determining the feeding amount, the compression ratio of lotion polymerized powdered polystyrene foam molding shall be considered, which is the ratio of the stacking volume of the mixed raw material to the volume of the pressed blank. This ratio depends on the quality of parison during pressing and affects the quality of parison foaming. Generally, the material density after mixing is about 600kg m, while the capacity of the blank after pressing is more than 900kg/m, so the compression ratio is 1: (1.5~1.6). In addition, the thickness of the parison should be limited, because the thermal conductivity of the resin and the heating method limit the thickness of the parison. It is generally believed that the thickness of the parison should not exceed 25mm, otherwise the center is not easy to be plasticized by heating, or the surface layer has been excessively heated during the central plasticization, resulting in damage to the parison. The parison forming process is as follows.
① Add the measured mixed materials into the mold for preloading. 2. There are fine holes around the mold. When the powder is compressed, the air in the material will be discharged from the hole to press the powder into a relatively tight block, and then the block will be sent to the calibration cavity of the hydraulic press.
③ Heating and temperature rise shall be carried out after the mold is closed and compacted. During heating, the heating speed shall be strictly controlled. Generally, the temperature rises gradually from room temperature to 145 ℃ within 17~20min. Hollow plate production line www.handern com
④ During the heating period, the material is gradually heated, melted and compacted, the volume is gradually reduced, and the phase gap is gradually reduced.
⑤ At this time, the pressure of the hydraulic press shall be maintained at about 19.6Mpa. After the gap of the die is basically eliminated, it shall be kept at 145 ℃ for about 25min.
⑥ The holding time is determined by the thickness of the pressed parison. If the thickness of the parison is within 25mm, the holding time will increase by about 1~1.5min for every 1mm increase in thickness
⑦ After heating and insulation, cool the mold with cold water to reduce the mold temperature to room temperature. This process takes about 25~30min. After cooling, the parison can be ejected.
⑧ At this time, the parison is transparent milky yellow, and the density is about 900~1000kg/m.
4. foaming molding
Place the pressed parison in the foaming mold and heat it with steam for about 60~90min and about 100 ℃. Cool and demould after heating. The resulting parison is expanded and foamed in about one week. If the parison is placed for too long, it will affect the foaming and even cannot expand to the predetermined density. If the foam is foamed immediately after pressing, the surface of the foam body is not smooth enough, and it is not easy to square around. Hollow plate production line www.handern com
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