polystyrene
DATE：2022/4/23 8:50:27 / READ： / SOURCE：This station
polystyrene
The first mock exam lotion of polystyrene foam is emulsion polymerization of powdered polystyrene resin. The process flow is as follows: liquid polymerization polystyrene powder - ball milling, mixing, screening, blowing agent, weighing, prepressing, forming, molding, melting, and forming one blank, and placing them one by one (1~7 days). The polystyrene powdered resin is mixed with foaming agent to heat and pressurize the mixture to form a blank and then heat up and form it into foam plastic. The foam plastics are closed cell vesicles with uniform pore size and good dielectric properties, and are widely used in the radio industry. Casting film production line www.handern.com comOne step molding process flow chart of Polystyrene Molding
(1) the main raw material specifications and formulation of raw materials and formula polystyrene foam are shown in table 8-4. When using iminodiisobutyronitrile as foaming agent, the decomposition residue is toxic tetramethylbutyronitrile and plasticizes polystyrene. Therefore, the amount of azo two isobutadiene increased and plasticizing effect increased, which made the bulk density of foam plastics affected. Therefore, azo two isobutadiene should be used in conjunction with ammonium bicarbonate when making foam plastics whose bulk density is below 0.1g/cm. If only ammonium bicarbonate is used as foaming agent, the foam structure is very poor, resulting in uneven pore diameter and pore size. Casting film production line www.handern.com com
(2) The mixing of concentrate and ammonia can usually be completed by ball mill. The mixing effect of the ball mill can be judged by the ball milling fineness and mixing uniformity of the observed ethylene resin and foaming agent. These two indicators can only be used after sub screening. Directly affects the molding quality of foam plastics. The mixed materials must be approved by the third party of the required specifications
(3) the foam material mixed with moulded parison is measured according to the size of the product. When determining the amount of lotion, the compression ratio of the polymerized polystyrene foam molded by emulsion polymerization method should be considered. This is the ratio of the volume of the raw material after mixing to the volume of the blank. This ratio depends on the weight of the parison during pressing and affects the quality of parison foaming. Generally, the bulk density of the mixed material is about 0.6g/cm, while the bulk density of the blank after pressing is required to be more than 0.9g/cm3, so the compression ratio is 1: (1.5 ~ 1.6). In addition, the thickness of the parison should be limited, because the resin thermal conductivity and 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 when the center is plasticized, the surface layer has been excessively heated and the parison is scrapped. The measured mixed materials are added into the mold for preloading. There are fine holes around the mold. When the powder is compressed, the air in the material will be discharged from the fine holes, so that the powder can be pressed from the most expensive material. Then feed the block into the die cavity of the hydraulic press; After the mold is closed and pressed, the heating rise shall be carried out. During heating, the heating speed shall be strictly controlled. Generally, it shall be selected from the base temperature to rise to 145 ℃ evenly within 17 ~ 20 minutes. During the heating period, as the materials are gradually heated, scorched and pressed, the body and broken strip are small, and the die gap is gradually reduced. At this time, the hydraulic press pressure should be maintained at about 19.6mps. When the die gap is basically eliminated, it shall be kept at 145 ℃ for about 25min. The holding time is determined by the thickness of the pressed parison. When the thickness of the parison is within 25mm, the holding time will increase by about 1-1.5min for every 1mm increase. After the completion of heating and insulation, pour in internal water to cool the item to reduce the mold temperature to room temperature. This process takes about 25 ~ 30min. After storage, the parison can be ejected. At this time, the parison is transparent and milky yellow, and the unit weight is about 0.90-1.0g/c ㎡. Casting film production line www.handern.com com
(4) Foaming molding place the pressed parison in the foaming molding mold and heat it with steam. The heating time is about 60 ~ 90min and the heating temperature is about 100 ℃. After heating, cool and demould. The resulting parison is expanded and foamed in about one week. If the parison is placed for a long time, it will affect the foaming, and can not even affect the expansion to the predetermined bulk density. If the foam is immediately pressed, the surface of the foam is not smooth enough. It's not easy to square around. Casting film production line www.handern.com com
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