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What are the conditions of PMMA injection molding
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| Time：2013.10.07 News Sources：Dongguan Zhongyu precise Mold Co., Limited Views： |
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| The processability of 1.PMMA. PMMA containing polar side methyl, hygroscopicity obvious, moisture absorption rate is generally 0.3%-0.4%, thus forming before drying, drying conditions for 80-85, 4-5 hours; PMMA melt viscosity, cooling rate and fast, easy to produce the internal stress of plastic parts, forming should be carried out after the post-processing; PMMA = no amorphous materials, molding shrinkage and range are small, usually 0.5%-0.8%, so the product precision is high; the flowability of PMMA melt is poor, in order to facilitate the melt filling, should be used for large size gate; PMMA melt has the melting characteristics of non Newtonian fluid, the obvious melting viscosity will vary with the increase of the shear rate decreased, the melt viscosity is very sensitive to changes in temperature; in order to reduce the viscosity of PMMA melt, can improve the molding pressure and temperature, in order to get better fluidity; PMMA forming the wider temperature range, the flow and the temperature was 160 degrees, the decomposition temperature of 270 degrees; as for PMMA melt filling flow, the mold gate area should be short as well, not with wide and thin cross section gate. The main injection molding conditions 2.PMMA. The barrel temperature, the thermal stability of PMMA belongs to the medium, the thermal decomposition temperature higher than 270 degrees, usually, the screw injection machine, barrel temperature control in 180-230 degrees, and the plunger type injection molding machine screw is higher than about 20 degrees. Nozzle temperature of barrel temperature lower than 20 degrees; the die temperature, the cooling rate of PMMA melt faster, plastic parts are easy to produce the internal stress, therefore, the mold temperature has a more strict control, the general temperature control in 40-80 degrees; injection pressure, the viscosity of PMMA melt is higher, the liquidity is poor, and so on the injection should be used when the injection pressure, higher injection pressure control in general 80-120MPa, and the packing pressure is 40-60MPa. |
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