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Analysis and Solution of Yellow Spots and Black Spots on PC Products

Feb. 08. 2020

PC has good heat resistance. Generally, when processing ordinary PC materials, its melting temperature can be set between 240 and 300. Even if it stays for a long time, it generally does not decompose. But why do we often see discoloration in the production of some electrical products? This is because the market is now highly competitive. In order to reduce production costs, most manufacturers use PC modified materials or recycled materials to produce low- and medium-grade electrical products. Some PC Compound Factory use compound materials such as flame retardants and fillers. Because these materials are mixed, and the plasticization requirements are high, it is difficult to control the process, which causes problems. But these problems can be solved. Our company is very experienced in this area and provides the following solutions to solve these problems:

Glass Fiber Reinforced PC Granules

Glass Fiber Reinforced PC Granules

(1) In terms of process conditions, the melting temperature is mainly considered. Generally, the barrel temperature should be lowered step by step, especially the temperature of the first two sections, and different temperatures are used for different materials. The temperature of the barrel is generally when using PC modified matetiald to produce lighting products. It should be controlled at around 280. Of course, the final selection of the molding temperature must also consider the product shape, size, mold structure, product performance requirements, and other aspects. The second is to fully dry the raw materials to reduce the possibility of trace moisture to the hot melt catalytic cracking. In addition, if the screw speed is too fast, the backpressure is too high, the injection rate is too fast, and the nozzle hole size, runner, and gate size are too small, etc., the melt will generate high shear heat, resulting in melt fracture of the PC. Moreover, it is easy for the gas in the mold cavity to be exhausted in time, resulting in partial burns and darkening of the product.

(2) In terms of equipment, due to the high melt viscosity of PC, the poor fluidity, the high injection pressure required, the strong bonding force with the metallurgy, and the decomposition products have strong corrosiveness to metals, so when selecting processing equipment, small or special Designed, chrome-plated screw, and the plasticizing system does not allow blind spots, dull materials, notches, cracks and so on. Generally speaking, if the process conditions are correct, and the melt is discolored during air injection, this indicates that there is a problem with the plasticizing system, and the plasticizing system needs to be checked one by one.

(3) If there are black spots found in the materials and operation methods as soon as the machine is turned on, this is mostly related to the barrel storage. Therefore, it is necessary to pay attention to the operation method. When the barrel is stocked with PC before starting, the barrel should be cleaned with new materials at the molding temperature 3 to 4 times. If the stored materials are other materials, especially those with poor thermal stability This requires that the temperature can not be increased when the machine is turned on, and the barrel can not be cleaned with PC materials. Only low-temperature materials with good thermal stability such as PS and PE can be used to clean the materials. The temperature of the cylinder is raised to the normal processing temperature of the PC and then washed with the PC material before processing. During the process, if the product needs to be temporarily suspended, the temperature of the barrel must be lowered below 160 to prevent the material from disintegrating and discoloring for too long.

Our company also has Glass Fiber Reinforced PC Granules on sale, welcome to consult.