Blow molding process of transparent plastic
Transparent plastics due to high light transmittance, must require plastic products surface quality requirements strict, can not have any markings, pores, white. Fog halo, black spots, discoloration, poor luster and other defects, so in the entire blow molding processing process on materials, equipment. Mold, and even product planning, should pay great attention to and put forward strict and even extra needs. Secondly, because the plastic is mostly high melting point and poor activity, in order to ensure the surface quality of the product, it is often necessary to make fine adjustments in the machine high temperature, injection pressure, injection speed and other technical parameters, so that the plastic injection can fill the mold, and will not produce internal stress resulting in product deformation and cracking. Therefore, Shanghai blow molding factory has to carry out strict operation in terms of material preparation, equipment and mold requirements, injection molding processing skills and material disposal of products.
(1) Preparation and monotony of materials Because any impurities contained in the plastic can affect the clarity of the product, so it can be stored and transported. During the feeding process, it is necessary to pay attention to sealing to ensure that the material is clean. In addition, the material contains water, which will lead to material disintegration after heating, so it must be monotonous, and in the injection molding, it is necessary to use a monotonous hopper. It should also be noted that in the monotonous process, the input air should preferably be filtered and dehumidified to ensure that it will not pollute the material. The monotonic skills of clear plastics: data skills monotonic temperature (℃) monotonic time (h) Material layer thickness (mm) whitening pmma70 ~ 802 ~ 430 ~ 40pc120 ~ 130>6<30 Use hot air circulation monotonic pet140 ~ 1803 ~ 4 Use continuous monotonic feeding equipment.
(2) The cleaning of the barrel, screw and its accessories in order to prevent material pollution and old materials or impurities in the depression of the screw and accessories, especially the existence of resin with poor thermal stability, so the screw cleaning agent is used before and after the shutdown to clean each part, so that it is not stuck with impurities, when there is no screw cleaning agent, pe, ps and other resins can be used to clean the screw. When temporarily shut down, in order to prevent the material from staying at high temperature for a long time, resulting in degradation, the temperature of the monotone machine and barrel should be reduced, such as pc, pmma and other barrel temperatures should be reduced to below 160 ° C. (Hopper temperature regarding pc should be reduced to below 100℃).
