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Name：Rebecca Dong
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How to improve the gloss and color difference of plastic products in injection molding? |
On the one hand, it improves the surface gloss of plastic products, which is called brightening modification. On the other hand, it reduces the surface gloss of plastic products, which is called extinction modification. In contrast, brightening is more important. Brighten up the improve plastic products of plastic surface gloss or finish, specific methods in addition to the reasonable raw material selection, and add the brightening method, blending brightening method, shape control to lighten up the control of the method, the molding equipment finish, secondary processing and brighten up method and surface coating on method, etc.
1. The characteristics of resin selection resin have great influence on the surface gloss of plastic products, which is the most effective way to control the gloss of plastic products. Their influence on corresponding plastic products surface gloss depends mainly on the following aspects: (1) resin varieties of different resin varieties corresponding products of gloss is very different, generally considered the following resin corresponding products gloss is better: melamine resin, ABS, PP, HIPS, PA, POM, PMMA, PPO, including two kinds of melamine resin and ABS gloss is most prominent. For the same resin, the synthetic method is different, and its resin is different in gloss. For example, in the case of PP, the gloss size of the synthetic variety of the different polymerization methods is as follows: no regulation copolymerization PP>, PP> block copolymerization PP. B. For PE, the size of three different varieties is as follows: LDPE>LLDPE>HDPE. C. For PVC, the emulsion method has a higher gloss than suspended PVC resin. D. For PS resin, the gloss of HIPS is larger than that of the general polystyrene (GPPS) (2) resin. Its specific characteristics are different, and the gloss is different. There are several characteristics of the influence on the gloss of resin in the properties of resin. The larger the melt flow rate (MFR), the greater the gloss of the corresponding products. B, the influence of molecular weight, molecular weight of shadow Ⅱ to mainly reflects on the molecular weight distribution width. The wider the molecular weight distribution, the glossiness of the corresponding products decreased. This is mainly because the molecular weight distribution is wide and the irregularity of the material increases. C. The water absorption rate influences the resin with high water absorption rate, and the water absorption rate has a great influence on the gloss of the corresponding products. Such as molecule containing ester (one COOR) and phthalic amino (a CONH2) PA, PI, PSF and PC, etc., such as not to dry or dry thoroughly, will produce the products surface ripples, bubble, silver, markings, defects such as MAO, so that the surface gloss. 2. The choice of additives in all plastics additives, the maximum impact on the gloss of the packing; Second, there are plasticizers, stabilizers and flame retardants, but the impact is small. (1) the influence of packing on the gloss can be divided into the following aspects: a, the variety of filler varieties has different influence on the gloss. Almost all fillers, except for glass beads, decrease the glossiness of the filling products, but only in a different way. The order of the effect of several fillers on the gloss of the filling products is as follows: metal salt > glass fiber < talc powder < mica. B. The shape of filler particles has different microshapes, and the effect on the glossiness of the filling products is different, and the order of influence size is: spherical < granular < needle type. C. The particle size of the filler, the smaller the size of the filler, the smaller the glossiness of the packing products. In addition, the distribution width of filler grain size is different, and the effect on the gloss effect of filling products is different. The influence rule is: the wider the particle size distribution, the lower the surface gloss of the filling products. This is mainly because the size range of the filler is larger, the surface of the filler is more uneven, and the incident light is more prone to diffuse reflection. D. The filling of filler fill increases, and the surface gloss of filling products decreases. In order to CaC0. Fill the PP system as an example, when CaC0. When the filling amount is 5%, the surface gloss of the filled product is 5O %. When CaC0. When the filling volume was 15%, the gloss of the filling decreased to 32%.
Second, the injection molding product color difference control the color difference is the common defects in injection molding, color difference affected by many factors, involving raw materials for resin, pigment, pigment mixed with raw materials, injection molding process, injection molding machine, etc., in the actual process we usually are used to control the color difference from the following five aspects.
1. To eliminate the influence of injection molding machine and mold factors, it is necessary to choose the injection molding machine with the capacity of injection molding main product. If the injection molding machine has the problem of material dead Angle, it is better to replace the equipment. For the mold casting system, the exhaust groove and so on the color difference, can be solved by the corresponding part of the mold repair mold. It is necessary to solve the problem of injection molding machine and mold before organizing production to reduce the complexity of the problem. The key to solve the color difference is to eliminate the influence of raw material resin and color mother. Therefore, when producing light products, the thermal stability of raw materials can not be ignored. In view of the fact that most injection molding manufacturers do not produce plastic masterbatches or color mothers, the focus will be on production management and raw material inspection. To strengthen the inspection of raw materials warehousing; Production of the same product in the same manufacturer, the same number of mother materials, the color mother production; For pigment, we will try to check the color before mass production, as well as with the last time to proofread, and in the comparison, if the color difference is not big, qualified, can be thought of as has slight color difference, color master batch can be used after mixing pigment back again, in order to reduce uneven mixing pigment itself the brightness of the photo. At the same time, we also need to focus on the thermal stability of raw material resin and color mother, and we suggest that the manufacturer should replace the thermal stability. 3. The effect of reducing cylinder temperature on color difference is often encountered due to the failure of some heating coil or the drastic change of the temperature of the heating control part. Such cause off color is easy to determine, general heating coil damage to produce off color and plasticizing uneven phenomenon, will be accompanied by a heating control part is out of control and long burning gas spot is often associated with products, severe discoloration even coking phenomenon. Therefore, it is necessary to check the heating part frequently in the production, to find that the heating part is damaged or out of control in time to replace the maintenance, so as to reduce the chance of such color difference. 4. Reduce the influence of the injection molding process adjustment The chromatism reason need adjust injection molding process parameters, as far as possible, don't change the molding temperature, the amount of back pressure, the injection molding cycle and masterbatch, adjust at the same time also need to observe the effects of process parameters change on colour and lustre, such as found color difference should be adjusted in time. Avoid using high injection speed, high back pressure, etc., to avoid the color difference caused by local overheating or thermal decomposition. Strictly control the temperature of each heating section, especially the nozzle and the heating part of the nozzle. . 5. It is necessary to know the trend of color change of product color with temperature and mother quantity before color adjustment. The change of the color variation of the product is different with the change of the temperature or the mother quantity. The change rule can be determined by the experiment color process. It is impossible to adjust the color difference very quickly unless you know the pattern of the color change.
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Up：The requirements and composition characteristics of the material properties of the hot mold. |
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