TPE|TPR injection molding product color difference control should pay attention to the six aspects

  • Time of issue:2022-12-05
  • Views:218

TPE|TPR injection molding product color difference control should pay attention to the six aspects

  • Categories:Elastomer knowledge
  • Author:SPP
  • Time of issue:2022-12-05
  • Views:218

  Color difference is a common defect in TPE injection molding, and it is not uncommon to see batches of injection molded products scrapped due to the color difference of matching parts. Not considering the subjective factor of different people's visual perception of color differences, there are many objective factors affecting the color difference of TPE|TPR products, including TPE raw materials, color masterbatch (or color powder), mixing of color masterbatch with TPE raw materials, injection molding process, injection molding machine, mold, etc.. Because of the wide range of factors involved, the color difference control is one of the more difficult techniques to master in TPE color matching injection molding. In the actual production process, we generally control the color difference of TPE products from the following six aspects.

  1, eliminate the influence of injection molding machine and mold factors

  To choose the injection molding machine with the same capacity as the injection molding products, if the injection molding machine has problems such as material dead space, it is best to replace the equipment. For the mold pouring system, exhaust slot, etc. caused by color difference, can be solved by the corresponding part of the mold maintenance mold. Must first solve the injection molding machine and mold problems before you can organize production to cut the complexity of the problem.

  2, eliminate the influence of TPE raw materials, color masterbatch

  Control of raw materials TPE is an important part of a thorough solution to the color difference. Especially when producing light-colored products, we cannot ignore the obvious impact of different thermal stability of TPE raw materials on the color fluctuations of the products. In view of the fact that most injection molding manufacturers do not produce plastic masterbatch or masterbatch, so that the focus of attention can be placed on production management and raw material inspection. That is, to strengthen the inspection of raw materials into the warehouse; production of the same product as far as possible using the same manufacturer, the same brand of masterbatch, masterbatch production; for color masterbatch, we have to carry out random color testing before mass production, both with the last calibration, but also in this comparison, if the color difference is not large, can be considered qualified, such as the batch of color masterbatch has a slight color difference, the color masterbatch can be mixed again before use, in order to reduce the color masterbatch itself mixed unevenly The color difference caused by the uneven mixing of the masterbatch itself. At the same time, we also need to focus on testing the thermal stability of the raw material resin and masterbatch, for the thermal stability is not good, we suggest the manufacturer to exchange.

  3、Eliminate the influence of uneven mixing of masterbatch and TPE main material

  TPE masterbatch and color masterbatch are not well mixed, which will make the product color change irregularly. After the TPE and masterbatch are mixed evenly, when they are fed into the hopper through the lower suction material, the masterbatch is separated from the TPE main material due to the electrostatic effect and easily adsorbed on the hopper wall, which inevitably causes the change of the masterbatch amount in the injection cycle and thus produces color difference. For this situation, we can adopt the method of manual mixing after the raw material is sucked into the hopper. For adding color powder to produce colored products, there is the most effective way is not to use the suction machine, and the use of hot air dryer, with the manual addition of materials to prevent color powder and masterbatch separation caused by the color difference.

  4、Reduce the influence of barrel temperature on color difference

  In the production, we often encounter a damaged heating ring or heating control part of the long burn out of control caused by the barrel temperature changes dramatically, resulting in color difference. This kind of reason produces the color difference is easy to determine, generally the heating ring damage failure produces color difference at the same time will be accompanied by uneven plasticization phenomenon, and heating control part of the uncontrolled long burn often accompanied by product gas spot, serious discoloration and even coking phenomenon. Therefore, the production needs to frequently check the heating part, found when the heating part is damaged or out of control, timely replacement and maintenance to reduce the chances of such color difference.

  5、Reduce the impact of the adjustment of the injection molding process

  When adjusting the injection process parameters for non-color difference reasons, do not change the injection temperature, back pressure, injection cycle and the amount of color masterbatch added as much as possible, and at the same time, observe the impact of the change of process parameters on the color, and adjust the color difference in time if found. As far as possible, avoid using high injection speed, high back pressure and other injection molding processes that cause strong shearing effect to prevent color difference caused by local overheating or thermal decomposition and other factors. Strictly control the temperature of each heating section of the barrel, especially the nozzle and the heating section close to the nozzle.

  6, master the barrel temperature, the amount of color masterbatch on the impact of product color change

  Before adjusting the color difference, we must also know the trend of product color change with temperature and masterbatch amount. Different color masterbatch with the change of production temperature or the amount of masterbatch, its product color change pattern is different. The color change pattern can be determined through the color test process. Unless the color change law of this masterbatch is already known, it is impossible to adjust the color difference quickly, especially when using new color masterbatch production for color mixing.


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