Eight common problems and countermeasures for TPE injection molding

- Jul 05, 2019-

Eight common problems and countermeasures for TPE injection molding

  The TPE injection molding process refers to the processing of raw materials to synthesize polymers. The quality and appearance of TPE injection molding products are affected by many factors. In the production process, the production process must be strictly controlled to ensure that no mistakes will be made in every link, especially in the temperature control. This article will introduce the problems and solutions that are easy to occur in TPE injection molding products.

First, the sticky phenomenon


  Soft TPE injection molded products are more susceptible to stickiness than resins. At this time, it is possible to reduce the molding temperature, low shear, and purify the inside of the hydraulic cylinder of the molding machine with nitrogen to solve the phenomenon that the surface of the product is sticky. Further, when the molding machine is suspended, the rubber is left in a molten state for a long time in the cavity of the molding machine, and sometimes it is sticky due to heat aging. In addition, articles used at high temperatures are prone to stickiness. Therefore, it is necessary to rationally select the choice and amount of stabilizers and softeners.


Second, aging


  TPE injection molding products are also prone to aging. Generally, the aging phenomenon can be suppressed to some extent by adding a UV absorber and a light stabilizer by blending a stabilizer such as heat resistance and weather resistance. Occasionally, the portion that is not filled to the end portion and the portion that is not filled with the cavity appears to be burnt like aging. It can be solved by improving the exhaust method.


Third, the concave hole, the color is not the same


  A pit hole often occurs in TPE injection molded articles. For such products, a model design with a glue injection port or a flow rubber channel around it should be used. In view of the phenomenon that the color of the molded product is not uniform, it is necessary to increase the back pressure of the screw and knead the filler.


Fourth, overflow


   Sometimes the resin overflows from the cavity and can cause burrs. At this time, you should first reduce the filling amount, reduce the holding pressure and shorten the holding time, and pay attention to repair.


Five, poor release


   The poor mold release property means that the molded article is difficult to remove from the mold or is completely deformed during the removal process. Adhesive materials can easily cause this problem, but the method of applying a release agent to the material or applying a release agent to the mold before molding can be improved. Insufficient cooling of the molded article (under-curing) is also likely to cause such a problem, and therefore it is necessary to sufficiently cool the molded article. In addition, the unreasonable design of the mold will become a cause of difficulty in demoulding, especially in the parts that are easy to stick to the glue injection port, the rubber feed path, etc., it is very important to increase the extraction angle of the injection port and widen the glue path. Effective.


Six, the flow of traces


There are different streaks of gloss on the surface of the molded article. Generally speaking, in the injection molding of resin:


(1) a narrow stripe of recording stripes;


(2) a relatively wide stripe pattern of the same phase appearing above and below the surface of the molded article;


(3) Three types of relatively narrow spaced stripes appearing above and below the surface of the molded article.


   Solution: It can be solved by these methods, such as adding pure monomer resin, increasing injection speed, mold temperature, increasing injection port, increasing resin temperature and injection rate, increasing molding temperature, mold temperature or reducing injection speed. It is effective by increasing the injection speed and the mold temperature.


Seven, uneven color


When the precursor mixture using TPE particles and dry blending as a pigment is colored, the color unevenness of the molded article is liable to occur. As a countermeasure, it is effective to increase the back pressure of the screw and to knead the filler.


Eight, whitening phenomenon


   It means that the compounding agent such as a stabilizer migrates to the surface of the molded article, and its surface appears as a white phenomenon as if it is sprayed with powder. When TPE is used in a general environment, there is little problem of whitening. However, in the case of high temperature, humidity, and outdoor use for a long period of time, it is necessary to add a heat-resistant stabilizer and a weather-resistant stabilizer to improve durability. Especially at high temperatures, the choice of stabilizer is also very important because it is highly susceptible to migration.

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