[Experience Sharing] A must-see for injection molding of TPE transparent/high transparent material products

  • Time of issue:2021-09-10
  • Views:510

[Experience Sharing] A must-see for injection molding of TPE transparent/high transparent material products

  • Categories:Industry News
  • Author:SPP
  • Origin:www.sptpe.cn
  • Time of issue:2021-09-10
  • Views:510

Due to the high light transmittance of TPE transparent materials, strict requirements on the surface quality of the material products must be required, and there should be no defects such as markings, pores, whitening, haze, black spots, discoloration, and poor gloss. The design of raw materials, equipment, molds, and even products must pay great attention to and put forward strict and even special requirements. Next, the author analyzes the key points of TPE transparent material molding from raw material preparation, equipment requirements, injection molding process and product raw material processing.

   1. Preparation and drying of TPE raw materials

  Because any impurity in the TPE material may affect the transparency of the product, it is necessary to pay attention to sealing during storage, transportation, and feeding to ensure that the TPE material is clean. Especially TPE raw materials contain water, which will cause the raw materials to deteriorate after heating, so they must be dried. During injection molding, a dry hopper must be used for feeding. It should also be noted that during the drying process, the input air should preferably be filtered and dehumidified to ensure that the raw materials will not be polluted.

   2. Cleaning the barrel, screw and accessories

In order to prevent the contamination of TPE raw materials and the presence of old materials or impurities in the recesses of the screw and accessories, especially the existence of materials with poor thermal stability, screw cleaning agents should be used to clean all parts before use and after shutdown to prevent impurities from sticking. .

   Three, the problems that should be paid attention to in the injection molding process (including the requirements of the injection molding machine)

  In order to reduce internal stress and surface quality defects, the following issues should be paid attention to in the injection molding process.

   1. Special screw and injection molding machine with separate temperature control nozzle should be used;

   2. The injection temperature should be higher if the material does not decompose;

  3. Injection pressure: generally higher, to overcome the defect of high melt viscosity, but too high pressure will cause internal stress and cause difficult demoulding and deformation;

  4. Injection speed: In the case of satisfying mold filling, generally it should be low, and it is best to use slow-fast-slow multi-stage injection;

  5. Holding pressure time and molding cycle: Under the condition of satisfying product filling without dents and bubbles; it should be as short as possible to minimize the residence time of the molten material in the barrel;

  6. ​​Screw speed and back pressure: on the premise of meeting the plasticization quality, it should be as low as possible to prevent the possibility of degrading;

  7. Mold temperature: The cooling of the product has a great impact on the quality, so the mold temperature must be able to accurately control the process. If possible, the mold temperature should be higher.

   Four, other issues

   In order to prevent the deterioration of the upper surface effect, generally use less release agent when injection molding; when using TPE regrind, generally 5%-10%, not more than 20%.

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