Solution to Common Problems in Injection Molding of TPE Materials
Source：德创化工Time：2019-06-19Hits：1993
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TPE product injection molding products surface if strict requirements, must be dry before injection molding. Generally dry for bucket type 70 ~ 80 °C / 2H or tray dry 80 ~ 100 °C / 1h. For tray drying, it should be noted that the thickness of the material layer is generally not more than 50mm. Tray drying is recommended. If there is a bubble on the surface of the molding material, or a cut material bar, a hole is found inside, or a scattered silver wire is found on the surface of the product, it can be determined that the TPE/TPR raw material contains too much water.
First, traces of flow
Stripes of different gloss appear on the surface of the molded product. In general, there are:
(1) Narrow recording stripes;
(2) A relatively wide interval stripe of the same phase appears above and below the surface of the molded product;
(3) Three types of relatively narrow spacing stripes appear above and below the surface of the molded product.
Solution: can be solved through these methods, such as adding pure monomer resin, increase injection speed, mold temperature, increase injection gum, increase resin temperature and injection rate, increase molding temperature, mold temperature or reduce injection speed. It is effective by increasing the injection speed and mold temperature.
II. Poor demodulation
The demolded differential finger molding product is difficult to remove from the mold or completely deforms during the extraction process. Adhesive materials can easily cause this problem, but can be improved by adding a demoulding agent to the material or applying a demoulding agent to the mold before forming. Insufficient cooling of the molded product(insufficient curing) is also prone to such problems, so it is necessary to fully cool the molded product. In addition, the mold design is not reasonable will be difficult to demoulding reasons, especially in the injection mold, such as the parts that are easy to stick mold, to increase the exit angle of the injection rubber, and to increase the width of the rubber duct is very effective.
III. Ageing
Phenomenon: The mechanical properties of the product are obviously reduced and the appearance quality is deteriorated.
Reason: Compared with inorganic materials and metal materials, the heat resistance and ultraviolet linearity of polymer materials cause aging of products. Due to aging, the mechanical properties of most products are significantly reduced and the appearance quality is deteriorated.
Solution: by adding ultraviolet absorbent and optical stabilizer, the aging phenomenon can be suppressed to a certain extent by cooperating with stabilizers such as heat resistance and weather resistance.
Four, uneven color one
When using thermoplastic elastomer particles and dry mixture to color the parent mixture, it is easy to produce uneven color of the molding product. As a countermeasure, increasing screw back pressure and reinforcing filler mixing are effective.
Whitening phenomenon: refers to the stabilizer and other binders migrated to the surface of the molded product, its surface like a powder sprayed on a white phenomenon
Reason: It is mainly caused by excessive coordination of stabilizers or incompatibility with polymers.
Solution: If this type of problem occurs, choose a stabilizer that is well compatible with the polymer or control the amount of stabilizer in the optimal range. Second, it is also very effective to replace it with a stabilizer of high relative molecular mass. In addition, there are stabilizers that function by migrating to the surface of the molding product.
For example, antistatic agents, lubricants, etc.. For this stabilizer, it is necessary to choose a stabilizer that is difficult to whiten even if it is transported. Whitening rarely occurs when used in general environments, but it is necessary to add heat-resistant stabilizers and time-resistant stabilizers to improve durability in cases of high temperature, humidity, and long-term outdoor use. Especially at high temperatures, because it is very easy to cause migration, the choice of stabilizers is also very important.
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