According to the characteristics and supply of the material, the appearance and process performance of the material should be tested before injection molding TPR. The particles provided by TPR usually contain varying degrees of moisture, flux and other volatile low molecular weight substances, especially the moisture content of TPR always exceeds the processing allowable limit. Therefore, it must be dried before processing and the water content must be measured. The dried material must be properly sealed and stored to prevent the material from absorbing moisture in the air and losing its drying effect.
TPE material is superior to most other TPR materials in color. Therefore, only a small amount of color masterbatch is needed to achieve a certain color effect during the injection of TPR, and the color produced is purer than other TPR. Generally speaking, the viscosity of the color masterbatch should be lower than TPR. This is because the melt index of TPR is higher than that of the color masterbatch, which will help the dispersion process and make the color distribution more uniform.
In the process of injection molding TPR, the key to product appearance and performance is the accuracy of temperature setting. The following are some suggestions for temperature setting in the injection process of injection molding tpr. The temperature of the feed zone should be set very low, so as not to block the feed port and allow the entrained air to escape. In order to improve the mixing state when using color masterbatch, the temperature in the transition zone should be set above the melting point of the color masterbatch, and the temperature of the region closest to the nozzle should be set close to the desired melting temperature. The mold temperature should be set higher than the condensation temperature of the injection zone. This can avoid moisture contamination of the mold and streaks on the surface of the product. Higher mold temperatures usually lead to longer cycle times, but can improve the appearance of the welding line and the product.
In the process of molding the injection molded TPR product into the cavity, if the filling performance of the product is not good, it will cause the pressure to drop too much, the filling time is too long, the filling is insufficient, etc., which will cause the product quality to drop. In order to improve the filling performance of the product during injection TPR molding, the control of injection pressure is usually divided into the control of primary injection pressure, secondary injection pressure (holding pressure) or more than three injection pressures. Whether the timing of pressure switching is appropriate to prevent mold If the pressure is too high, it is very important to prevent flash or lack of materials.