What are the reasons for injection molding defects of common PC materials

1. Analysis of the reasons why the air pattern of the water inlet of PC parts has become a problem in injection molding
   Among many transparent materials, such as GPPS, K material, transparent ABS and PC material, PC parts are the easiest to produce air lines at the water entry position, and it is also the most difficult to eliminate.
   
   
   Because of the fluidity of PC material, it is relatively the worst among these materials, and fast injection must be used during injection molding, otherwise it is easy to run unevenly or produce vibration lines. The consequence of rapid injection is the slight trapping of air caused by the rapid rebound of the molten glue on the surface of the cavity at the water inlet, and the thicker the injection molded part, the larger the trapped air area. Due to the high temperature of the material, the surface of the melt at the air trapped position is oxidized, and an air film is formed here, which isolates the melt from the surface of the mold, so that the surface of the injection molded part forms a sub-color air pattern, which affects the transparency of the injection molded part.

   

2. Reasons and process problems of PC parts becoming brittle and white fog
   A few years ago, we rarely saw the problem of brittleness of PC injection molding parts. That is because there were relatively few brands of PC materials used at that time, and now there are more and more manufacturers producing PC materials, and there are naturally many brands and grades.

   
   

   
   

3. Extending the cross-flow channel can reduce the radiation and vibration of PC parts
   Sometimes because the runner is too long, the molten glue walking at the front is cooled too much, which leads to the injection molding parts to produce shot lines and vibration lines, and the performance of PC materials is particularly prominent in this regard, followed by transparent PVC.

   
   

This is why sometimes the melt temperature has risen very high, and the injection molding still does not eliminate the shot or vibration.


4. The reason why the reverse cable cannot be used after the PC material is melted
After the glue is melted, the cable is reversed, the screw moves backward, and the air is drawn into the nozzle and mixed with the high-temperature PC material. Because the PC material is easy to absorb moisture, a small amount of moisture in the air can make the injection molded parts produce silver streaks.

In a similar situation, the transparent PVC melt adhesive cannot be reversed. Because transparent PVC is very easy to burn glue, it will cause a chemical reaction immediately when it encounters air, resulting in yellow spots on the injection molded parts, and even many black spots of burning glue.