Technology

Reasons and solutions for brittle plastic products

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PTJ was established in 2007 and has 13 years of experience in the plastic mold industry. It is a high-quality mold factory that integrates mold opening and injection. So when injecting products, what are the reasons and solutions for product fragility? Compared with the raw materials, the impact performance of plastic machining parts after injection molding has been greatly reduced. This phenomenon is commonly known as brittleness. The direct cause of brittleness is excessive internal stress of the plastic parts.

1. Materials

Set appropriate drying conditions before injection molding. If the material is dried continuously for several days or the drying temperature is too high, although volatiles and other substances can be removed, it will also lead to material explanation, especially heat-sensitive plastics, and secondly, it will reduce the use of recycled materials. Increase the proportion of virgin materials, select suitable materials, and use high-strength plastics.

2. Mold design

Increase the size of the main runner, runner and gate. The runner should avoid sharp corners. If the runner is too small, the runner or mouth size and sharp will lead to the decomposition of the polymer.

3. Injection molding machine

The appropriate screw should be selected to make the temperature distribution more uniform during plasticization. If the temperature of the material is not uniform, it is easy to accumulate too much heat locally, leading to material degradation.

4. Process conditions

First of all, it is necessary to reduce the temperature of the barrel and nozzle, reduce the back pressure, injection pressure, screw speed and injection speed, reduce the generation of excessive shear heat, avoid polymer decomposition, reduce the mold opening speed, ejection speed and ejection pressure.

5. Plastic parts design

When designing, there should be no too thin wall thickness in the part where the fluid in the middle of the plastic part will flow. The product has sharp corners that are prone to stress cracking, inserts, gaps or thicknesses that vary greatly.

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