General-purpose polyethylene injection molded products surface bubbles/voids（Variant: Strengthened Measures）

Round or elliptical bubbles of various sizes appear inside or on the surface of the product, with bulges or depressions visible on the surface. Bubbles not only affect appearance, but also significantly reduce product density and mechanical strength, especially severe in thick-wall products.In particular, extra attention is needed on top of the original basis, this problem is more prominent and requires key attention.

（1） The raw material is not fully dried, moisture vaporizes at high temperature producing water vapor bubbles\ （2） Injection speed too fast, air in the cavity has no time to escape and is drawn into the melt\ （3） Holding pressure insufficient or holding time too short, voids produced by shrinkage at thick-wall parts are not fed\ （4） Barrel temperature too high （exceeding the 160-260°C upper limit）, material thermally degrades producing gas\ （5） Air is drawn in during screw retraction, and insufficient back pressure causes inadequate venting\ （6） On top of the original basis, extra attention is needed: process parameter fluctuations or equipment status changes aggravate this problem

（1） Fully dry the raw material, general-purpose polyethylene dried at 60-80°C for 2-4h, moisture content controlled below 0.02%\ （2） Adopt multi-stage injection, slow-fast-slow, reduce injection speed at the initial and final filling stages to reduce gas entrainment\ （3） Increase holding pressure to 80-120MPa, extend holding time to 15-25s, ensure thick walls are fully fed\ （4） Appropriately lower the barrel temperature to a reasonable value within the 160-260°C range to avoid thermal degradation\ （5） Increase back pressure to 5-10MPa, ensure adequate venting during screw pre-plasticization\ （6） And strengthen process monitoring; on top of the original basis, extra attention is needed, paying special attention to parameter stability

Bubbles and voids are mainly caused by moisture vaporization, gas entrainment or insufficient feeding, and need to be systematically solved from raw '2079851475616104451, injection process and holding pressure parameters.Targeted preventive measures need to be taken in different production scenarios.