Material Drying
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Bubbles/pores on the surface of linear low density polyethylene extruded products (Variant: strengthened measures)
Fenómeno del problema
Bubbles or pores appear on the extrudate surface or cross-section, reducing product density.
Bubbles not only affect appearance but also reduce mechanical strength and pressure resistance; common in pipe and profile extrusion.
In particular, additional attention is needed on the original basis; this problem is more prominent and requires key attention.
Análisis de la causa
(1) Raw material moisture content exceeds standard; moisture vaporizes at high temperature producing bubbles
(2) Poor screw venting; air entrained in the melt
(3) Barrel temperature too high; material thermal degradation produces gas
(4) Screw rotation speed too fast, insufficient venting time
(5) High low-molecular volatile content in raw material
(6) On the original basis, additional attention is needed as process parameter fluctuations or equipment status changes have aggravated this problem
Solución
(1) Fully dry the raw material; control linear low density polyethylene moisture content below 0.02%
(2) Check venting section design; use a vented extruder when necessary
(3) Appropriately reduce barrel temperature to a reasonable value within the 190-250°C range
(4) Reduce screw rotation speed, increase material residence time in the venting section
(5) Select raw material grades with low volatile content
(6) And strengthen process monitoring; on the original basis, additional attention is needed, with special attention to parameter stability
Conclusión clave
Bubbles are caused by moisture vaporization or gas entrainment; they need to be solved from raw '2079851475616104451 and the venting system.
Targeted preventive measures need to be taken in different production scenarios.
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