Processing Machinery
3 görüntüleme
Poor Thermal Stability of High-Density Polyethylene Raw Material Causing Degradation During Processing
Sorun Belirtisi
The product color turns yellow or darkens, black spots or burnt marks appear on the surface, and the mechanical properties decline.
Material degradation is a manifestation of molecular chain breakage, and in severe cases, a large amount of low-molecular substances is produced, affecting product quality.
Neden Analizi
（1）The barrel temperature is set too high, exceeding the thermal stability temperature of the material
（2）The material stays in the barrel for too long, and the accumulated thermal history causes degradation
（3）The screw rotation speed is too fast, and shear overheating causes degradation
（4）The antioxidant content in the raw material is insufficient or has been consumed
（5）The regrind is used multiple times, and the antioxidant is exhausted
Çözüm
（1）Control the barrel temperature at a reasonable value within the 180-260°C range to avoid overheating
（2）Reduce the residence time of the material in the barrel and avoid long-time high-temperature retention
（3）Reduce the screw rotation speed to 50-100rpm to reduce shear heat generation
（4）Select grades with good thermal stability, and add antioxidants when necessary
（5）Control the regrind ratio to no more than 20%, and use the regrind no more than 2 times
Temel Çıkarım
Thermal degradation is caused by high temperature, long residence time, or excessive shear, and needs to be solved from temperature control, rotation speed, and regrind management.
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