Processing Machinery
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Random copolymer polypropylene pipe special material (Nordic standard） extruded products degradation discoloration（Variant: Mass Production Scenario）
Problem Phenomenon
The extrudate color yellows or darkens, the surface is rough, and there may be an odor.
Degradation discoloration indicates that the material has undergone thermo-oxidative degradation, mechanical properties are severely reduced, and the product is unusable.In particular, during continuous mass production, this problem is more prominent and requires key attention.
Cause Analysis
（1）Barrel temperature too high, the material undergoes thermal degradation in the barrel\
（2）Screw speed too fast, shear overheating causes degradation\
（3）The material stays in the barrel too long, thermal history accumulates\
（4）Screw and barrel worn, producing metal-catalyzed degradation\
（5）The raw material antioxidant is insufficient or has expired\
（6）In continuous mass production, process parameter fluctuations or equipment status changes aggravate this problem
Solution
（1）Lower the barrel temperature to a reasonable value within the 200-220°C range\
（2）Reduce screw speed, reduce shear heating\
（3）Check the screw and die head runners, eliminate dead corners to prevent stagnation\
（4）Regularly check screw and barrel wear, replace in time\
（5）Add an appropriate amount of antioxidant (0.1-0.5%) or select grades with good thermal stability\
（6）And establish standardized work instructions, paying special attention to parameter stability in continuous mass production
Key Takeaway
Degradation discoloration is caused by overheating or excessive shear, and needs to be prevented from three aspects: temperature control, rotational speed and material selection.Targeted preventive measures need to be taken in different production scenarios.
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