Processing Machinery
4 조회수
Degradation discoloration of linear low density polyethylene extruded products (Variant: mass production scenario)
문제 현상
The extrudate turns yellow or darkens, with rough surface and possible odor.
Degradation discoloration indicates the material has undergone thermal oxidative degradation, mechanical properties are severely reduced, and the product is unusable.
In particular, in continuous mass production, this problem is more prominent and requires key attention.
원인 분석
(1) Barrel temperature too high; material undergoes thermal degradation in the barrel
(2) Screw rotation speed too fast; shear overheating causes degradation
(3) Material residence time in the barrel too long, heat history accumulates
(4) Screw and barrel wear, producing metal-catalyzed degradation
(5) Insufficient or ineffective antioxidants in raw material
(6) In continuous mass production, process parameter fluctuations or equipment status changes have aggravated this problem
해결 방법
(1) Reduce barrel temperature to a reasonable value within the 190-250°C range
(2) Reduce screw rotation speed, reduce shear heat generation
(3) Check screw and die head flow channels, eliminate dead corners to prevent retention
(4) Regularly check screw and barrel wear, replace in time
(5) Add appropriate antioxidants (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
핵심 요약
Degradation discoloration is caused by overheating or excessive shear; it needs to be prevented from three aspects: temperature control, rotation speed, and material selection.
Targeted preventive measures need to be taken in different production scenarios.
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