Plastic scorch is a common quality defect in the plastic extrusion process. Its main performances are as follows: super high temperature display; a large amount of smoke, strong irritating odor in the die at the head, and popping noise in severe cases; extruded plastic layer has coke particles, etc. .
Common defects and processing methods in the extrusion process:
1. Plastic scorch: Plastic scorch is a common quality defect in the plastic extrusion process, its main performance is: the temperature shows ultra-high; head die mouth has a lot of smoke, a strong stimulating taste, severe cracking sound; Extrusion The plastic layer has coke particles; there are continuous bubbles at the glue seam; the main causes are:
a. The temperature is controlled to reach the plastic thermal degradation temperature;
b. The screw has not been cleaned for a long time, and the accumulated burned product is extruded with molten plastic;
c. Heating or down time is too long, so that the plastic in the barrel is decomposed by heat for a long time;
d. The temperature control instrument is out of control or inaccurate, resulting in pyrolysis;
e. Extruder cooling system is not turned on, causing material shear friction to overheat. Therefore, in the extrusion process should be strengthened to check the heating, cooling system is working properly; extrusion temperature settings should be based on process requirements and the screw speed; reasonable control of temperature and time, regular cleaning of the extrusion system.
2. Bad plasticizing of extrudates In the above mentioned temperature control requirements, plasticizing problems have been mentioned. The main manifestations of poor plasticizing are: extruded hama skins; plastic surface, black, dull, and Small cracks; Extrusion layers have obvious seams at the glue; the main causes are:
a. Temperature control is too low, especially at the nose;
b. Insulation or sheathing material mixed with other plastic particles of different properties;
c. Turning the screw too fast, the plastic is not fully plasticized; the plastic itself has quality problems.
d. For the above reasons, it is necessary to pay attention to the rationality of extrusion temperature control; to confirm the quality of the used materials; to increase the extrusion speed without blindly pursuing production; to strengthen the storage of raw materials, especially in the plastic drying process; Mold to enhance extrusion pressure and screw backflow.
3. There are pores or bubbles in the extruded clad section. The main causes are:
a. Excessive temperature control (especially feed section);
b. plastic damp moisture;
c. Long-term parking, decomposition of plastic has not ruled out clean;
d. High humidity in the natural environment;
e. The core contains excessive water or vapors.
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