Extrusion & Post
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Pre-crosslinking in cross-linked polyethylene XLPE extrusion process
Problem Phenomenon
During XLPE extrusion, the material pre-crosslinks in the screw or die head, producing gel particles and clogging the die head.
Pre-crosslinking causes extrusion difficulty, rough product surface and even scorched particles.
Cause Analysis
(1) Extrusion temperature too high, exceeding the peroxide decomposition temperature
(2) Material residence time in the extruder too long
(3) Improper screw design, stagnation dead corners exist
(4) Peroxide decomposition temperature and processing temperature window narrow
(5) Screw rotation speed too high, shear heat generation aggravates pre-crosslinking
Solution
(1) Strictly control extrusion temperature within 170-200°C, must not exceed 200°C
(2) Reduce material residence time in the barrel
(3) Optimize screw design, eliminate stagnation dead corners
(4) Select peroxide varieties with moderate decomposition temperature
(5) Reduce screw rotation speed to 30-60rpm to reduce shear heat generation
Key Takeaway
Pre-crosslinking is the most common process problem in XLPE processing; the key is to strictly control the temperature not to exceed the peroxide decomposition temperature.
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