Extrusion & Post
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PC Product Melt Fracture Marks
Problem Phenomenon
PC extruded profiles show periodic rough marks on the surface, or hazy shear marks on the surface during high-speed '2079851475616104452.
Cause Analysis
Exit shear stress exceeding the critical value triggers melt fracture; low mold temperature and excessive line speed are extrusion inducements; for '2079851475616104452 it is excessive gate shear and excessive speed; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience.
Solution
①Extrusion: increase the die temperature and reduce line speed; ②'2079851475616104452: reduce the speed through the gate and enlarge the gate; ③Polish the die lip/gate; ④Evaluate adding processing aids (such as PPA); ⑤Optimize the injection speed curve to keep the melt front advancing steadily.
Key Takeaway
PC melt fracture marks = 'shear exceeding the limit': for extrusion lower temperature of the melt and raise die temperature, for '2079851475616104452 reduce speed and enlarge the gate; PC has high viscosity and high shear sensitivity, and speed management must leave margin.
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