Extrusion & Post
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Metallocene linear low density polyethylene MLLDPE high extrusion torque/high energy consumption
Problem Phenomenon
During MLLDPE extrusion, the screw torque is large, the main motor current is high, and output is limited.
MLLDPE has a narrow molecular weight distribution and high melt viscosity, and its processing energy consumption is significantly higher than conventional LLDPE.
Cause Analysis
（1） Metallocene-catalyzed MLLDPE has narrow molecular weight distribution and high melt viscosity\
（2） Screw design does not match, compression ratio or mixing section not suitable for MLLDPE\
（3） Extrusion temperature too low, melt viscosity high\
（4） Die resistance large, runner design improper\
（5） No processing aid used
Solution
（1） Select a screw design suitable for MLLDPE, generally L/D ratio above 30:1\
（2） Increase extrusion temperature to the higher value within the 190-260°C range （240-260°C）\
（3） Add PPA processing aid to the formulation （fluoroelastomer 0.05-0.2%）\
（4） Optimize die runner design to reduce pressure loss\
（5） Appropriately reduce screw speed, control at 30-50rpm
Key Takeaway
MLLDPE high energy consumption is caused by narrow molecular weight distribution and high melt viscosity, and needs to be solved by optimizing screw design, increasing temperature and adding processing aids.
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