Extrusion & Post
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Metallocene linear low-density polyethylene MLLDPE high extrusion torque/high energy consumption (variant: startup commissioning scenario)
Problem Phenomenon
During MLLDPE extrusion, screw torque is large, main motor current is high, and output is limited.
MLLDPE has a narrow molecular weight distribution and high melt viscosity, and processing energy consumption is significantly higher than conventional LLDPE.
Especially during new machine commissioning or initial startup, this problem is more prominent and requires focused attention.
Cause Analysis
(1) Metallocene-catalyzed MLLDPE has a narrow molecular weight distribution and high melt viscosity
(2) Screw design does not match; compression ratio or mixing section is not suitable for MLLDPE
(3) Extrusion temperature is on the low side and melt viscosity is high
(4) Die resistance is large and flow channel design is improper
(5) No processing aid is used
(6) During new machine commissioning or initial startup, process parameter fluctuations or equipment condition changes aggravate this problem
Solution
(1) Select a screw design suitable for MLLDPE, generally with a length-to-diameter 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 (fluoroelastomer 0.05-0.2%) to the formulation
(4) Optimize die flow channel design to reduce pressure loss
(5) Appropriately reduce screw speed, controlling it at 30-50rpm
(6) And do a good job of parameter recording and archiving; pay special attention to parameter stability during new machine commissioning or initial startup
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.
In different production scenarios, targeted preventive measures need to be taken.
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