Linear Low Density Polyethylene

Symbol: LLDPE
Crystallinity: Crystalline
Trade Names: -

Description:

LLDPE Lg Bins Fotolia_37164669_S.jpgLLDPE has a density of .916 to .940 and no long-chain branching, as compared with LDPE which is branched and processes like an amorphous resin. LLDPE has improved tensile, impact and tear resistant properties and is useful at both high and low temperatures.

Processing Considerations:

  • Residence Time: Residence time is 1.5 minutes or greater.
  • Back Pressure: Recommended back pressure is 250 PSI (or 2500 plastic pressure) or less.
  • Drying: Drying of this material is not required. .
  • RPM: Recommended RPM is 30 or greater.

Screw Design Based on:

  • Medium Compression Ratio
  • Medium Transition Length
  • Medium Meter Channel Depth

Other Information:

  • Mixer: Low to high shear mixing screws can be used to process PA.
  • Barrier: A barrier screw design is recommended when processing LDPE.
  • Custom Design: Screw designs range from standard metering screws to barrier or combination barrier & mixing screws.
  • Recommended Valve: Valves can be 3-piece free-flow, 3-piece locking, 4-piece or ball check.
  • Screw & Barrel Material Recommendation: Screws and barrels can be manufactured from standard materials.
  • Similar to Resin: LDPE processes similar to PP (Polypropylene).

Most LLDPE is very viscous in the lower melt index ranges and melt fractures cold. The thinner molecular weight distribution and shorter chain branching found with LLDPE makes this resin less shear sensitive. When a process calls for shear, as in extrusion, the melt becomes highly resistant to flow which makes it harder to process than a similar LDPE. It is important to understand the melt properties of LDPE and LLDPE as each is unique.

Various additives and/or fillers can have an effect on a resin’s process behavior. For more detailed information, please contact Reiloy Westland Corporation.

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