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Polymers (LLDPE (Cons (Less common (Customer concerns?, Less availability…

- - - - More forgiving to ground surface during installation
      - Less pronounced yield point at ~40% strain
      - Not as flexible as PVC
      - Better accommodate differential ground movement
    - - More resistance to Environmental Stress Cracking (ESC)
      - Higher puncture resistance
  - - - Customer concerns?
      - Less availability of resins
    - - Typically, they are therefore heavily stabilised, or buried/covered
- - - - Wider availability of compounded resins
      - Technically, MDPE is used as HDPE is too stiff and suffers environmental stress cracking
        
        Carbon black is then added to increase density into range required for HDPE
  - - - Relatively defined yield point at 12% strain
        
        Used in installs where strains in service are very low to minimise risk of creep and ESC
      - Less conformance to uneven ground
      - Subtle ground movements can induce stresses in the HDPE
    - - Scratches when dragged over rough ground - can become precursors to stress cracking
    - - Most important property in geomembranes that determines long term stability
    - - Typically, a minimum thickness of 1.5 mm is specified for most installs for this purpose
    - - Can expand and form wrinkles during hot weather
      - Can contract and develop tensile stresses at low temperature
    - - For this reason, textured patterns are commonly employed on the surface
- - - - High puncture resistance
      - Low coefficient of thermal expansion
      - High tear resistance
        
        After puncture, tears will not propagate easily
      - Higher surface friction
  - - - Increases flexibility of the polymer sheet to acceptable levels