PVC MECHANICAL PROPERTIES

PVC's mechanical properties are quite different to those of HDPE:

• The uniaxial stress-strain curve does not display a yield point (a point of instability). It is a "predictable" curve of decreasing slope with no discontinuities up to a break of over 300%.
• The multiaxial stress-strain curve displays a lower break stress than HDPE but a much higher break strain.

• Much of PVC's deformation (up to the break strain) is recoverable. In HDPE strain in excess of about 12% (the yield point) is not recoverable.

• PVC will conform to geometrical profiles much more readily than HDPE. HDPE has a higher puncture stress but a lower puncture strain than PVC.

Being different, each will perform better in different environments. Neither is the best under all circumstances.

Useful strain in HDPE is 10%.

Useful strain in PVC is 300%.

HDPE yield point is a point of instability.

 

Figure 4. Multiaxial Stress vs. Strain For Five Geomembrane Materials

PVC has excellent ductility - ability to conform to subgrade.

 PUNCTURE TESTING

HDPE has high resistance to puncturing but with little deformation.

PVC will deform significantly before puncturing.

HYDROSTATIC TESTING

PRESSURE TO FAILURE

PVC conforms to subgrade better than HDPE.

HDPE has higher apparent strength but PVC conforms better and maintains an impermeable barrier.