PVC/HDPE COMPARISON
MINIMUM GEOMEMBRANE THICKNESS
There are many ongoing discussions of the durability of the various geomembranes available on the market today. Much of this discussion of durability has centered around the thickness of the polymer materials. In September of 1990, Fred P. Rohe participated in a four day meeting at the U.S. Environmental Protection Agency's Center Hill Research Laboratory regarding the drafting of the EPA's Technical Guidance Document on "The Fabrication of Field Seams for Flexible Membrane Liners". Prior to this meeting, the U.S. Army Corps of Engineers had requested the EPA review the Corps' specification for geomembranes and geotextiles. Many of the EPA's comments centered around thickness and seam testing. The following is a direct quote from the EPA's review of the Corps of Engineers Specifications:
"Thickness of materials should be a function of design which implies site specific information and considerations. Although other thicknesses, 30 and 60, are allowed (Page V), this approach, we believe, ties the hands of the designer and will force the use of generic designs and could lead to increases in overall project costs. We also strongly believe and as part of our recommendation to consultants that a minimum thickness of material type should be specified then let the consultants "design" the system. Our recommendations based on seamability, punctureability and installability is as follows:
Geomembrane
Min. Thickness (mil)
PVC
20-30 (30 is very tough)
CPE
30
CSPE-R
36
Polyethylene*
60
*Polyethylene is set as a 60 mil minimum primarily from a seamibility stand point. It has not been clearly demonstrated to us that PE products less than 60 mil can be consistently seamed in the field. There is also concern that this is at the lower limit for creating conditions that encourages stress cracking. While stress cracking is still under review we are starting to see improvements in seaming techniques. It is interesting to note that the West Germans are now requiring PE thickness greater than 100 mil."
The preceding is typed exactly as presented to the Corps by the EPA. As you can see from this discussion, the EPA is very concerned that generic designs using only material thickness criteria can be not only costly, but detrimental in many situations. The design engineer must have the flexibility of using the most effective material to provide a secure containment. The requirement of a minimum 60 mil thickness without regard to material does not encourage continuing design improvement. The EPA is concerned about seaming of PE (HDPE, VLDPE, LLDPE) below 60 mil thickness. This is not the case with PVC, CPE, or CSPE-R. Designs using 20 or 30 mil PVC, for example, can provide very effective, secure, and affordable solutions to containment problems.
If you have any questions relative to this information, please feel free to contact:
Mr. Bob Landreth, Chief Engineer
Landfill Technology Section
Municipal Solid Waste and Residuals Management Branch
Waste Minimization, Destruction and Disposal Research Division
Mr. Dave Carson, Environmental Engineer
Municipal Solid Waste and Residuals Management Branch
Waste Minimization, Destruction and Disposal Research Division
These gentlemen can be contacted at the U.S. Environmental Protection Agency in Cincinnati, Ohio.
If we can answer any other questions you may have regarding geomembranes, please feel free to contact GeoCHEM at your convenience. Thank you.
HDPE "A" and HDPE "B" signify materials from two different manufacturers.
Testing conducted by Occidental Chemical in November 1993 and reported by the PVC Geomembrane Institute (PGI)
HDPE "A"
HDPE "A"
PVC
PVC
HDPE "B"
HDPE "B"
Gauge
40
60
30
50
40
60
ASTM D1593 Thickness
MD
41.9
60
30.2
50.2
41.9
62.1
TD
52.3
61.6
30.2
49.9
41.9
63.1
ASTM D792 Specific Gravity
0.95
0.95
1.296
1.285
0.0954
0.955
ASTM D882 Tensile Properties 1" Strip
Tensile at yield psi
MD
2959
3293
No Yield
No Yield
3360
3773
TD
3045
3305
No Yield
No Yield
3551
3848
Breaking Factor psi
MD
2492
2227
3623
3693
2632
2649
TD
2262
2162
3040
3365
2537
2501
Elongation at yield %
MD
15
15.5
No Yield
No Yield
16.7
19
TD
15
16.5
No Yield
No Yield
14.2
19
Elongation at break %
MD
1060+
1364+
490
530
750
600
TD
1040+
8604+
480
559
750
600
Modulus at 100% psi
MD
2158
2132
1788
1671
2334
2515
TD
1957
1997
1553
1495
2294
2399
ASTM D638 Tensile properties die C
Tensile @ yield psi
MD
2473
2640
No Yield
No Yield
2854
2969
TD
2374
2799
No Yield
No Yield
2979
3125
Tensile @ break psi
MD
3800
3547
3536
3219
4544
4122
TD
2979
3383
2980
2878
4649
4311
Elongation at yield %
MD
10
9
No Yield
No Yield
9.2
10.6
TD
8
7.8
No Yield
No Yield
8.6
8.8
Elongation at break %
MD
530
550
240
240
600
560
TD
520
560
240
260
630
620
Modulus at 100% psi
MD
2053
1933
2000
1721
2291
2274
TD
1730
1818
1695
1515
2129
2174
ASTM D1004 Tear
MD
36.5
52.9
11.6
20.9
39.9
59.5
Resistance Lbs.
TD
32.9
50.6
12.7
22.9
39.4
60.8
ASTM D1790 Low Temperature
ASTM D3083 Water Extraction %
0.04
0.05
0.08
0.17
0.02
0.02
ASTM D1203 Volatile Loss %
0.07
0.05
0.25
0.28
0.1
0.07
Testing conducted by Occidental Chemical in November 1993 and reported by the PVC Geomembrane Institute (PGI)
Notations:
ASTM D638 is test normally conducted on PE-not PVC.
ASTM D882 is normally conducted on PVC-not PE.
ASTM D1790 Cannot be conducted on PE because it requires the material to be folded and PE cannot be folded.
HDPE "A" and HDPE "B" signify materials from two different manufacturers.
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