TABLE 1.  GENERAL PHYSICAL REQUIREMENTS
(HDPE GEOMEMBRANES)

Property

Characteristic

Standard Values

Test Methods, Testing Regulations

1.  Appearance

1.1 

1.2

1.3

1.4

1.5

1.6

Surface

Homogeneity of material

Carbon black content

Homogeneity of carbon black distribution

Straightness

Flatness

Closed surface, free of scratches,  bubbles and pores, no damage.

Free of pores, lumps, foreign inclusions

The content by weight of carbon black must be between 1.8 and 2.6%.  The value set out in the certificate must be maintained to within a tolerance of 10%.

See Appendix A.

Maximum distance of geomembrane edge from straight edge £50 mm in a section 10 m long of an unrolled 12 m section of geomembrane.

Maximum distance of undulating geomembrane from plane base £50 mm in a section 10m long of an unrolled 12m section of geomembrane.

Visual assessment in accordance with DIN 16726, Sec. 5.1

Visual assessment in accordance with

DIN 16726, Sec. 5.1

Thermogravimetric analysis or determination in accordance with ASTM 1603-75 (see Appendix A).

See Appendix A.

Determination of straightness in accordance with DIN 16726, Sec. 5.2

Determination of flatness in accordance with DIN 16726, Sec. 5.2

2.    Thickness

2.1

2.2

Nominal thickness and mean value

Individual values

Thicknesses of 2.5, 3.0, 3.5, 4.0, 4.5, and 5.0 should be used as nominal thicknesses.  The arithmetical mean of the thickness measurements must always be ³ than the nominal thickness.

The least thickness shall be 2.50 mm.  At a nominal thickness of 2.50 mm, the individual values must therefore be ³ 250 mm, the individual value = normal thickness –0.0/+0.3mm.  At other nominal thicknesses individual value = nominal thickness ± 0.2 mm holds.

Under DIN 16726, the thicknesses will be determined in accordance with DIM 53353.  Samples will be taken over the entire extent of geomembrane at distances of 0.2 m.

3.    Density

For resin densities without carbon black between 0.932 and 0.942 g/cm³, the allowable densities for the geomembrane can be obtained depending on carbon back content.

Determination in accordance with DIN 53479, Procedure A, see Table 5,1.

4.   Melt Index and Viscosity

4.1

4.2

Change of melt index while processing resin into geomembrane.

Change of viscosity number while processing resin into geomembrane.

The following must apply:

DMFI £ 0.2g/10 min,, 190/5,

DMFI £ 2g/10 min, 190/211/6.

DMFI = MFI (e) – MFI (a).

No significant change due to processing.

Determination of melt index 190/5 or 190/21.6 in accordance with DIN 53735 on resin (MFI (a)) and on a sample from geomembrane (MFI (  e)).

DIN 53728, Part 4.

5.   Ovenageing 
performance

5.1

5.2

5.3

5.4

5.5

5.6

Change of dimension along and across the direction of extrusion.

Change in external properties.

Change in mechanical properties (yield stress, elongation at yield and elongation at break).

Change in stress crack resistance.

Change of folding behaviour at low temperatures.

Change of dimensions in short-term, strong heating.

Maximum relative change of dimension after 112 days of oven ageing must be less than 1% along and across the direction of extrusion.

No change, see 1., especially no bubbles.

Relative change of yield stress and elongation at yield £10%.  Elongation at break > 400% *.

After oven ageing the samples must pass the stress crack test, see 15.

No failure in accordance with DIN 53361.

The maximum relative change of dimension must be £ 1% both across and along direction of extrusion.

Oven ageing in accordance with DIN 16726, Sec. 5.13.1 at 80°C.

Determination of change of dimension in accordance with DIN 53377 after 7, 28, 56, 112 days of oven ageing.  Samples are taken across the width of geomembrane at 1m intervals.

See 1.1 and 1.2 period of oven ageing 112 days.

Tensile tests in accordance with DIN 53455, see 8.2, period of oven ageing 112 days.

Stress crack test, see Table 3, 15.

Determination of folding behaviour in accordance with DIN 53361, across and along the direction of extrusion.

Determination of the change of dimension in accordance with DIN 53377 after conditioning for 1 hr at 120°C.

6.                  6.   Weathering performance

See Appendix A.

At a carbon black content > 1.8% by weight the test for HDPE geomembranes can usually be omitted.  For test method see Appendix A.

7.    Permeation of hydrocarbons (watertightness)

7.1

7.2

Rates of permeation for trichloroethylene.

Rates of permeation for acetone.

Rate of permeation at 23°C < 80g/m² d

Rate of permeation at 23°C <0.5g/m² d

Measurement at steady state, 23°C, 80mm active sample diameter and 2.5mm sample thickness.  At rates >3g/m² d in accordance with DIN 53532, otherwise by more sensitive methods, see Appendix A.