Geosynthetics July/August 2024 - 42

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GEOSYNTHETIC
INSTITUTE
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By George R. Koerner
Color, color comparison and
colorfastness of geomembranes
he Geosynthetic Institute is developing a new geomembrane specification for colored
polyethylene geomembranes. It is called GRI Standard GM-39 " Standard Test Method
for Determining the Color, Color Comparison and Colorfastness of Geomembranes. " This
method is needed to access color difference as a Manufacturing Quality Control (MQC)
tool to control production or to evaluate colorfastness as a durability evaluation.
The surface color and subsequent colorfastness of a geomembrane is one of the basic
appearance properties project stakeholders use to evaluate quality. For an exposed geomembrane,
one does not want to have extreme color differences between rolls, as this situation
might be visually unappealing. This method can be used in conjunction with laboratory or
field procedures for evaluating the relative resistance of geomembranes to change in color
when exposed to UV radiation or weathering. Geomembranes may change in color because of
exposure over time. The test method is applicable to all commonly available colored geomembranes
such as black, white, green and blue, regardless of texturing or scrim reinforcement.
This test method uses colorimeters to capture, communicate and evaluate color as
George R. Koerner, Ph.D.,
P.E., CQA, is the director of
the Geosynthetic Institute
in Folsom, Pa.
shown in Figures 1 and 2. For geosynthetics, color measurement devices help ensure the
color being produced matches the color that originally was specified. The industry uses
colorimeters for QC because they use wavelengths
that are only in the visible range, while spectrophotometry
can use wavelengths in a wider
range, which is the preferred choice for research
and development. Colorimeters are affordable,
portable and easier to use, making them suitable
choices for basic color measurement applications.
The ability of a polymer to resist fading after
being subjected to the elements is a basic durability
challenge of any colored geomembrane. Fading
can be evaluated in the following five ways:
* Color fastness due to abrasion
* Color fastness due to washing/dry cycling
* Color fastness due to chemical solutions
(e.g., acid/base, salt, chlorine)
* Color fastness due to sunlight
* Color fastness due to heat and/or pressure
FIGURE 1 As received and weathered
GM specimens
The ability of a plastic material to resist deterioration caused by exposure to the above is
an indication of the quality of the geomembrane and stability of the polymeric formulation.
This practice is intended to induce property changes associated with end-use conditions.
There is color everywhere, but the perception of that color changes based on changing
parameters. Each person has a different visual perception of an object, depending
on the object's material composition, surface texture and the type of light directed at it.

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Geosynthetics July/August 2024

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