Geosynthetics February/March 2022 - 10

Q & A: GMA Techline
ABS GEOSYNTHETICS
Q: Infrequently, I note geosynthetic products
manufactured using acrylonitrile butadiene
styrene (ABS) (e.g., geogrid, binding line,
a few molded specialty products). Can
you provide a summary of most of the
geosynthetic product types using ABS, as
well as the general benefits and limitations
of ABS in geosynthetics?
A: Thank you for your GMA Techline question
on ABS in geosynthetics. ABS-chemical
formula [(C8H8)x · (C4H6)y · (C3H3N)z] is a
common thermoplastic polymer made by
polymerizing styrene and acrylonitrile in
the presence of polybutadiene. It provides
favorable mechanical properties, such as
impact resistance, toughness and rigidity
when compared with other common
polymers. Even though ABS plastics are
used largely for mechanical purposes, they
have been used in geosynthetics such as
geopipes, geogrids, cores of geocomposites
and geocells. ABS can be recycled, although
it is not accepted by all recycling facilities. It is
manufactured in a variety of grades, which can
complicate recycling efforts.
ABS polymers are resistant to aqueous
acids, alkalis, concentrated hydrochloric and
phosphoric acids, and animal, vegetable
and mineral oils. But they are swollen
by acetic acid, carbon tetrachloride and
aromatic hydrocarbons, and are attacked
by concentrated sulfuric and nitric acids.
They are soluble in esters, ketones (such as
acetone), chloroform and ethylene dichloride.
They offer poor resistance to chlorinated
solvents, alcohols and aldehydes. All of this
indicates that they are not the best choice
for landfill applications and some uses in the
transportation sector.
ABS is flammable when it is exposed to
high temperatures. It will melt and then
boil, at which point the vapors burst into
intense, hot flames. ABS combustion
does not typically produce any persistent
organic pollutants, and the most toxic
products of its combustion or pyrolysis are
carbon monoxide and hydrogen cyanide.
Unfortunately, ABS is damaged by sunlight,
and, when it decomposes, it reverts into its
constituents, which are possibly carcinogenic.
Response from questioner
Thank you for your unexpectedly timely
and detailed response far beyond what
I had expected.
You confirmed that the range of geosynthetic
product usage corresponds to my impressions
over the years.
The only point in your presentation with which
I may take exception is the UV deterioration
of the ABS products. I have worked with ABS
in various applications (marine, industrial
structural components, etc.) over the last 40
years. I am aware that UV resistance of many
thermoplastics can be enhanced by various
proprietary stabilizers, which, unbeknown to
me, must have been the reason that so many
of the ABS items lost little of their mechanical
properties due to daily exposure to sunlight,
except a bit of brittling due to aging, seemingly
less than, for example, polyvinyl chloride (PVC).
Years ago, I adapted an ABS specialty tools/
parts box of aircraft industry origin for use
as a marine battery box for four large lead
acid batteries. The combined spilled/sloshed
sulfuric acid and marine exposure took a toll
on everything, but the box held up well over
the years with only some interior portions
developing a surficial slime that is easily
removed with a wire brush.
Geosynthetics magazine has become a truly
professional technical publication. And I do not
know what we would do without the Industrial
Fabrics Association International (IFAI).
Keep up the good work.
FUSION-WELDED HDPE
GEOMEMBRANE PATCH
GEOSYNTHETICS FOR
PIPE WRAPPING
Q: I need an impervious geosynthetic to wrap
a pipe that will be placed within a heavy clay.
Do you have any suggestions?
A: One wraps nonpolymeric pipes for many
reasons. Below are some examples:
* Insulation (sound and thermal)
* Corrosion protection
* Waterproofing
* Impact resistance
Most wraps are tapes or mastics. Polyvinyl
chloride (PVC), butyl rubber and bituminous
wraps are common. A large part of this
industry is covered by W. R. Grace and Co.'s
Bituthene. It is a hybrid product with a
formulation that has evolved over the last 20
years and is good at covering a wide variety
of applications.
Q: I need to make sure of what the minimum
area is for an HDPE geomembrane with a 60mil
(1.5-mm) thickness patch that should be
fusion welded instead of extrusion welded.
Also, when does one need to replace a panel
that is damaged (i.e., the percent of damage
allowed to be repaired)?
Thank you for your time!
A: The U.S. Environmental Protection
Agency (EPA) Technical Guidance Document
suggests that a patch should extend 4 inches
(100 mm) beyond damage that has been
blunted. This means if there is a 12-inch
(300-mm) slit in the geomembrane, the ends
should have circles punched in them and
then the patch area would be 160 square
inches (0.1 m2) or 20 inches (500 mm) long ×
8 inches (200 mm) wide.
For punctures, patches are rounded and have
a minimum diameter of 8 inches (200 mm).
The installers will have to get permission from
QA/QC inspectors or the site engineer to
repair damages with an extrusion bead only.
Your question of " when do we need to
replace a damaged panel? " is a common one.
I have not seen a percent damage number in
specifications allowed for repair per panel. I
have seen numbers like no more than 10-15
repairs in any 10,000 square feet (929 m2)
of geomembrane area. If there are more
instances of damage than the prescribed
number, panels are cut out and replaced.
Unfortunately, there is no International
Association of Geosynthetic Installers (IAGI)
or ASTM International guidance in this
regard. The European standard, EN 18482:2001
" Flexible Sheets for Waterproofing-
Determination of Length, Width, Straightness
and Flatness, " is also silent in this context. G
>> For more, search Techline at
www.GeosyntheticsMagazine.com
or email your technical questions
to gmatechline@ifai.com.
10
Geosynthetics | February March 2022
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Geosynthetics February/March 2022

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