Manufacturers of Energy and Resource Saving Products
Chemical Guide
Content
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What are the industry standards?
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How to identify chemical degradation?
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Case study – CSI-Plastipack who killed the cover?
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Useful tips
© Plastipack 2014
Deflation
This effect is very rare and can be
caused by the build up of Nitrogen
trichloride (NCI3) which is one of the
chloramines produced by the reaction of
Hypochlorous acid (HOCl) and
Ammonia (NH3), derivatives in the
warm water.
4NH3 + 3Cl2 = NCl3 + 3NH4Cl
NCL3 is the gas which produces the
characteristic chlorine smell of a pool
and is both toxic and corrosive.
When using an indoor pool it is
important to have good ventilation to
prevent eye, nose and lung irritation.
High levels and prolonged exposure to
NCL3 is thought to cause asthma.
Used in its 3NH4Cl liquid state trade
marked as ‘Agene’ it is a substance that
is used to age wooden floors.
Deflation can be simply prevented by
keeping the total dissolved solids at a
safe level.
© Plastipack 2014
Over
Chlorination
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Cover degradation due to over
chlorination
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Brittle and bleached material on the bubble side.
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Bleaching on the hem material in contact with the water.
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White residue between the bubbles and on the surface of the cover.
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Oxidation of metal eyelets and pool fittings.
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Strong chlorine smell.
© Plastipack 2014
A swimming pool is a weak salt acid bath. It is important to maintain its chemical stability for
both the health of the pool and to prevent chemical degradation of the cover.
Sodium Hypochlorite
NaOCI + H₂O = HOCI + Na+
Calcium Hypochlorite
Ca(OCI)₂ + H₂O = HOCI = Ca+²
Lithium Hypochlorite
LiOCI + H₂0 = HOCI + Li+
Salt Chlorinators
*Salt chlorinators can over chlorinate a pool! There is a large amount of Chlorine suspended
in salt water as Sodium Chloride. In fact, if you released all the chlorine suspended in sea
water on earth it would weigh 5 times more than the earth’s atmosphere! *
All these reactions result in the production of Hypochlorous acid (HOCI) the active sanitising
agent in the swimming pool.
© Plastipack 2014
Shock Dosing
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High levels of chlorine will place the cover under excessive strain, oxidising the cover
and creating free radicals that start chain reactions. This results in chain scissoring of
the polymer, which is why the material becomes brittle.
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To prevent this, the stabilizers and antioxidants in the cover material bond with the
free radicals.
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At first the cover will show no damage but the UV stabilizers have been deactivated
by the shock dosing process and the cover will begin to degrade prematurely.
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It is important to remove the cover during shock dosing and only place the cover back
onto the pool when the levels have fallen back into the industry stated levels.
© Plastipack 2014
High
temperatures
and high
chlorine
demand
Hot tubs are a example of an area of
constant high chemical levels, and
elevated temperatures that can
bleach the material.
Bubble material is most commonly
used as a protective membrane to
maintain the hot tub’s external cover.
© Plastipack 2014
Bubble Swell
Bubble swell is a rare cause for complaint and is often mistaken for shrinkage.
Although it is not entirely clear what exact conditions produce this effect, key factors seem
to be atmospheric pressure, pool temperature and chemical levels.
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The bubble will resist compression.
The cover material will have the appearance of lumps.
© Plastipack 2014
Shrinkage
Polyethylene has a natural shrinkage rate of around 2%. We encourage our customers to
oversize the pool cover in the length only, increasing the overall length of the cover by 2%.
Should the cover shrink more than the suggested 2%, of the total length, we ask that you
contact us with images, the QC number or date stamp.
© Plastipack 2014
Bird pecks
This is more common than would be imagined. Small groups of punctured or torn
holes are often caused by birds.
At our test tank site we have a particular seagull family who seem very fond of
pecking through our test covers.
* Note: No legal action has been taken against the seagull family at this point!
Herring Gull Attack!!
Magpie
© Plastipack 2014
Improper storage without a
Reflective Cover
The air in the material is a good insulator. A pool cover left exposed
and uncovered on a reel system will heat up close to its vicat
softening point. As it cools, it will mould to the reel system.
Tests conducted found temperatures of up to 80˚C .
Other noticeable effects are oxidation of pigments and degradation
of the pool cover material.
© Plastipack 2014
Delamination
This is extremely rare. Delamination is when the flat layer of
material separates from the bubble layer.
The most common cause is the result of heat damage from an
improperly stored cover. If this is not the case please contact us
with images, date stamp or QC numbers.
© Plastipack 2014
What killed the cover ?
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A pool cover which had degraded before its
expected lifespan was sent to us for testing.
We used an impartial university laboratory who
used combustion and X-ray fluorescence (XRF)
tests to determine the chlorine content in the
material.
The tests showed the pool cover was over
chlorinated. The chlorine content in the cover
material was between 2000-6000ppm.
The cover had undergone chemical attack,
caused through shock dosing or extended high
chemical levels.
Though the pool water may have returned to
the industry standards, the damage to the
cover had already been done.
Another case solved !!
© Plastipack 2014
Chlorine is an oxidiser
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HOCI is the active sanitising agent used in a swimming pool.
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Of all the HOCI in the pool, only 10% is used as the sanitising agent. The remaining 90%
works as an oxidiser which physically breaks down organic matter in the pool.
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When a pool is over chlorinated, the oxidising effect of the HOCI causes a drop in the
molecular weight of the pool cover material, reducing tensile strength, which causes the
breakdown of the polymer chain resulting in the pool cover becoming brittle.
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HOCI also bleaches the colour out of the material by attacking the molecule responsible
for the colour of the pigment.
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The above can be easily avoided by keeping the pool balanced and by removing the
cover during shock dosing!
© Plastipack 2014
Ideal/healthy chemical levels
Chemical Balance Summary
Substance
Salt
Stabiliser
Free Chlorine
Combined Chlorine
Total Chlorine
Total bromine
Ph
Total Alkalinity
Calcium Hardness
Total Dissolved solids
Phosphate
Heavy Metals
© Plastipack 2014
Ideal Range
2500-4000
depends on chlorine demand
2.0-4.0ppm
<0.2ppm
TC=FC+CC
4.0-6.0
7.2 -7.8ph
80-120ppm
150 -400ppm
<2000ppm
as little as possible
as little as possible
Conclusion
LDPE is a very inert and rigorously tested plastic. Polymer and additives will reach their
expected lifespan when the pool cover is used properly. Factors that can effect the lifespan of
the material are:
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High Oxidiser exposure
UV degradation
Excessive heat
Mechanical damage
If the pool cover material does not match these common issues or has degraded prematurely
without a clear cause, please contact us with:
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Type of material (thickness and colour) :
Images
Chemical levels if available
Age of cover
Type of sanitizers used
QC number or date stamp
© Plastipack 2014
Secret to a long life
Its all about balance.....water balance!
© Plastipack 2014
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Reference
http://www.poolcenter.com/chlorine_generator.htm
http://www.poolcenter.com/color.htm
Pool & Spa Water Chemistry – A testing and treatment guide – Part#2004B © 2003 Taylor technologies, Inc Sparks, Maryland (Really useful book highly
recommended)
http://www.plastipack.co.uk/trans-ENGLISH/use.htm
http://www.plastipack.co.uk/trans-ENGLISH/uv-stabilised.htm
http://www.plastipack.co.uk/trans-ENGLISH/chemical-resistant.htm
http://www.plastipack.co.uk/trans-ENGLISH/use.htm
http://www.chemicool.com/elements/bromine.html
http://www.chemicool.com/elements/chlorine.html
http://chlorine.americanchemistry.com/What-is-Chlorine/Chlorine-101
Chemical Resistance of Thermoplastics edited by William Woishnis, Sina Ebnesajjad
Polyethylene – chemical Resistance Table Low Density and high Density Polyethylene- ART254 10.12.1999 Ed.2
http://www.professionalplastics.com/professionalplastics/HDPE-LDPEChemicalResistanceChart.pdf
http://www.borealisgroup.com/pdf/chemical-resistance/chemical-resistance-hdpe-ld.pdf
http://www.jonesco-plastics.com/en/pdf/chemical_resistance.pdf
http://www.mitsuchem.com/Admin/Disposal/chemicalresistancedata.pdf
http://www.cdc.gov/niosh/hhe/reports/pdfs/2007-0163-3062.pdf
http://www.drydenaqua.com/instruments/products/nitrogen_trichloride/index.htm
http://www.drydenaqua.com/instruments/products/nitrogen_trichloride/pdf/leaflet/Nitrogen_Trichloride_Monitor_in_Air.pdf
http://www.coleparmer.co.uk/Chemical-Resistance
http://www.ccmr.cornell.edu/education/ask/index.html?quid=457
Energy Smart Pool-United States of America–Department of Energy.
http://www.taylortechnologies.com/ChemistryTopicsCM.ASP?ContentID=27
http://www.cheaphottubchemicals.com/Page/PoolHelp/Metal-stains.htm
http://www.laticrete.com/portals/0/tds/tds179.pdf
"Bromine." Chemicool Periodic Table. Chemicool.com. 20 Oct. 2012. Web. 10/29/2012
<http://www.chemicool.com/elements/bromine.html>.
http://www.azwestern.edu/downloads/NSF%20Grants/pool%20chem-UV-cyanuric%20acid.pdf
© Plastipack 2014
Manufacturers of Energy and Resource Saving Products
Thank you
Manufacturer
www.plastipack.co.uk
Product Information
www.geobubble.co.uk
Water Storage
www.vapourguard.com
Wainwright House, 4 Wainwright Close, Churchfields Industrial Estate, St Leonards-on-sea,
TN38 9PP UK
t: +44 (0) 1424 851 659
f: +44 (0) 1424 853 909
e:[email protected]
©Plastipack 2014