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Nylon
Nylon is the most popular fiber used in flat web slings. Tests indicate
that the nylon fiber seems to be much more 'forgiving' if subjected
to bunching
and placement over irregular hardware shapes than Polyester. At working
load Nylon stretches about 6-10% which is roughly double that of the
competing
polyester fiber. Nylon fibers are unaffected by common grease and oil and
have good resistance to aldehydes, hydrocarbons, ethers and some alkalis,
while degradation ranging from none to moderate occurs with exposure to
certain alkalis. Nylon slings are not suitable for use with acids and
bleaching
agents (as found in boat hull cleaners). Exposure can result in degradation
from none to total. Dilute acid such as hydrochloric and sulfuric in
10%
concentrations at room temperature cause a significantloss in strength
in 10 hours. Nylon products lose 15% of their Rated Capacity (WLL) when
wet.
It is not recommended to wash Nylon slings in commercial- or household
washing machines as this process damages surface yarns resulting in
unpredictable
loss of strength. Nylon fibers are affected by UV rays and sunlight resulting
in considerable strength loss over time. We recommend to have all nylon
slings which are exposed to UV-rays proof loaded and inspected at least
twice a year.
Nylon is NOT significantly affected by compounds of the following classes:
alcohol, dry cleaning solvents, halogenated hydrocarbons, ketones, soaps
and synthetic detergens or water. |
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Solvents for Nylon include:
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Concentrated formic acid |
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Phenolic compounds at room temperature |
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Calcium chloride in methanol
at room temperature |
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Hot solutions of zinc chloride
in methanol |
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Benzyl alcohol at the boil |
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Hot solutions of calcium cloride
in:
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Glacial acetic acid |
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Ethylene Chlorohydrin |
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Ethylene Glycol |
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Polyester
Polyester is not significantly affected by most compounds of the following
classes: alcohols, dry cleaning solvents, halogenated hydrocarbons, ketones,
soaps and synthetic detergents or water. Polyester also has good to excellent
resistance to aqueous solutions of most weak acids at the boil, and to most
acids at room temperature, but is disintegrated by concentrated sulfuric
acid (95%) at room temperature. Polyester products also have good resistance
to most aqueous solutions or strong alkalies at room temperature, but are
degraded by the same solution at the boil. Oxidizing agents and bleaching
treatments ordinarily used by the textile industry also do not degrade polyester
fiber.
However, some preliminary tests have shown that Polyester slings are much
more affected than Nylon slings when subjected to bunching and small curvatures
found in some rigging attachments. Stretch at Rated Capacity (WLL) is approximately
3-4%. Polyester does not lose strength as a result of moisture absorption.required.
Polyester fibers are affected by UV rays and sunlight resulting in considerable
strength loss over time. We recommend to have all Polyester slings which
are exposed to UV-rays proof loaded and inspected at least twice a year. |
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| Twin-Path® K-Spec® fiber Slings are
used to lift a heavy refinery vessel in Alberta. A typical 'cold weather'
application. |
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K-Spec®
K-Spec® fibers are a specialty high performance combination of High
Density Polyethylene and Aramid fibers. Chemical and performance characteristics
are those of the primary fibers, Aramid and High Density Polyethylene. Stretch
at work load limit is approximately 1% and the acceptable temperature exposure
range is the same as conventional fibers.
High Density Polyethylene resists many chemical agents and retained 100%
of the original strength when immersed for 6 month in the following:
1 M Hydrochloric acid, Perchloroethylene, 5 M Sodium Hydroxide, Glacial
acetic acid, Ammonium Hydroxide (29%), Sea Water, Hypophosphite solution
(10%), 10% detergent solution, Gasoline, Hydraulic fluid, Toluene, Kerosene.
Clorox® degraded High Density Polyethylene fibers by approximately 10%
after the same 6 month immersion test. |
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| Twin-Path® Slings were used in the construction
of the addition to the New-York Hospital, New York City. The slings
lifted concrete floor section weighting around 500 tons each. |
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Nomex® (Aramid)
Aramids are resistant to most ketones, alcohols, dry cleaning solvents and
many other organic solvents. Its acid resistance is superior to that of
nylon but is not as good as that of polyester. Aramids show good resistance
to alkalis at room temperature, but is degraded by strong alkalis at higher
temperatures.
Aramids are compatible with flourine-containing elastomers, resins, and
refrigerants at high temperatures, and is resistant to flouride compounds
in concentrations usually encountered in stack gases from metallurgical
and rock-processing operations. The resistance of aramids to oxides of sulphur
at temperatures above the acid dew point is superior to that of polyester.
Below the dew point, concentrated sulphuric acid may condense on the fiber
and cause a progressive loss in strength.
In moderate to strong acid or alkali environments, evaluation of aramids
should be made to ensure that the sling will perform acceptably.
Stretch of Aramid load bearing sling yarn is below 1% at Rated Capacity
(WLL). |
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| Comparison Table |
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Nylon |
Polyester |
Nomex®/Aramid |
K-Spec® |
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| Strength (gr.p.denier) |
8.0 to 9.0 gpd |
6.5 to 9.0 gpd
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23 gpd |
27 gpd |
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| Specific Gravity |
1.14 |
1.38 |
1.44 |
1.10 |
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| Ability to Float |
Sinks |
Sinks |
Sinks |
Sinks (slow) |
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| Stretch @ Break |
16 to 20% |
10 to 12% |
3.6% |
3.6% |
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| Stretch @ WLL |
6 to 10% |
3 to 4% |
> 1% |
> 1% |
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| Moisture Absorbency |
9% of weight |
1% of weight |
5% of weight |
2% of weight |
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| Effect of Heat |
Melts at 235°C
Max. Working 90°C |
Melts at 480°C
Max. Working 90°C |
Chars at 430°C
Max. Working 150°C |
Chars at 150°C
Max. Working 90°C |
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| Identification |
Melts before burning.
Forms bead.
Celery odor. |
Melts before
burning.
Forms bead.
Pungent odor. |
Melts before burning.
Forms bead.
Celery odor. |
White colour
with red ID marker |
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| Abrasion Resistance |
Good |
Good |
Kevlar: Fair
Slingmax Aramid: Excellent |
Excellent |
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| Working Temperature |
82°C / 180°F |
82°C / 180°F |
150°C / 300°F |
82°C / 180°F |
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