Outerwear
The fabric
we found was part of a jacket from the brand NorthBend. A search on google.com
doesn’t give a lot of information about the brand. We found a site selling NorthBend
outdoor shoes, which indicates the brand is specialized in outerwear. The
jacket has a coated fabric called airtech, it is made of 100% polyester with a
coating, which “meets the needs of the prople who demand superior protection
from elements and exceptional durability.” as the brand says.
Fabric construction
and production process
The fabric
is made of a plain weave of non-twisted polyester filaments with a high density.
There are about 27 warps and about 11 wefts per 5 millimeter, which makes about
54 warps and 22 wefts per cm or 21 warps and 9 wefts per inch. The more warps
and wefts per inch the finer the fabric is. The high density is useful to make
the fabric closed, but fine fabric is not as strong. Therefore polyester is
used. Polyester has the highest tensile strength besides nylon, and it doesn’t loses
its strength when its wet.
Polyester
is made in a similar way as nylon. Polymer chips are melted at 280 degrees and
extruded through spinnerets. After drawing, the flat filaments can be spun into
yarn, textured or non-textured, directly used or cut into staple fibres. After the
polyester is woven in a fabric it goes to the coating process. The clothing
technology book explains: “Coating is the application of a layer of natural or
synthetic polyemer to one side of the fabric, followed by fixation in a curing
oven.” The coating is applied directly to the fabric. The combination of the
coating and the fabric gives the fabric new properties.
Airtech is
a special coated fabric. It is protective rainwear, but still breathable. The
outer shell is made of polyester, which gives the needed strength for the
outdoor clothing. Inside of the jacket a membrane is applicated. We guess that
the airtech coating is similar to a gore-tex coating, since they have the same
properties.
On the
inner shell a PTFE-membrane is applicated, outside is a lining out of polyester
to make the jacket comfortable to wear. The membrane is very porous. On 1
square centimeter you will find up to 1.4 billion pores. These pores are 20.000
times smaller than a water drop, so a water drop cannot get through. But the
pores are still big enough to let water vapour through. All in all the fabric
is windproof and waterproof but still breathable. Breathability is not about
air coming through the fabric, but about the ability to let water vapour
escape. This is important for outdoor clothing, since wet clothes make you lose
heat 3 times faster than dry clothes. Every seam has a risk of a possible leak
in the fabric. It is very important to protect the seams by using a seam tape,
which closes the small holes of the sewing machine. The coating is a synthetic
polymer. This polymer is applicated to one side of the fabric. After the
application the fabric has to run through a curing oven to fix the membrane.
Testing
Whereas the
label implies the jacket is water and windproof and the jacket should let water
vapour out of the jacket to breath, we performed several tests to proof it. We
performed a water resistance test, a water vapour permeability test and a
tearing test.
Water resistance test
The water
resistance test uses pressure to press water to the surface of the fabric and
measures at which pressure the water goes through the fabric. When the test
starts the observer should press a
button when he/she sees the first water drop. After seeing the third water drop
the machine stops the process and measures the pressure in mili meter water
column. Mili meter water column means the pressure it gives of putting a column
of water of a mili meter on top of the fabric.
We
performed 3 tests. During the first test the third tinny water drop ran through
the fabric at 392 mmWC. During the second test the machine stopped at 384 mmWC.
Compared to other jackets with a similar coating the mmWC can go up to 10.000,
so these results are not that good. Another sample has been tested a couple of
weeks ago and had result of 955 mmWC. We figured that we were testing the lower
back of the jacket. Since it is a secon hand jacket, this part may have lost
its performance. We did a third test using the upper part of the back and we
let the machine run until all the water would splash through. As you see in the
movie the machine stopped the test at a 12.500 mmWC when the fabric started to
tear from the pressure. It took 16 minutes and a lot of water came through the
fabric.
Water vapour permeability
It is
pretty difficult to measure the breathability of a fabric, whereas it is
difficult to measure vapour going through a piece of fabric. In the lab of TEKO
it is possible to measure it. The test consist out of a can filled with water
and on top lies the fabric which is sealed so no water can go out. The can will
be placed in a machine which makes it slowly circle. Before the can is placed
in the machine it will be weighted. If the fabric has circled for 24 hours, the
can should be weighted again. Using a formula is it now possible to calculate
the water vapour permeability.
We started
the test at 6-3-2013 at 14.22 and we ended the test at 11-3-2013 at 13.22. the
test has run for 54 hours. We tested two functional textile to make
comparisons. Our textile started with a weight of 135.22 grams and ended with a
weight of 120.54 grams. It lost 14.68 grams of water. The other fabric was of
135.32 grams ended with a weight of 107.14 grams. It lost 28.18 grams of water.
When we opened the cans we could see our fabric significantly lost less water. The
table also shows that the other textile has a much better breathability than
our fabric. The jacket we’ve found is probably not a nice to wear when you are
sweating and it is cold outside, whereas all the sweat cannot leave through the
fabric and you will get wet and cold wearing the jacket.
The formula
which is used is: (weight before – weight after)/ (factor of surface X time) X
24 hours = Water vapour permeability. The higher the outcome the better the
breathability.
Tearing test
The jacket
should also be strong. Therefore we did a tearing test. We performed 4 tests
both in the warp and the weft direction. During the first test we used load d
to tear a piece of fabric in the warp direction. The result was 10.64 Newton and
the machine advised to use a lighter load. So for test 2 we used a C load in
the warp direction and the result was 12.41 Newton. We also tested the fabric
in the weft direction. The third test we used a B load and tested in the weft
direction and the result was 16.51 Newton. The last test gave a result of 16.85
Newton. The fabric is stronger in the weft direction, whereas there are more
warps. But we were surprised that the results are significantly lower than the
tearing test we performed with the silk fabric. It is really easy to tear the
fabric.
Weight is
152 grams per square meters and 4.50 ounces per square yard.
Properties
We already
wrote about the strength, the water resistance and the breathability and tested
all of these properties. Polyester has a high abrasion resistance. As mentioned
before the wet strength is the same as dry and also should be, whereas it
should not lose strength when the jacket will get wet.
The breaking
extension is between 15 and 50%. Probably the coating will break easier than
the polyester itself, which lower the property of the polyester. Polyester is
wrinkle resistant, which is a good quality for this jacket, whereas the coating
shouldn’t be ironed at a very high temperature. Polyester scarcely absorbs
water, but it can transport liquid. Therefore the breathability of the coating
should be good.
It is
possible to create polyesters with a lot of different properties, like high
strength, flame resistance, high shrink, high crimp, antistatic or low pill. We
are not sure which treatments are used to apply which properties to this
fabric.
Care instruction
The care
instruction states the jacket can be washed at 40 degrees, it should not be
tumble dryed, nor bleached. It can be ironed on the lowest temperature and the
jacket should be washed with similar colors. Probably the jacket can withstand
a higher temperature, but it is not certain what will happen with the coating.
References
Clothing
Technology from fibre to fashion fifth edition 2008
Fabric
for fashion, The swatch book first edition 2010
Gore-tex.com
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