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How can I test the performance of a diaper?
The best way to measure diaper performance is to evaluate its
most important attributes: Absorbent Capacity, Absorbent Retention, Speed of
Absorption, Diaper Re-wet, Fit and Comfort. I will refer to the first three
because they are more objective and easier to measure. It is important to use a
saline solution in all of your experiments because that is the easiest way to
simulate urine (think of it as "synthetic urine"). Salts in the water affect
the performance of the super-absorbent (SAP) so much, that your data will be
meaningless if you use plain tap water. And remember that babies' urine too has
minerals - 0.9% is the average minerals content in the urine of a healthy baby.
A performance gain of as much as 35% can be achieved just by
using plain water instead of the "synthetic urine", depending on the amount of
SAP in a diaper. So if you think that using water will make the test fair to all
diapers... STOP! Not all diapers are made with the same amount of SAP
and it is only the SAP that is affected by the salts. By showing respect to
individual properties of all the components, you are exercising a scientific
criterion. Make sure that you record all relevant information in your "experimental
record's table". This is what the Science Fair is all about - learning how
to have and use a scientific approach. Just to confirm that this is not a
simple theory but a hard fact, test one diaper with plain tap water and another
with water after adding plenty of salt. You will be surprised by the huge
differences in results. Another way to verify this phenomenon without damaging
two diapers is to add a tablespoon of salt on top of a used wet diaper. You
will see how much liquid is released due to the inability of SAP to retain
liquids having highly concentrated dissolved salts. Grown-ups, please skip
the following part because it was written just for kids.
A bed time story for little kids not to
take too seriously:
"Once upon a time, many years ago,
there was a nasty wicked old witch who visited supermarkets disguised as a
"demo" lady in order to trick innocent mothers into buying low quality diapers.
Luckily for us, a handsome prince watched one of her presentations and caught
the old witch doing her wicked tricks. The bad witch owned a very large
disposable diaper factory. That is why she was conducting diaper tests in front
of the consumers to convince them that her diapers were the best in the land.
But the trick was that she was using altered water; in one jar she had water
with a lot of salt and in another jar she had plain water. She tried to convince
mothers that her diapers were the best (using only plain water on her diapers
and water with a lot of salt on all other diaper brands, including diapers made
by the handsome prince's little diaper factory). Guess which diaper performed
better? You are right! Diapers made by the wicked old witch seemed to be
better. But you know that it was just a wicked trick. The happy end of the
story is that the handsome prince, whose name was Carlos, was able to uncover
the fraud and later married the beautiful young manager-in-charge of the diaper
department, Adriana, and lived happily ever after. The wicked witch never sold
another diaper in town and later moved to New York where she was last seen
driving a Taxi!"
Diaper Tests
to do:
Absorbent Capacity: Prepare a few liters of saline
solution, mixing water with regular table salt at 0.9% (This is the same as 9
grams per liter of solution, and simulates the minerals in babies urine). Find
a large container in which you can immerse the diaper. Start by weighing the
dry diaper, using a scale, and record the data. Put the saline solution into the
container and place the diaper flat upside down at the bottom of the container,
using a chronometer or stop watch set for exactly ten minutes. Do not apply
any additional pressure to the diaper as it is soaking the solution. After the
ten minutes have elapsed, remove the diaper, holding it from the corners, and
let it drip for two minutes. Hang the diaper with cloth pins or something
similar (or use your own hands), in such a way that it drips vertically. After
the two minutes, measure the weight on the scale. The Absorbent Capacity will
be the difference between the two recorded weights. The best diaper for this
performance attribute will be the one with the highest Absorbent Capacity.
Record the data in your
table.
Absorbent
Retention: I am going to explain a simplified test
that you can carry out without elaborate equipment. You will need only a
washing machine. This experiment lets you assess how much liquid a diaper will
hold under pressure. First weigh a new dry diaper on a scale and record the
data in your table. Then allow it to soak liquid for ten minutes, using the same
saline solution and the container you used in the previous experiment. After
ten minutes have elapsed, remove the diaper and let it drip for two minutes.
Instead of just recording the weight difference (as in Absorbent Capacity
experiment), this time we need to place the diaper flat on the inside wall of
the washing machine. Important: You will use only the centrifugal cycle.
If you are 13 years old or less, please ask permission of your parents before
you use the washing machine. A very angry parent once sent me an E-mail
complaining about this situation and the thing is that I agree with her - a
washing machine can be a dangerous equipment. She made me realize that I could
be responsible for anything happening to her child (it seems her kid made a mess
with water all over the floor and she was angry with me); yes, even when I was
just trying to offer a little help. Life many times is not fair and you should
know this by now. It is up to all of us to make it a little better for everybody.
Never give up an action when your intentions are good and honorable. It is
much better to have your parents involved with the project; this way I am also "off
the hook"... By the way, sometimes your parents can also help you with the
writing. You will need to improve your negotiating skills. For example, in
exchange for cleaning your room ... (ups!!). Enough chat already, let us get
back to the experiment ....
Select the centrifugal
cycle in the washing machine and let it spin for two minutes. Remove the
diaper from the machine and measure its weight. The weight difference will be
the total diaper retention. Be consistent by always using the same washing
machine with all the diapers you test. The best diaper will be the one with the
highest retention. Record the data in your experiment's data table.
Speed of Absorption: You will need a flat table and
the means to hold the diaper (pins if you use a cork table, or adhesive tape).
You will also need a plastic pipe (or equivalent) with an internal diameter of
one inch, about ten inches long, though the length is not so important. You will
need to prepare a stand for the pipe, by using a 10 CMS X 10 CMS (4" x 4")
Plexiglas square, with a hole in the center where you can attach the one inch
pipe. Start by measuring 100 ml of saline solution @ 0.9%. Place the diaper
flat on the table, avoiding wrinkles by stretching the diaper before you apply
the pins. Put the stand with the pipe on top of the diaper at the target area of
the pad. With your chronometer (stop watch?) on hand, start the timer at the
same time when you pour the solution into the pipe. Record the time required
for all of the 100 ml of liquid to penetrate the diaper. This will be the speed
of absorption or First Strike Trough Time. Repeat the test again after ten
minutes with an additional 100 ml for a Second Strike Trough. You can also try
a Third Insult if you please. The best diaper for this performance attribute
will be the one with the least time. The second time is more important than the
first, in terms of diaper performance.
These tests are fine for a school project but
please be aware that if you want more precise results, you should not use tap
water or regular table salt as they have an effect on the performance of the
super absorbent due the the variable mineral content of the water. Please
visit the following link if you want to download formal instructions on diaper
performance:
Diaper Performance
Now that you played with your diapers, let me
tell you that if you are looking for a truly professional laboratory to test the
performance of your diapers, we will do the testing for you. We are confident
that our report will be the best you have ever seen. Please click here if you
are interested in our professional Laboratory Services to test your diapers :
Diaper
Lab
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