Insulation for a Thermos Through the Use of Recycled Materials and Nanofoam

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Authors

Kahyee Fong – Damin Hashash – Gabe Kooreman – Crystal Mckenzie – Elaine WangFong – Damin Hashash – Gabe Kooreman – Crystal Mckenzie – Elaine WangKahyee Fong – Damin Hashash – Gabe Kooreman – Crystal Mckenzie – Elaine Wang
Abstract:
The goal of this project was to take advantage
of the capabilities of nanotechnology by using
the room temperature sol-gel process to form a
silica nanofoam composite with a common
household foam, in an effort to synthesize a
cheap, lightweight insulator for use in a
thermos. Through testing of hybrid insulators, it
was determined that a silica nanofoam and
packing peanut composite combines the natural
insulating properties of the packing peanuts and
of the silica nanofoam to make an insulator for
a thermos.
Introduction – Nanofoams and Gels:
With rising temperatures and record levels of
pollution, global warming is becoming an even
more pressing problem. Because of this,
concern for the well-being of the environment
has grown to levels that have never been seen
before. This new trend in environmental
concern has developed into hundreds of “green”
solutions and energy-saving schemes requiring
recycled materials and interesting new ideas.
Examples of these “green” innovations are
UltraTouch, an alternative insulation made of
recycled denim, and a modified cellulose foam
[3]. Simultaneously, the alarming rate of sizereduction
in technology has spurred a flood of
high-performance materials and innovative
processes of material synthesis. Coined by
Norio Taniguchi, “nanotechnology” provided
an extremely promising solution to the
problems of scaling down machine sizes [2].
Materials that have a dimension measuring less
than 100 nm, or one ten-millionth of a meter in
length or are made one atom or molecule at a
time qualify as nanotechnology. In this project
sol-gel a nano-material synthesis method was
used to synthesize a cheap, efficient insulator of
nanofoam while utilizing the most common
“green” solution: recycling.
Background Information – The Sol-Gel
Process:
Due to the pockets of air in foams, foams have
a low density compared to other materials.
They are extremely useful as commercial
materials due to their light weight. The pockets
of air within foams give them numerous
characteristics that allow them to act as
efficient sound and heat insulators. Nanofoams
are very similar to normal foams in that they
have small pockets of air, but they have other
qualities that regular foams usually do not have,
such as transparency. Nanofoams, unlike other
nanomaterials, have nano-dimensions that do
not pertain to the foam itself but to the pockets
of air that are dispersed throughout it. The
unique quality of nanofoams, the size of their
holes, and their varied means of synthesis make
them interesting materials with several
manifestations capable of many different
applications. One method used to synthesize a
nanofoam is the sol-gel process. This process
uses the chemical processes of hydrolysis and
polymerization, which both occur at room
temperature and can make macromolecules
without the use of high temperatures. This is
important because it means that the sol-gel
process can be done at minimal expense under
ordinary room temperature conditions.
Nanofoams that are made through this process
are very porous, and their pores are less than
100 nm in diameter. Because the pores are
smaller than the wavelength of visible light,
they are invisible to the human eye, making
them indistinguishable from their non-foam
counterparts. The amorphous quality of foam
created through the sol-gel process allows the
foam to be easily shaped into a mold; it can
form around other objects, making it a useful
and flexible adhesive. Research has already
been conducted to discover new ways to
produce and shape nanofoams, such as
spinning, dipping, spraying, ink-jet printing or
roll coating [4]. Sol-gel film has been used as a
durable adhesive in metal coating and as a
preventative measure against rust due to the
film’s ability to bond to metal [1]. Not only are
sol-gels versatile on their own, but they can
also take on the properties of other materials.
Through the technique of “doping,” other
materials are introduced into the nanofoam
during creation, and the foam takes on the
qualities of that composite material, making it
possible to create a variety of different foams.
These foams can be molded into dielectric
foams, thin membranes or even conductors for
a variety of different applications.
Our project involves preparing a silica (SiO2)
by nanofoam using the sol-gel process. Silica,
most commonly found in sand, is usually
melted at high temperatures to form glass. In
the sol-gel process, silica is prepared as a
solution of monomers of silicon ions attached
to four alcohol groups. Through hydrolyzation
and polymerization, the silicon compounds are
formed once again into SiO2 this time in the
form of a gel. When left out to air-dry, the
water in the gel evaporates, and its surface
tension causes the silica nanofoam to shrink.
Once all of the water is gone, the final product
is once again SiO2, but this time it is in the
form of glass. When glass is created with the
sol-gel process, however, it has the additional
property of being a nanofoam. The solid
nanofoam appears to look the same as normal
SiO2, but it is really filled with nano-sized
holes.
Experimental Design:
To experiment with the sol-gel process, five
different silica sol-gel samples were created.
Silica gel was chosen because it is the cheapest
of the gels and an effective insulator. These
samples had different materials acting as
catalysts to speed-up the gelling process.
Isopropyl alcohol, table salt, nitric acid, acetic
acid, and cobalt were used. One of the samples
of silica sol-gel was composed of nitric acid
and cobalt, which gelled into a soft, uniform,
pink gel that was slippery and moist to the
touch. This gel hardened incredibly slowly, and
as each day passed, it gained more cracks due
to its shrinking and its adhesion to the petri
dish. Another sample used only cobalt. This
sample gelled rather quickly and cracked into
many smaller, iridescent pieces of glass that
resembled amethyst. The most active of the
additives to the silica was table salt (NaCl).
Within minutes of adding the salt to each of
these mixtures, the colloid began to gel.
From these samples, it was evident that table
salt was the most effective gelling agent. It
greatly accelerated the sol-gel process. Cobalt
was relatively ineffective; the sample that
contained only cobalt did not harden until
several days later. Nitric acid was also not
nearly as potent a gelling agent as table salt: the
smooth, pink sample, when observed thirteen
days later, was still not completely gelled.
Using this information, it can be concluded that
table salt was the quickest gelling agent. Table
salt was the best gelling agent because it ionizes
well in water. When silica molecules disperse
in water, they have a slightly negative surface
charge, which causes them to repel each other.
When salt is also disassociated into the water,
the silica molecules form around the positively
charged sodium ions, and as the water
evaporates, the silica molecules move closer
together so that they eventually form a solid
nanofoam.
To test the insulation capabilities of common
foams, eleven different foams were collected:
packing peanuts, polyurethane sponge, bubble
wrap, dish sponge, vermiculite, cotton balls,
shaving cream, ceramic balls, marshmallows,
and two types of polystyrene foam. These
foams were chosen because they are readily
available, cheap, and they represented a wide
variety of different types of foam.
First, an ice water bath was prepared. Then, a
sample of foam was used to cover the bulb of
the thermometer. After recording the
temperature of the room, the thermometer was
placed in the ice water bath, and the timer was
started. The lengths of time that it took for the
temperature reading to drop by one degree, five
degrees, and ten degrees Celsius were noted.
All of the foams were tested by repeating this
process.
Next, a hot water bath was prepared. Aside
from observing one degree, five degree, and ten
degree increases in temperature, the same
essential procedure was implemented in testing
the insulation capabilities of all eleven types of
foam using a hot water bath.
Finally, seven different possible samples of
composite materials that could effectively
insulate a thermos were created. First, colloidal
silica and table salt were poured into a small
jar, and this solution was carefully stirred.
Then, four plastic test tubes were stuffed with
packing peanuts and filled with the colloidal
silica and salt solution. Two of these four test
tubes were capped and put aside to dry. The
other two were left open to air dry. Following
this, another test tube was filled with shaving
cream and the colloidal silica and salt solution
and left open to air dry. A sixth test tube was
stuffed with cotton balls and filled with the
colloidal silica and salt solution and also left
open to air dry. Lastly, broken pieces of
packing peanuts were placed in a petri dish,
which was then filled with the colloidal silica
and salt solution. This sample was closed and
put aside to dry.
The Results
The results of the heat insulation experiments
indicated that polystyrene packing peanuts,
cotton balls, and shaving cream were the three
foams that took the longest overall times to
conduct heat and, therefore, were the best
insulators. The data indicated that dish sponge,
polyurethane sponge, and bubble wrap were the
least effective heat insulators.
When the samples of composite foam insulators
were examined, all of the samples that included
packing peanuts had hardened exactly as
expected, forming a hard glaze around the
packing peanuts and holding them together.
The cotton balls in the cotton-ball-silica
composite were hard to the touch, and they, too,
had adhered to each other very well. Both the
packing peanuts and the cotton balls formed
into a usable composite material. However, the
results of the shaving cream sample were not as
ideal because the shaving cream and silica
separated while drying. These experiments
were useful in determining the composition of
our final product.
The experiment with heat insulating properties
of foams yielded the following results:
Figure 1. Average time required to change the
temperature of a foam by one degree Celsius for each
tested foam
Discussion:
The first experiment dealt with which materials
could be added to colloidal silica in order to
form a better gel in the least amount of time.
All of the solutions that included nitric acid
took more than a week to fully harden. The
mixture that included nitric acid and cobalt
turned a uniform, translucent pink color after
the first day of gelling, but even after a week, it
remained soft to the touch. In the mixture with
only cobalt, the cobalt clumped together into
large, purple chunks, and the mixture hardened
and cracked very quickly. By the first
examination, the other solutions, which
contained silica and salt, had already gelled,
and a few days later, had hardened completely
into very small pieces of opaque glass. The
colors of each of these samples differed,
depending on the amount of cobalt present, but
all of them were opaque, hard and fractured.
Due to the time intensive nature of this project,
a quick-gelling mixture of silica was very
important, so salt was chosen to be used for all
subsequent silica mixtures.
There were three obvious tiers of insulating
effectiveness. The least effective insulators
were sponge and vermiculite. Both the sponge
and the vermiculite insulated thermometer
increased in temperature by over ten degrees in
less than five seconds when added to the hot
water. The foams that could be placed in the
middle tier in terms of their effectiveness in
insulating the thermometer were the small
ceramic spheres, the polyurethane sponge and
the bubble wrap. For these three foams, the
thermometer took about twenty-five seconds to
increase in temperature by ten degrees Celsius.
Finally, the foams that would be classified in
the highest tier were packing peanuts, cotton
balls, and shaving cream. These three foams
each took over a minute to rise in temperature
by ten degrees Celsius. Not only this, but when
surrounding a thermometer placed in cold
water, the cotton-ball-wrapped thermometer
took three minutes and thirty seconds to drop
by five degrees, and the thermometer wrapped
in packing peanuts had even more pronounced
insulating properties, as it took four minutes
and fifty seconds for it to cool by only two
degrees Celsius. In cold water, the shavingcream-
insulated thermometer performed well,
but not nearly as well as the cotton balls or the
packing peanuts had performed. The
thermometer insulated with shaving cream lost
ten degrees Celsius in one minute and fifty-one
seconds.
Based on the observations of the sponge,
vermiculite, packing peanuts and cotton balls,
smaller pore size correlates with better
insulating properties.
The aim of the final experiment was to find out
which of the foams would be the most useful in
the final product. The samples were made of
cotton ball and silica composite, packing peanut
and silica composite, and shaving cream and
silica composite so that they could be examined
and inspected for any flaws. After drying, the
shaving cream and silica composite had
separated into powdery, dry shaving cream on
top and pure silica nanofoam underneath. Both
the packing peanut and the cotton ball silica
composites formed into their own solid objects
held together by the silica nanofoam. The
cotton balls and packing peanuts both worked
well as a composite material with the silica
nanofoam. From this information, only two
choices remained for the composition of the
final product. Either the final product would be
made with cotton balls or packing peanuts.
After some deliberation, it was decided that
packing peanuts were the best choice for the
composite material. They exhibited excellent
properties as insulators; they easily joined with
the silica gel into a composite material, and
they are cheap, available, and often recycled. It
was concluded that the best insulating material
for the thermos would be the packing-peanutand-
silica nanofoam composite, which would
be gelled using salt.
The final result of the project was a lightweight,
cheap, easy-to-produce insulator that
can be molded into any shape.
Future Work – There’s Still More To Be
Done:
Besides building a thermos using the composite
foam product, an additional step can be taken to
research further the insulating properties of
various other nanofoams including aerogel,
which was a foam of interest at the start of this
project. Due to time constraints, making aerogel
was not feasible in this project, but given more
time and additional resources, experimentation
with aerogel, which is a lightweight insulator,
and other nanofoams could result in better
insulation.
Several aspects of the final product could be
improved in the future. Since there was not
enough time for the seven composite foam
samples to adequately dry, it is important, in the
future, to test the relative insulation capabilities
of the seven foams using the process outlined in
this project and compare their insulation
capabilities to that of pure colloidal silica. From
these comparisons, it would be possible to
determine how much the addition of a common
foam to colloidal silica improves overall
insulation.
It is also a possibility to gel multiple common
foams into one nanofoam composite. Packing
peanuts, cotton balls, and shaving cream were
gelled separately, but a combination of all three
or two of the three may provide better
insulation.
Increasing the concentration of colloidal silica
could also provide better insulation, and thus, it
is important to experiment with different
concentrations of colloidal silica to make a
more effective insulator in the future.
Further investigation could be done to assess
the utility of our foam in other applications
including building insulation. Our material can
potentially be used in walls, floors, and
ceilings. It is lightweight and inexpensive,
which allows for a variety of usages. In
addition, the sol-gel process is such that the
composite foam can be easily molded into any
given shape. This allows for the foam to serve
as a lightweight, inexpensive container for
almost anything that requires insulation. Organcarrying
apparatuses, for example, rely on
strong insulation to preserve the organ, and
thereby ensure that a patient is not given a
defective organ. Our insulation can also be used
in refrigerated semi-truck trailers, which need
to insulate large supplies of fresh food.
Within the broad scope of nanofoams, creating
composite foam that can both insulate and
provide soundproofing is a useful endeavor
since such a foam is useful in a variety of ways.
A soundproofing and insulating foam would be
valuable in the walls, floors, and ceilings of
apartment buildings where families living in
tightly-packed units would appreciate more
privacy. There is still a lot of research to be
done in the field of using nanofoam composite
materials as insulators and beyond. Some day,
perhaps, nanofoams will be as ubiquitous as
common materials such as plastic.
Conclusion:
While foams may seem simple at a first
examination, the depth of knowledge required
to understand their properties and uses is vast.
Nanofoams can be used for a variety of
purposes, and as we found out, they work well
as both insulators and as adhesives. When we
began our project, we sought to garner a deeper
understanding of foams, especially nanofoams,
by making an insulator that would use recycled
materials and would be suitable for use in a
thermos. But when we completed our project,
we had gained so much more. We
accomplished our goals, and created a sample
of our insulation using silica nanofoam and
packing peanuts, and we also acquired valuable
insight into the way that a material science
laboratory works.
Acknowledgments:
First and foremost, we’d like to thank Dr. Lisa
C. Klein, our primary project advisor and
mentor. While helping us focus on our final
project, Dr. Klein also gave us access to her lab
to conduct experiments, gain experience in
laboratory work, and investigate the properties
of nanofoam. After investigating all the
properties of nanofoam, we were able to choose
a project idea and make a sample of our product
with the help of Dr. Klein.
In Professor Klein’s absence, Professor Andrei
Jitianu aided our group in our investigations.
With Professor Jitianu we investigated the
ability of nanofoams to pack tightly and
absorbency. Professor Jitianu also assisted our
group in thinking of a project idea. Without the
help of Professors Klein and Jitianu, we would
have had a much more difficult time with this
project
Secondly, we would like to show gratitude to
all the participants in our tour of Rutgers
Materials Science and Engineering Department.
Professors Manish Chowalla, Dunbar Birnie,
Richard Riman, Ahmad Safari, and George
Sigel all participated in teaching our group the
basics in different aspects of the material
science field. During the tour we visited the
Solid Freeform Fabrication, Photovoltaics,
Carbon Nanotubes, Fiber Optics, and Self
Assembly labs, and were see exactly how parts
of the field differed.
We would also like to thank Sean DiStefano,
whose absence would have meant group
meetings that would not have run as smoothly
as they did. Sean was also our group’s
counselor advisor and very helpful with any
questions we had, regarding both our project
and our final paper.
Last but not least our group would also like to
thank Ms. Jane Oates and the rest of the
Governors School Board of Overseers, Dean
Don Brown, Dean Ilene Rosen, and Blase Ur,
without whom none of us would have had this
opportunity.
References:
1. Blohowiak, Kay Y.. “Sol-gel coated
metal.” Patentopedia.
.
2. Klaes, Larry. “What is
Nanotechnology? Well, it’s very, very,
very small.” TheIthicaJournal.
.
3. “New and Alternative Insulation
Materials and Products.” Do it yourself.
.
4. Reed , Scott. “Sol-Gel Glasses.”
Manufactoring Science and Technology
center.
.

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