University of Oregon – Thailand Distance Learning Program – Green Chemistry
2010
Polymer Packing “Peanuts”
Chemical Concepts
Polymers; solubility; carbohydrates.
Green Concepts
Safer products; renewable feedstocks; design for degradation. (Consider Green Principles 1,
2, 3, 4, and 10.)
Introduction
Shipping fragile items always presents a risk of breakage, and through the years many
methods of cushioning such items have been developed. In the mid-1960‟s, Dow Chemical
Company introduced peanut-shaped pieces of polystyrene foam that quickly became known
as “packing peanuts.”
http://www.turtlerescues.com/images/packing%20peanuts%20on%20top%20of%20inside%20box.jpg
This light-weight and highly effective solution to the packing problem quickly became
popular, and it was not long before it seemed that the world would soon be covered in packing
peanuts. Fortunately, recycling of polystyrene packing peanuts is possible, although it seems
likely that many of them still end up in landfills. Peanuts that contain 70% or more recycled
polystyrene are often colored green. Problems associated with the use of polystyrene packing
peanuts include their production from a petrochemical starting material and their inability to
degrade in the environment, as well as their propensity to develop static charge, leading to
their clinging to anyone and anything close to them. (Pink colored packing peanuts have been
treated with an antistatic agent.) Polyurethane packing peanuts, generally shaped like the
numeral „8,‟ have been developed, and while they are less likely to develop static charge, they
are similar to the polystyrene peanuts in terms of environmental issues and concerns.
In the 1990‟s, starch-based packing peanuts were developed. They do not represent a perfect
solution, however. Although they are prepared from a renewable (plant-derived) feedstock
rather than petrochemicals, biodegradable, nontoxic (and even edible, though we do not
advise eating them), they are less resilient (more crushable) than polystyrene packing peanuts
and weigh and cost more. In addition, since they are edible, it is conceivable that rodents and
insects will be attracted to them. Finally, given their solubility in water, there will be issues
associated with their use in humid and rainy environments.
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2010
Laboratory
Materials needed
Two polystyrene packing peanuts
Two cornstarch packing peanuts
Two small containers (non-polystyrene)
Graduated cylinder or measuring spoon
Tap water
Acetone
Stirring rod or spoon
1. Examine and compare the physical properties of a polystyrene packing peanut and a
cornstarch packing peanut. Some things to examine are how each feels, how each
sounds when it is squeezed, and the color of each. Does each seem capable of
protecting an item during shipping?
2. Measure 3 tablespoons (45 mL) of tap water into each of the two containers.
3. Predict what will happen when you add each packing peanut to its container of water;
record your predictions.
4. Add a polystyrene packing peanut to one of the containers and stir; record your
observations. Repeat with a cornstarch packing peanut in the other container.
5. Repeat Steps 2–4, using 3 tablespoons (45 mL) of acetone instead of water.
Questions
1.
2.
3.
4.
5.
What were the similarities among the different types of packing peanuts?
What were the differences among the different types of packing peanuts?
What were your predictions about the behavior of the packing peanuts in water?
What were your predictions about the behavior of the packing peanuts in acetone?
Why do the different types of packing peanuts act differently in water? In acetone?
Research Questions
1. How many pounds of packing peanuts are produced each year world-wide?
2. If all the packing peanuts were to be made from starch instead of from polystyrene,
how much starch would be needed? Where does starch come from? Are there
environmental issues associated with the production of this much starch? (Compare
the impact on food costs that resulted from the production of bioethanol.)
3. What happens to starch in water when it is returned to the environment? (For example,
can it lead to eutrophication of water supplies?)
4. Are there other alternatives to starch-based packing peanuts that might be even better
for the environment? Other alternatives to packing peanuts (newspaper, air-filled
plastic bags, excelsior (“wood wool,” http://en.wikipedia.org/wiki/Wood_wool)?
Other approaches to transportation of fragile items??
Reference(s)
This is an adaptation of “Pondering Packing Peanut Polymers,” Perry A. Cook,* Sue Hall,
and Jill Donahue, JCE Classroom Activity #57, J. Chem. Ed. 2003, 80(11), 1288A-1288B. A
reproduction of that article is provided on the following pages of this packet.
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2010
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University of Oregon – Thailand Distance Learning Program – Green Chemistry
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2010
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University of Oregon – Thailand Distance Learning Program – Green Chemistry
2010
Carbohydrates
Chemical Concepts
Properties of covalent compounds; carbohydrates; food chemistry; polymers.
Green Concepts
Renewable feedstocks; safer chemicals and solvents. (Consider Green Principles 2, 3, 4, 8,
and 10.)
Introduction
The word “carbohydrate” literally refers to a hydrate of carbon, representing the empirical
formula (C·H2O) of the original members of this class of compounds to be studied, such as
glucose (C6H12O6). Representing the most abundant naturally occurring organic compounds,
carbohydrates (“sugars”) are well-known to all, in the form of table sugar (sucrose), glucose,
starch, and cellulose. Many carbohydrates are comprised of two or more simple carbohydrates
linked chemically; these more complex molecules are referred to as disaccharides,
trisaccharides, etc. When many carbohydrates are linked together – as in starch and cellulose,
for example – the resulting molecule is referred to as a polysaccharide. Polysaccharides
represent one of the three major classes of naturally occurring “polymers,” large molecules
constructed by linking of many identical (or near-identical) smaller molecules. (The other
naturally occurring polymers are the nucleic acids – DNA and RNA – and polypeptides –
proteins.) Synthetic polymers, of course, are well-known – polystyrene, polyesters,
polycarbonates, etc. all form the essence of modern societies textiles, packaging materials,
furnishings, and, seemingly, almost everything.
Polymers generally display very different properties than the small molecules from which
they are formed. One particularly dramatic difference is in their solubility. Whereas small
molecules are often freely soluble in various solvents, very large polymer molecules can
behave very differently toward a solvent. In essence, they not infrequently will act to dissolve
the solvent, rather than themselves dissolving in the solvent, leading to “solvent-swollen”
polymers.
Demonstration of formation of solvent-swollen polymers is frequently used as a simple but
graphic way to illustrate the fundamental differences between small molecules and polymers.
Such demonstrations often use synthetic rubber or plastics and organic solvents – for
example, placing a rubber “o-ring” in benzene or toluene leads to its swelling to many times
its original size, while retaining its shape and solid consistency. In this experiment, we will
explore similar phenomena using edible carbohydrates and water, avoiding possible exposure
to hazardous organic solvents and making disposal safe and inexpensive.
We will explore what happens when pectin, a water-soluble, rather complex polysaccharide,
is treated with sugar and an organic acid (found in naturally occurring fruit juice). Under these
conditions, in a manner that is dependent on the sugar concentration, pectin molecules
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2010
undergo covalent linkage, forming larger polymers that are extensively “cross-linked,”
leading to a change in solubility behavior – from solution to solvent-swollen polymer (“gel”).
Laboratory
Note: For this workshop, each group will carry out only one of the three parts, then share
their observations with other groups.
Materials needed
Pectin
Concentrated fruit juice (apple or grape)
Granulated sugar
Water
600-mL beaker
Hot plate
Scale or cup measure
Graduated cylinder
Heatproof gloves
Cork ring or heatproof pad
Stirring rod, spoon, or wooden stick
Part 1.
1. Weigh or measure 53 g (1/4 cup) of sugar.
2. Place 18 mL of fruit juice concentrate, 60 mL of water, and 7 g of pectin in a 600 mL
beaker.
3. Place the beaker on a hot plate and heat, with constant stirring, until it is close to
boiling, as indicated by the formation of bubbles around the edge.
4. Add the sugar, then bring the mixture to a boil while continuing to stir. Heat at a hard
boil for one minute, adjusting the heat as necessary and being very careful to avoid
having the mixture boil up and over.
5. Using heat-protective gloves, remove the beaker from the hot plate and place it on a
cork ring or heatproof pad to cool.
6. As the mixture cools, use a spoon to skim off any foam that has formed on the top.
7. Record your observations about the mixture after it has cooled.
Part 2.
1. Repeat the above procedure, using only 26 g (1/8 cup) of sugar.
2. Record your observations about the mixture after it has cooled.
Part 3.
1. Repeat the above procedure, using 106 g (1/2 cup) of sugar.
2. Record your observations about the mixture after it has cooled.
Questions
1. How did the consistency of the jelly change when you changed the ratio of sugar to
pectin?
2. Why did the consistency of the jelly change when you changed the ratio of sugar to
pectin?
Research Questions
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2010
1. Locate a procedure for demonstrating the phenomenon of solvent-swollen polymers.
What materials were used? How do they compare with the materials used in this
experiment, with regards to environmental and health issues?
2. Can you find other examples of safer (“greener”) demonstrations of this phenomenon?
3. Can solvent swelling of polymers be a problem? How so? What can be done to reduce
the problem of solvent swelling?
References
This is an adaptation of the Institute of Food Technologists‟ Experiments in Food Science
Series: Food Chemistry, Unit 1: Carbohydrates. A copy of this article is provided on the
following pages. A student version of the article is available on-line
(http://members.ift.org/IFT/Education/EduResources/fc.htm).
Various companies have been reported to supply pectin in Thailand, including Foodland Bkk
and Rimping C-M in Bangkok, and Berli Jucker Company. The following article reports an
additional potential source of pectin and is particularly interesting from the perspective of
green chemistry – pectin is produced from a renewable source that otherwise is viewed as
waste.
ISHS Acta Horticulturae 680: III WOCMAP Congress on Medicinal and Aromatic Plants Volume 6: Traditional Medicine and Nutraceuticals
SEMI-PILOT SCALE PRODUCTION OF PECTIN FROM LIME PEEL WASTE FOR
CHOLESTEROL LOWERING AGENT
Authors:
P.A. Pirshahid, K. Thisayakorn, R. Giwanon, C. Phoonsiri, T. Kajsongkram, K.
Chawananorasest, T. Suntorntanasart, S. Trangwacharakul
Keywords: Citrus aurantifolia, hypolipidemic
Abstract:
Pectin was obtained from pilot scale extraction of fresh lime peel wastes [Citrus aurantifolia
(Chistm.) Swingle] to yield 12%. Four varieties of lime which are available in Thailand were
investigated: Paen Puang, Paen Ramphai, Si Khiew, and Nam Hom Thun Klao. The percent
yields of pectin were 12, 11, 11, and 10%, respectively. The purity of four varieties of pectin
extracts were investigated by microbial limit tests. The results showed that all extracts
conformed to the specification of Thai Herbal Pharmacopoeia. A preliminary study of the
effect of TISTR pectin on hypolipidemic in rats induced by Triton WR-1339 (400 mg/kg i.p.)
was conducted. The dosages of TISTR pectin in this study were 500, 1,000 and 2,000 mg/kg,
and fenofibrate (Lipanthyl 200M) was used as a standard drug. The results showed that it
could reduce the serum lipid profiles: cholesterol, triglyceride, HDL and LDL. It also
exhibited a dose response activity.
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2010
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2010
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2010
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2010
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2010
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2010
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University of Oregon – Thailand Distance Learning Program – Green Chemistry
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2010
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University of Oregon – Thailand Distance Learning Program – Green Chemistry
2010
Analysis of Charge with Polymer Gels
Chemical Concepts
Properties of ionic and covalent compounds; cation analysis; solubility; polymers.
Green Concepts
Safer reagents and solvents; design for degradation. (Consider Green Principles 1, 2, 8, 10,
11, and 12.)
Introduction
Super absorbent polymers (SAP) are reticulated polyacrylates or polyacrylamides. They are
granular solids that quickly absorb and retain large volumes of aqueous solutions. Due to their
large molecular weights they do not dissolve but form clear gels of separated particles. These
intriguing materials are quite different from sponges, from which water can easily be expelled
– the hydrated gel particles retain the absorbed water even under pressure. This is perhaps
their main advantage, leading to their widespread use. Sodium polyacrylates are used in
diapers and other personal hygiene products, while polyacrylamides are mainly used as soil
additives to decrease irrigation needs. Other uses for SAP´s include solidification of
biological refuse and spills and flame retardation, and they are also used as the basis for
scientific toys and artificial snow.
In this experiment, we will isolate a SAP from a common commercial source – a disposable
baby diaper. (As any parent of s small child who has waded into water wearing such a diaper
knows, the SAP can absorb a lot of water.) We will then explore its properties – in particular
its behavior when it contacts water. Finally, we will examine the effect of various compounds,
including acids and bases, salts, and organic dyes, on the hydrated polymer, using the
observed behavior and an understanding of the SAP‟s structure to deduce information about
the ionic or covalent nature of the added compounds.
One could readily envision the adaptation of this procedure to allow for the qualitative or
quantitative determination of cations in unknown mixtures, and indeed superabsorbent
polymers are being used as chromatographic adsorbents for the analysis of a variety of such
mixtures, both organic and inorganic. Standard procedures for cation analyses call involve
lengthy protocols that use large volumes of water, employ hazardous and/or odoriferous
reagents, and generate considerable amounts of hazardous waste. In contrast, the SAP‟s offer
promise for simple chromatographic analysis. While the SAP‟s are in general made from
nonrenewable (petrochemical) feedstocks, they are biodegradable, and with some creativity,
one might anticipate success in preparing polymers with analogous properties from renewable
feedstocks. (Compare, for example, the properties of cross-linked pectin, examined in the
Carbohydrates experiment earlier in this packet.)
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2010
Laboratory
This is a very enjoyable experiment. However, it is rather time consuming in its entirety. We
have included the full procedure here, and would be delighted to work with you in order to
make it possible for you to try this experiment with your students. For this workshop,
however, we will follow a much simpler published procedure, reproduced at the end of this
experiment description – it introduces the same concepts, though in much simpler form, and is
much faster to perform.
Materials needed
Disposable baby diaper
Plastic bag
Plastic container (6, 20 mL)
Test solutions (see procedure)
Distilled water
Tap Water
Mineral water
Polymer separation
1. Remove the interior layer of a large disposable
Polypropylene
Composite fiber
baby diaper. (It can be saved and used as a filter if
Polyacrylate
desired.)
2. Place the lining contents (cotton and SAP) in the
plastic bag. Put one hand in the bag; use the other
hand to hold the beg closed around your wrist, to
prevent fine particle inhalation.
Polyethylene
3. Break up the cotton and gently shake the bag,
allowing the SAP granules to separate toward the
bottom of the bag, from which they may be
retrieved manually. A typical diaper will provide 5 to 6 g of a SAP (normally enough
for an entire class).
Polymer hydration
[ CH2
CH2]n
C
O- +
Na
[ CH2
O
Wet
D ry
H2O
+ Na+
CH2]n
C
O
OSodium ion
Water molecule
Polyacrylates are super absorbing polymers because of their structure. In the case of sodium
polyacrylate, the sodium carboxylate groups (-COONa) hang from the main chain. Sodium
ions (Na+) are released upon contact with water, thus freeing negative carboxylate groups (COO-) that repel each other and the polymer “unrolls” and absorbs water as a result. Sodium
polyacrylate can absorb up to 800 times its own weight of distilled water. If other substances
are present (e.g., urine, tap water, mineral water) the absorbing capacity gets substantially
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2010
reduced; ions and dissolved salts can decrease this capacity in a factor of 10 or more. Ca2+ and
Mg2+ present in mineral waters reduce this capacity even more due to the formation of
covalent bonds between two carboxylates, which prevents polymer expansion.
1. Place approximately 30 mg of SAP in each of three 20-mL plastic containers (e.g.,
gelatin molds).
2. Add 15 mL of distilled water to one, 15 mL of tap water to the second, and 15 mL of
mineral water to the third. Allow the mixtures to stand for 15 minutes, with occasional
swirling.
3. Prepare three filters by puncturing 5-8 small holes on the bottoms of three plastic
containers (like those just described). This can be done with a red-hot paper clip.
Caution: Handle with care - hot! Note: if the SAP particles are too small they may go
through the holes. To prevent this, use an additional filter aid by cutting circles from
the interior layer of the diaper (saved in part 1 above) or from a coffee filter so as to fit
the bottoms of the punctured containers.
4. Weigh the circles, and filter the hydrated granules. Place each filter over paper towels
or napkins until no more water comes out of them. Weigh again and calculate the
weight of each one by difference. (If a balance is not available, compare the volumes
by simple observation.)
5. Typical results are: 9.6 g of SAP + distilled water, 7 g with tap water, and 2.3 g with
mineral water.
Treatment with salts, acids, and bases
A polyelectrolyte expands because its charges of the same sign repel
T he polymer particles are randomly
wound like a hank of thread
Salts provoke dissolved polymer collapse
1. 500 mg of SAP are hydrated with distilled water, the resulting gel is filtered and 1-2
teaspoon size portions are placed in 6 plastic molds (as those described above) for the
following experiments.
2. Place in each one 15 mL of one of the following 1% solutions: HCl, NaOH, NaCl,
CaCl2, CuSO4. Then add 14 mL of deionized water and 1 mL of a commercial
KMnO4 solution (e.g., the kind sold in aquarium stores).
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2010
3. Allow to stand for 15 minutes, then, as described above, filter each solution and either
weigh it or observe the gel volume.
In all cases the gel volume decreases, but with HCl, CaCl2, and CuSO4 it practically collapses,
returning to semi-solid particles. Furthermore, in the case of Cu+2 all the copper is retained
and the polymer becomes bluish, whereas the filtrate comes out colorless. In these three cases
the carboxylate is no longer available to re-hydrate; even if the polymer were washed, the
reaction is not reversible. With NaOH, NaCl and KMnO4 the volume decreases but upon
washing and eliminating the ions, it increases again although it does not go back to
the original volume. Since the color of KMnO4 comes from the anion instead of the cation, the
gel is not colored by it.
Treatment with dyes
Methylene blue
Malachite green
Crystal violet (Gencian violet)
Red dye # 40
Red dye # 3
Yellow dye # 5
(seducing red)
(enthrosine)
(tarthracine)
Blue dye # 1
Green dye # 3
(brilliant blue FCF)
(fast green FCF)
1. The polymer preparation is repeated as above.
2. Before placing the SAP in six plastic molds, place 15 mL of distilled water and in
three of these molds also add: 1 drop of the blue, green and red food dyes,
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2010
respectively; in the other three, place 1 drop of methylene blue, crystal violet and 4
drops of malachite green, respectively.
3. Then, add the SAP. After 15 minutes, filter each mixture as described above and wash
with abundant water.
The gel volume remains essentially constant with the food dyes, and most of the color is
washed away. With the other three dyes, the gel granules slightly decrease and retain the
color; the wash water is colorless as a result. This is due to the anionic structure of these dyes
(just as in the case with KMnO4) which prevents their retention, whereas the other three dyes
have a cationic structure and are retained by the carboxylate ions. In this last case, the gel
does not lose much water since the cations are rather large and maintain the polyacrylate
molecule expanded.
Questions
1. Describe your results.
2. Examining the structures of the SAP provided above, discuss the chemical factors that
contribute to the observed results.
Research Questions
1. Locate an example of a SAP being used for the separation of cations. Describe the
procedure, and explain the chemical factors that lead to the observed separation.
2. Are there polymers derived from renewable materials (e.g., carbohydrates instead of
acrylates or acrylamides) that might be expected to behave as SAP‟s? What might be
some advantages of their use? Any disadvantages?
References
This procedure is adapted by Jorge G. Ibanez (Universidad Iberoamericana – México) from
Rosa María Mainero Mancera, Centro Mexicano de Química Verde y Microescala,
Universidad Iberoamericana, Ciudad de México. We also gratefully acknowledge invaluable
personal communication with Dr. Angela Köhler, Romaine Rolland High School, Berlin,
Germany.
Web pages:
http://www.chemicalsolutionsintl.com/sapgi.htm
http://www.creativechemistry.com/saps.cfm
http://www.tramfloc.com/tf62.html
http://che.oregonstate.edu/sesey/97/super.htm
http://centros5.pntic.mec.es/ies.victoria.kent/Rincon-C/Curiosid/Rc-39/RC-39.htm
http://www.pslc.ws/macrog/activity/trans.htm
Home > Easy Science Experiments >
http://www.asme.org/education/precollege/magic/pdf/1milktrick.pdf
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