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Cornstarch-Based
Biodegradable
Packing Peanuts
A next-gen product is one which greatly improves or expands on the technologies
present in society. The shipping industry, albeit efficient, still relies on
environmentally unfriendly packing fillers to protect goods. In particular, packing
fillers, such as packing peanuts, have not been heavily improved. The currently
used polymer-based packing peanuts unnecessarily pollute the environment. A
better alternative is to create biodegradable packing peanuts of shipping costs and
mechanical properties similar to polymer-based packing peanuts. This project will
discuss methods undertaken to expand the knowledge base of creating starch-
based biodegradable packing peanuts.
Team Packingjins:
Mick Blackwell
Graham Gearhart
Brian Lang
Caryn Martin
Project Brief
Is it worth polluting
the planet?
Is there a better
alternative to
polymer foams?
1
Overview Countless packages are sent and received daily.
Appropriately, companies and consumers alike
expect their goods to remain unscathed during
transport. As such, a means to protect goods during
transport is required; the means commonly used is
packing filler. Examples of a commonly used
packing filler are polymer-based packing peanuts.
Polymer based packing peanuts maintain
appropriate mechanical properties for the shipping
processes, however, polymers can take years to
degrade. Thus, the polymer-based peanuts pollute
the environment.
A better alternative to such peanuts are
biodegradable packing peanuts made from
starches. If a biodegradable packing peanut (BPP)
was fabricated which maintained similar
mechanical properties relative to a polymer-based
peanut and remained inexpensive to manufacture,
then the benefits would be immediately apparent.
This project attempts to determine alternative
methods for producing the BPP using various
surfactants and characterize the mechanical
properties of starch-based foams. Results from
SEM testing and tensile testing were compared to
recent literature for validation.
[1] A shoreline polluted with non-degradable polymers. (Hickman, Bill. "Two Plastic Reduction Victories in Santa Cruz." Surfrider
Foundation. July 25, 2012. Accessed May 3, 2015. http://www.surfrider.org/coastal-blog/entry/two-plastic-reduction-victories-in-santa-
cruz.)
[2] A post production gel for a BPP with the surfactant additive DTAB.
2
Using the 5 pillars of engineering to
establish the need
Environmental
Political Economic
Technological Social
The Kyoto Protocol allocates a certain
number of credits to countries for
greenhouse gas emissions [8]. If a country
wants more credits, the country can benefit
by implementing a green movement in
developing nations [8]. A green movement
could be establishing a postal service which
utilizes biodegradable packing peanuts,
saving the country from having to purchase
and use petroleum based packing fillers.
The goal of this project is to optimize
shipping costs while adhering to shipping
standards. In other words, by making the
starch-peanuts more lightweight, shipping
costs will be reduced. However, the
mechanical properties of the peanuts must
not drop below acceptable standards.
Additives, such as surfactants, could be a
solution to the cost vs. sustainability
dilemma.
All starch-based peanuts are inherently
static free therefore minimizing the hassle
associated with packing objects. In
addition, packing peanuts are much less
hazardous when compared to petroleum
based peanuts; although not recommended,
starch-based peanuts can be consumed
without life threatening side effects.
The food industry manufacturing processes
are becoming more refined and corn yields
have never been higher [9]. Increasing the
amount of corn available opens up the
market for new products based on corn
derivatives, such as starch-based packing
peanuts.
Developing starch-based polymers will conserve
petrochemical resources [7]. As petrochemical
resources are nonrenewable, efforts must be taken as
soon as possible to alleviate the pressure always present
on the petroleum market. Further, the processing of
petroleum based packing peanuts is well-known to
release toxins into the atmosphere and waterways. The
manufacturing process for starch-based peanuts is more
benign and the peanuts will degrade back into the
environment safely at the end of their lifecycle.
Creating a foundation
Foam peanuts, or packing peanuts, are loose-fill packaging material used as a cushion to
prevent damage to objects during shipping. Traditionally made of polystyrene, the packing
peanuts can be used and reused, then later recycled at packing or shipping stores [4].
However, many peanuts eventually end their lifecycle in nature, unable to be processed
naturally by the environment for many years. Luckily, in the early 1990s, the ecofriendly
alternative of starch-based packing peanuts were industrialized [5].
Starch-based peanuts are attractive as each peanut is non-toxic, static-free, and
biodegradable. Currently used starch-based peanuts are more expensive than petroleum-
based peanuts and offer lower mechanical resilience. In addition, the environmentally
friendly peanuts cost more to ship due to an average density three times the density of
traditional packing peanuts (0.4-0.8 lb/ft3 vs. 0.17-0.2 lb/ft3) [6]. An attempt was made in
this research to revolutionize the shipping industry by creating a low-density, biodegradable,
starch-based packing peanut that meets shipping standards as outlined by the TEN-E packing
services, removing the extra cost of remaining environmentally friendly. Although the results
obtained may have not been industry changing, gains were made toward deriving an adequate
solution to the starch-peanut dilemma.
Refining methods
As how most proud, eco-friendly ideas sprout, research and development began with using
what the Earth had provided—fifty pounds of raw corn. Corn starch was extracted by first
mashing the corn kernels in a bag with water. After picking out the remaining larger grains
of corn, the water-starch solution was filtered. Left behind on the filter was readily usable
corn starch that could be made into a cornstarch-gel, and eventually, into a foam peanut. For
consistency’s sake, during the repetition of mechanical properties testing, the extracted corn
starch was replaced with store bought 100% corn starch.
With an established method for creating cornstarch-gels (see the Creation of cornstarch-gels
section), various surfactants were added and studied to see how the resulting structure
changed. Dawn© dish soap, baby soap, CTAB, DTAB, and SDS were individually added to
the cornstarch and water mixture prior to the gel forming process. Only DTAB showed
promising results after initial experimentation, thus was used in the following molding
process. However, all gels were examined with an SEM to characterize apparent physical
structure differences. Select gels were processed into a moldable cornstarch aggregate able
to be compression/explosion molded. In addition, the mold used was the D638-10 standard
dogbone for polymer tensile testing. Since the explosion molding process allows the
expanding starch aggregate to completely fill the mold cavity, the dogbone testing method
was confirmed feasible.
Creation of cornstarch-gels
Making surfactant biased cornstarch-gels
Forming aggregates from gels
Explosion molding for tensile testing
To make starch-based packing peanuts, starch gelatins were
required. Starch gelatins are made from a specific starch and
water mixture (10% w/w) boiled until viscosity remains
constant [1]. Once the boiling process was completed, the
mixture was cooled overnight between 50-60°C. After cooling,
the gelatin was extracted from the original container. The
substance should resemble the familiar food brand Jell-O.
As mentioned directly above, starch gelatins are required to
make starch-based packing peanuts. The process conceived to
create surfactant biased starch-based gelatins was similar. The
testing surfactant used was DTAB. 3 grams of DTAB was
added into 100g of cornstarch (3% w/w). The same boiling and
cooling process was used to create the gelatin as before.
Noticeable differences in gelatins were immediately apparent,
as the DTAB gelatin was covered with air filled bubbles (image
to the left).
After the gelatins were made, a secondary process was required
to make the starch aggregates. The gelatins were weighed,
finely chopped, and added to a plastic container. Cornstarch
was added into the same container at a ratio of 1:1 w/w. After a
thorough mixing, the starch-gel mixture was set out to dry
overnight, producing a similar aggregate as shown in the image
directly to the left [1]. Notice the individual aggregates were no
larger than a few millimeters in size.
In order to make a standard testing sample, the D638-10 standard
for thin polymers was replicated with an aluminum mold [2]. The
compression/explosion foam making process requires the mold
cavity to be filled with moist starch aggregate. After filling, the
mold is covered with another aluminum plate, compressed, and
heated at 230°C for approximately 20 seconds [1]. The mold is
then released and the starch-gel expands due to the change in
pressure, creating foam in the shape of a dogbone.
SEM Testing Results
DTAB Gelatin CTAB Gelatin
Dawn© Dish soap Gelatin Carbonated Water Gelatin
SEM testing was used to compare samples on the microscopic level. Pore size, fine structure,
and overall quality observed were the product of different surfactants added to samples. Gels,
manufactured packing peanuts, and cornstarch foam were all tested to provide insight towards
how the development of the gel and the later processing into foam compares to commercial
packing peanuts.
DTAB and CTAB are hydrocarbon chains of different lengths commonly used to create micelles
found in detergents. Dawn© dish soap and carbonated water were also studied for having foam-
like qualities. The hydrocarbon surfactants made the gelatin become extremely foamy upon
initial creation, but both hardened into gelatins with large pores and defects in the form of holes.
The use of dawn product and carbonated water resulted in gels of similar topographic texture
with hundreds of small beads and a few pores.
Manufactured Petroleum Packing Peanut Manufactured Cornstarch Packing Peanut
Pore Diameter = 105.0 µm Pore Diameter = 358.0 µm
Developed 10% Premoist Foam 1 [Overview (left) and Zoomed (right)]
Pore Diameter = 250.5 µm
Manufactured and commercially used packing peanuts: petroleum-based (top left) and starch-
based (top right) are shown above. While similar in structure to one another, the petroleum
peanut had a small pore diameter of 105 µm and the cornstarch peanut had a larger pore
diameter of 358 µm. Also pictured (bottom two pictures in above image) is the experimentally
developed cornstarch foam. Zooming up on the foam showed the foam had a pore diameter of
250.5 µm. The structure of Premoist Foam 1 was consistent throughout the sample, an ideal
characteristic for packing materials. The consistent structure was also seen in both store bought
peanuts.
Developed 10% Premoist Foam 2 [Overview (left) and Zoomed (right)]
Pore Diameter = 247.1 µm
Developed 10% Premoist Foam 3 [Overview (left) and Zoomed (right)]
Pore Diameter = Indiscernible
Similar pore structure was observed in the above experimentally developed pore samples, with
the only discernable pore being 247.1 µm in size. The different angle of observation for
Premoist Foams 2 and 3 form a complete topographical image of the lab made foams. The
foam structure was course with a bead-like quality at the pores.
‘
Tensile Testing Results
Preparing samples for tensile testing
The starch dogbones were created from an aluminum mold (D638-10). A CNC machine
was used to fabricate the model created in the modeling software SolidWorks. Starch
dogbones were tested under a tensile load to obtain mechanical properties needed for
literature comparison. Shown below are the aluminum mold (left) and a couple of
starch-based foam dogbones made using the mold (right).
0
10
20
30
40
50
60
0 0.02 0.04 0.06 0.08
Stre
ss (
lbf/
in^2
)
Strain (in/in)
Stress vs. Strain Sample X
Sample Y
Sample Z
Testing results from tensile testing
As resources were limited, only a subset of tests were conducted (see the
Recommendations section for more information). Shown below are the results for three
samples tested. Every sample was created from the same 10% w/w aggregate of
cornstarch and water. The surfactant dogbone failed during the molding process and
resources would not allow a second attempt. Each 10% w/w sample was distinctly
different in the amount of stiffness preserved during explosion molding. Sample X was
the stiffest and sample Y the least. Sample X was relatively brittle and did not flex under
its inherent weight. Sample Y was soft to the touch and completely flexible. Lastly,
Sample Z was able to flex but relatively firm to the touch. The difference in stiffness
was conjectured to be from the amount of time the aggregate was heated under
compression or/and the amount of moisture left in the mold cavity during the heating
process. Results from the testing conducted are shown below.
The main takeaways from the figure shown directly above were the following:
1. The length of heating and/or moisture content during the molding process directly
affects the strength and toughness of the product foam. This was expected, as
literature predicts the same [1].
2. The mechanical properties of a pure cornstarch packing peanut is NOT adequate for
packing filler. Even the lowest grade peanuts maintain above 400 lbf/in^2 tensile
strength; the max for the testing samples was 57 lbf/in^2 [3].
The next step would be to create a starch-based biodegradable polymer reinforced packing
peanut with surfactant additives for a better packing peanut (See Recommendations).
Conclusions Recommendations
Currently used packing peanuts are a hazard
to the environment; companies have not
taken the initiative to refine package filling
methods. A more benign way to protect
goods during transport is to use
biodegradable packing peanuts (BPP), since
the peanuts will eventually be absorbed as
nutrients. This experiment made progress
toward creating a BPP that was similar in
weight relative to current manufactured
peanuts. If the weight of BPPs decrease,
then companies will be more obligated to
use BPPs because weight is directly
proportional to shipping cost. Different
surfactant gels were created for this purpose
as well as starch-based dogbones for
mechanical validation. The surfactant
DTAB yielded the most notable results by
retaining air pockets after being made into
gelatin, i.e. reducing weight. Mechanical
tests proved to be feasible, but the peanuts
did not meet the basic mechanical properties
needed for industry based on tensile strength
values obtained.
The research conducted laid a foundation for
additional study. Surfactant biased
cornstarch-gels had noticeably different
physical structures apparent from SEM
testing. Each surfactant has potential to alter
the foam product created from the cornstarch
aggregate. Additional products should be
created using various amounts of the
surfactants using a constant pressure and
temperature explosion molding process.
Likewise, the explosion molding process
needs refinement. The mold used was
ineffective at maintaining the pressure
required for the molding process. An
explosion molding setup similar to the one
found in "Properties of Starch-based Foam
Formed by Explosion Processing” [1] should
be used with the D638-10 mold to obtain
values appropriate for the standard. In brief,
a more effective testing setup would be to
have the entire mold enclosed between two
heated plates placed in a hydraulic press.
References
[1] Glenn, G., and W. Orts. "Properties of Starch-based Foam Formed by Compression/explosion Processing." Industrial Crops and Products 13,
no. 2 (2001): 135-43. Accessed May 2, 2015. http://www.sciencedirect.com/science/article/pii/S0926669000000601.
[2] ASTM D638-14, Standard Test Method for Tensile Properties of Plastics, ASTM International, West Conshohocken, PA, 2014,www.astm.org
[3] Lu, D. R., C. M. Xiao, and S. J. Xu. "Starch-based completely biodegradable polymer materials." Express polymer letters 3, no. 6 (2009): 366-
375.
[4] McPortland, Joanne. "Packing Peanuts." Business.com. October 27, 2011. Accessed May 3, 2015.
http://www.business.com/packaging/packing-peanuts/.
[5] "Corn Starch Packing Peanuts." Green-Trust. Accessed May 3, 2015. http://www.green-trust.org/wordpress/.
[6] "Polymers, Solubility, and Recycling." Accessed May 3, 2015. chem-faculty.lsu.edu/Stanley/webpub/demo-3-styrofoam.pdf demo-3-
styrofoam.pdf.
[7] Park J. S., Yang J. H., Kim D. H., Lee D. H.: Degradability of expanded starch/PVA blends prepared using calcium carbonate as the expanding
inhibitor. Journal of Applied Polymer Science, 93, 911–919 (2004). DOI: 10.1002/app.20533
[8] "United Nations Framework Convention on Climate Change." Clean Development Mechanism (CDM). January 1, 2014. Accessed April 1, 2015.
http://unfccc.int/kyoto_protocol/mechanisms/clean_development_mechanism/items/2718.php.
[9] "Corn: Background." USDA ERS. January 15, 2015. Accessed April 1, 2015.
http://www.ers.usda.gov/topics/crops/corn/background.aspx.