Jins_Final_Report

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.