Bioplastics Investigation: Fork It Over!
Introduction:
There are many types of plastic used in our everyday life. The source, type and chemical composition
of plastic determines the size of its carbon footprint (total amount of greenhouse gasses produced in
its manufacture, use and breakdown). The majority of plastic used today comes from petroleum, or
crude oil, a type of nonrenewable fossil fuel. Some types of plastic are hydro-degradable (broken
down by water) or photodegradable (broken down by sunlight). However, most plastic ends up in
landfills and stays there indefinitely because it is not biodegradable (broken down by bacteria and
fungi). One of the great challenges of the modern era is to develop inexpensive, durable and
biodegradable plastic made from renewable sources.
In this investigation and our final project, we will engage in the engineering design process to create,
test, evaluate and improve a bioplastic fork made from an animal, alga or plant source. In doing so, we
can learn about the composition of plastic and how it's made as well as the difference between
degradable, biodegradable and compostable plastic and their environmental impact.
Guiding Questions: How is plastic made? What chemical chemical reactions are involved in making
plastic? What makes material degradable, biodegradable or compostable? Which type of material
would have the least impact on the environment?
Tasks:
1. Understand the chemical processes in which plastics are made.
2. Engage in the engineering design and testing process to develop and improve a viable product.
Hypothesis: What source of material, animal, algae or plant-based, do you think produces the most
durable plastic product? Which source of material do you think would biodegrade the fastest and have
the least environmental impact? Explain your reasoning!
Pre-lab: With your lab group, read the handout “Plastic: An Overview” and answer the following
questions:
1. What are polymers? What is polymerization (the process in which plastics are made)?
2. What is the problem with plastic production now? What makes most plastic difficult to degrade?
3. What are the differences between degradable, biodegradable and compostable plastic?
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Bioplastics Investigation: Fork It Over!
Task: Develop fork handle molds out of aluminum foil, create different types of bioplastic to pour into
your molds, and then test the materials’ strength and flexibility.
Materials:
Aluminum foil
Unflavored gelatin
Glycerin
Dropper
Non-stick spray
Corn starch
Heat-resistant bowl
Stirrer
Water
Agar
Graduated cylinder
Procedures:
Part 1: Building the Molds
1. Create three molds in the shape of a fork handle for each substrate type using aluminum foil.
Make three molds for each plastic substrate (organic material that is composed of polymers and
can be molded when soft and then into a certain shape). Molds can be simple but should be the
same size and shape to test and evaluate the characteristics of the different types of bioplastic.
The molds should be designed so they won’t leak as the plastic dries and sets.
2. Label the outside of each mold with a Sharpie marker to keep track of the substrate samples.
3. Spray the molds with non-stick spray before pouring the bioplastic.
Part 2: Making the Bioplastics
Source Type
Substrate
Substrate Amount
Water
Glycerin (Plasticizer)
Animal
Gelatin
12g (3 tsp.)
50mL
5 drops
Algae
Agar
3g (1 tsp.)
50mL
2.5 drops
Plant
Cornstarch
9g (2 tsp.)
50mL
5 drops
1. For each of the three source types, mix tap water, substrate and glycerin (plasticizer) in a heat
resistant bowl using the proportions in the chart. Stir each cup thoroughly until there are no
clumps.
2. Heat each mixture separately in a microwave until it begins to froth, usually less than a minute. To
prevent boiling over, carefully watch the mixture through the microwave window. Stir after heating.
3. Pour each mixture type into three molds. Try to pour the plastic to the same thickness in each
mold (about 0.5 - 0.75 cm).
4. Allow the mixture to dry in a warm place, such as the top of a refrigerator, a food dehydrator or an
oven set to 150° F. This can take three to five days.
5. Test and record the materials’ characteristics listed in the data chart on the next page after the
forks are completely dry. Record your results.
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Bioplastics Investigation: Fork It Over!
Part 3: Testing the Bioplastics
Characteristic
Initial Observations
Corn Starch
Agar
Gelatin
Color & Opacity:
Can you see light through
the material?
Flexibility:
Rate 1 = cracks easily; 2 =
stiff; 3 = somewhat flexible; 4
= very flexible
Freezing:
To simulate winter condition,
freeze a sample then rate
flexibility
Heat:
To simulate summer
conditions, heat samples up
to 120° under a lamp or in
an oven. Rate for flexibility.
Stain Resistance:
Place a drop of coffee or
mustard on the plastic. Does
it stain when you try to wipe
it off? Y or N
Tensile Strength:
Tape pennies, one at a time
on to the end of the samples.
Hold sample by one end.
How many pennies can you
tape on before it breaks?
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Bioplastics Investigation: Fork It Over!
Analysis Questions:
1. What is the purpose of the substrate? The purpose of the plasticizer? The purpose of the
non-stick spray?
2. If you were to change the amount of the substrate or plasticizer, how do you think that would
affect your product?
3. Explain the role of chemical reaction, polymerization, in making the bioplastics.
4. Research the different types of chemical bonding structures in different kinds of biodegradable
and non-biodegradable plastic. How is their chemical bonding similar and different?
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Polyethylene bonds (non-biodegradable)
Polyvinyl chloride bonds (non-biodegradable)
Polyester bonds (non-biodegradable)
Gelatin bonds (biodegradable)
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Starch bonds (biodegradable)
Agar bonds (biodegradable)
Casein bonds (biodegradable)
Cellulose bonds (biodegradable)
5. What type of elements are involved in non-degradable plastic vs biodegradable plastic?
6. Based on the initial experiment results, which substrate do you think provides the best strength for
a fork handle? Explain your reasoning.
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Bioplastics Investigation: Fork It Over!
7. Would you recommend making fork handles out of the bioplastic you designed? What would be the
advantages and disadvantages?
8. Why are some types of the bioplastic flexible and others brittle? How do you think chemical
bonding influences their flexibility?
9. What type of chemical bonding are microbes able to degrade? What type of degradation would be
ideal for plastic bottles? For plastic utensils?
10. If you were to redo the experiment, what would you change to improve the bioplastic? What other
materials or substrates could you use to produce bioplastics that you could test?
11. What is the difference between biodegradable plastic and bioplastic?
12. If we were to address the problem of reducing greenhouse gas emissions into the atmosphere,
should plastic be biodegradable? Why or why not?
13. How could you test the bioplastic to see which would have the least environmental impact?
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