Problem Overview
Polymers play in integral role in modern life by providing the basis for almost all plastics, films, and rubbers used today. However, nearly 100 percent of the commercial synthetic polymers used to create plastic products are fabricated from crude oil, natural gas, and petroleum [2]. Prevalent examples of such products include plastic garbage bags manufactured from polyethylene, a petroleum-based polymer. According to the New York State Energy Research and Development Authority, about 10 percent of all the crude oil and natural gas in the United States is used to develop polymers [5]. These sources for polymer synthesis are neither renewable nor environmentally sustainable. As a result, there has been an increased emphasis on finding bio-based alternatives to non-renewable polymers. Bio-based polymers would decrease reliance on non-renewable sources, lessen the negative effects of natural gas and petroleum extraction, and provide a sustainable solution to the issue of synthetic polymers.
Another issue related to synthetic polymers from
petroleum and natural gas is their inability to readily biodegrade in landfills.
It is a known fact that the earth’s landfills are steadily increasing in volume, greatly
due to the lack of biodegradable items being collected in the landfills. In
fact, the U.S. Environmental Protection Agency estimates that 21 percent of all
municipal waste in the United States is due to plastics alone [2]. One major
culprit is the plastic garbage bag. Unlike grocery bags and other materials,
garbage bags are not generally recycled and contribute significantly to landfills on
Earth. This problem may be addressed by developing biodegradable polymers for
plastic bags.
In
light of these issues related to plastic garbage bags from non-renewable sources,
a bio-based and biodegradable polymer is sought as a replacement. This project
will focus on creating a polymer film from renewable sources to replace the non-renewable
polyethylene polymer that is currently used to fabricate plastic garbage bags
based on durability, biodegradability, and cost factors.
Design Constraints
Several factors must be considered in order to
develop an effective biodegradable replacement for polyethylene
garbage bags. To design a marketable product for consumers, the polymer film must have equivalent tensile strength and durability when compared to
the original petroleum-based garbage bags. In addition to strength and
durability, the product must be able to be manufactured in a cost-effective and
timely manner, keeping the price relatively close to that of a standard
polyethylene garbage bag.
In order to produce a viable test product, issues such as
common meeting times for lab research and lack of experience with
polymers must also be considered during the overall development of the project. Consequently, the development of the garbage bag material for this
project will be limited to time constraints, available materials and equipment, and affordability.
Pre-Existing Solutions
Several solutions have been proposed to address the issue of non-renewable and non-biodegradable plastic bags. Bio-based plastic bags have already been developed using polylactic acid (PLA), a renewable polymer. PLA is a synthetic polymer that is fabricated from bio-based monomers [6]. In the process of fabricating PLA, starch is first extracted from agricultural products, such as corn. Then, the starch is converted into lactic acid by microorganisms through fermentation. The lactic acid is then treated in order to cause the lactic acid molecules to form long chains of polymers. These polymer chains bond to form PLA. PLA is durable, bio-based, and biodegradable in heat and moisture [1]. Despite the availability of the materials used to synthesize PLA, the main drawback to its use is the cost of fabrication. Therefore, PLA plastic bags would be considerably more expensive than traditional polyethylene plastic bags.
Another proposed
solution to the issue of non-biodegradable plastic garbage bags is
incorporating starch into polyethylene films used to create the bags. Starch is
a natural polymer found in plants, and it is composed of many glucose molecules
bonded together. The chemical structure of starch is shown in Figure 1 below.
As seen in the diagram, multiple hydroxyl groups of oxygen and hydrogen are
seen throughout the starch molecule [8]. The hydroxyl groups cause starch to break
down in moist conditions, allowing starch-based polymers to readily biodegrade.
This feature has been exploited to add biodegradable properties to polyethylene
films for plastic bags. For example, the company, Coloroll Ltd., has produced a
biodegradable polyethylene bag containing 7-10 percent starch [4]. While this
solution does offer a biodegradable alternative to non-renewable plastic bags,
it still utilizes mainly petroleum-based polyethylene.
In order to effectively
address the issues of polyethylene bags, this project will aim to combine these
two strategies by developing a polymer film from a combination of plant starch
and PLA. This approach may offer a cost-effective and environmentally-friendly
solution.
Figure 1: Starch
Chemical Structure
The deliverables for this project will include a bio-based and biodegradable polymer film that is suitable for plastic garbage bag manufacturing. The film will be produced using plant-based starch, PLA, and other additives necessary for fabrication. The desired qualities of the polymer film will include durability, low cost, and biodegradability. To assess the performance of the polymer in these three aspects, tensile strength and biodegradability testing will be conducted, as well as budget tracking. The results of the testing and observations will then be presented. In addition to the polymer film itself, a detailed final report and presentation will be created to include all data, findings, and results of the development process. Observations and specific findings will also be reported on a weekly basis through blog postings.
Design Goal
Currently, garbage bags are fabricated from petroleum-based polyethylene polymers, which are both non-renewable and detrimental to
the environment. The goal of this project is to design an environmentally friendly polymer film that is comparable to
polyethylene used in standard garbage bags by primarily utilizing natural, renewable polymers. This will be done by combining corn and potato starches with PLA and other additives in order to develop a durable, cost-effective, and biodegradable polymer film. As opposed to previous attempts to create plastic bags by either adding a small quantity of starch to polyethylene or utilizing only PLA, this project will focus on combining PLA and starch-based materials in order to develop a suitable and environmentally-friendly product for garbage bags.
This product will potentially provide a competitive alternative to standard polyethylene plastic bags. To keep the bio-based polymer bags competitive with current petroleum-based bags, another major design goal will be to limit the time and cost of producing the bags in order to keep the price of the product low and make it a more appealing option for consumers.
This product will potentially provide a competitive alternative to standard polyethylene plastic bags. To keep the bio-based polymer bags competitive with current petroleum-based bags, another major design goal will be to limit the time and cost of producing the bags in order to keep the price of the product low and make it a more appealing option for consumers.
Project Deliverables
The deliverables for this project will include a bio-based and biodegradable polymer film that is suitable for plastic garbage bag manufacturing. The film will be produced using plant-based starch, PLA, and other additives necessary for fabrication. The desired qualities of the polymer film will include durability, low cost, and biodegradability. To assess the performance of the polymer in these three aspects, tensile strength and biodegradability testing will be conducted, as well as budget tracking. The results of the testing and observations will then be presented. In addition to the polymer film itself, a detailed final report and presentation will be created to include all data, findings, and results of the development process. Observations and specific findings will also be reported on a weekly basis through blog postings.
Projected Schedule
The development of the bio-based plastic bag polymer film will take place over the course of ten weeks. Table 1 displays the weekly schedule for the various stages of the project. The first three weeks have been dedicated to research and thorough planning for the project. Preliminary synthesis of polymers from corn and potato starches, as well as lab equipment familiarity, will begin during
week four. The preliminary synthesis of the starch-based polymers will be used as a baseline for the
remaining polymer films created in the following weeks. The film will be tested for tensile strength and biodegradability. By week five, several different films based on PLA and food starch will be prepared for
synthesis and testing. During week six, the results of the previously synthesized polymer films will be analyzed to determine the final composition and development procedure for the polymer film. The final product will be synthesized and tested for tensile strength and biodegradability in moist environments. By week seven, the results will be compiled, and a preliminary report will be written based on findings. The preliminary report will include the compiled results
and research. During week eight, the final report will be completed with the addition of a conclusion, and the final presentation will be prepared. At the latest, all project deliverables will be completed by week nine, including preparation for the research presentation. Week ten will include presenting the project results and research, as well as submitting the final report.
Table 1: Project Schedule
Week 1
|
Initial Project Research and Idea
Proposal
|
Week 2
|
Further Project Research and
Planning
|
Week 3
|
Complete Proposal and Specific
Project Plan
|
Week 4
|
Lab Equipment Familiarity; Initial
Starch Polymer Synthesis and Testing
|
Week 5
|
Starch/PLA Polymer Development and
Testing
|
Week 6
|
Final Polymer Film Synthesis and Testing
|
Week 7
|
Results Compilation; Preliminary
Report
|
Week 8
|
Finish Report; Begin Presentation
|
Week 9
|
Prepare for Presentation; Complete
all Deliverables
|
Week 10
|
Present Findings and Submit Report
|
Projected Expense
The projected expenses for this project will include all of the materials needed for the synthesis of the bio-based polymer films. In addition to materials, other equipment will be necessary for the research and development process. The project will require corn starch, potato starch, PLA, and glycerin for the synthesis of the bio-based polymer films. The prices of each product based on local availability are displayed below in Table 2. The price of cornstarch has been placed at approximately one dollar per kilogram, and potato starch costs about three dollars per kilogram. The total cost of glycerin will come to approximately 12 dollars for one liter, and PLA resin will cost a total of about nine dollars for two kilograms. In terms of equipment, polymer fabrication and testing will require a cooking pot, heat source, silicone stirring
utensil, and tensile strength testing equipment. As indicated in Table 2, the required
amount of funds for this project should amount to no more than 40 dollars.
Table 2: Projected Expenses
Item
|
Price Per Unit
|
Quantity
|
Total Cost
|
Corn Starch
|
$1.00 per kg
|
2
|
$2.00
|
Potato Starch
|
$3.00 per kg
|
2
|
$6.00
|
Vegetable Glycerin
|
$11.89 per liter
|
1
|
$11.89
|
PLA resin
|
$4.53 per kg
|
2
|
$9.06
|
Net Cost
|
$28.95
|
