Week Three: Initial Polymer Synthesis

Week 3 marked the beginning of starch and PLA polymer film synthesis. One film was made using 15 mL of corn starch, 5 mL of glycerin, 60 mL of water, and 5 mL vinegar. These ingredients were heated in a beaker on top of a burner and constantly mixed until the mixture came to a clear gel-like consistency. This process took approximately 30 minutes. The polymer mixture was then spread out onto an aluminum sheet to dry for about 48 hours. Pictures from experimental bio-plastic made from starch, glycerin, vinegar, and water are shown below. The resulting dry polymer film was fairly rigid, which was undesirable. A decision was made to conduct another trial with a larger proportion of glycerin in order to increase the pliability of the film.

Starch Films
Trial	Starch Volume (mL)	Glycerin Volume (mL)	Vinegar Volume (mL)	Water Volume (mL)
1	15	5	5	60
2	7	3	2.5	30

In addition to the synthesis of starch-based polymer films, a PLA film was also synthesized in order to use as a control group for future composite films. The method of synthesizing the PLA films involved completely dissolving the PLA in chloroform and then allowing the chloroform to dry off in a petri dish and reveal a thin PLA film. First, the thickness of the film was chosen to be 0.05 mm, based on research of the thickness of commercial garbage bags. To calculate the amount of PLA necessary to form a 0.05 mm film, the surface area of the petri dish was measured and multiplied by the desired film thickness to obtain the necessary volume of PLA. The calculated volume was 0.3619 mL. Then, the density of PLA, 1.24 g/mL, was used to determine the required mass of PLA, which was 0.44885 g. A solution of 3% PLA to 97% chloroform by mass was favorable in order to create the films, so 14.96 g of chloroform was the proper quantity. This value for mass was converted to 10.11 mL using the density of chloroform, which was 1.48 g/mL.

After calculating and measuring out the materials, the PLA and chloroform were thoroughly mixed for about 30 minutes using a magnetic stir bar. The resulting solution was poured into a petri dish in order to dry for 3 days. Then, the petri dish with the film was placed in an oven at 60 degrees Celsius for 24 hours. The final dried PLA film was then delicately extracted from the dish using tweezers.

Starch Polymer Film Synthesis:

 

Starch, Water, Glycerin, and Vinegar mixed and heated in a beaker on a hot plate

Starch Polymer Mixture Spread on Aluminum Foil

Resulting Starch Film on Aluminum Foil

Week Two: Design Proposal

In week two, the previous idea of using strictly starch-based polymers for the garbage bag polymer film was reconsidered. A decision was made to develop a composite material made of PLA and food starch for a more durable product. This would result in a stronger bag, and the combination of the two materials would help to alleviate several issues of concern, such as the lack of durability of starch polymers and high cost of PLA alone. Going into week three, a reasonable time table was developed, and the specific materials necessary to further pursue the project were considered. A design proposal was developed based on previous research and detailed project plans.

Below is a link to the Design Proposal for the project:

Design Proposal

Week One: Polymer Research

Most synthetic polymers today are created using petroleum, a non-renewable resource. The objective of this project will be to create a polymer from renewable resources that may replace petroleum-based polymers in function and application. Week one was dedicated to researching bio-based and natural polymers fabricated using renewable resources in order to gain a general understanding of the topic. After compiling information from a variety of sources, a presentation was prepared that highlighted findings. Research was also used to narrow down specific possibilities for the renewable polymers to be fabricated in the project.

After consulting several sources, the focus for the project was placed on plastic garbage bags. Renewable alternatives were sought for polyethylene, a non-renewable polymer that is currently used to produce plastic bags. The desired qualities and characteristics for the polymer films used to synthesize plastic bags included durability, limited flexibility, and biodegradability. Several environmentally friendly solutions were investigated, including the use of starch, polyhydroxylakanoate (PHA), and polylactide (PLA). Both starch and PLA exhibited biodegradable properties, and PHA appeared to be one of the most durable polymers. After investigating the general uses of bio-based polymers and their applications in commercial products, such as plastic bags, a presentation was prepared to communicate the research with classmates and the adviser, Dr. Palmese. The presentation slides are displayed below.

Presentation Slides: