Task

Our task was to explore the topic of sustainability and seek natural alternatives to petroleum-based plastics, beginning with a thorough research into bio-materials we could produce ourselves.

Our goal

There were many different bio-materials to try out, but from the very beginning, we envisioned developing a vegan, semi-transparent, flexible, and elastic bio-material that would not tear easily and could be sewn into a wallet or a bag.

Base recipe

For our envisioned bio-material, we selected a agar-only bioplastic recipe as our foundation from the book “ICS MATERIALS, Interactive, Connected, and Smart Materials” by Valentina Ragnoli and Venere Ferraro (eds.).

The ingredients included 100 ml water, 10.0 g agar and 1.5 g glycerin.

All the ingredients were mixed together and heated up on the stove. After that, the mixture could be poured into molds and left to dry for several days.

Modifications

Our first attempt was not very satisfactory. The mixture was difficult to spread, thick, prone to breaking easily, and did not achieve the transparency we had anticipated. Thus, we embarked on our journey of improvements and modifications.

Modification 1: 100-150-200 ml water

Our first modification of the base recipe was to gradually increase the amount of water. We increased the water content twice, by 50 ml each time (from 100 ml to 150 ml to 200 ml).

First conclusion was that increasing the water made it easier to spread the material and improved its translucency. However, a new issue arose with the higher water content: the material molded quickly during air drying and tended to tear easily.

In consideration of these new problems, we began measuring the temperature of the mixture with a thermometer as it boiled to ensure it reached the desired 95 degrees Celsius. This was done to assess whether achieving this temperature would improve the texture and suppress moulding.

Additionally, we also considered reducing the thickness of the material to help the product dry faster and thereby reduce the risk of mould growing, while at the same time making the material more flexible. Another approach to increase the flexibility of the bioplastic was to raise the glycerol content.

Modification 2: Measuring and maintaining higher temperature

We implemented the use of the thermometer and from this point on, we used 200 ml of water. Additionally, we increased the glycerin content to 4.3 g. These changes made the material more translucent, and we were now able to easily pour and evenly distribute the mixture into molds.

One issue we noticed after the material was dried out was that, although it was relatively flexible, it still tore easily. Our solution to this was to add gum arabic to the mixture, as it is known to enhance flexibility (due to the properties of natural gum/rubber).

Modification 3: agar-agar + gum arabic (+ orange peels)

For the third modification, we introduced gum arabic and dried orange peels into our recipe. We added 2.5g of gum arabic, approximately 10% of the dry matter, which enhanced the material's flexibility and tear-resistance. Additionally, we decided to incorporate dried orange peel to give it a special touch – something that not only looks good, but smells nice as well. We grounded the dried orange peels with a blender and added it to the mixture after removing it from heat.

However, a new issue arose with the addition of orange peel: it caused mould to form again.

Modification 4: Preservatives (Oven/ Ethanol/ Potassium Sorbate)

Thus, we tried different ways to avoid that:

1. Spraying the material with ethanol after pouring it into the casting molds,

2. Drying the material in the oven and

3. Adding potassium sorbate to the mixture.

Ethanol effectively disinfected the surface but did not completely prevent mould buildup since it only desinfected the surface. Drying the material in the oven at 45°C prevented mould growth but resulted in shrinkage, deformation, and increased fragility. Potassium sorbate solved these problems and preserved the material without altering its properties significantly.

Initially, we added potassium sorbate directly to the heated mixture, but it did not fully dissolve. In our second attempt, we dissolved it in water before adding it to the mixture, ensuring it integrated completely. This modification successfully prevented mould growth during drying.

Modification 5: hardwood fibers

In this series of tests, we gradually increased the length of the fibers, starting with 60 μm hardwood fibers, then 200 μm, and finally, 700 μm. The goal was to enhance the tear-resistance of our material.

As a result, the material became thicker and slightly cloudy (opaque) but remained easy to spread. After drying, we noticed that the material containing 700 μm fibers was the most translucent among the three variations. This transparency was crucial for our requirements, so we continued using the 700 μm fibers.

We also tried reducing the amount of fibers to create a material with higher resistance and less

opaque.

Modification 7: hydrophobic impregnation

Lastly, our material was not waterproof, prompting us to explore impregnation as a solution, given that the material tended to tear more easily when wet.

We attempted an impregnation using dammar resin. However, this caused the bioplastic to become cloudy and left streaks behind. Despite diluting the mixture with more ethanol and applying multiple layers, the issues persisted. Upon drying, we observed that the impregnation started to crumble off, particularly when exposed to moisture.

Ultimately, we decided against using the impregnation as our goal was to use the bioplastic for sewing a wallet. The chances of a wallet getting soaking wet are very low, which is why we went with the visually more appealing option of leaving it without impregnation.

Sewing a wallet

Since we wanted to sew our bioplastic into a small wallet we also tested some stitches.

We encountered that wetting the parts we wanted to sew made it easier for the needle go through and also prevented it from breaking. We chose to use a whip stitch since it appeared to be more durable. During our first trial we had sewn the edges of a bioplastic sheet together like an envelope and tried to use a button. Using a button was hard since it caused the material to ripp. To ensure easier access we decided to add a zipper and sew two sheets together to create a larger purse. To attach the zipper we used a normal running stitch because with a whip stitch the sewing thread might have obstructed the zipper.

Conclusion

In the end, we successfully developed our envisioned vegan, semi-transparent, flexible, and elastic bio-material that met our criteria of being tear-resistant and suitable for sewing and holding light to medium-heavy objects. Despite encountering numerous challenges along the way, each obstacle provided us with valuable lessons and insights that enhanced our understanding of bio-materials and their applications.