Bioplastic testing – Day one

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Conor Buckley started our bioplastic journey to develop an art material for use in the Trinity Trees Project by explaining about the cellular make up of the different base materials we would be using. This was a great help for me to understand how the material would act and react depending on what you added to it.

We stared by talking about how one would make a starch based bioplastic.

Starch bioplastic: the recipe:

9.95grams of corn starch

60ml distilled water

5ml Acetic acid (vinegar) 5% solution

5ml glycerol (a light sensitive animal fat)

Cornstarch is a complex carbohydrate called a polysaccharide. It has a polymer chain with branches. When we add vinegar to the starch and water solution it cleaves the branches from the polymer chain separating them into whats called an amalose mix i.e. the starch and vinegar solubalise in water. When you add glycerol (the plasticiser), which is like an oil, it allows the chains to slide over each other. The stiffness or flexibility of the final product depends on the amount of glycerol we add to it. The more glycerol the more plasticised it becomes.

Starch bioplastic: the method:

Add water and corn starch to a graduated beaker. Add vinegar to create amalose. Add glycerol to plasticise. Put the beaker with all the ingredients over the heat and gradually increase the temperature from 100 to 140 and up to 160 degrees over about 10-15 minutes all the time stirring the mixture.

When the mixture changes from opaque to clear it is the time to scoop it out and spread it out on the chosen dish to dry. In our case we used petri dishes. Then the dish was placed in an oven set at 65 degrees to dry. For this starch how you dry it is important. If you leave it on bench to dry over a long period of time the top layer will dry faster and form a skin. Drying in the oven in @65 would allow for the material to dry more evenly.

Conor and I were delighted with the result, which was much more opaque than the samples I had created the year before. As most of last years samples ended up white in colour when I tried to add colour I ended up with varying shades of pastel colours. I had also tried many different ways of adding colour to this bioplastic. But now thanks to Conor’s knowledge I realise that what I thought was a good idea, adding acrylic (plastic based) paint to the mix, was in fact reacting with the cellular chains and making the material more brittle.

On the down side this and last years cornstarch bioplastics were very thick, lumpy and hard to spread evenly. If I were to use it to cover elements of my sculptures we would have to spread it when it was at its most liquid form when it was really hot and sticky As it looses heat quite quickly cools and becomes more unworkable it would be a tall order to use it as a material. A really fantastic matieral but unfortunately not one that I could use.

Two handy pieces of information that Conor imparted to me that I thought useful to share are:

1. When you are trying to optimise the mechanical properties of a material change one thing at a time. You don’t change the base amount of starch, water and vinegar components only the glycerol.

2. If you want to colour a bioplastic materials it is best to use three drops of food colouring and only after all the ingredients have been solubalised. If you add the colour earlier you might not be able to see the point at which the material changes from opaque to clear indicating that it is ready to use.

The second type of bioplastic we said we would explore was an Agar based one. 

Agar is a generic term for seaweed and alginate is a made by processing a type of seaweed. The algae base material that we are using is called agarose. This is a thermoreversable material i.e. it melts in water when you heat it up, sets when cool and can be reheated to liquid form again. It is important to note that the more times one heats and cools the material the weaker the material becomes. Conor explained what happens when the agarose is heated up in water. As it is made of nano scale helical shaped chains, they unravel when heated and straighten out and then return to the helical shape when they cool down.

In our initial experiment we just used the pure agarose.

Agar bioplastic: recipe 1:

agarose

1.5 grams agar

50 ml of water

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Agar bioplastic: recipe 2: agarose and glycerol version

1.5 grams agar

50ml of distilled water

4ml of glycerol

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Agar bioplastic: the method:

Measure out the 1.5 grams of agarose. Boil distilled water. Add agarose. Stir continuously over heat for 10-15 minutes until all the agarose strands have disappeared. Pour solubalised agrose into petri dish and leave to set. If glycerol is to be added do this after the agar has solubalised and before pouring into the petri dish.

Interestingly after describing what I was looking for from a bioplastic Conor suggested that by using a paint brush when this material was hot we could paint the bioplastic onto the fabric, which would then set and dry over time.

I also wondered if this material would be flexible enough to be able to move with the fabrics i use or would it be too brittle and tear. Conor decided to try and add some gylcerol to the mixture to act like a plastisier. He decided to start off with 2ml of glycerol, which we added to the solubalised mix. We planned to leave it over night to dry to see how that would look and work.

Another really interesting idea that Conor suggested on this first day is that he wanted to try adding bubbles to the mix. By adding bubbles to the recipe without glycerol he hoped to add an extra element of flexibility. So I was asked to bring in some alka selser for our next batch of experiments.

Bioplastics

 

bioplastic ingredients 3 lo res

During my recent mind mapping sessions in the studio I was reminded of some experimentation I completed about a year ago on bioplastics. I didn’t delve too deeply into the subject at the time but did try out a few recipes.

The reason I started thinking about bioplastics is that I am conscious for this project that I will be creating works of art that will be installed in living trees. That these trees are part of a cycle of life and decay, constantly changing and adapting to their surroundings, is something that I would like to engage with to a greater or lesser extent in my choice of what materials to use in creating the works of art.

In an ideal world one wouldn’t install man made plastic, perspex or lycra based fabrics in the trees but these are the materials I commonly use in my practice because of their vibrance of colour and glossy qualities. I am sure some of the Bioplastic options that I investigate will lead me to creating some interesting pieces for this project but I still think that the qualities of my core materials will be necessary to fulfill the artistic goals of the project.

With this in mind I have decided to explore the world of bioplastics again but in a more in depth way. After visiting the really informative site called green-plastics.net I got a few recipes to start with and set off on an unusual shopping spree. One of the hardest things was to try and find some of the ingredients they mentioned. Instead of Agar powder I ended up with dried Agar. On the plus side I found red and green coloured dried Agar options as well as the clear one. I thought I had the glycerol/ glycerine situation under control when I bought a little bottle by Dr. Otker (the only brand available in any shop I tried) but despite an internet search I couldn’t figure out what percentage glycerine was in the mixture. Currently I am assuming that it 100% as is seems quite viscous but if this isn’t the case then I am in the dark regarding how much to use. It might end up being a bit of a case of trial and error. The next dilemma was the common one of Corn starch v’s Corn flour. Most internet searches say that they are both the same. Where corn flour is readily available in most stores corn starch is much harder to find. In actual fact I have been told that corn starch is more glutenous and the resultant plastic is more transparent than the corn starch, which is whiter. So I eventually found some corn starch in my small local Asian store (where I also found the Agar). Finally some recepies mention sorbitol, which is a type of sugar. After visiting a few supermarkets and health food stores I came away empty handed. It is available to order from home brew websites and I will endeavor to find some locally in the next week or so. In the meantime I will try the recipes where I have the ‘correct’ ingredients.

bioplastic ingredients lo res

On the plus side the selection of ingredients that I did manage to acquire did go together to make a lovely colourful image – see above.

At this point I think it’s important to know that like all other plastics, bioplastics are composed of three basic parts: one or more polymers, one or more plasticizers, plus one or more additives. Roughly speaking: polymers give plastic its strength, plasticizers give it its bendable and moldable qualities, and additives give it other properties (color, durability, etc). This information helps when the recipes online get a little complicated. It also helps when troubleshooting if the results seem too sticky (less plasticiser) or too brittle (more Plasticiser).

The three types of bioplastics that I will look at are the Starch-based, Gelatin-based and Agar-based plastics. Starch, Gelatin and Agar are all biopolymers. Most of the recipes I plan to try will use glycerine/ glycerol for the plasticiser.

Starch-based plastic:

Corn starch is the starch derived from the corn (maize) grain or wheat. The starch is obtained from the endosperm of the kernel. Corn starch is a popular food ingredient used in thickening sauces or soups, and is used in making corn syrup and other sugars.

Gelatin-based plastic:

Gelatin or gelatin is a translucent, colorless, brittle, flavorless food derived from collagen obtained from various animal body parts. It is commonly used as a gelling agent in food, pharmaceutical drugs, vitamin capsules, photography and cosmetic manufacturing. It is found in most jelly candy, as well as other products such as marshmallows, gelatin desserts, and some ice creams, dips and yogurts. Gelatin for recipe use comes in the form of sheets, granules, or powder. Instant types can be added to the food as they are; others need to be soaked in water beforehand.

Gelatin is actually easier to work with than starch and will produce some nice, strong pieces of solid plastic.

Agar-based plastic:

You can make your own bioplastic from algae. The specific chemical that we are interested in is agar, which appears in red seaweed in abundance. Agar is used as a food additive in confectionaries, desserts, beverages, ice cream and health foods. It’s also used as a non-food additive in toothpaste, cosmetics, and adhesives.

There are numerous combinations and a huge range of recipes available online that one can try. For examples each of the following combinations will produce slightly different plastics with different properties. The only way to find out how they all look, perform and last over time is to really get stuck into following the recipes and see what excites me!!

I will post some of the resulting images in a later post.

Agar Only

3 g (1 tsp) agar

240 ml (1 cup) of 1% glycerol solution
180 ml (3/4 cup) water

Agar-Starch Blend

1.5 g (1/2 tsp) sorbitol
3.0 g (1 tsp) starch
300 ml (1 1/4 cup) water
0.75 g (1/2 tsp) agar
120 ml (1/2 cup) of 1% glycerol solution

Gelatin-Agar Blend

 

2.25 g (3/4 cup) sorbitol
2.25 g (3/4 cup) gelatin
2.25 g (3/4 cup) agar
180 ml (3/4 cup) of 1% glycerol solution
240 ml (1 cup) water

Of Interest:

Anyone interested in this subject might like to purchase the following book by E.S. Stevens. Green Plastics, an Introduction to the New Science of Biodegradable Plastics.

The book offers a wide variety of recipes and step-by-step instructions on making bioplastics with different properties, ranging from hard inflexible plastics to thin flexible sheets and laminates. In addition, the book carefully explains the theory behind bioplastics, with in-depth discussions of chemistry concepts as well as environmental concepts related to biodegradability and renewability.