Materials Processes | Sodium Alginate & CMC¶

Two materials have been used to create the inflatables and ultimately, the installation. The first being Sodium Alginate and the second being CMC.

Material Experimentation¶

To begin to tackle the effect of the installation, I began with testing different materials to see which is the most suitable for the 'object'.

Date Leather + Gelatine + Glycerine¶

In this process, I boiled the dates and separated them from the pits. I then mixed in the gelatine as normal with the glycerine.

Date Leather + Guar Gum¶

Alginate Trials¶

Sodium Alginate¶

“The sodium salt from alginic acid and gum is mainly extracted from the cell walls of brown algae. Brown seaweeds are usually large, and range from the giant kelp that is often 20m long, to thick, leather-like seaweeds from 2 - 4m long, to smaller species 30 - 60cm long.” (Material Archive TextileLab Amsterdam)

Properties:

Hydrophilic (strong affinity for water)
Thickening agent (ability to increase viscosity)
Gelling agent (forms strong elastic gels)
Film-forming (can form thin flexible films, protects from moisture)
Biocompatible + Biodegradable (safe for human consumption)
pH stability (stable over wide range of pH levels)
Compatibility with other ingredients (can be combined with other ingredients without significant adverse effects on its functionality)
Emulsifying properties (can stabilize emulsions by preventing separation of oil and water phases)

Sodium alginate was the perfect choice for this project for its gelling properties. Its affinity for water then drove the exhibition design process.

In addition, Glycerol has been added in the recipes. Glycerol is a natural compound derived from vegetable oils or animal fats. It’s a clear, colorless, odorless, and syrupy liquid with a sweet taste.

The benefits of adding glycerine in bio-based polymers are:

Viscosity modification
Moisture retention
Prevention of drying and cracking
Reduced brittleness
Enhanced stability

Glycerol as plasticizer serves to reduce the stiffness and improve the flexibility of the plastics through both functions increasing the mobility of the polymer bonding and improving the water holding capacity (De Roza et al. 2012). The experiment found that the water content is increasing linearly with glycerol addition in the mixture. As water content is directly proportional to glycerol, higher concentration of glycerol results in more flexible film.

Recipe:

The recipe used for the alginate at this point is:

1L water
25g sodium alginate
100ml glycerine

with a cation solution of:

200ml water
15g calcium chloride

Technique to be used found by Gabriela Lotaif¶

Through my research on creating biobots, I found Gabriela's documentation where she clearly outlined the technique of creating a 'shell' using the alginate.

The technique is now working very well. I purchased aquarium accessories to place inside the hole made and seal it to the alginate to eliminate the previous issue of the leaks.

I found a sealing method using gelatine which was to heat gelatine and water in a hot bath until it becomes viscous and sticky. However, due to the context of my project, I was adamant on not using gelatine.

Working with this technique I found an updated alternate method that helped create stronger bonds in the outer layers, thicker outer layers, and less leaks. The technique included updating the whole process from prepping the alginate to drying and inflating it.

New recipe:

1L water
20g sodium alginate
60>x<100 glycerine

with the same calcium chloride solution

Making the Mixture:

Mix the water with the alginate in a pot on a heated water bath on the stove. Let it simmer but do not bring to a boil.
Mix very slowly with a spatula as if folding dough. It takes around 30-45 minutes to fully dissolve in the water without creating too many bubbles.
When the algiante fully dissolves, add the glycerin and continue mixing softly.
Pour into a container and let sit until the bubbles are gone.
Pour into the calcium chloride sprayed mold/frame.

Mixing the alginate on a hot water bath decreases the amount of bubbles, allow for the bubbles to rise and exit the solution quickly, and makes stronger bonds within the alginate. These stronger bonds allow for a thicker shell layer with less leaking or breakage.

Inflating Technique:

Spray calcium chloride generously on the frame or mold to be poured in.
Once the alginate no longer has bubbles, pour it into the mold.
Let the alginate sit comfortably and spread out well before spraying the top with calcium chloride.
Let it gellify for some time. When pinching it softly, you should begin to feel two thick layers with a gap in the middle.
Poke a hole and place the aquarium piece and tube inside.
Press gently to push the alginate towards the created hole. Some alginate will pour out, that is what we want! Once the alginate has coated the tube and the hole, spray it with calcium chloride.
Let it sit until it gellifies again.
Inflate the alginate with minimal movement to the tube and hole.
Pour calcium chloride into the pipe and let it flow around the whole alginate piece.
Keep moving the solution inside around and inflating the piece to ensure it gellifies without sticking to one another.

The bottom layer is going to be thicker than the top layer. This effect is desirable in my case to allow for it to sink in the water when it is deflated.

CMC¶

CMC cellulose, or carboxymethyl cellulose, is a versatile compound derived from cellulose, a natural polymer found in plant cell walls. CMC cellulose is produced by chemically modifying cellulose through carboxymethylation, which involves adding carboxymethyl groups to the cellulose molecule. This modification enhances the water solubility and thickening properties of cellulose, making CMC cellulose useful in a wide range of applications. It is commonly used as a thickening agent, stabilizer, and emulsifier in food products, pharmaceuticals, cosmetics, and various industrial applications. Additionally, CMC cellulose is often employed in the production of paper, textiles, and adhesives due to its ability to improve strength, viscosity, and binding properties.

Properties:

Water solubility (highly soluble)
Thickening agent (ability to increase viscosity)
Stabilizer and emulsifier (can stabilize emulsions by preventing separation of oil and water phases)
Film-formin (can form thin flexible films, protects from moisture)
Binder and adhesive (used as a binder in a variety of applications and improves adhesion and strength of mateirlas)
Suspension agent (ensures uniform distribution of active ingredients and enhances stability of the formulation)
Moisture retention (has the ability to absorb and retain water)

Due to its adhesion qualities, CMC cellulose allows for the creation of bio-bots with any shape and allows for sealing of any air leaks.

Recipe:

100ml water
30g CMC solution
35g glycerine
20g cornstarch
5ml vinegar

CMC Solution:

100ml water
3g CMC powder

Technique:

Mix the water, vinegar, and glycerine very well.
Once mixed, add the CMC solution and mix again.
Add the cornstarch last and mix. Make sure to dissolve all the clumps and powder.
Place in a pump on the stove top and mix continuously. After a while it will begin to thicken and become viscous.
Once it begins to boil, remove off heat.
Pour onto baking paper and shape. Use a frame if available.
Make sure to add a thick layer and that it is level in thickness to avoid cracking. It will shrink once dry.
Place in the oven for 24 hours on 50 degrees celsius.

Once it is dry, make the same recipe again and use it to glue all the edges of the two parts together and place it back into the oven. Place the tube inside while gluing around it very well. Any cracks can also be sealed with the same mixture.

The CMC does not stretch but is quite flexible and allows for the air to fill up the gap created in the middle. It also is a great material to use if layering and specific shapes are needed.