Under normal circumstances, a fabric made from cotton is very flammable. However, scientists have developed a new method for making cotton much more fire resistant using the DNA from herring sperm. This was discovered in Italy at the Polytechnic University of Turin where the preliminary tests were run. So far, the results look promising.
How it Works
To create the flame-resistant substance, the researchers followed a very straightforward process. This is how they did it:
Extraction – Extract the DNA from a herring sperm.
Dissolution – Dissolve the DNA in water.
Application – Apply the DNA to cotton fabric.
Drying – Let the fabric dry.
Once the coating had been applied, the team attempted to burn the fabric with a methane torch. Not only would the fabric not ignite, but it would also not allow the flame to spread. This was in direct contrast to the control sample of cotton fabric that did burn from the methane torch.
Why it Works
Herring sperm DNA works as a flame retardant for several reasons. First of all, phosphoric acid is created by the phosphate that’s given off when the material is heated. This causes water to be pulled from the cotton which in turn leaves a strong carbon substance behind. This carbon substance is incredibly resistant to burning and protects the fabric from heat.
A secondary process involving nitrogen is also at play. This is because the nitrogen found in the herring sperm DNA will dilute flammable gasses by releasing ammonia. This, along with the phosphoric acid, creates a foam that leaves behind a glassy coating rich in flame-resistant carbon.
Video Proof
To show this process, the research team simultaneously put a methane torch on regular cotton fabric and cotton fabric that had been treated with the herring sperm DNA flame retardant. In the video, the regular cotton fabric was slowly consumed by the flames after being exposed to the torch. On the other hand, the fabric treated with the DNA experienced only a small area of blackening where the flame was applied, then refused to burn or allow the flame to spread. All subsequent attempts to burn the fabric failed.
Challenges
While using herring sperm DNA as a flame retardant does look promising, there are a few challenges that the team will have to overcome before this is a reality. For one thing, they will have to find a way to ensure that the DNA that is applied to fabrics will not make its way into the human body. This could be problematic for the person wearing the material.
The cost is also a factor that is being looked at. Using current methods, the application of herring sperm DNA as a flame retardant is up to five times more costly than current ways of doing it. This could make fabrics treated in this way prohibitively expensive.
Perhaps the biggest issue that this new flame retardant is facing is the fact that it won’t survive washing. This is because the substance is highly biodegradable. While this is good from a sustainability perspective, it isn’t practical when used in materials that must be washed.
Science Facts
Below are a few science facts taken from the research team’s abstract.
1. Herring sperm DNA increases the flame retardant properties and thermal stability of the cotton fabric.
2. DNA contains the three components necessary for intumescent formulation. These are:
- phosphates
- deoxyribose units
- nitrogen-containing bases
The phosphates produce phosphoric acid, while the deoxyribose units are blowing agents and carbon sources. This means that upon heating water is released and char is formed. The nitrogen bases consist of cytosine, adenine, guanine, and thymine. These substances release ammonia when heated.
3. Cotton fabric treated with the herring sperm DNA flame retardant would not burn after a three-second application of the methane torch.
4. Further exposure to an irradiative 35 kW m−2 heat flux produced no ignition.
5. Untreated fabrics carry an LOI value of 18%. Fabrics treated with the herring sperm DNA flame retardant achieved an LOI of 28%.
