New Coatings Catch: Fire-Retardant Fish
Italian researchers see a new bio-based future for flame-retardant coatings in a novel source: DNA extracted from the sperm of herring.
This is the first attempt to use DNA for the flame retardancy of a polymeric material, the researchers believe.
The researchers are investigating the flame retardancy of cotton fabrics treated with DNA from herring sperm. They are reporting a viable, environmentally friendly alternative to the potentially harmful flame-retardant chemicals now in widespread use.
Novel and Green
The research is the subject of a forthcoming article in the Journal of Materials Chemistry A.
"DNA: A novel, green, natural flame retardant and suppresant for cotton" was researched and written by Jenny Alongi, Riccardo Andrea Carletto, Alessandro Di Blasio, Federico Carosio, Francesca Bosco, and Giulio Malucelli, of the Department of Applied Science and Technology at the Politecnico di Torino, a public research university in Italy.
|Photos: Alongi, J., et al|
Researchers in Italy have found that DNA derived from herring sperm has the desired properties for a flame retardant coating. Shown here: treated and untreated sections of a cotton specimen after a horizontal flame test.
For decades, industrial and academic researchers have sought chemicals able to prevent the combustion of polymers, or at least delay the spread of fire after ignition, the authors said.
The most widely used flame retardants are made from halogen-based compounds, which the researchers state "have been proven to be persistent, bioaccumulative, and/or environmentally toxic for animals and humans."
A possible alternative to traditional flame retardants, or those usually containing nitrogen and phosphorus, could be found in biomacromolecules like proteins and nucleic acids.
Now the team has found that the complex double helix of deoxyribonucleic acid (DNA) "represents a potential and intrinsically intumescent flame retardant system."
Intumescent Material Properties
The paper explains that intumescent materials react in three ways when exposed to fire.
First, the material develops a multicellular carbonaceous shield on its surface (often called char) after being subjected to heat. This acts as a physical barrier to limit the transfer of heat, fuel and oxygen between the flame and the polymer.
Next, the material's sources of acid (such as ammonium phosphates) and a carbon source add to the char.
Last, a blowing agent, when heated, releases expandable or non-combustible gases such as water vapor, ammonia or carbon dioxide.
DNA already contains all three components of an intumescent material in a single molecule: the phosphate group, deoxyribose units that act as a carbon source and blowing agents, and nitrogen-containing bases that may release ammonia.
Testing the Theory
After purchasing DNA powder from herring sperm (unfortunately, the researchers do not disclose how herring sperm is harvested to begin with), the team slowly dissolved the material in acidified distilled water under magnetic storing before applying it to cotton fabrics.
SEM micrographs of untreated samples are shown in A and B; DNA-treated samples are shown in C and D. All samples were subjected to horizontal and vertical flame tests, after which the DNA-treated samples did not ignite.
The coated cotton samples were then exposed to both three horizontal and three vertical flamability tests by applying a methane flame to the cotton for three seconds.
Untreated specimens were completely burned within 80 seconds, but the DNA-treated cotton extinguished its flame in about two seconds. Not only that, but after the flame went out, it was impossible to ignite the specimen again, the researchers found.
Additionally, the texture of the cotton was maintained.
"These findings clearly indicate that the DNA coating can be considered an effective flame retardant system," the authors conclude.
Unfortunately, the new material has one major drawback: The DNA coating comes off when the material is washed.
Testing will continue.