NIST Shells Out Greener Fire Retardant
Clay, crab shells and DNA are the unlikely key ingredients in a promising nontoxic flame retardant being developed by federal researchers.
The National Institute of Standards and Technology (NIST) has unveiled technology that uses these materials in a bio-based coating that can be applied to polyurethane foam to dramatically reduce flammability.
When the coatings were tested on common furniture padding exposed to an open flame, peak and average heat release rates were reduced by 48 percent and 77 percent, respectively, NIST said in a research announcement.
“This is the biggest reduction in flammability that we have achieved to date,” team leader Rick Davis said in the release.
The product was assembled in a layer-by-layer process. Davis says the coatings outperform other experimental retardants but require stacks of about 20 layers (rather than six or seven) to do so.
The NIST team tested the three ingredients in four ways, and with stacks up to 30 layers. The winner: a combination of 10 repeating bilayers of chitosan (crustacean shell) topped by a mixture of DNA and montmorillonite (clay).
That recipe provided both the highest level of fire protection and “is likely to be easier, faster, and less expensive to fabricate” than the other combinations, the team said. However, the coating also increased the weight of the foam by 16 percent.
Healthcare management giant Kaiser Permanente is among the organizations that is seeking safer flame retardants for polyurethane-padded furniture.
A lighter alternative provided slightly less fire protection. However, “both recipes are great candidates” for environmentally benign fire-retardant coatings, the team said.
Ongoing research aims to simplify processing, enhance effectiveness, and test strategies to ensure durability, said the team.
The researchers have published their findings, "DNA-based nanocomposite biocoatings for fire-retarding polyurethane foam," in the journal Green Materials.
The new technology comes on the heels of Kaiser Permanente’s decision to phase out the use of upholstered furniture treated with flame retardants. The Oakland, CA-based nonprofit spends roughly $30 million a year furnishing its hundreds of hospitals, medical offices and other buildings.
The flame-retardant industry has asked Kaiser Permanente to reconsider its decision.