What's new in safe flame retardants?

I get tired of always pointing out the bad chemicals that can do us harm, so I thought it might be fun to try to find if there is new research on flame retardants which may be on the market – and which don’t harm us or our planet!

More than 175 flame retardant compounds are currently on the market, and the industry is worth over $600 million dollars per year in the U.S. and nearly $2 billion worldwide, according to the European Flame Retardants Association.

Flame-retardants are far more common than most of us realize. Many materials contain quite high levels of flame retardants: cellulose insulation is about 20% flame retardant by weight, plastic television and computer cases are often 10–20%, and polyurethane foam cushioning can be up to 30%. Some materials have very low levels of flame-retardants: polystyrene foam insulation is typically 0.5–2.0% HBCD (hexabromocyclododecane) by weight.

Manufacturers of products with less than 1% flame retardant are not required to list it on the Material Safety Data Sheets (MSDS), since it falls below the threshold for required listing. Some products use flame-retardants as secondary components, which can also render an MSDS misleading.

Most of the current concern about flame-retardants focuses on brominated flame- retardants (BFRs). Brominated flame-retardants are widely used for plastics, due to their effectiveness and relatively low cost. More than 75 of these compounds or mixtures are recognized commercially. Some are generic compounds made by a number of manufacturers; others are proprietary formulations that differ slightly from product to product. The best-known BFRs today are PBDEs, HBCD, and TBBPA – none of which anybody wants to live with.

So is there a safe flame retardant available today on the market? Not yet, but there is promising research. Here are three discoveries that may change the FR landscape:

  1. Researchers in Italy have demonstrated that caseins—proteins found in milk that are a by-product of cheese production—may be an alternative to flame-retardants. Some types of flame-retardants, such as organophosphate esters, get their fire-blocking properties from their high phosphorus content. When they burn, a polymer layer of phosphoric acid forms and creates a char that blocks heat transfer to unburned areas of the material, slowing the spread of the fire. Jenny Alongi of the Polytechnic University of Turin and her colleagues decided to investigate a family of proteins called caseins as alternative flame-retardants because they contain a large number of phosphate groups. Caseins are found in the whey which is a by-product of cheese production, so in countries that produce a lot of cheese, such as Italy and France, the proteins are cheap and abundant, Alongi says.

The team coated three materials—cotton, polyester, and a blend of 65% polyester and 35% cotton—with the proteins by soaking the fabrics in distilled water mixed with casein powder. The researchers then submitted the samples to a battery of flammability tests. The results were encouraging: In cotton- and polyester-only fabrics treated with caseins, flames extinguished themselves, leaving 86% of the cotton and 77% of the polyester unburned. The cotton-polyester blend burned completely but took 60% more time to do so than the untreated material. The flame-retardant properties of caseins also compared well to those of ammonium polyphosphate (APP), a flame retardant used for flame proofing polyolefins and polyurethanes. The caseins effectively form a char layer on the fabric samples and don’t produce toxic fumes during combustion.

Before caseins can be used as flame retardants, researchers need to work out many issues, such as preventing the proteins from washing off materials. The team is now testing light-curable resins and molecules such as urea that could bond the casein molecules to the surface of the fabric, Alongi says. Another problem is that materials treated with caseins smell rancid. Alongi and her colleagues are looking for ways to remove the molecules associated with casein that produce the odor.[1]

  1. What sounds like fixings for a wizard’s potion—a dash of clay, a dab of fiber from crab shells, and a dollop of DNA—actually are the ingredients of promising safe fire retardants invented by researchers at the National Institute of Standards and Technology (NIST).

Applied to polyurethane foam, the bio-based coatings greatly reduced the flammability of the common furniture padding after it was exposed to an open flame. Peak and average rates of heat release—two key indicators of the magnitude of a fire hazard—were reduced by 48 percent and 77 percent, respectively, the NIST team reports in the journal Green Materials.

“This is the biggest reduction in flammability that we have achieved to date,” says team leader Rick Davis. The all-natural coatings outperform other promising experimental fire-retardants that the NIST researchers have devised with their layer-by-layer assembly method. But Davis says the bio-based coatings must be applied more generously, in stacks of about 20 layers as compared with six or seven layers.

The new coatings use negatively charged DNA molecules to link two positively charged materials known to enhance fire resistance: montmorillonite, a type of soft clay that forms tiny crystals, and chitosan, a fiber derived from the shells of shrimp, lobsters and other crustaceans. For its part, DNA, which was obtained from herring sperm, may also confer added protection because it bubbles and swells when heated, protecting the material beneath.[2]

  1. In September, 2015, researchers at the University of Texas at Austin (UT) published their discovery of a flame-retardant that is nontoxic and won’t accumulate over time in the bodies of people who come in contact with it. It’s made entirely from the chemical dopamine—the neurotransmitter in our brains associated with reward and pleasure. The researchers took their cue from marine mussels, who secrete a mucus-like “glue” made of dopamine that allows the mussels to stick to nearly any surface, including Teflon, widely considered nonadhesive. The mussel’s “glue” has been the focus of several studies, especially for its use as a bio adhesive; it’s nontoxic, making it attractive for uses in the body, like closing incisions without stitches

Christopher Ellison, associate professor in the Cockrell School of Engineering at UT, and his team found that the dopamine-based coating performs wonderfully as a fire retardant. In fact, according to the team’s paper, the dopamine retardant reduces a fire’s intensity 20 percent better than retardants currently on the market. “We beat them all,” Ellison says.[3]

So, there may be safe flame retardants on the horizon – and I can tell you this:  lots of people are looking for them.


[1] http://cen.acs.org/articles/92/web/2014/03/Milk-Proteins-Protect-Fabrics-Fire.html

[2] http://www.nist.gov/el/fire_research/fire-060314.cfm

[3] http://www.newsweek.com/2015/10/23/new-nontoxic-flame-retardant-derived-dopamine-381616.html

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