Teasing Out Properties of Clay-Polymer Fire Retardants

Researchers have figured out how to make clay-polymer fire retardants better
Researchers have figured out how to make clay-polymer fire retardants better.

There are people who literally play with fire. A team of U.S. scientists from the National Institute of Standards and Technology (NIST) and University of Maryland (UMD) have figured out how to improve a type of fire retardant that contains clay and polymers. They recently demonstrated that the fire retardant material worked better against flames when the nanoscale plates of clay were more widely and uniformly dispersed in the polymer.

Mark Bello of NIST Tech Beat explains that the polymer in the material tested by the team is similar to polystyrene. The polymer is embedded with “nanometer scale plates of montmorillonite, a type of clay with a sandwich-like molecular structure. The combination can create a material with unique properties or properties superior to those achievable by each component — clay or polymer — on its own.”

Over the past 10 years or so, polymer-montmorillonite nanocomposites have attracted interest in academic and industrial research and development. Studies have suggested that how the clay plates disperse, stack or clump in polymers affects the fire-retardant properties of the material. But it’s been hard to tease out the details.

Spearheaded by NIST guest researcher Takashi Kashiwagi, the NIST-UMD team tested five specimens, each with the same amount of the clay. The sample with the most widely dispersed clay plates was more greatly resistant to igniting and burning than the specimen in which the plates mostly clustered in crowds.

When the two samples were exposed to the same amount of heat for the same length of time, the sample with the more widely dispersed clay nanoparticles degraded far much more slowly.

Bello explains:

The researchers found that with better dispersion, clay plates entangle more easily when exposed to heat, thereby forming a network structure that is less likely to crack and leading to fewer gaps in the material. The result, they say, is a heat shield that slows the rate of degradation and reduces flammability. The NIST team, led by Rick Davis, is now exploring other approaches to reduce flammability, including the use of advanced materials and novel coating techniques.

Source: “Promising Fire Retardant Results When Clay Nanofiller Has Space,” NIST Tech Beat, 07/06/11
Image by Matthew Venn, used under its Creative Commons license.

Rajendrani "Raj" Mukhopadhyay is a science writer and editor who contributes news stories and feature articles on scientific advances to a variety of magazines. Raj holds Ph.D. in biophysics from Johns Hopkins University.