Consortium studies flame retardancy of plastics
Silicate-nanocomposites may yield some solutions to the flame retardancy issues surrounding certain plastics. This will be one area of study for the Flammability of Polymer-clay Nanocomposites Consortium, sponsored by the National Institute of Standards and Technology (NIST).
The clay-nanocomposites group of plastic materials has clay plate-like particles, one nanometer (40 billionths of an inch) thick by a thousand nanometers in diameter, dispersed throughout the polymers involved. Research conducted to date has indicated that molecularly dispersing clay boosts flame retardancy in many polymers. A major objective of the research is to reduce the deaths, injuries, and property damage associated with fires involving synthetic fabrics found in furniture and carpeting, but the Consortium will also be concerned with other issues, according to Dr. Jeff Gilman of NIST.
“In the pursuit of improved approaches to fire retarding polymers, a wide variety of concerns must be addressed in addition to the flammability issues,” Gilman explains. Among those he cites are the following:
The retardant must be low-cost, since many commodity polymers are low-cost. This factor, Gilman notes, “limits solutions to the problem, primarily to additive-type approaches.” Also, says Gilman, the additives must be easily processed with the polymer.
The “additive must not excessively degrade the other performance properties of the polymer.”
The additive must be environmentally safe and not cause disposal problems related to the final product.
Polymer layered-silicate (clay) nan-ocomposites, points out Gilman, may fulfill the above requirements for a high-performance flame retardant, since they have demonstrated excellent flame retardant qualities.
Gilman reports that he, in collaboration with Dr. Cathryn Jackson of the Polymers Division of NIST`s Materials Science and Engineering lab, has used X-ray diffraction and Transmission Electron Micro-scopy to characterize the high performance of the carbon-silicate multilayer char structure responsible for the improvement in flammability, which results from as little as two percent clay in the nan-ocomposites.
Eight companies have joined in the study of the nanocomposites` flame retardant mechanism: the PQ Corporation, So. Clay Products, Nanocor, 3M, GE, Great Lakes Chemical, Sekisui America, and Raychem. Agency members in addition to NIST are the Air Force Research Lab and the Federal Aviation Administration.
The project, which got underway in December 1998, is ex-pected to continue for at least two years. It will include examining a variety of materials to determine if the flame retardancy depends on physical properties, chemical properties, or both. For additional in-formation, contact Dr. Gilman at (301) 975-6573, e-mail: jeffrey. gilman@nist.gov. n
