Coatings for Plastics Provide Flame Retardancy
|Flame-resistant coatings were used on the molded parts of an endoscope reprocesser.|
Intumescent coatings from Flame Seal Products Inc. (Houston; www.flameseal.com) have recently received a UL 94V-0 rating. Minntech Corp. (Minneapolis; www.minntech.com), a medical equipment supplier, funded the tests of the flame-retardant coatings in anticipation of using them on its plastic products. The thin-film Flame Seal coatings, which provide flame resistance without compromising tensile strength, were used on the molded parts of an endoscope reprocessor.
Flame Seal president Michael Kiser says it is difficult for a plastic to obtain the UL 94V-0 rating. "It is unusual for polyethylene or any other plastic to have a coating with sufficient flame retardancy," he says.
The basis of the FX-100 and FX-PX coatings is an amine polymer system. The clear system, composed of a 4:1 ratio of polymer to curing agent, is cross-linked and applied to substrates in three layers, each air dried and measuring from 2.0 to 2.5 mil in thickness. When a fire occurs, the coated products change dramatically, going through various stages of expansion and performing distinct yet simultaneous functions. The coatings automatically react with fire or heat to convert combustible gases and tars into noncombustible carbon char, nitrogen, and carbon dioxide.
The chemical reaction creates an intumescing action as water vapor is released to cool the plastic substrate and as nitrogen and carbon dioxide are liberated. The escape of the gases causes the coating to expand up to 100 times its original thickness. The expansion results in a pure carbon char that provides an intumescent seal around the underlying plastic substrate.