UMass team develops fireproof plastic

The Republican Newsroom By The Republican Newsroom The Republican
on May 31, 2007 at 4:54 PM, updated May 31, 2007 at 4:55 PM


AMHERST - Some plastics burn so readily that they are referred to as "solid gasoline," so the quest for a fireproof plastic has been the search for the holy grail for everyone from NASA to the makers of children's clothing.

Promising a potential revolution in plastics manufacturing, a team of scientists at University of Massachusetts in Amherst has developed a polymer - which is the basic building block of plastic - that has the dual benefits of being nearly fireproof and "green." It contains none of the compounds typically added to plastics as flame retardants that can be damaging to human health, chemicals that have been banned in some countries.

The synthetic polymer, called bishydroxydeoxybenzoin or BHDB, was developed by a team led by UMass polymer scientists Richard J. Farris, E. Bryan Coughlin and Todd S. Emrick.

The researchers presented an update on their work May 14 to industry representatives and scientists from the Federal Aviation Administration, the National Institute of Standards and Technology and the U.S. Army. The team described the new polymer in the journal Macromolecules last year.

"We're very excited about this," said Coughlin. "The great thing about BHDB is that it's really a two-birds-with-one-stone approach for a new polymer."

"It is extremely fire-safe, and does not contain halogenated additives, which are known to be environmentally hazardous," he said.

The polymer is clear, flexible, durable and much cheaper to make than the high-temperature and heat-resistant plastics in current use, which tend to be brittle and dark in color, the researchers said.

Immediate applications would be for airplane and automobile interiors, fire-fighting gear and military clothing and equipment. However, it's likely products made of a nearly non-combustible plastic would also interest consumers, especially parents, who are worried about house and apartment fires and the threat posed by current, highly flammable plastic goods.

While optimistic about the range of applications the polymer ultimately will have, Emrick said there are still some questions that will only be answered when production of the polymer is increased.

"As time moves forward and we're making kilos of this material instead of grams, then we're going to learn more about what exactly this can be used for. But we know enough about it that we know its potential is clear," he said.

The researchers said patents would be held by UMass and the researchers, and that patent applications have been made concerning the discovery and its applications.

When a plastic burns, it decomposes. Some of it becomes a gas, which burns as flame. But what doesn't burn becomes what polymer scientists refer to as "char," which is the solid that is left behind. The goal when creating fire-resistant plastics is to have a very high char yield. More char means less fire and fewer volatile chemicals being released.

Most common plastics burn readily. For instance, polypropylene has a char yield of zero. BHDB has a char yield of 70 percent. When burned, it releases water vapor.

"It has a very delayed onset of combustion. It's a slow-burning material with very little heat release in the process. In effect, it's nearly fireproof," Coughlin said.

Fire-resistent plastics currently in use contain fire-retardant additives. Often, these are halogenated molecules that contain reactive chemicals such as chlorine, bromine or phosphorous. These additives have come under increased scrutiny for being potentially damaging to human health and the environment. They have shown up in dust in homes and offices, and they have been found in fish, fat cells and breast milk.

"A lot of these additives are being banned in Europe and elsewhere. Some of these things aren't so nice. And if you don't burn them but you bury them in landfills, some of these materials can leach out," Farris said.

The state of Washington recently banned a class of flame-retardants from use in household items from mattresses to computers - the first state to do so.

Richard E. Lyon, manager of the fire research program for the Federal Aviation Administration, the principal sponsor of the research, said, "This is an environmentally friendly solution with a lot of economic potential."

It's estimated that 40 percent of passengers who survive the impact of an airplane accident die in the fire that follows because of the extensive use of lightweight plastics in the plane's interior. The FAA requires that aircraft use the most flame-resistant plastics that are available, but "we're shooting for a fireproof cabin," Lyon said.