Polymeric protection for valuables.

In the war against corrosion and decay, gaseous sulfide and chloride compounds are guerrillas that infiltrate even protected environments. In clean rooms used in electronics manufacturing or in museum storage cases, these substances may exist in concentrations of just a few parts per billion; yet they can still do damage, says John P. Franey of AT&T Bell Laboratories in Murray Hill, N.J. Eventually, they will tarnish a silver surface or pit an electronic device.

The polyethylene film that curators often use as protective wrapping for artifacts "is merely a piece of cheesecloth with holes that you cannot see," he adds. And another type of protection, activated charcoal, only temproarily captures these molecular terrorists, releasing them when temperatures rise.

To halt such corrosion, Franey invented a "reactive" polymer system. When making a polymer film or resin, for example, he chemically inserts scavenger molecules that neutralize any corrosive gas seeping through the polymer. "It's a copper-like material that is bound up in the polymer," he explains.

So after five years in reactive polymer bag, a silver spoon looked as if it had been polished that day, while a similar spoon not bagged for that time was black with tarnish, he reports. The polymer darkens as pollutants exhaust its scavenging ability, but Bell Labs' studies show that a bag no thicker than a plastic garbage bag would last about 30 years before needing to be replaced. Other polymers made with this technology, called Intercept, protect sensitive electronic devices from electrostatic discharge, Franey adds.