Curators at the Smithsonian Institution's National Air and Space Museum are racing against time to preserve the Apollo spacesuits.
The moon suits are brittle, sticky and stained, results of chemical reactions in 24 layers of materials that include plastics and other components such as rubber and metal. If the deterioration continues at this pace, experts say, the suits that once protected man against harsh elements will exist no longer.
The cooling tubes and the life-support hoses — made of PVC — are oozing and discoloring in a fashion uglier than anything an astronaut might encounter in outer space.
"They started oozing plasticizer," said Lisa Young, a conservator with the museum. "When plasticizer comes out, it discolors. It really was a mess."
The plasticizer used in the PVC, dioctyl phthalate, breaks down into an acidic product over time, Young explained.
Used most frequently since the 1950s to soften PVC, the degradation occurs when DOP migrates from the body of the plastic to the surface and forms a sticky layer, said Yvonne Shashoua, a conservation scientist with the National Museum of Denmark.
The first stage of degradation is the surfacing of the plasticizer, Shashoua explained.
"The DOP itself breaks down to form phthalic acid crystals," she said. "According to industrial literature, the breakdown only takes place above 200§C (392§F) but is accelerated by the breakdown of the PVC itself [which produces acidic hydrogen chloride]."
The breakdown with the suits seems to have happened at ambient temperatures, she said.
The National Air and Space Museum, based in Suitland, Md., is halfway into a two-year grant program, dubbed "Save America's Future," to analyze how much damage already has occurred, produce preservation options and provide guidelines for handling and storing the suits. The grant is publicly and privately funded.
Counting 12 lunar suits and about 238 others used in various space missions, the museum has the world's most extensive collection of suits and other components.
"We had to recall a lot of the lunar suits that were out on loan," Young said.
Assisted by an advisory group of more than 25 materials scientists, industry experts, chemists, engineers and other conservators, the group will provide guidelines on storing and handling the suits by August.
For now, they will be conducting acidity tests, performing X-rays and photographing the suits to further understand what's going on.
"We're trying to arrest it and slow it down," Young said, explaining that the overall decay process cannot be stopped and that deterioration is inevitable.
According to Mary T. Baker, a polymer chemist and museum conservator, the chemical reactions that cause the discoloration, brittleness or stiffening are temperature-dependent, most occurring at a slow and measurable pace.
"For day-to-day life, these reactions are slow enough that these things take years to wear out — usually longer than we want to keep them anyway," she said. "In museum time, where we want objects to last decades, if not centuries, the additive effect of these slow processes is more obvious."
Cold storage and nitrogen-filled cases that exclude oxygen are among the preservation techniques considered by conservators. When a curator noticed the brittleness of the suits' rubber components 15 years ago, no one knew it would result in such disintegration, Young said. Chemists are just now learning why the materials deteriorate.
Possible conservation treatments fall into two categories, Shashoua explained: preventive, where the aim is to inhibit deterioration reactions by improving storage conditions; and active, where the aim is to stabilize the condition of the object for display purposes by actively applying a surface coating or adhesive.
"The advantage of preventive treatments is that, usually, they can be reversed to return to the original state, for analysis, for example," she said. "Usually, active treatments cannot be undone fully."
Hopes for slowing the PVC decay may be found in Shashoua's research work, which points to applying absorbents, placing a coating on the PVC or enclosing the suits to bring the reactions to a point of equilibrium.
But Shashoua cautions that these possibilities require further investigation. For plastic artifacts, it's just a matter of time.
"If we collect a new PVC object today, it is very unlikely it will be in the same condition years from now," she said.