Hanover, MA What keeps the stars in your eyes? Live aboard the International Space Station and you may answer, "an adhesive."
To create windows for the station's laboratory module and copula, Eyesaver International used an optically clear laminating adhesive from 3M Co. (St. Paul, MN) to bond a clear film, or "scratch pane," to an outer glass window. Designed to protect the space station occupants from a shattered window, the scratch pane had to be clear enough to permit close viewing of the station's robotic-arm operations and even allow photographs to be taken through it, according to Steve George, Eyesaver's co-owner. Once the film has been bonded to the glass and polished, the company also solders a glass-warming conductive bar to the coating around the window.
While Eyesaver has more than 13 years experience laminating and fabricating glass for a variety of computer and electronics displays, finding a truly clear laminating adhesive has always represented something of a challenge. "Most of the clear adhesives available to us in the past were for covering posters with a protective film," George notes. Though these graphic-arts adhesives could normally meet Eyesaver's strength requirements, they tended to spread inconsistently, leaving voids in the adhesive layer. What's more, George also noticed more particulants in adhesives formulated for graphics applications, creating even more optical defects. "When you have to look at a monitor or through a piece of glass all day, a piece of dust can look like a boulder," he says.
The 3M 8141 adhesive, however, doesn't seem to suffer from the voids and particulates George has noticed in previous clear adhesives. It has 99% opacity.