News

A sticky issue

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7:41pm, March 18, 2008

From New Orleans, at a meeting of the American Physical Society

Old decals die hard. Try removing one from a wall by pulling its side, and usually only a small wedge will come off. The same tends to happen with pieces of adhesive tape. Unless the glue is weak or the tape is strong and doesn't break, the removal takes patience.

"Why is it so frustrating?" says Benoît Roman of the National Center for Scientific Research in Paris. Now Roman and his collaborators have found the answer.

The researchers tried pulling tape off surfaces using a machine that also measured the forces involved. Every time they began pulling a strip of tape off, the strip's edges tended to close up toward each other, forming a wedge (and making it impossible to pull the tape off in one clean sweep). For a given kind of tape and a given rate of pulling, the wedge's angle was always the same, regardless of the width of the initial strip.

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