March 31, 2008

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Why You can't Unwrap a DVD

Physicists have explained the so-called Wallpaper Problem, which governs the frustrating tearing of wallpaper, tape rolls and DVD packaging. Steve Mirsky reports.

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Podcast Transcript: You’re pulling tape off the roll and it starts to tear.  Or you’re removing wallpaper and it refuses to strip off in strips.  Or, in what may be the most infuriating case, literally, you’re trying to unwrap a CD or DVD.  And you’re confronted with shards of plastic everywhere.  Well, the universe has truly conspired against you.  Because when it comes to tearing these layers, the laws of physics now show that that’s just the way it is.
 
Physicists address the so-called “Wallpaper Problem” in the March 30th online edition of the journal Nature Materials. What happens is that when you tear things, you get triangles.  Because of three properties of the adhesive materials being torn: the stiffness, the strength of the adhesion and how tough the material is to rip.  When you pull on the strip, energy builds up where the tape or coating is still attached to the surface below.  That energy can get released in two ways—by unpeeling from the surface, which you want.  Or by becoming narrower, ultimately making those annoying little triangles.

—Steve Mirsky  

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Why You can't Unwrap a DVD