Why is peeling off tape so irritating?

March 31st, 2008 - 2:06 pm ICT by admin  

Washington, March 31 (IANS) Have you been frustrated by tape that won’t peel off the roll in a straight line or angry at wallpaper that refuses to tear neatly off the wall? “You want to redecorate your bedroom, so you yank down the wallpaper. You wish that the flap would tear all the way down to the floor, but it comes together in a triangle and you have to start all over again,” said Pedro Reis of the Massachusetts Institute of Technology (MIT) and co-author of the study.

This pattern applies not only to wallpaper but other adhesives (tape) and non-adhesive plastic sheets that envelop compact discs. It even extends to fruit: The skin on a tomato or a grape typically forms a triangle when peeled off.

A joint research team from National de la Recherche Scientifique (CNRS) Paris, Universidad de Santiago, Chile, and MIT found that those ubiquitous triangular tears arise from interactions between three inherent properties of adhesive materials: elasticity (stiffness), adhesive energy (how strongly it sticks to a surface) and fracture energy (how tough it is to rip).

They developed a formulation that predicts the angle of the triangle formed, based on those three properties. They also figured out just how those triangular tears arise.

As the strip is pulled, energy builds up in the fold that forms where the tape is peeling from the surface. The tape can release that energy in two ways: by unpeeling from its surface and by becoming narrower. It does both.

In a possible industrial application, materials engineers could use this method to calculate one of the three key properties, if the other two are known.

The findings could be particularly useful in micro-technologies like stretchable electronics, where the characterisation of thin material properties is very difficult.

The study has been published in the online issue of Nature Materials.

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