Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Kaybee on 27/05/2009 22:30:02

Title: Why did the plastic film on my iPod lift up on during an aeroplane flight?
Post by: Kaybee on 27/05/2009 22:30:02
Kate Broughton  asked the Naked Scientists:
   
Hi Chris

Great show everyone (http://www.thenakedscientists.com/HTML/podcasts/), keep up the good work.

Question
 
Recently whilst on a flight to Lesvos, Greece, I was listening to the latest Naked Scientist podcast (http://www.thenakedscientists.com/HTML/podcasts/) on my ipod with the iplayer on the table in front of me.  

I saw that the thin plastic removable protective cover on the front screen was slowly peeling off. I pressed it back into place but it started again and continued to lift itself from the edges inwards.

I wondered what was happening to the plastic to produce this effect. At first I thought that the plastic cover might be changing size in reaction to the cabin pressure in some way but if it was just that then after a time should not the cover stop changing size and stick back?

The process repeated continuously for the whole of the flight and the same thing happened on the return flight. Can you please explain what was happening?

Thank you
Kate Broughton, Nottingham

What do you think?
Title: Re: Why did the plastic film on my iPod lift up on during an aeroplane flight?
Post by: Edster on 16/06/2009 05:12:50
Just a semi informed guess, but many of the clear plastics that "stick" used for this have some water content. An aircraft`s cabin air system has quite a low Relative humidity at cruising altitude. Possibly this is drying the plastic much more quickly than would be the case in free air and normal weather changes, and making it curl.
Title: Re: Why did the plastic film on my iPod lift up on during an aeroplane flight?
Post by: Kaybee on 26/06/2009 18:58:01
Thanks Edster - that sounds reasonable. If the water content was thereby reduced then that could explain why it didn't stay re-stuck.
Title: Re: Why did the plastic film on my iPod lift up on during an aeroplane flight?
Post by: chris on 26/06/2009 23:21:39
Actually, it could be a pressure effect; the plastic remains adherent to the screen because when it is applied to the screen surface the air beneath it is squeezed out. As a result the surrounding air pressure pushes the plastic onto the screen, overcoming in the process the natural elasticity of the plastic and its tendency to curl up.

But in a lower pressure environment, like the aircraft cabin, the force applied by the surrounding air is lower than normal. Coupled with a temperature change (from air conditioning) which might cause the plastic to change shape too, this might mean that the force of the air pressure holding the plastic against the screen is no longer sufficient to oppose the lifting of the film...

Chris
Title: Why did the plastic film on my iPod lift up on during an aeroplane flight?
Post by: chris on 10/11/2009 11:36:31
Anyone else had an airborne-iPod-related experiences?