Rubber elasticity physics/chemistry

[b0f0s0f]

Hey all,

I stumbled across this 1962 Bell Labs video about the origin of the elastic properties of rubber, and figured some here may be interested in it:

https://www.youtube.com/watch?v=xsy_Deby9C4

I learned this exact stuff when I took statistical mechanics during my physics degree so I can confidently confirm that this video is a fantastic explanation and demonstration, better than anything else I've found without involving math. And they did it with nothing but a tank of water and string of beads! Great stuff (they don't make 'em like they used to).

Cheers

[Meililoon]

Re: Rubber elasticity physics/chemistry

One thing I've noticed that was mentioned in the video is how balloons becomes warmer when you stretch them. It's really easy to detect if you stretch the neck of an uninflated balloon.

[b0f0s0f]

Re: Rubber elasticity physics/chemistry

Yep, and also why they get cold when you deflate them. And also why heating them helps them shrink back to normal after being deflated. You blow the balloon up, the rubber heats up due to the expelled heat energy, and then it cools back down to room temperature via normal heat transfer. Then, when you deflate the balloon, its (reduced) heat energy is absorbed as the chains contract, and when it gets cold the process is starved of energy, so introducing more heat helps the chains continue to contract.

I wish I had more information about the failure modes, but I'm guessing that being in a warm environment helps balloons get larger since there is more energy available to agitate the chains past each other to find configurations where the stress is most evenly distributed. Some sort of annealing process during slow inflation might help maximize the size. Someone should test this

[BusterBill]

Re: Rubber elasticity physics/chemistry

Some sort of annealing process during slow inflation might help maximize the size. Someone should test this

.
If you want to see a balloon grow tremendously bigger than you've ever seen before, get yourself a quiet, high capacity aquarium air pump. A dual-outlet 10 watt Hygger pump or similar works great. One of my looner friends used to do this -- he used a Y-adapter to direct the air from both outlets into a single tube. The he attached a Qualatex 16" to the end of the air tube and suspended it from a hook on the wall. After quite a while of the pump quietly humming away, you'd glance up and see this friggin ENORMOUS GIANT balloon and think "there is NO WAY that can be a Q16!!!" The extremely slow rate of inflation, the balloon not being disturbed, and the warm air caused the balloon to expand beyond all expectations. Not even the most careful and slow blow-to-pop by mouth could come close to inflating a balloon as big as that slow pump.

[b loony]

Re: Rubber elasticity physics/chemistry

Yeah the fish tanks pumps take ages to blow up a balloon, but for whatever reason the inflate a lot larger than by mouth or balloon pump.

[balloonPatcher]

Re: Rubber elasticity physics/chemistry

I think this thread is cool! I looked up some articles of rubber deterioration. There seems to be two types of oxidative degradation. 'Chain hardening' - latex gets harder and 'chain scission' - the latex gets softer. So, if I had to guess(hypothesis), the slow inflation allows for some chain breakage and long chain rearrangement to occur delaying rupture.

[aron_crow]

Re: Rubber elasticity physics/chemistry

Hey all,

I stumbled across this 1962 Bell Labs video about the origin of the elastic properties of rubber, and figured some here may be interested in it:

https://www.youtube.com/watch?v=xsy_Deby9C4

I learned this exact stuff when I took statistical mechanics during my physics degree so I can confidently confirm that this video is a fantastic explanation and demonstration, better than anything else I've found without involving math. And they did it with nothing but a tank of water and string of beads! Great stuff (they don't make 'em like they used to).

Cheers

This thread is cool. There was a page in the balloons wiki that taught me so much about the elasticity of the rubber and all before I learned them in my Physics degree. The link is https://balloons.fandom.com/wiki/Inflation.

I also attest to the fish tank pump making the balloon massive before it burst. I tried it once. Balloons generally can be made to achieve almost 3-5cm more than their actual sizes by just inflating and deflating them 3-4 times.