Question, after the material has yielded and you stopped the elongation or stretching, would the material recover (some amount) or it will be 100% of plastic deformation without any recovery?
A perfectly crystalline polymer would have a very small elastic regime. That's because Van der Waals forces holding the crystallites together act over such a short range. Disrupting them would pull the crystallites apart and cause the material to deform plastically.
If I remember correctly, the third law of thermodynamics defines the entropy of a perfect crystal at absolute zero to be zero. Since crystalline polymers never reach 100% crystallinity, that would imply that they cannot reach zero entropy. However, sort of reversing the logic, does the amorphous structure within polymer crystals influence the minimum temperature that can be achieved with the polymer crystal? In other words, is the lowest temperature limit of polymer crystals higher than the lowest temperature limit of small molecule crystals?
That's an excellent question. Honestly I don't know. Your reasoning related to polymer samples does indeed seem logical since polymer chains in void volumes will be less constrained than atoms in a lattice.
Definitely! Mylar is a good example. It is biaxially oriented polyethylene terephthalate (BOPET). Sometimes it is metallized with a sputterer to make a shiny surface, like Mylar balloons.
Glassy is high elastic recovery? that's not very intuitive. Why did they term it glassy?
A glass is an amorphous solid. I wouldn't say it has high elastic recovery. It has a high elastic modulus, but a small elastic range.
Question, after the material has yielded and you stopped the elongation or stretching, would the material recover (some amount) or it will be 100% of plastic deformation without any recovery?
Love your expository Video. Thumbs up!
Why is stress no long linear proportion to strain when a polymer's in the regime between the proportion elastic limit and elastic limit?
Would more crystalline polymers have lower elastic regimes? or would they have similar elasticity, but maybe break before?
A perfectly crystalline polymer would have a very small elastic regime. That's because Van der Waals forces holding the crystallites together act over such a short range. Disrupting them would pull the crystallites apart and cause the material to deform plastically.
Great lecture.
Why is the thermal conductivity of single polymer chain so greater than the bulk polymer?
If I remember correctly, the third law of thermodynamics defines the entropy of a perfect crystal at absolute zero to be zero. Since crystalline polymers never reach 100% crystallinity, that would imply that they cannot reach zero entropy. However, sort of reversing the logic, does the amorphous structure within polymer crystals influence the minimum temperature that can be achieved with the polymer crystal? In other words, is the lowest temperature limit of polymer crystals higher than the lowest temperature limit of small molecule crystals?
That's an excellent question. Honestly I don't know. Your reasoning related to polymer samples does indeed seem logical since polymer chains in void volumes will be less constrained than atoms in a lattice.
In DSC of polymers, is the heat produced at the crystallization temperature related to the heat needed at the melting temperature?
In principle the latent heat of melting should have the same absolute value as the latent heat of solidification.
Is it possible to preserve a polymer in its strengthened state of strain for other uses?
Definitely! Mylar is a good example. It is biaxially oriented polyethylene terephthalate (BOPET). Sometimes it is metallized with a sputterer to make a shiny surface, like Mylar balloons.