CHEM 4214 Lecture Notes - Lecture 29: Shear Modulus, Rubber Band, Modulus Guitars
Document Summary
Rubber: only polymer materials can give rubbery materials. Vulcanizaiton: make network from polymer that already exists. Elasticity (why do we get elasticity from polymers but not metals: how to quantify. Quiz question depends on thermal energy, size of particle, and how viscous our solution is. If zoom in, stress stress this one has more entropy reduce entropy polymer wants to go back to state of more entropy so that"s why it stretches back. This is hooke"s lawthe prefactor before h represents spring constant. Ideal rubber: network of gaussian chains proportional to x-link density: affine deformation. Engineering stress this one"s easier to measure b/c we"re not worrying about how surface area changes but true stress is more rigorous. Chem4212 polymers page 4 then calculate young"s modulus. E = 3g when poisson"s ratio = 1/2 means barely stretching. Equal partition thoremeach degree of freedom ( ) has energy of kt.
