Balloon expansion

A spherical rubber balloon has an initial thickness of 0.45mm, and diameter 250mm. Final diameter of 1000mm. Find final thickness, true stress in the plane of the balloon wall, Air pressure required. (Assume rubber is idea and obeys Guassian statistics, and take the shear modulus to be 1MPa.)

Gaussian statistics

How does Gaussian theory for elasticity compare to actual experiments (in compression and tension), and why?

Glass transition, copolymers

Homopolymer A has a Tg of 80C, homopolymer B has Tg of 70C. Estimate Tg of a 30/70 random copolymer of A and B. What assumptions should be made and compare all relationships that can be used and discuss which is more accurate.

Entropy of mixing

I am trying to figure out how, for the entropy of mixing of two polymers, one gets from: Change in entropy of mixing (delta S sub m) = k[(N1 + N2) ln (N1 + N2) - N1 ln N1 - N2 ln N2] to the result: change in entropy of mixing (delta S sub m) = -k(N1 ln v1 + N2 ln v2) where v1 and v2 are the volume fractions of the two polymers 1 and 2 respectively. What assumptions need to be made to go from the first equation to the second? How algebraically does one make the rearrangements necessary? Please be explicit. Note that the first equation arises from Bolztmann's relationship: delta S sub m (entropy of mixing) k ln (Omega) where omega is the number of possible arrangements in ... click for more

short question

A brittle sample of polystyrene behaves elastically in tension, until it breaks in two when extended 2.2%, under a load of 55MPa. What is the toughness of this sample? i know i may use the stress strain curve to solve this problem? (Force vs elongation)... but how do i solve the toughness of the sample?