CHEM 4214 Lecture Notes - Lecture 30: Shear Modulus, Rubber Band, Legislature Broadcasters In New Zealand
Document Summary
Chem4212 polymers page 1 sqrt comes from the fact that we"re balancing from 2 directions. Engineering stress change in volume is 0 --> Mx = molecular weight between 2 cross links. When you heat up a polymer network, you increase entropy effects, so elasticity increases. Mx on average, all segments have mw of mx even dangling ends fraction of dangling ends = small correctionusually m is really large. If stretch really far (beyond 2x original length), theory doesn"t work anymore. Mooney-rivlin eqn c1 and c2 are material constants. Assme m = 2 --> 2 s per x-link. How much s added to 3x1 mm2 rubber band if 100g mass doubles length? the more x-links, the stronger the rubberthe less, the weaker. Mass of rubber = 10 cm x 3 mm2 x 0. 9 g/cm3 = 0. 27 g. 2 for the 2 ends of a strand each crosslink is shared by 4 strands so each strand has mass s: for sulfur crosslink.
