Loss Tangent for Uncross-Linked Polymers

Minimum in Loss Tangent for Uncross-Linked Polymer 

How high must the molecular weight of polyisobutylene be in order to be sufficiently rubbery to have a loss tangent as low as 0.05 in the frequency region of the loss tangent minimum  

The appropriate relation is equation 10 of Chapter 13 with a correction factor of 0.75 on M as explained in the associated discussion. If Me is taken as 15,200 from Table 13-11, this equation gives = 9 X lO. The result gives the number-average molecular weight if there are no species with M Me- Experimentally, a minimum loss tangent of 0.1 was observed for a sample with = 15X10 which 

---