MECHANICAL PROPERTIES OF POLYMERS 



147 



against the frequency times the static viscosity. All the viscosity data 

 can be represented within the experimental error by a single curve, but 

 the stiffness curves appear to reciuire different curves for different tem- 

 peratures. On analyzing the data in terms of a distribution of relaxation 

 frequencies, a single curve for all temperatures could be obtained if the 

 stiffness of each mechanism were independent of the temperature and 

 the relaxation frequency were inversely proportional to the static vis- 

 cosity, i.e., had an activation energy variation equal to that for the 

 static viscosity for each relaxation mechanism. This condition holds 



40 80 120 160 



NUMBER OF CHAIN ELEMENTS 



10'° lO 



109 



Fig. 19— Curves showing better fit to e.xperimental data obtained by assuming 

 the relaxation regions shown by Fig. 17. 



