140 



THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1952 



of the molecular weight. The viscosity decreased by a factor of 6.25 

 and consequently the relaxation frequency increases from 230 to 660 

 cycles. 



The second "entanglement" relaxation has a stiffness of about 3100 

 dynes/cm for a 1 gram per cc solution of the 3.93 X 10 molecular 

 weight solution and about 2650 dynes/cm for the 1.18 X 10 molecular 

 weight solution. The variation with temperature, if any, is small. The 

 corresponding viscosities 773 for the two solutions are nearly equal as 

 shown by Fig. 14, and have an activation energy of 4.25 kilocalories 

 per mole. The final high frequency "short segment" relaxation has a 

 high stiffness of 83,000 dynes/cm^ for a 1 per cent solution of 3.93 X 10*^ 

 molecular weight. The corresponding viscosities for the two solutions 

 shown by Fig. 14 have nearly identical values and an activation energy 

 of 4.25 kilocalories per mole, i.e. very closely equal to the "entangle- 

 ment" relaxation viscosity. 



These upper two relaxations persist in pure liquid polymers as dis- 

 cussed in the next section, although they are spread out over a small 

 range of relaxation time values. The highest one can be traced in meas- 

 urements of mechanical properties of solid plastics such as polyethylene 

 and nylon which indicates that these materials should have rubber like 



0.1 



0.08 

 0.06 



0.002 



1.18X10^ MOLECULAR WEIGHT 

 3.93 XIO6 MOLECULAR WEIGHT 

 CYCLOHEXANE SOLVENT 



3.2 3.3 



VALUE OF 1/T 



Fig. 14 — Viscosities for the three components of the motion and for the solvent 

 plotted against the inverse of the absolute temperature. 



