Hoyt and Fabula 

 Table 1 (Continued) 



^C]^ = concentration required (in weight parts per million) for 35% disk-torque 

 reduction at 40 rev/sec with lake water as the solvent. 

 M = approximate molecular weight of the polymer according to the literature. 



'^The source of each polymer for this work is indicated by the letter after its 

 name: b = Braun Div., Van Waters and Rogers, Inc.; d = Dow Chemical Co.; 

 e = E. I. Dupont; f = General Aniline and Film Corp.; g = B. F. Goodrich Chem- 

 ical Co.; h = Hercules Powder Co.; m = Meer Corp.; s = Stein, Hall and Co.; 

 u = Union Carbide Chemicals Co.; w - Westco Research. 



Cj^ values in parenthesis are for solutions given heat treatment to increase 

 polymer solubility. 



moment, the molecular chain flexibility which will produce a Gaussian- coil con- 

 figuration for such long molecules. Thus the linearity of the molecule appears 

 to play an important role in the drag- reducing effect. 



Molecular Weight 



Accompanying the linearity is a corresponding increase in molecular weight. 

 However, from the experiments with Gum Karaya (Table 1) it appears that high 

 molecular weight in itself is not as effective as the linearity. The poly(ethylene 

 oxide) is some 65 times more effective than the heavier Gum Karaya molecule, 

 on a weight basis. 



The effect of molecular weight (or linearity) can be demonstrated by replot- 

 ting the disk data of Fig. 3 taken at a constant rotative speed of 40 rev/sec for 

 poly(ethylene oxide) to give the logarithmic presentation of Fig. 5. In addition 

 to showing the dependence of friction- reduction on molecular weight, Fig. 5 also 

 indicates that substantial increases in molecular weight (degree of polymerization) 



950 



