MECHAXICAL PROPERTIES OF POLYMERS 



163 



0.19 



0.09 



10 



70 



20 30 40 50 60 



TEMPERATURE IN DEGREES CENTIGRADE 



Fig. 32 — Attenuation per wavelength for longitudinal waves in polyethj'lene 

 plotted as a function of temperature and frequencj-. 



FOR 30' 



10^X0.9 



5§ 



liJij 

 Uiij 



fo = 8 X 10^ CPS 

 77, = 24 POISE 



/Z, = 1.2 X 10^ DYNES/Cm2 

 IX\ = 4.75x10^ DYNES/ Cm2 

 jlz = 2.6x 10^ DYNES/Cm2 

 >Ui,= 1.3x108 dyNES/CM2 



8 12 16 20 24 28 32 



FREQUENCY IN MEGACYCLES PER SECOND 



Fig. 33 — Shear velocity of polyethj-lene as a function of frequency and temper- 

 ature. Equivalent circuit shows elements necessary to account for the velocity 

 and attenuation changes at 30°C. 



