. The Bell System technical journal . 10 20 30 40 50 TEMPERATURE IN DEGREES CENTIGRADE Fig. 40—Value of Lame X elastic constant for poh-ethylene and nylon 6-6plotted as a function of frequencj^ and temperature. MECHANKWL PKOIMORTIES OF POLYMERS 167 against \/T where T is tlie absolute temperature. Both are plotted for8 me and 30 mc. The dispersion in both materials is evident. Below30°C^ the shear elasticity of polyethylene varies exponentially with thetemperature with an activation energy of kilocalories per this temperatiue a deviation occurs due to the approach to themelting
. The Bell System technical journal . 10 20 30 40 50 TEMPERATURE IN DEGREES CENTIGRADE Fig. 40—Value of Lame X elastic constant for poh-ethylene and nylon 6-6plotted as a function of frequencj^ and temperature. MECHANKWL PKOIMORTIES OF POLYMERS 167 against \/T where T is tlie absolute temperature. Both are plotted for8 me and 30 mc. The dispersion in both materials is evident. Below30°C^ the shear elasticity of polyethylene varies exponentially with thetemperature with an activation energy of kilocalories per this temperatiue a deviation occurs due to the approach to themelting temperature. Nylon has a smaller variation with the longitudinal and shear wave measurements one cancalculate the Lame X elastic constant and this is shown plotted on Fig. 40for both polyethylene and nylon 6-6 as a function of temperature for. 12 14 16 1S 20 22 24 26FREQUENCY IN MEGACYCLES PER SECOND Fig. 41—Equivalent shear and compressional viscosities for polyethylene andnylon 6-6 plotted as a function of frequency for a temperature of 25°C. two frequencies. The dispersion of X for polyethylene is small but is moreprominent in nylon 6-6. This correlates with the larger compressionalviscosity component present for nylon 6-6 which as shown from Fig. 41is as large as the shear viscosity. According to the structural rearrange-ment theory of compressional viscosity due to Debye, compressionalviscosity can enter when some part of the chain can rearrange from onestable state to another stable state as a function of pressure. This re-arrangement occurs across a potential barrier and hence requires a finiteamount of time to occur. This lag in the rearrangement results in acompressional viscosity and as the frequency is increased, a frequencyis found for which the motion can no longer occur in the time of a single « P. Debye,
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
