Diffusion in Ethylene Polymers. IV

Abstract

Self‐diffusion coefficients have been measured for two low molecular weight fractions (M = 4100 and 5800) of a linear polyethylene. The activation energy for the M = 4100 fraction is 5.3 kcal/mole which is near the value 5.6 kcal/mole found for n — C32H66. At 150°C, for this fraction, D = 1.6×10—7 cm2/sec and as 10—7 is near the lower limit of detectability the activation energy is probably not accurately determined. The diffusion coefficient for the M = 5800 fraction is 1.1×10—7 cm2/sec at 150°C. These results, combined with previous results, show that D = κn —5/3, where D is the coefficient of self‐diffuison for the normal paraffin C n H2n+2. κ is a constant at a given temperature, 4.5×10—3 cm2/sec at 200°C and 2.5×10—3 cm2/sec at 150°C.