Maximum relaxation times in polytetrafluoroethylene
Arthur V. Tobolsky, Dov Katz, Adi Eisenberg · Journal of Applied Polymer Science · 1963
Molecular weights of polytetrafluoroethylene are presently measured by a density method. We have found that polytetrafluoroethylene exhibits a sharply defined maximum relaxation time, τm, above its melting point. There is a clear correlation between τm at 380°C. and the “molecular weight” Mn of the polymer based on the measurement of density. However, log τm vs. log Mn gives a slope of 0.78 as against a value of 3.4 obtained for other polymers. Either polytetrafluoroethylene has flow behavior very different from other polymers or the molecular weight of the polymer based on the measurement of density is only approximate.