Properties of amorphous and crystallizable hydrocarbon polymers. I. Melt rheology of fractions of linear polyethylene

Abstract

AbstractThe dynamic moduli G′(ω) and G″(ω) for two groups of linear polyethylene fractions (reported Mw/Mn < 1.2) were measured in the melt state using the eccentric rotating disk method. Values of zero shear viscosity η0 were obtained and compared with published results on similar fractions. Molecular weight data were converted to a common basis through intrinsic viscosities in trichlorobenzene (TCB) at 135°C. With recent data on Mw (light scattering) vs. [η]TCB, for linear polyethylene, the relationship at 190°C, η0 = 3.40 × 10−14(Mw)3.60, was obtained. The flow activation energy Ea was 6.4 kcal (T = 140–195°C). The plateau modulus G at 190°C was determined from the area under the loss modulus peak in one high‐molecular‐weight sample. The value obtained, G = 1.58 × 107 dyn/cm2, corresponds to an apparent molecular weight between entanglements of 1850. The storage compliance J′(ω) becomes anomalously large at low frequencies. The recoverable compliance J could not be determined for any of the fractions.