| Abstract: | By comparing the relaxation spectra respectively calculated on the basis of the iterative and approximation methods, it is confirmed that the latter may be used to describe the viscoelastic properties of polyethylene melts. A method is proposed for identifying the form of the frequency relaxation spectrum by three characteristic numerical quantities. The effect of the molecular-mass, the molecular-mass distribution, and the long-chain branching characteristics on the form of the frequency relaxation spectrum is considered. The question of the geometrical similarity of the relaxation spectrum is discussed, and it is shown that, in general, these spectra are not linearly similar. The asymmetry of the spectrum depends solely on the index representing the rate of fall of the dynamic viscosity with increasing frequency of deformation. Methods of determining the characteristic relaxation time without constructing a frequency relaxation spectrum are proposed; ways of determining the characteristic relaxation time from experimental data are indicated.For communication 2, see 10].Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 322–330, March–April, 1976. |
