Methods of capillary viscometry were used in studying the rheological properties and behavior of a broad range of rubbers, including polymers with narrow and wide molecular-weight-distribution as well as commercial rubber grades, at widely varying shear rates and stresses. As is shown, in full conformity with the previously conducted experiments, during transition from a fluid to highelastic (quasi-cross-linked) state, they are chracterized by spurting followed by sliding over the channel walls. This relaxation transition is characterized by a critical shear stress value invariant with respect to the molecular weight, molecularweight distribution and temperature. The parameters defining spurting of polymer flow as a function of molecular-weight characteristics, temperature, and channel geometry have been investigated in detail. It is shown for the first time that under supercritical conditions the rate of polymer flow through channels does not depend, in the first approximation, on the molecular weight of the polymer, its molecularweight distribution, temperature, and filling, but is determined only by the shear stress.

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A study has been made into electrification of linear flexible-chain polymers extruded through metal and dielectric ducts. Most of the work concerns 1,4-polybutadienes prepared by anionic polymerization, with different molecular masses and molecular mass distributions. A pre-requisite for intense static electrification is the relaxation transition of the polymer from fluid into forced high-elastic state in which the polymer slides over the duct wall surface. The relation between electrification of polymers and their molecular mass, molecular-mass distribution, temperature, sliding velocity, and the duct length has been established. Electrification of polybutadiene in dielectric ducts and the effect of the chemical nature of polymers on their static electrification were also examined.

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