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Alexander Malkin, Alexander Semakov, Valery Kulichikhin
Macroscopic modeling of a single entanglement at high deformation rates of polymer melts

Appl. Rheol. 22:3 (2012) 32575 (9 pages)

We constructed a macroscopic model illustrating behavior of a single entanglement knot of macromolecules in a melt and examined its behavior at different deformation rates. A model consists of flexible elastic strips, which are tied in a granny knot (modeling not a real geometrical form of entanglements but their behavior at relatively easy sliding). This scheme models the situation when elastic energy exceeds the energy of the Brownian motion. The behavior of a knot chosen for modeling is different at low and high deformation rates. In the previous case knots disentangle as predicted by the .tube. model, elastic strips slip out a knot and this is an illustration of flow. In the latter case, knots tighten up, further extension of strips leads to the increase in stresses up to breakup of a strip. This effect imitates the transition from the flow to the rubbery-like behavior of polymer melts, when flow becomes impossible due to the formation of quasi-permanent entanglements. The general dimensionless correlation for the process under discussion has been proposed.

Cite this publication as follows:
Malkin A, Semakov A, Kulichikhin V: Macroscopic modeling of a single entanglement at high deformation rates of polymer melts, Appl. Rheol. 22 (2012) 32575.

Vadim E. Dreval', Gleb Vasil'ev, Elena Borisenkova, Alexander Semakov, Valery Kulichikhin
Influence of Molecular Weight of SAN on Rheological and Mechanical Properties of ABS-plastics

Appl. Rheol. 17:4 (2007) 44745 (11 pages)

Rheological and mechanical properties of acrylonitrile-butadiene-styrene polymers (ABS) prepared via bulk polymerization depending on the molecular weight (Mw) of styrene-acrylonitrile copolymer (SAN) have been investigated.The tendencies of attaining the yield stress at steady-state shear flow and approaching to the .plateau. region of storage modulus at low frequencies in oscillatory tests were observed. Both these phenomena are induced by formation of the structural skeleton consisting of polybutadiene (PB) particles arranged in the SAN-matrix. Growth of Mw of SAN leads both to increase of the .plateau. value of storage modulus at low frequencies and the yield stress.This fact can be explained by the influence of Mw of SAN chains grafted onto PB particles on structure formation in ABS melts because of a redistribution of the ratio particleparticle / particle-matrix interactions. The elongational viscosity of ABS melts is a power function of Mw of SAN matrix. The power index of this function increases with the polymer straining that reflects orientation of SAN chains with their length increase. The strain-hardening index of ABS melts increases considerably with increase of SAN matrix Mw. However, it does not depend on presence of PB particles in the material. It means that the value of this index is governed by orientation effect in the SAN matrix.The impact strength of the investigated ABS samples is interrelated with rheological characteristics of ABS melts as well as Mw of SAN. The dependence of impact strength on Mw can be explained by increasing role of orientation effects of SAN chains with Mw increase in the copolymer fibrils connecting the walls of crazes formed at impact action.

Cite this publication as follows:
Dreval VE, Vasilev G, Borisenkova E, Semakov A, Kulichikhin VG: Influence of Molecular Weight of SAN on Rheological and Mechanical Properties of ABS-plastics, Appl. Rheol. 17 (2007) 44745.

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