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Abstract
This paper is about rheological properties of plasticized polymer solutions with different concentration of plasticizer. It was established that the investigated polymer solutions were threedimensionally structured systems which were shear thickened at low shear rates and maintained the thixotropic structural state under high shear rates. However, addition of different amount of plasticizer had an ambiguous influence on rheology of solutions and led to formation of transient polymer network with a complicated character of structuration because of the features of interaction in the polymer - plasticizer system. It was found that the plasticization results in changing of EC molecules conformation and simultaneous breaking of the polymer continuity due to DBP adsorption on EC macromolecule. Herewith, the formation of smaller crystallites took place. Besides, the investigated solutions showed causal link between structural states.
Keywords: rheology, polymer, rheopexy, pseudoplasticity, thixotropy
Kulcsszavak: reológia, polimer, reopexia, pszeudoképlékenység, tixotrópia
(ProQuest: ... denotes formulae omitted.)
1. Introduction
Rheological behavior of concentrated suspensions is an important area of research because it provides rich information, concerning flow and storage of relevant materials under operation conditions. There are many publications focusing on rheology of polymer concentrated suspensions filled with metal oxide powders of various particle diameters. The rheological properties depend on the solid phase concentration [1-3], particle size[2, 4-6], concentration and molecular weight of polymer [1-3,5-7] and also interaction between particles, solvent and polymer molecules [2, 5, 9]. Because of rapid development of microelectronics, the suspensions based on nanopowders represent the most promising objects for rheological investigations. Herewith, nanosized particles allow obtaining green ceramic layers with thickness of 700 to 800 nm and surface parameter Ra commensurable with size of nanoparticle [10].
It is known that screen printing pastes based on micron powders are generally required to be shear thinning, thixotropic over definite time scale and shear rate, stable for screen/shelflife and low solvent evaporation [11-13]. Therefore, terpineol [14-21] and its derivatives [17, 20, 22-25, 26-29] are used as a solvent, ethylcellulose as an organic binder [14, 15-21, 3042] because of their ability to form thixotropic systems with suspensions of particles of various origination [43]. However, there is almost no information about rheology of ethyl cellulose solutions in terpineol with the exception of [44], In turn, it is the main factor that reflects...