Roles of phase separation and crystallization in the structure formation of new segmented polyurethane ureas and their n
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Russian Chemical Bulletin, International Edition, Vol. 69, No. 9, pp. 1740—1748, September, 2020
Roles of phase separation and crystallization in the structure formation of new segmented polyurethane ureas and their nanocomposites with single-walled carbon nanotubes* M. A. Gorbunova,a,b D. V. Anokhin,a,b,c V. Yu. Zaitsev,b A. A. Grishchuk,a and E. R. Badamshinaa aInstitute
of Problems of Chemical Physics, Russian Academy of Sciences, 1 prosp. Akad. Semenova, 142432 Chernogolovka, Moscow Region, Russian Federation. E-mail: [email protected] bM. V. Lomonosov Moscow State University, 1-51 Leninskie Gory, 119991 Moscow, Russian Federation cMoscow Institute of Physics and Technology (National Research University), 9 Institutskiy per., 141701 Dolgoprudny, Moscow Region, Russian Federation Crystal structure and supramolecular organization of new segmented thermoplastic polyurethane ureas and their nanocomposites with ultra-small additives (less than 0.1 wt.%) of single-walled carbon nanotubes (SWCNTs) have been been investigated using DSC and X-ray diffraction analysis. Taking into account the Avrami model, effects of physical aging and thermal history of the samples on the crystallization rate was described. It was demonstrated that the introduction of ultra small amounts of SWCNTs does not decrease the crystallinity, but decreases the crystallization rate. Key words: polyurethane, polyurethane urea, thermoplastic elastomer, single-walled carbon nanotubes, crystallization, phase separation, DSC, X-ray diffraction analysis.
Thermoplastic elastomers (TPEs) are block copolymers consisting of thermodynamically incompatible soft and rigid blocks, whose phase separation leads to the formation of nanodomains. Such a structure provides the opportunity to transform TPE-based materials into a viscous-fluid state at an elevated temperature using an environmentally friendly technology for molding and processing products. Among the existing types of TPEs, segmented thermoplastic polyurethanes and polyurethane ureas (TPUUs) are of great interest, and they have already become widely applied in industry due to their unique mechanical properties, durability, easy processing, etc.1—5 The rigid domains contain a large number of urethane or urethane urea units maintaining physical crosslinking through hydrogen bonds. The soft domains are hydroxycontaining polyesters capable of crystallizing at room temperature. In this case, the crystals play a role of additional nodes of the physical network, providing high strength characteristics to the material.6 On the one hand, TPUUs possess one among the highest values in terms of fabrication amounts, so improvements of their functional properties will expand the area * Based on the materials of the XXI Mendeleev Congress on General and Applied Chemistry (September 9—13, 2019, St. Petersburg, Russia).
of their application.7—9 On the other hand, these polymers are an interesting example of the structure formation at various levels, thus being the excellent model system to explore the effect of morp
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