Thermal Behavior of Polyurethane Ionomers Based on Amino Ethers of Orthophosphoric Acid
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CTURE AND PROPERTIES
Thermal Behavior of Polyurethane Ionomers Based on Amino Ethers of Orthophosphoric Acid I. M. Davletbaevaa,*, O. O. Sazonova, A. R. Fazlyeva, I. N. Zakirova, R. S. Davletbaevb, S. V. Efimovc, and V. V. Klochkovc a
Kazan National Research Technological University, Kazan, 420015 Tatarstan, Russia b Kazan National Research Technical University, Kazan, 420111 Tatarstan, Russia c Kazan Federal University, Kazan, 420008 Tatarstan, Russia *е-mail: [email protected] Received March 18, 2019; revised April 24, 2020; accepted May 6, 2020
Abstract—The products of triethanolamine- and triethylamine-catalyzed reactions of etherification of orthophosphoric acid using poly(oxypropylene glycol)-1000 are studied. It is shown that the nature of tertiary amine markedly influences the completeness of the etherification reaction. When using triethanolamine, its hydroxyl groups are also involved in the etherification of orthophosphoric acid. The resultant tertiary ammonium, which is a central unit of the synthesized branched amino ethers of orthophosphoric acid, is responsible for incomplete etherification and existence of space-separated ionic pairs in the structure of amino ethers. In the case of triethylamine, the etherification of orthophosphoric acid occurs almost completely to yield polyphosphates. The thermal behavior of ionomeric and nonionomeric polyurethanes is investigated. It is found that, for polyurethanes containing ionic groups, the glass transition temperature is much higher than that of nonionomeric polyurethanes. It is shown that phosphorus-containing nonionomeric polyurethanes possess higher thermal stability in inert atmosphere than phosphorous-containing polyurethane ionomers. The onset temperature of the thermal degradation for nonionomeric polyurethanes decreases considerably with an increase in the content of polyphosphates. Polyurethane ionomers synthesized using phospholipids feature a lower thermal stability than polyurethanes based on amino ethers of orthophosphoric acid. DOI: 10.1134/S0965545X2005003X
INTRODUCTION Polyurethanes are generally thermally stable materials. The thermal behavior of polyurethanes is affected by the chemical structure of oligodiols and diisocyanates used for their synthesis [1]. In thermal stability studies, thermal (in inert medium) and thermo-oxidative (in air atmosphere) degradations and pyrolysis (Т > 500°С) occurring by different mechanisms are distinguished. In inert atmosphere, the degradation temperature is defined by the structure of the hard segment, and under exploitation in air, degradation begins in the elastic phase and proceeds by the radical-chain mechanism [2]. The dissociation of urethane groups is usually observed at 230°С. The nature of diisocyanate is among the main factors controlling the thermal stability of polyurethanes. Polyurethanes based on aromatic diisocyanates are more stable than PUs synthesized using cycloaliphatic and aliphatic diisocyanates. Aromatic diisocyanates are characterized by a lower sensitivity to thermal oxidat
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