INFLUENCE OF CHAIN EXTENDER STRUCTURE AND RIGID BLOCK SIZE ON STRUC-TURE AND PROPERTIES OF ESTER URETHANE THERMOPLASTIC ELASTOMERS FOR CONSTRUCTIONAL PURPOSES

The influence of the structure of the chain extender and the size of the rigid block on the properties of urethane thermoplastic elastomers obtained on the basis of oligobutylene glycol adipate with a molecular weight of 1800 and 4,4'-diphenylmethane diisocyanate is considered. An aromatic diol, 2,2-bis-[4-(2-hydroxyethoxy)phenyl]propane, and an aliphatic diol, 1,4-butanediol, were used as a chain extenders.The synthesis of thermoplastic elastomers was carried out at a general molar ratio of [NCO]/[OH] = 1, which ensured the production of a linear polymers with terminal hydroxyl and isocyanate groups. At the same time, the formulations provided for a variation in the size of the diolurethane hard block due to a change in the molar ratio [diisocyanate]/[chain extender] = 2-3/1-2. X-ray diffraction analysis showed that samples obtained using an aromatic diol are amorphous, while the use of the aliphatic diol leads to the formation of amorphous-crystalline thermoplastic elastomers. The absence of a crystalline phase in the samples is due to the introduction of aromatic nuclei, methyl groups in the form of side branches and flexible simple ether bonds into their rigid block due to the use of 2,2-bis-[4-(2-hydroxyethoxy)-phenyl]-propane. As a result, the degree of phase separation decreases, phase compatibility increases and the ability of the polymer to elastic recovery improves. The use of 1,4-butanediol leads to the formation of a more ordered polymer structure, which contributes to the crystallization of the oligoester block. It has been established that replacing the aliphatic chain extender with an aromatic one results in obtaining low-modulus thermoplastic elastomers, reducing their hardness values, no residual deformations after removing the load, a slight decrease in strength, and an increase in thermal stability. An increase in the length of the rigid block causes an increase in the elastic modulus, strength, and hardness of the material. For citation: Bakirova I.N., Mineeva T.A. Influence of chain extender structure and rigid block size on structure and properties of ester urethane thermoplastic elastomers for constructional purposes. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2025. V. 68. N 6. P. 117-125. DOI: 10.6060/ivkkt.20256806.7192.