Effect of diacylhydrazine as chain extender on microphase separation and performance of energetic polyurethane elastomer

Abstract

It is low cost and feasible to improve the mechanical properties of polyurethane by using the chain extender with hydrogen bonding function to improve the degree of microphase separation. In this article, hydrazine hydrate was used to react with ethylene carbonate and propylene carbonate, respectively, to synthesize diacylhydrazines as the polyurethane chain extender with amide bonds, which were characterized by 1H nuclear magnetic resonance. Polyurethane with different contents of hard segment were prepared from poly-3,3-bis(azidomethyl)oxetane-tetrahydrofuran as the polyol and 4,4′-diphenylmethane diisocyanate as the isocyanate components. Fourier transform infrared spectroscopy showed that with the increase of the hard segment content, the proportion of hydrogen-bonded ordered carbonyl group increased to 94%, proving that diacylhydrazines could improve the degree of ordered hydrogen bonding, which led to clear microphase separation observed by field emission scanning electron microscopy and higher storage modulus of the polyurethane. Differential scanning calorimetry and dynamic mechanical analysis showed that polyurethane with higher hard segment content is likely to exhibit multiple thermal transitions caused by microphase separation. When the hard segment content was 40%, compared with polyurethane with 1,4-butanediol as the chain extender, the tensile strengths of polyurethanes with diacylhydrazines also improved by 30% and 76%, respectively.

A review on microphase separation measurement techniques for polyurethanes

“…The higher the phase separation, the higher the hydrogen bonded N-H (C=O) stretching intensity will be. 101,102 Hydrogen bonding index (HI) is another criterion which can be calculated based on the FTIR spectra and is considered as a powerful criterion for measuring phase segregation (equation ( 4)). Higher HI represents higher phase segregation 78…”

“…The hydrogen bonding between hard segments strongly correlates with PU microphase separation. Therefore, in this method, the vibrations arise from the hydrogen bonded N-H or C=O moieties of the urethane group as well as those of free N-H or C=O moieties are considered and the degree of phase separation is calculated by the equations (2) and (3) 101,102 where…”

“…The higher the phase separation, the higher the hydrogen bonded N-H (C=O) stretching intensity will be. 101,102…”

A bioinspired Janus polyurethane membrane for potential periodontal tissue regeneration

“…50 Regarding the micro-pit morphology, a possible explanation is that the LDA chain extender contains a benzene ring structure with a large steric hindrance, which leads to large phase separation from the hard segments of polyurethane and even then a small amount of LDA does not participate in the chain extension reaction. 51,52 During the process of forming the membrane, the quaternary ammonium salt group migrates to the upper surface of the polyurethane membrane, while the unreacted LDA molecules and enriched dopamine segments are repelled to the bottom substrate-contact surface. 24,25 When immersed in water, the unreacted LDA molecules and soluble dopamine segments dissolve out from the bottom side.…”

Polyhydroxylated Nanosized Graphite as Multifunctional Building Block for Polyurethanes

“…The polar groups on the carbon surface would indeed be beneficial. Moreover, PU/GRM nanocomposites could be used for shape memory materials [ 43 , 44 ].…”