Abstract
The latest investigations on producing more efficient catalytic aqueouspolyurethane systems are in the domain of metal complexes with mixed ligands. In ourprevious research works, the high selectivity for the isocyanate-hydroxyl reaction inaqueous polyurethane systems has been shown by the manganese(III) mixed-ligandcomplexes. The two new complexes have been prepared with two acetylacetonate (acac)ligands and one maleate ligand and its hydroxylamine derivative of the general formula[Mn(C5H7O2)2L]. Their structures have been established by using the fundamental analyses,the FTIR and UV/VIS spectroscopic methods, as well as the magnetic measurements. Inorder to explain the different selectivity of the manganese(III) mixed-ligand complexes, theUV and ESR spectroscopy have been employed to determine the kinetics of the complexes’decomposition. The thermal stability of the complexes has been determined by way of thedynamic TG method at the heating rate of 5°C⋅min-1 and at the temperature ranged 20-550°C. It suggests the decomposition of the complexes by loss of acid ligand. The main factor in the selective catalysis control in theaqueous polyurethane systems is the nature of the acid ligands and their impact on themanganese(II)/manganese(III) equilibrium.
Highlights
The main problem in formulating the aqueous polyurethane systems is the isocyanate-water side reaction, which can lead to gassing/foaming, pinholes, loss of isocyanate functionality, low gloss, and a reduced pot life
In our previous works [5], the high selectivity is showed by the manganese(III) mixed-ligand complexes with two acetylacetone ligands and one maleate ligand and its hydroxylamine derivative
In order to explain the lower selectivity of Mn(III)diacetylacetonehydroxylaminmaleate in comparison to Mn(III)-diacetylacetonemaleate, as well as the different impact of inductive time on film hardness [11,12], the UV and electron spin resonance (ESR) spectroscopy have been used to determine the kinetics of the complex decomposition of the manganese(III) mixed-ligand
Summary
The main problem in formulating the aqueous polyurethane systems is the isocyanate-water side reaction, which can lead to gassing/foaming, pinholes, loss of isocyanate functionality, low gloss, and a reduced pot life. In our previous works [5], the high selectivity is showed by the manganese(III) mixed-ligand complexes with two acetylacetone ligands and one maleate ligand and its hydroxylamine derivative. The band at ~3564 cm-1 (-OH stretching vibration) indicate the acetylacetone ligand’s replacement with the maleic acid in the compound (I).
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