Synthesis and characterization of carborane containing polyester and derived polyuretahne adhesives

B ₁₀ H ₁₄ was prepared from NaBH ₄ via oxidation of B ₁₁H _I4 ^-1, and the Lewis base acetonitrile attacked the high electron density vertices on the B ₁₀H ₁₄ cage to form the complex, 6, 9-bis-(acetonitrile) decaborane. 1, 2-Bis-(acetoxymethyl) carborane (BAMC) was obtained by the reaction of 6, 9-bis-(acetonitrile) decaborane and 1, 4-diacetyl-2-butyne, which was then hydrolyzed to form 1, 2-bis (hydroxymethyl) carborane (BHMC). Hydroxy-terminated polyester containing carborane was prepared via the condensation polymerization of 1, 2-bis-(hydroxymethyl) carborane and adipyl chloride by controlling the molar ratios of diol and dichloride. The structures and purity of the monomers and polyester were confirmed by FTIR, ¹H-NMR, ¹¹B-NMR and element analysis. It was found that the ¹¹B-NMR of BAMC and BHMC was similar, which demonstrated carborane had high chemical stability. Two kinds of solvent-free polyurethane adhesives (PUA and PUB) were prepared based on carborane-polyester, N100 and PAPI, and their shear strength and thermal properties were determined. The results showed PUA and PUB could be used in the range of - 150 ∼200°C, and they could provide higher stability of adhesive joints to elevated temperatures than the normal PU adhesives. DSC showed that the exothermic peak of PUA appeared at 250°C, while the one of PUB appeared at 300°C, which demonstrated PUB had better thermal stability than PUA. The difference in properties of PUA and PUB derives from the different structures of curing agents. Therefore, introduction of carborane into PU adhesives not only retains the excellent low temperature resistance of PU, but also improves their thermal resistance.