Characterization of polyester-based polyurethane elastomers plasticized with energetic ionic liquids

Energetic ionic liquids (EILs) were used as plasticizers in polyester-polyol based polyurethane elastomer samples. The polyol was Desmophen® D2200 cured with Desmodur® N3400. The elastomer samples were characterized in terms of dynamic mechanical properties, tensile strength and thermogravimetry. The EIL samples are based on 4‐Amino‐1‐alkyl‐1,2,4‐triazolium nitrate and are mixtures with different alkyl length, named aN1 and bN2. The first is a mixture containing longer alkyl substituents (4, 6 and 8 carbons), whereas the second one has shorter alkyl substituents (1 and 4 carbons). The addition of ionic liquids to the elastomer did not affect the main glass-rubber transition temperature (Tg) of the binder. However, the dynamic mechanical properties are changed especially after Tg. Tensile testing showed that at ambient temperatures the addition of ionic liquids increased substantially the strain capability of polyester-based polyurethane binder. In the case of the addition of molecules with shorter aliphatic substituents, also higher maximum tensile stress is achieved. EILs as plasticizer impart a very soft rubbery behaviour to the binder, reflected also by the decrease in Young moduli. Thermogravimetry analysis showed a relatively high thermal stability of the EILs compared to other common energetic plasticizers in the elastomer bulk.