Isocyanate-Free Curing of Glycidyl Azide Polymer (GAP) with Bis-Propargyl-Succinate (II)

Four different GAP mixtures with di- and tri-functional GAP types were successfully cured with bis-propargyl-succinate (BPS) via 1,3 dipolar cycloaddition reaction between the azido groups of GAP and the triple bonds of the propargyl ester. Investigation of one series of curing on di-functional and another series on trifunctional GAP was done and compared with two additional curing series on mixtures of di- and tri-functional GAP. The BPS which acted as a curing agent analog to isocyanate in classical polyurethane systems, was varied in its content, and the influence on the mechanical properties of the cross-linked binders was measured by tensile tests. The mechanical properties could be adjusted in a wide range by varying the amount of BPS. The E modulus of the tested samples was in the range of 0.06 - 0.674 N mm(-2) at elongations between 50 and 95% and the maximum stress was in the range of 0.05 - 0.32 N mm(-2). Increasing contents of BPS showed, in thermal analysis by DSC, only a small decrease in the decomposition energy and slightly raised glass transition temperatures. The required amount of inert curing agent for complete cure of GAP is lower for BPS in comparison to isocyanate, so this will result in a higher total energy content in the binder system. However, BPS-cured systems can lead to higher glass transition temperatures than isocyanate-based binder systems. The curing process has been monitored by measuring the increasing viscosity at 50 and 60 degrees C. The curing time of the investigated binder systems for quantitative curing at 65 degrees C is around four days, which was checked by measuring the surface hardness, but at room temperature the premixed curing samples staid liquid for around 1 week.