Preparation and Properties of Azide-Modified Nitrocellulose and Its Click Reaction Curing Elastomer

To improve the toughness of the semi-rigid chain of nitrocellulose (NC), and to avoid the phenomenon of small molecule gas generated by isocyanate polycondensation reaction in the curing of propellant, glycidyl azide polymer (GAP)-hexamethylene diisocyanate (HDI)-NC (GAP-HDI-NC) graft polymer and its click reaction elastomer were successfully fabricated by azide-alkyne cycloaddition click reaction in this contribution. In addition, the formulations of GAP-HDI-NC graft polymer and its elastomer were optimized on the basis of improving the mechanical properties, thermal stability and safety. With the increasing of GAP content, the peak value of α transition at high temperature increases, that is, mechanical loss increases and tensile strength decreases. When the mass ratio of GAP to NC is 45:55, the tensile strength (σm) and breaking elongation (εb) of GAP-HDI-NC graft polymer are 44.1 MPa and 58.7% respectively, and the Tg1 of GAP-HDI-NC click reaction curing elastomer reaches the minimum value of 105.7 °C, which is much lower than that of pristine NC. When R2 value is 1.0, the σm of GAP-HDI-NC click reaction curing elastomer reaches the maximum value of 47.6 MPa, while when R2 value is 0.9, its εb reaches the maximum value of 55.8%. In addition, the click reaction of azide group is beneficial to improve the thermal stability and safety performance of GAP-HDI-NC click reaction curing elastomer, which has good potential as solid propellant binder.