A Study On Isocyanate-free Curing Of Energetic Binders-GAP

To achieve isocyanate-free curing of glycidyl azide polymer (GAP), the 1,3-dipolar cycloaddition reaction between terminal alkynyl and azide was used for curing of GAP. Three novel multiple acetylene-terminated compounds were used or synthesized as curing agents of GAP according to the request of cross-linked network. The curing behavior of isocyanate-free curing system were investigated via differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). The curing reactivity of isocyanate-free curing system and triisocyanate (N100) curing system were compared by FT-IR tracking experiment. The curing reaction kinetics of isocyanate-free curing system was explored by non-isothermal DSC and isothermal DSC. The static and dynamic mechanical properties of different curing films were characterized with tensile test and dynamic mechanical analysis (DMA) respectively. The energy characteristics was tested by DSC and the internal morphology was observed by microscope. Following are the conclusions of the study.(1) Bis(2-methylbut-3-yn-2-yl)hexane-1,6-diyldicarbamate(HDPC) and Di(but-3-yn-l-yl) hexane-1,6-diyldicarbamate (DHD) are synthesized respectively via isocyanate method with the raw materials of dimethyl propargyl carbinol,3-Butyn-l-ol and hexamethylene diisocyanate. GAP is cured with TPTM, HDPC and DHD via 1,3-dipolar cycloaddition reaction and triple cross linkages is ready to form. The sequence for curing reactivity with GAP of four curing agents is TPTM> N100> HDPC≈DHD.(2) TPTM system initial curing temperature is 75℃ and the HDPC system and DHD system about for 96℃ when the heating rate is 10℃/min. TPTM system can be cured completely in 8 hours when the isothermal curing temperature is 60℃, however, N100 system must be cured for 55 hours at least. HDPC system and DHD system can’t be cured totally under 60℃, and it is necessary to be reacted for 45 hours under 70℃ for curing idealy.(3) The mechanism of isocyanate-free curing system are consistent, and their curing reaction model belong to the n-model together. The kinetic equation of TPTM system can well predict the isothermal curing reaction process during whole curing course, while HDPC system and DHD system can be predicted well when curing degree a are less than 0.72 and 0.76 respectively.(4) Compared with the actual application of N100 film, TPTM film and DHD film can reached its mechanical properties with fewer curing agent, and the thermal decomposition energy of TPTM film and DHD film is larger, at the same time the glass transition temperature Tg of TPTM film is lower; HDPC film has better mechanical performance, and the glass transition temperature and the thermal decomposition energy between HDPC film and N100 film are similar. There is much air holes in N100 film, and three kinds of isocyanate-free curing film without any air hole.