Polyurethane binder systems based on hydroxyl-terminated polybutadiene (HTPB) possess several superior properties such as superior adhesion, high solid-loading capacity, outstanding mechanical performance, etc. They have been widely used in coatings and adhesives as well as in medical and military industries. The cure reaction between hydroxyl-terminated polybutadiene (HTPB) and diisocyanates plays a key role in the properties of final products as well as the adjustment of process parameters. FT-IR spectroscopy is applied to investigate the kinetics of the curing reaction of HTPB and isophorone diisocyanate (IPDI) in the presence of a low toxic and low viscosity catalyst, stannous isooctoate (TECH). The concentrations of the isocyanate groups (NCO) characterized by FT-IR during the cure reaction with respect to time were recorded at different temperatures and at constant stoichiometric ratio R_n[NCO]/n[OH] = 1.0. The kinetic parameters, i.e., activation energy (E_a), pre-exponential factor (A), activation enthalpy (ΔH) and activation entropy (ΔS) were determined. In addition, the curing process and mechanism of the HTPB-IPDI reaction are discussed.

In this research, rheokinetics is used to study the curing reaction of hydroxyl terminated polybutadiene (HTPB) and trimer of hexamethylene-1,6-diisocyanate (HDI-trimer) with 1,4-diazabicyclo[2.2.2]octane (DABCO) as catalyst under different catalyst mass fraction. The results show that the pot life of the system depends on the catalyst mass fraction in the binder system. Furthermore, with increased catalyst mass fraction, the fitting diagram obtained by plotting ln (viscosity) versus curing time shows a better linear relationship. Therefore, the amount of catalyst required to achieve a certain pot life can be calculated through the formula. It is worth mentioning that the applicable pot life equations are proposed in the paper. From the equations, we find that under isothermal curing conditions at 35 °C, when the mass fraction of DABCO was 0.216 wt.%, the pot life of the HTPB/HDI-trimer binder system reaches 4 h.

Boron possesses the second greatest heating value of any element that can be adopted as an energetic material in the processing of propellants and explosives. It has become the first choice as a high energy fuel for solid fuel-rich propellants because of its advantages of high theoretical combustion heat. In the actual condition, the combustion efficiency of boron-containing fuel-rich propellants is low, and the potential energy of boron cannot be fully utilized. The compound containing-boron can be used as a new way to improve the combustion efficiency of fuel-rich propellants. In this paper, the progress in the synthesis of energetic borides is reviewed from the perspectives of molecular design, synthesis strategy and route optimization. The situation of the synthesis methods of energetic borides (nitrogen-rich boron esters, poly(azole)borates, nitroboranes, nitrogen-rich borazines and azide boron compounds) is reviewed. The research focus and development trend of various boron compounds are analyzed, and the potential application prospect in the propellant is investigated.

A new energetic organic potassium salt of dihydridobis (3-nitro-1,2,4-triazolyl) borate was synthesized from 3-nitro-1,2,4-triazole and potassium borohydride at 110 °C, and structurally characterized by elemental analysis, IR spectra, 13C NMR and singlecrystal X-ray diffraction. Results show that the crystal belongs to monoclinic system with space group of p21 / C and cell parameters of a = 10.335 (8) Å, B = 10.812 (8) Å, C = 9.821 (8) Å, α = 90 ˚, β = 106.470 (13), γ = 90 °, z = 4. Its crystal density is 1.755g/cm3. Thermal properties were studied with TG-DTA and DSC. There was only one sharp decomposition peak temperature of 270 °C at the heating rate of 10 °C/ min-1. The activation energies EK = 48.0kJ/mol-1 and EO = 49.8kJ/mol-1 were calculated by the Kissinger method and Ozawa method respectively (CCDC: 1975139).