In this study, a nano-SiO₂ modified waterborne polyurethane (WPU) adhesive with remarkably low VOC content and high adhesion performance was successfully synthesized via in situ polymerization.

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.

As the hydroxyl-terminated polybutadiene (HTPB)-based binder system is widely applied in many industries, the curing process plays an important role in the final properties of the resulting product containing such a binder system. This study used a viscometer to measure viscosity buildup in the curing process of the binder system with various curing agents under isothermal conditions. Key parameters such as rheological reaction rate constant (k_ƞ) and pot life of different were measured and calculated. The rheological reaction rate constants of the HTPB-based binder systems included 0.0423 min⁻¹ (MDI), 0.0049 min⁻¹ (HDI-trimer) and 0.0014 min⁻¹ (HMDI). The pot lives of the HTPB-MDI, HTPB-TDI, and HTPB-HDI-trimer were 0.6 h, 3.6 h and 8.1 h, respectively. One interesting finding is that HTPB-HDI-trimer binder, which had the long pot life, exhibited an accelerated trend in the viscosity buildup in the late phase. This feature is of great significance to improving the final properties of the products generated in propellant manufacturing and other fields. The cause of this phenomenon and the curing process of HTPB-HDI-trimer binder system were analyzed and discussed in the present study.

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.

Polymer bonded explosives (PBXs) are a kind of rubbery explosives, in which the explosive components are bound together by a polymeric binder. The hydroxyl terminated polybutadiene (HTPB)-based polyurethane binder systems possess a unique combination of properties, including superior adhesion, excellent mechanical properties and have been widely used in rocket propellants, PBXs and other weapons. The cure reaction between HTPB and diisocyanates in the castable PBXs plays an important role in the adjustment of process parameters as well as properties of explosive formulations. In this paper, viscosity measurements were carried out at different temperatures (15 o C, 25 o C, 35 o C, 45 o C, 55 o C) to a series of systemic studies on the viscosity build-up and rheological reaction rate constant during the curing process of the of HTPB-dioctyl adipate (DOA)-diphenyl methane diisocyanate (MDI) binder system, discovered and explained the phenomenon that the pot-life of the binder system was prolonged when the curing temperature raised and the curing reaction rate was accelerated. And the rheology kinetic model of the HTPB-DOA-MDI binder system was established.

4,4′-Dichloro-2,2′,3,3′,5,5′,6,6′-octanitroazobenzene (DCONAB) is a kind of new heat-resistant energetic material. In the paper, its thermal decomposition kinetics was investigated by means of the thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The properties of the DCONAB, such as geometry, theoretical density, enthalpy of formation, detonation parameters, were studied by using the density universal culvert theory at the B3LYP/6-31+G (d, p) level. The results indicated that the density distribution of the DCONAB was up to 1.99 g/cm³ and its detonation rate was close to 8851 m/s. We obtained thermal analysis curves of the DCONAB at different heating rates and we analyzed the kinetic parameters such as activation energy (E _a) and exponential factor (A) with Kissinger and Flynn-Wall-Ozawa methods. Meanwhile, we investigated the decomposition mechanism of the DCONAB with the Satava-Sestak method. The results indicated that the thermal decomposition mechanism of the DCONAB related to nucleation and growth, with the reaction order n being 1. The integral form of the kinetic function was g(α) = α. The activation energy was 131 kJ/mol and the pre-exponential factor 1.375×10¹² min⁻¹.