Search Results (3)

Hydroxyl-terminated polybutadiene (HTPB) is widely used in polyurethane binders, adhesives, and elastomers, but its low polarity and unsaturated backbone limit adhesion and long-term stability. Epoxidation presents a promising approach to addressing these limitations. However, most prior studies have focused on high-cis polybutadiene (PB), and systematic tuning of epoxidation in industrial low-cis HTPB has not been thoroughly examined. In this work, the epoxidation conversion of low-cis HTPB was systematically controlled by varying the equivalent amount of 3-chloroperbenzoic acid (m-CPBA). Conversion was governed solely by oxidant stoichiometry, while reaction time, concentration, and temperature had minimal effect, consistent with rapid, mixing-controlled epoxidation. Selective modification of 1,4-cis and 1,4-trans units enabled direct evaluation of how epoxidation degree influences polyurethane network formation and performance. Polyurethanes derived from epoxidized HTPB (EHTPB-PU) exhibited a clear correlation between epoxidation degree and network formation. Mechanical, adhesion, and chemical-resistance measurements revealed optimal performance at 10% epoxidation, where polarity and network compactness are effectively balanced. At this level, polyurethanes showed enhanced tensile strength, broad substrate adhesion, and increased resistance to acidic, basic, polar, and nonpolar environments, along with reduced water uptake. These results identify moderate epoxidation as a practical and efficient strategy for improving HTPB-based polyurethane materials. Full article

This study investigates the influence of selected combustion rate catalysts on the ballistic, physicochemical, and mechanical properties of non-isocyanate heterogeneous solid rocket propellants. Methods for curing prepolymers and modifying hydroxyl-terminated polybutadiene (HTPB) to obtain carboxyl-terminated polybutadiene (CTPB) and its epoxidized derivative (EHTPB) are discussed. The initial stage involved the synthesis of CTPB and EHTPB. The obtained compounds were analyzed for viscosity, comparing their properties to those of the base polymer HTPB. FTIR spectra of the synthesized compounds were recorded. Crosslinking systems were formulated based on the synthesized substances and tested for tensile strength. The final stage consisted of preparing solid heterogeneous rocket propellants containing selected catalysts—catocene and iron nanopowder—and evaluating their burning rate, hardness, and density. The results of the rocket propellant tests indicate that both catalysts perform effectively in the proposed system. Significantly higher burning rates were achieved compared to the catalyst-free formulation. The addition of 1% catocene resulted in a 2.5-fold increase in burning rate. Even better performance was observed with iron nanopowder—1% addition led to an almost threefold increase in burning rate. Neither catalyst significantly affected the hardness of the propellant; all samples exhibited hardness values in the range of 71–76 Shore A. Increasing the catocene content led to a decrease in the final propellant density, whereas the addition of iron nanopowder increased the density relative to the base formulation. Full article

In this research, differential scanning calorimetry (DSC) was employed to compare the curing reaction kinetics of the epoxidized hydroxyl terminated polybutadiene-isophorone diisocyanate (EHTPB-IPDI) and hydroxyl terminated polybutadiene-isophorone diisocyanate (HTPB-IPDI) binder systems. Glass transition temperature (T_g) and mechanical properties of the EHTPB-IPDI and HTPB-IPDI binder systems were determined using the DSC method and a universal testing machine, respectively. For the EHTPB-IPDI binder system, the change of viscosity during the curing process in the presence of dibutyltin silicate (DBTDL) and tin 2-ethylhexanoate (TECH) catalysts was studied, and the activation energy was estimated. The results show that the activation energies (Ea) of the curing reaction of the EHTPB-IPDI and HTPB-IPDI binder systems are 53.8 and 59.1 kJ·mol⁻¹, respectively. While their average initial curing temperatures of the two systems are 178.2 and 189.5 °C, respectively. The EHTPB-IPDI binder system exhibits a higher reactivity. Compared with the HTPB-IPDI binder system, the T_g of the EHTPB-IPDI binder system is increased by 5 °C. Its tensile strength and tear strength are increased by 12% and 17%, respectively, while its elongation at break is reduced by 10%. Epoxy groups and isocyanates react to form oxazolidinones, thereby improving the mechanical properties and thermal stability of polyurethane materials. These differences indicate that the EHTPB-IPDI binder system has better thermal stability and mechanical properties. During the EHTPB-IPDI binder system’s curing process, the DBTDL catalyst may ensure a higher viscosity growth rate, indicating a better catalytic effect, consistent with the prediction results obtained using the non-isothermal kinetic analysis method. Full article