Chemical Modification of Hydroxyl-Terminated Polybutadiene and Its Application in Composite Propellants

Abstract

In this article, hydroxyl-terminated polybutadiene (HTPB) was chemically transformed into multiamine, hydroxy polybutadiene (AEHTPB) by the adoption of appropriate synthesis strategies. The structure of AEHTPB was confirmed by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR). The modification degree was altered by adjusting reaction conditions to find out the effect of structural change on various physical properties, including the viscosity and glass transition temperature (T g ) of AEHTPB. Adding AEHTPB to the HTPB binder system could improve the cross-link density and strength of the polyurethane elastomer. Meanwhile, the experiment results indicated that AEHTPB could inhibit the low-temperature decomposition of ammonium perchlorate (AP) by forming a dense coating on the surface of AP. Then, the propellant level studies were conducted with the use of AEHTPB/HTPB mixture as a binder. As a result, the burning rate of propellant containing AEHTPB (5 wt %) was found to be reduced by 10.8% compared to HTPB-based propellant, and the mechanical properties of the propellant were superior to those of HTPB-based propellant with an improvement of 46.2% in tensile strength and 35.1% enhancement in elongation at break. Finally, tensile testing and observation of fracture surface morphology further demonstrated that AEHTPB had a significant bonding effect on AP-based propellant.

Properties of Hydroxyl‐Terminal Polybutadiene (HTPB) and Its Use as a Liner and Binder for Composite Propellants: A Review of Recent Advances

“…Numerous papers have been reported on the incorporation of energetic functional groups such as nitro [81] and others [17,18,22] having a positive effect on the combustion rate, although not on the mechanical properties, which are gen- erally outside the specifications [81]. Several polymers were made by chemically modifying HTPB using different methods [22,[132][133][134][135][136][137].…”

“…Numerous papers have been reported on the incorporation of energetic functional groups such as nitro [81] and others [17,18,22] having a positive effect on the combustion rate, although not on the mechanical properties, which are gen- erally outside the specifications [81]. Several polymers were made by chemically modifying HTPB using different methods [22,[132][133][134][135][136][137]. For example, a [4-(dimethylsilyl)butyl]alkyl ferrocene grafted HTPB derivative was appropriate to be used as burning rate accelerator catalyst in the preparation of a composite gas generator [138].…”

“…Due to the mismatch of different kinds of material bonded together, micro-voids, micro-cracks and, other defects are unavoidably introduced in the rocket manufacturing process. The interfaces turn out to be the weakest part of the whole structure [22,23,80,86,117,139]. Several strategies were developed to preserve the integrity of each layer and the interfaces.…”

“…Since then, still only a minor number of reports were published giving a general overview of HTPB properties [13][14][15][16] as far as our investigation has found. Other publications concentrated in particular aspects such as chemical modifications of HTPB [17,18] and its spe-cific role as binder in composite propellants [19][20][21][22], as a liner [23][24][25], and as thermal insulation [26][27][28].…”

Solid Propellant Formulations: A Review of Recent Progress and Utilized Components

“…Materials 2021, 14, 6657 2 of 17 In this work, we have aimed at summarizing the most relevant recent developments in the field of solid propellant formulations. Although the majority of recent reports focus on CPs and their modification.…”