On the functionalization and characterization of hydroxyl‐terminated polybutadiene with octyl‐1‐azide and the evaluation of polyurethane elastomers based on such modified HTPB

Abstract

Hydroxyl-terminated polybutadiene (HTPB) has been modified with azidocontaining substances to be applied in propulsion systems. Pristine HTPB has compatibility issues with energetic polar substances and plasticizers, which is a drawback to develop new high-energy propellants. This work presents a path for the functionalization of HTPB, carried out through a controlled bulk reaction of it with octyl-1-azide. Then it was reacted with isophorone diisocyanate with or without dioctyl adipate (DOA). Structural, thermal, rheological, and dynamic-mechanical assessments were accomplished. Infrared revealed the arising of absorption bands associated to the C N stretching. From 13 C and 1 H nuclear magnetic resonances, it is possible to deduce the presence of amine, aziridine, and imine chemical groups, which may promote compatibilization with other polar and energetic substances. The chemical modification induced an increase of viscosity. With respect to the glass-liquid and glass-rubber transitions, the modification shifted them slightly to higher temperatures, but created stiffer networks, in agreement with the increase of polarity and chain interaction due to the presence of N-containing functionalities. Regarding the solid elastomer binder, the storage shear modulus and molecular mobility were influenced by the type of HTPB and DOA content. In general, the modified HTPB has physical properties like pristine HTPB.

Synthesis and Comparative Study of Polyether-b-polybutadiene-b-polyether Triblock Copolymers for Use as Polyurethanes

“…The 1 H NMR spectra and 13 C NMR spectra of all samples were tested using a Bruker Avance-400 NMR instrument (Bruker Corporation, Berlin, Germany). Deuterated chloroform (CDCl 3 ) was used as a solvent, and tetramethylsilane (TMS) was used as an internal reference.…”

“…However, HTPB is non-polar and, therefore, poorly compatible with polar components. As such, there have been numerous reports on modification strategies to increase the polarity of HTPB, such as main-chain epoxidation, side-group polarization, and polyester or polyether block modification [ 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. Among these strategies, polyether block modification of HTPB, which refers to the preparation of triblock copolymers, is one of the more feasible routes for HTPB polarization and has been widely investigated [ 15 , 16 , 17 ].…”

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]. 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].…”

Rheological kinetics of ferrocenylsilane functionalized polyurethanes based on 4,4'‐methylenediphenyl diisocyanate for advanced energetic materials

“…In addition, novel functionalized polyols based on HTPB are of interest for the development of a new class of advanced PUs. [11][12][13] This class of molecules includes, butacene, which consists of a (ferrocenylbutyl)dimethylsilane grafted onto HTPB (see Scheme 1). Butacene is used as a binder and nonmigrating burning-rate catalyst for solid composite propellants with higher combustion kinetics.…”

“…TPUs based HTPB are popular binders used in the production of energetic materials, such as composite solid propellants, pyrotechnics, explosives, and liners in the aerospace field. In addition, novel functionalized polyols based on HTPB are of interest for the development of a new class of advanced PUs 11–13 . This class of molecules includes, butacene, which consists of a (ferrocenylbutyl)dimethylsilane grafted onto HTPB (see Scheme 1).…”