Synthesis and characterization of HTPB-GAP cross-linked co-polymers

Abstract

Abstract-Cross-linked co-polymers containing glycidyl azide polymer (GAP) and hydroxyl-terminated poly(butadiene) (HTPB) segments have been obtained by chemical reactions. The reactions involves two steps. In the first step the GAP macroinitiator (GAPMI) is synthesized by the condensation reaction of GAP-diol with 4,4 -azobis(4-cyanopentanoic acid) (ACPA) in the presence of N-methyl-2-chloropyridinium iodide (MCPI). The GAPMI obtained is used for the cross-linking or grafting reactions with HTPB at an elevated temperature in the second step. The cross-linked co-polymers are isolated from the crude reaction mixture by fractional precipitation technique using chloroform as solvent and methanol as non-solvent. The co-polymers have been well characterized by using IR, 1 H-NMR and 13 C-NMR spectral analysis, and the molecular weights of the co-polymers have been determined by gel permeation-chromatography (GPC) and vapour pressure osmometry (VPO). The co-polymer exhibited two glass transition temperatures for HTPB-GAP co-polymer, at −74.03 • C and −35.84 • C. During the thermal analysis, the cross-linked co-polymers exhibited two exothermic peaks and one endothermic peak, indicating the presence of HTPB and GAP polymeric chain segments in the co-polymers. Further, the TGA studies revealed a four step-weight loss, suggesting the decomposition of the co-polymer is similar to that of their homo-polymers.

Structure and mechanical properties of fluorine-containing glycidyl azide polymer-based energetic binders

“…However, it has been recognized that GAP‐based propellants have certain drawbacks associated with them, such as poor machinability, low solid loading and inferior mechanical properties in energetic formulations owing to the highly polarity of azido groups and poor flexibility of the backbone. Especially, they suffer from poor low‐temperature properties such as critical temperature, below which the binder starts to rapidly lose its elastomeric properties …”

Structure and mechanical properties of novel composites based on glycidyl azide polymer and propargyl‐terminated polybutadiene as potential binder of solid propellant

“…Furthermore, GAP shows a good compatibility with advanced oxidizer like ammonium dinitramide. The as-synthesized copolymer showed two glass transition temperatures located at 274.03and 235.84 C assigned to HTPB and GAP, respectively, 16 whereas the decomposition of the components in copolymer was similar to that of their homopolymers. 5,6 As a result, the polyurethane-type binder systems based on GAP and/or HTPB have been explored, and the crucial crosslinked structure and mechanical performances were optimized by changing the diisocyanate categories, 7-9 applying chain extender and/or crosslinker of small molecular polyols, 10 regulating the molar ratio of isocyanate group versus hydroxyl group, 7,10 incorporating other polymer component, [11][12][13][14] and so on.…”

Improvement of mechanical characteristics of glycidyl azide polymer binder system by addition of flexible polyether

“…In recent years, improving the mechanical properties of GAP propellant by blending modification has been paid more attention for its efficiency and simplification. The mechanical properties of GAP elastomers can be improved markedly by introducing different contents of polymers that have a flexible backbone, such as poly(ethylene glycol) (PEG), polycaprolactone (PCP), poly(ethylene oxide‐ co ‐tetrahydrofuran) [P(EO ‐co‐ THF)], and HTPB . Although many polymers have been found to have a positive effect on improving the mechanical properties of the GAP binder system, the specific effect of these polymers on a GAP‐based network has rarely been reported.…”