Fluoropolymer/Glycidyl Azide Polymer (GAP) Block Copolyurethane as New Energetic Binders: Synthesis, Mechanical Properties, and Thermal Performance

Abstract

In order to enhance the application performance of glycidyl azide polymer (GAP) in solid propellant, an energetic copolyurethane binder, (poly[3,3-bis(2,2,2-trifluoro-ethoxymethyl)oxetane] glycol-block-glycidylazide polymer (PBFMO-b-GAP) was synthesized using poly[3,3-bis(2,2,2-trifluoro-ethoxymethyl)oxetane] glycol (PBFMO), which was prepared from cationic polymerization with GAP as the raw material and toluene diisocyanate (TDI) as the coupling agent via a prepolymer process. The molecular structure of copolyurethanes was confirmed by attenuated total reflectance-Fourier transform-infrared spectroscopy (ATR–FTIR), nuclear magnetic resonance spectrometry (NMR), and gel permeation chromatography (GPC). The impact sensitivity, mechanical performance, and thermal behavior of PBFMO-b-GAP were studied by drop weight test, X-ray photoelectron spectroscopic (XPS), tensile test, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA), respectively. The results demonstrated that the introduction of fluoropolymers could evidently reduce the sensitivity of GAP-based polyurethane and enhance its mechanical behavior (the tensile strength up to 5.75 MPa with a breaking elongation of 1660%). Besides, PBFMO-b-GAP exhibited excellent resistance to thermal decomposition up to 200 °C and good compatibility with Al and cyclotetramethylene tetranitramine (HMX). The thermal performance of the PBFMO-b-GAP/Al complex was investigated by a cook-off test, and the results indicated that the complex has specific reaction energy. Therefore, PBFMO-b-GAP may serve as a promising energetic binder for future propellant formulations.

Review on energetic copolymer binders for propulsion applications: Synthesis and properties

“…However, they are thermoset‐polymers that are often difficult to recycle. Furthermore, owing to the strong polarity of azide groups and the relatively inflexible nature of the polymer chain, they display both marked sensitivity and compromised mechanical characteristics 20–22 . To overcome these drawbacks and improve its performance, various azido‐based copolymers have been developed as binder for CSPs.…”

Nanoenergetic Composites with Fluoropolymers: Transition from Powders to Structures

“…Xu et al [ 64 ] reported an alternate type of GAP-based fluorinated polyurethane, synthesized by the copolymerization of GAP and 3,3-bis(2,2,2-trifluoroethoxymethyl) oxetane] glycol (BFMO) using toluene diisocyanate (TDI) as the crosslinker ( Scheme 4 ).…”

High Performance Thermoplastic Energetic Composites Using Fluorinated Energetic Polyurethanes as Binder

“…Xu and coworkers [17] reported the synthesis of the fluorinated glycidyl azide polymer poly (2, 2, 2‐trifluoro‐ethoxymethyl epoxy‐ r ‐glycidyl azide), and the cook‐off test results indicated that the poly (TFEE‐ r ‐GA)/Al mixture gave a larger reaction energy than GAP/Al mixture. In another report from the same group, the fluorine‐containing polyurethanes of poly [3, 3‐bis (2, 2, 2‐trifluoro‐ethoxymethyl) oxetane] glycol‐block‐glycidyl azide polymer were synthesized, and the cook‐off test results also indicated that the PBFMO‐ b ‐GAP could enhance the energy release of the PBFMO‐ b ‐GAP/Al composites [18]. However, up to date, there have been very limited examples of energetic fluorine‐containing polymers, let alone a comprehensive understanding of their effect on the resultant energetic composites, including their basic properties, energy level and combustion, and so on.…”