Energetic Binder Research Articles

Preparation of Azido Polycarbonates via Bulk Polymerization of Halogenated Diols

AbstractAzido polymers find use as energetic binders in a variety of composite explosive and propellant applications, but few azido polyesters have previously been reported: a method is introduced for the preparation of two azido polycarbonates, poly(2,2’‐bisazidomethyl‐1,3‐propyl carbonate) and poly(3‐azido‐1,2‐propyl carbonate), possible binder candidates for energetics applications. The preparation method for these polymers involves a two‐step synthesis starting from the bulk polymerization of the commercially sourced diols with diphenyl carbonate in the presence of lanthanum (III) acetylacetonate as a neutral catalyst, and subsequent azidation in cyclohexanone. The physical and thermal characteristics of each are reported, indicating properties similar to other azido‐polymers. The thermal and mechanical properties of cured azido polyester resin mixtures are the subject of ongoing research.

Exploring the telechelic block copolymers of polybutadiene and ϵ-caprolactone for composite propellant application

In this study, synthesis of three hydroxyl-terminated block copolymers of varying molecular weight by ring opening polymerization of ԑ-caprolactone using hydroxyl-terminated poly butadiene as the initiator and stannous octoate as the catalyst was attempted. These block copolymers were specifically synthesized for its application in solid rocket propellants as an energetic binder. The desired chemical links between blocks were noticed in 1H nuclear magnetic resonance (NMR) and 13C NMR spectra, followed by confirmation in 1H/13C heteronuclear single quantum coherence and Fourier transform infrared spectra. To specify these block copolymers, various properties such as hydroxyl value (OH value), number average molecular weight (M¯n), specific gravity (ρ), rheological properties, glass transition temperature (Tg), thermal decomposition, and miscibility with nitrate ester plasticizers were determined. Additionally, the mechanical properties of the samples were evaluated using isocyanates as curators at NCO/OH equivalence ratio of 0.8 and 1.0. Finally, the best combination was selected based on physicochemical properties and miscibility with nitrate esters for further evaluation in composite propellant. We also theoretically studied the ballistic parameters of composite propellants by the NASA CEC-71 program to observe the gain of density impulse as the plasticizer to polymer ratio was increased.

Synthesis and characterization of carboxylated PBAMO copolymers as promising prepolymers for energetic binders.

The carboxylated poly[3,3-bis(3-azidomethyl)oxetane] (PBAMO) copolymers (poly(BAMO-carboxylate)) were synthesized by substitution of poly[3,3-bis(3-chloromethyl)oxetane] (PBCMO) with potassium carboxylate and sodium azide in DMSO. The synthesized compounds were characterized using various analytical techniques, such as Fourier-transform infrared (FT-IR) spectroscopy, inverse-gated decoupling 13C-nuclear magnetic resonance (13C NMR) spectroscopy, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), calorimetry, friction, and impact sensitivity analysis. These poly(BAMO-carboxylate) compounds have better thermal properties, with lower glass transition temperatures (ranging from −43 °C to −51 °C) than PBAMO (−37 °C) and higher thermal decomposition temperatures (233–237 °C) than PBAMO (211 °C). Moreover, poly(BAMO0.80-octanoate0.20) and poly(BAMO0.78-decanoate0.22) have higher heats of combustion (5226 and 5665 kJ mol−1, respectively) and negative formation enthalpies (−0.17 and −0.55 kJ g−1, respectively), while PBAMO has lower heat of combustion (3125 kJ mol−1) and positive formation enthalpy (0.06 kJ g−1). The poly(BAMO-carboxylate) compounds have higher values (38–50 J) than that of PBAMO (14 J) in the impact sensitivities. This is a valuable study for improving the properties of PBAMO, which is a high energetic polymeric binder but difficult to handle because of its sensitivity. Therefore, poly(BAMO-carboxylate) could be a good candidate as a prepolymer for designing the energetic polymeric binder.

Experimental and Simulation Study on Glass Transition Temperatures of GAP with Ionic‐Liquid‐Based Energetic Plasticizers

AbstractMolecular dynamics (MD) simulations and experiments were carried out to study the glass transition temperature of glycidyl azide polymer (GAP) which is widely used in propellants as an energetic binder. A modification method was applied to improve the mechanical properties of GAP at low temperatures, through the addition of energetic ionic liquid plasticizers to the polymer matrix. The design and simulate under the COMPASS force field, with the ensembles of constant particle number, pressure, temperature (NPT) done. The variation of density and free volume of polymers was observed with decreasing the temperature, and the glass transition temperatures (Tg) were estimated based on the variation of density and free volume vs. temperature. Simulation and experimental results revealed that the addition of energetic ionic liquid plasticizer to the polymer matrix reduced Tg. Also, by changing the anion of ionic liquid, the size of the molecule and the number of atoms, the value of Tg was changed. The variations were 235 K (GAP), 233 K (GAP/IL‐N3), 230 K (GAP/IL‐NO3) and 214 K (GAP/IL–DCA).

Glycidyl Azide Polymer and its Derivatives-Versatile Binders for Explosives and Pyrotechnics: Tutorial Review of Recent Progress.

Glycidyl azide polymer (GAP), an energetic binder, is the focus of this review. We briefly introduce the key properties of this well-known polymer, the difference between energetic and non-energetic binders in propellant and explosive formulations, the fundamentals for producing GAP and its copolymers, as well as for curing GAP using different types of curing agents. We use recent works as examples to illustrate the general approaches to curing GAP and its derivatives, while indicating a number of recently investigated curing agents. Next, we demonstrate that the properties of GAP can be modified either through internal (structural) alterations or through the introduction of external (plasticizers) additives and provide a summary of recent progress in this area, tying it in with studies on the properties of such modifications of GAP. Further on, we discuss relevant works dedicated to the applications of GAP as a binder for propellants and plastic-bonded explosives. Lastly, we indicate other, emerging applications of GAP and provide a summary of its mechanical and energetic properties.

Nitramine-Group-Containing Energetic Prepolymer: Synthesis, and Its Properties as a Binder for Propellant

A composite solid propellant which generates high propulsive force in a short time is typically composed of an oxidizer, a metal fuel powder and a binder. Among these, the binder is an important component. The binder maintains the mechanical properties of propellant grains and endures several thermal and mechanical stresses in the engine. Several studies have been reported for the development of energetic propellant binders for increasing the propellant′s propulsive force. While several materials have been studied for the synthesis of energetic prepolymers, a nitramine-group-containing prepolymer is a suitable candidate because these types of prepolymers are less toxic and more cost-effective when compared to the traditional glycidyl azide polymers (GAP) and triazole-based prepolymers. Considering the lack of studies for the binder using a nitramine-group-containing prepolymers, we synthesized a nitramine-group-containing monomer and polymerized a nitramine-group-containing prepolymer. The prepolymer was then used for the preparation of the binder and its thermal and mechanical properties, as well as the effect of the plasticizer, were studied. The binder that was prepared using the prepolymer containing a nitramine-group showed very high elongation, tensile strength. Nitrate-ester (NE)-type plasticizer could reduce the glassy transition temperature (Tg)of the binder successfully. Also, high-energy is released due to the decomposition of the nitramine-group at around 245 °C, thus exhibiting the efficiency of the nitramine-group-containing prepolymer as an excellent energetic binder material.

Chemical Modification of β-Cyclodextrins: Balancing Soft and Rigid Domains in Complex Structures.

Crystalline polymers such as β-cyclodextrin (βCD) can be modified with polyethylene glycol (PEG) diglycidyl ether cross-linkers (262, 394, 500 Da). In this work, the authors show that the quantity and length of the PEG soft segments influence the solubility and malleability of the products, which are water soluble and easily converted to nitrated analogues under standard reaction conditions. Inert and nitrated derivatives containing longer PEG segments showed the ability to self-heal. The degree of cross-linking and decomposition temperatures and energies depended on the quantity and length of the soft segment. Nitrated cross-linked βCD containing longer PEG segments did not ignite following an electrostatic discharge of 4.5 J. The chemical stability of βCD/PEG binders was tested by heat flow calorimetry at 80 °C. The balanced incorporation of soft PEG and rigid βCD segments was found to improve the processability of cross-linked βCDs and desensitised their nitrated derivatives, offering new solutions for inert and energetic binders.

A Promising Energetic Polymer from Posidonia oceanica Brown Algae: Synthesis, Characterization, and Kinetic Modeling

AbstractIn this study, microcrystalline cellulose nitrate (MCCN) as energetic polymer is successfully obtained from Posidonia oceanica brown algae (POBA). Fourier transform infrared spectroscopy (FTIR) results show alterations in the intensities of some absorption bands, suggesting a significant difference in the chemical structure between microcrystalline cellulose and the emergent MCCN samples. X‐ray diffraction (XRD) measurements indicate that MCCNs are more crystalline than conventional nitrocellulose (NC). According to scanning electron microscopy (SEM), both NC and MCCN reveal a compact structure and a rough surface. Differential scanning calorimetry (DSC) displays that the thermal degradation of MCCNs shifts to lower temperatures compared to the respective NCs. Furthermore, in comparison with NC samples, MCCN samples exhibit high density, high nitrogen content, low viscosity‐average molecular weight, and good thermal stability. On the other hand, kinetic modeling based on DSC data is carried out by isoconversional integral methods to determine Arrhenius parameters and the decomposition mechanisms. It is found that MCCNs present lower activation energies than conventional NCs with a decrease of ≈6%. Finally, this work opens a new pathway to prepare MCCN from POBA, and it is expected to have applications in several areas such as propellants, energetic binders, and gas generators.

Examining the compatibility of energetic plasticizer DNDA-5 with energetic binders

The requirement of developing energetic binders with suitable energetic plasticizers is to enhance the mechanical properties and to reduce glass transition temperature of propellant and explosive formulations. Compatibility of energetic plasticizer 2,4-dinitro-2,4-diazapentane (DNDA-5) with four different energetic binders viz. poly glycidyl nitrate (PGN), poly(3-nitratomethyl-3-methyloxetane) (PLN), glycidyl azide polymer (GAP) and tetra functional glycidyl azide polymer (t-GAP) was studied by using differential scanning calorimeter (DSC) and density functional theory (DFT) methods. Results obtained for the pure binder was compared with the results obtained for binder/plasticizer blend in the parameters of decomposition temperature and the format of the peak which indicated the compatibility or incompatibility of DNDA-5 with the studied binders. Glass transition temperatures of all these blends were determined by low temperature DSC and showed desirable lowering of glass transition temperature with single peak in the case of PLN. The proposed energetic plasticizer DNDA-5 has displayed its compatibility with three binders PGN, PLN and GAP employing thermal techniques. DNDA-5 has been found as incompatible when it is mixed with t-GAP. The predicted relative trend of interaction energies between plasticizer and binder has provided concurrence to results drawn from thermal studies.

PolyNIMMO-HTPE-polyNIMMO triblock copolymer as a potential energetic binder: Synthesis and characterization

A novel energetic polymer binder was developed through ring opening copolymerization of 3-nitratomethyl-3-methyloxetane (NIMMO) with (HTPE) as a macroinitiator to form tri-block copolymer polyNIMMO-HTPE-polyNIMMO. The structure of tri-block copolymer was confirmed by FTIR, 1H NMR, 13C NMR and GPC. In comparison with HTPE, polyNIMMO-HTPE-polyNIMMO has a higher viscosity because of its increased molecular weight with additional ONO2 as side groups and strengthened intermolecular interaction. The glass transition temperature studies show two glass transition processes in their DSC curves. One signal around −69 °C arises from the HTPE segment, while the other signal around −30 °C is related to the terminal polyNIMMO segments in the tri-block polymers. The TGA-DTG and DSC curves indicate that polyNIMMO-HTPE-polyNIMMO has a good thermal stability and its exothermic decomposition peak is found to be around 220 °C. The kinetic parameters and the thermodynamic parameters for the thermal decomposition of polyNIMMO-HTPE-polyNIMMO-IV are obtained from the DSC data by non-isothermal methods proposed by ASTM E698 and FWO. These results demonstrate that tri-block copolymer polyNIMMO-HTPE-polyNIMO might be a potential energetic propellant binder.

Investigations on Non‐isocyanate Based Reticulation of Glycidyl Azide Pre‐polymers

AbstractGlycidyl azide polymers (GAP) are being used as energetic binders in explosives and propellant formulations. The elastomeric properties of the binder are normally given by a urethane‐based reticulation process involving isocyanate compounds. Alternatively, azides bearing polymers can be cured by reaction with dialkynes as a result of the so‐called “click chemistry” process. This work investigates the reaction kinetics of GAP with five different dialkynes: one ether, three esters and one alkane derivative. The reactivity parameters of these compounds towards low molecular weight GAP have been established, along with the corresponding exotherm for each curing reaction. In light of the energetic nature of GAP, these results will allow the use of the same dialkyne compounds on a larger scale by making it possible to predict the behavior of these reacting mixtures and to allow a safe control over their exothermic curing process.

Direct access to poly(glycidyl azide) and its copolymers through anionic (co-)polymerization of glycidyl azide

Glycidyl azide polymer or poly(glycidyl azide) which is considered as an excellent energetic binder or plasticizer in advanced solid propellants is generally obtained by post-modification or azidation of poly(epichlorohydrin). Here we report that glycidyl azide can be directly homopolymerized through anionic ring-opening polymerization to access poly(glycidyl azide) using onium salts as initiator and triethyl borane as activator. Molar masses of poly(glycidyl azide) up to 11.0 Kg/mol are achieved in a controlled manner with a narrow polydispersity index (PDI ≤ 1.2). Similarly, alternating poly(glycidyl azide carbonate) are also prepared through alternating copolymerization of glycidyl azide with carbon dioxide. Lastly, the copolymerization of glycidyl azide with other epoxide monomers is carried out; the azido functions carried by glycidyl azide which are successfully incorporated into the backbones of polyethers and polycarbonates based on cyclohexene oxide and propylene oxide subsequently served to introduce other functions by click chemistry.

Comparison study of the ignition and combustion characteristics of directly-written Al/PVDF, Al/Viton and Al/THV composites

The aluminum–fluorine reaction is attracting growing interest due to its higher density over aluminum–oxygen. Fluorine rich polymers are particularly interesting for their applications as an energetic binder in advanced additive manufacturing of energetic materials. In this paper, three soluble polymers of PVDF (59 wt% F), Viton (66 wt% F) and THV (73 wt% F) are incorporated with aluminum nanoparticles (Al NPs) and prepared as free-standing films using solvent-based direct writing. The three composite films are compared for their mechanical properties as well as the ignition and combustion performance. Tensile stress was found to order as Al/PVDF > Al/THV > Al/Viton while the elasticity of Al/Viton is much higher than the other two. The burn rate of different composite films increases with Al content, while the flame temperature peaks slightly fuel-rich. The Al/PVDF had the highest burn rate, however, the flame temperature ordered as Al/THV (∼2500 K) > Al/Viton (∼2000 K) > Al/PVDF (∼1500 K), consistent with fluorine content. With higher fluorine and lower hydrogen content, THV releases more CFx gas than HF, which generates higher temperature. However, HF which is predominantly produced from PVDF has the lowest ignition by far and may be responsible for its high flame speed.

Synthesis and kinetic study on the thermal degradation of triblock copolymer of polycaprolactone‐poly (glycidyl nitrate)‐polycaprolactone (PCL‐PGN‐PCL) as an energetic binder

In this study, an energetic binder is synthesized via ring opening copolymerization of ε‐caprolactone with poly (glycidyl nitrate) (PGN) of low molecular weight (Mn = 1350 g mol−1) as a macroinitiator to form triblock copolymer polycaprolactone‐PGN‐polycaprolactone (PCL‐PGN‐PCL) (Mn = 4128 g mol−1). The effects of catalyst type and its concentration, reaction time, and solvent are investigated in this polymerization reaction. The resulting triblock copolymer is characterized by Fourier transform infrared spectroscopy (FT‐IR), nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). The DSC result shows that the glass transition temperature of triblock copolymer (Tg = −50°C) is lower than PGN (Tg = −35°C). Also, the decomposition kinetics of this energetic binder is studied by DSC, TGA, and its derivative (DTG). An advanced isoconversional method is applied for kinetic analysis. Activation energy is calculated by Flynn‐Wall‐Ozawa (FWO) and Kissinger methods. The resulting activation energy from Kissinger method for the first and the second steps are 42.98 and 74.56 kJ mol−1, respectively. Also, it is found from FWO results that the activation energy for the copolymer increases with degradation degree (α).

Finite-size scaling of Monte Carlo simulations for the fcc Ising antiferromagnet: Effects of the low-temperature phase degeneracy

The Ising antiferromagnet on a face-centered cubic (fcc) lattice with nearest-neighbor interaction only is well known to exhibit a macroscopic (exponential in the system size $L$) ground-state degeneracy. With increasing temperature, this degeneracy is expected to be lifted and the model undergoes a first-order phase transition. For a model with an exponential degeneracy in the whole low-temperature phase, it was recently found that the finite-size scaling behavior is governed by leading correction terms $\sim L^{-2}$ instead of $\sim L^{-3}$ as usual. To test the conjecture that such a transmuted behavior may effectively persist also for the fcc antiferromagnet up to some crossover system size, we have performed parallel multicanonical Monte Carlo simulations for lattices of linear size $L \le 18$ with periodic boundary conditions and determined various inverse pseudo phase transition temperatures, as well as the extremal values of the specific heat and the energetic Binder parameter. We indeed find that, for the simulated lattice sizes, the conjectured transmuted finite-size scaling ansatz fits the data better than the standard ansatz. On this basis, we extrapolate for the transition temperature an estimate of $T_0 = 1.735047(46)$.

Investigation of thermal behavior of energetic and non-energetic binders on luminous efficiency of high performance miniature flares

Abstract Miniature flares containing magnesium/sodium nitrate compounded with different binders were studied for increasing luminosity and luminous efficiency in various fuel oxidizer ratio and flare diameters. Unsaturated polyester, Bisphenol-A epoxy resin, calcium resinate, and nitrocellulose were used as binders for construction the flares. Experimental results showed that luminous efficiency was higher for polyester based flares. Due to the difference in decomposition progress of various binders and the exothermic reaction between binder and oxidizer the luminous efficiency of the mixtures were 31000, 28900, 27800 and 25100 cd respectively for polyester, epoxy, calcium resinate, and nitrocellulose. It was found that nitrocellulose as an energetic binder produces the highest light intensity in comparison to other binders, but the burning rate is higher and the burning time is lower than the other binders. Thermal analysis of four binders showed that the heat of reactions was directly related to the amount of light output and luminosity.

Synthesis and Characterization of PolyNIMMO-HTPB-polyNIMMO Triblock Copolymer as a Potential Energetic Binder

Synthesis and Characterization of PolyNIMMO-HTPB-polyNIMMO Triblock Copolymer as a Potential Energetic Binder

Synthesis of High-Energy Polymer – Glycidyl Azide Polymer (GAP)

Glycidyl Azide Polymer (glycidyl polyazide) (GAP) is one of the best known energetic binders, applicable as a component increasing a calorific value of rocket propellants. In this article, a synthesis of GAP is described allowing to obtain a polymer of different molecular masses. The change of a molecular mass can influence on properties of the obtained compounds. The synthesis was carried out according to an active monomer mechanism. The obtained products were characterized using such methods as FTIR, GPC, MALDI-ToF, TG, and NMR.

Reactive Energetic Plasticizers Utilizing Cu-Free Azide-Alkyne 1,3-Dipolar Cycloaddition for In-Situ Preparation of Poly(THF-co-GAP)-Based Polyurethane Energetic Binders.

Reactive energetic plasticizers (REPs) coupled with hydroxy-telechelic poly(glycidyl azide-co-tetrahydrofuran) (PGT)-based energetic polyurethane (PU) binders for use in solid propellants and plastic-bonded explosives (PBXs) were investigated. The generation of gem-dinitro REPs along with a terminal alkyne stemmed from a series of finely designed approaches to not only satisfy common demands as conventional energetic plasticizers, but also to prevent the migration of plasticizers. The miscibility and rheological behavior of a binary mixture of PGT/REP with various REP fractions were quantitatively determined by differential scanning calorimetry (DSC) and rheometer, respectively, highlighting the promising performance of REPs in the formulation process. The kinetics on the distinct reactivity of propargyl vs. 3-butynyl species of REPs towards the azide group of the PGT prepolymer in terms of Cu-free azide-alkyne 1,3-dipolar cycloaddition (1,3-DPCA) was studied by monitoring 1H nuclear magnetic resonance spectroscopy and analyzing the activation energies (Ea) obtained using DSC. The thermal stability of the finally cured energetic binders with the incorporation of REPs indicated that the thermal stability of the REP/PGT-based PUs was maintained independently of the REP content. The tensile strength and modulus of the PUs increased with an increase in the REP content. In addition, the energetic performance and sensitivity of REP and REP triazole species was predicted.

Study of Ignition of High-Energy Materials with Boron and Aluminum and Titanium Diborides

This paper describes the ignition of high-energy materials (HEMs) on the basis of ammonium perchlorate and ammonium nitrate and an energetic binder, containing the powders of Al (base composition), B, AlB2, AlB12, and TiB2, upon initiation of the process by a CO2 laser in the heat flux density range of 90–200 W/cm2. The ignition delay time and surface temperature of the reaction layer during the heating and ignition of HEMs in air are determined. It is obtained that the complete replacement of a micron-sized aluminum powder by amorphous boron in the composition of HEMs significantly reduces the ignition delay time of the sample (by 2.2–2.8 times) with the same heat flux density, and this occurs due to the high chemical activity of and difference between the mechanisms of oxidation of boron particles. The use of aluminum diboride in HEMs reduces the ignition delay time by 1.7–2.2 times in comparison with the base composition. The ignition delay time of the HEM sample with titanium diboride decreases slightly (by 10–25%) relative to the ignition delay time of the base composition.