Qi-Long Yan

The effect of polymer matrices on the thermal hazard properties of RDX-based PBXs by using model-free and combined kinetic analysis.

In this paper, the decomposition reaction models and thermal hazard properties of 1,3,5-trinitro-1,3,5-triazinane (RDX) and its PBXs bonded by Formex P1, Semtex 1A, C4, Viton A and Fluorel polymer matrices have been investigated based on isoconversional and combined kinetic analysis methods. The established kinetic triplets are used to predict the constant decomposition rate temperature profiles, the critical radius for thermal explosion and isothermal behavior at a temperature of 82°C. It has been found that the effect of the polymer matrices on the decomposition mechanism of RDX is significant resulting in very different reaction models. The Formex P1, Semtex and C4 could make decomposition process of RDX follow a phase boundary controlled reaction mechanism, whereas the Viton A and Fluorel make its reaction model shifts to a two dimensional Avrami-Erofeev nucleation and growth model. According to isothermal simulations, the threshold cook-off time until loss of functionality at 82°C for RDX-C4 and RDX-FM is less than 500 days, while it is more than 700 days for the others. Unlike simulated isothermal curves, when considering the charge properties and heat of decomposition, RDX-FM and RDX-C4 are better than RDX-SE in storage safety at arbitrary surrounding temperature.

Thermal behavior and decomposition kinetics of ETN and its mixtures with PETN and RDX

Erythritol tetranitrate (butane-1,2,3,4-tetrayl tetranitrate, ETN) has become one of the most synthesized improvised explosives nowadays as it can be found on public internet discussion boards. However, the low melting point, nitrocellulose gelling ability, high energy content, and availability of its precursor make the substance potentially useful in industry as an energetic component or additive in certain gun propellants. Mixtures of ETN with other high explosives are also frequently discussed on web pages dealing with improvised explosives. This article describes thermal behavior and decomposition kinetics of pure ETN and its mixtures with pentaerythritol tetranitrate and cyclonite (1,3,5-trinitro-1,3,5-triazinane, RDX). The thermal behavior and decomposition kinetics of such mixtures are described using non-isothermal DSC and TG techniques. Kissinger method, Soviet manometric method, and modified Kissinger–Akahira–Sunose method were used for data evaluation.

Highly insensitive and thermostable energetic coordination nanomaterials based on functionalized graphene oxides

In this research, a group of new energetic coordination nanomaterials (CNMs) based on functionalized graphene oxide sheets (FGS) have been designed and characterized. GO was first functionalized with N-rich energetic ligands such as triaminoguanidine (TAG), and then the resulting FGS was coordinated with metal ions to prepare energetic CNMs with high thermostability and insensitivity to mechanical stimuli. The density of GO–TAG–Cu(II)/Cu(I) is as high as 3.14 g cm−3, while it has a Tp of 495 °C and VoD of 7723 m s−1 by using 40 wt% ammonium perchlorate as the oxidant. These insensitive (Im > 81 J) and highly thermostable energetic CNMs in combination with oxidizers are good candidate ingredients of low-vulnerability solid propellants and charges of deep-well perforating guns.

Formation of Highly Thermostable Copper-Containing Energetic Coordination Polymers Based on Oxidized Triaminoguanidine

A series of novel highly thermostable energetic coordination polymers (ECPs), with promising mechanical sensitivity properties, were prepared by an in situ oxidation-coordination reaction of triaminoguanidine hydrochloride with copper nitrate in aqueous solution. The molecular structures and properties of these ECPs could be tuned, by varying the ratios and concentrations of the starting materials. Our ECPs exhibit remarkable thermostability (>390 °C) and very low sensitivity to impact (Im > 98 J). The best-performing material (ECP-5) has a calculated detonation velocity of 8969 m·s(-1) and a decomposition peak temperature of 396.9 °C, demonstrating an outstanding balance between two inherently contradicting properties: high detonation performance and very low sensitivity.

Novel nitrogen-rich energetic macromolecules based on 3,6-dihydrazinyl-1,2,4,5-tetrazine

Nitrogen-rich energetic macromolecules were synthesized by reacting dihydrazinyl-1,2,4,5-tetrazine (DHTz) with various diisocyanates. It has been shown that polymerization or cyclization reactions could take place depending on solvent systems and reaction conditions. The formed macrocycles and polymers were comprehensively characterized by IR, NMR, high resolution MS and SEM, while the thermal stability was studied by DSC. The energetic properties of our new compounds were investigated by bomb calorimetry, along with calculations using the EXPLO-5 code. It was found that macrocycle C-DHTZ-TM and corresponding polymer P-DHTZ-TM prepared on a basis of DHTZ and tetramethylene diisocyanate have larger heats of combustion than RDX, GAP and polyGLYN. C-DHTZ-TM has a comparable density and larger detonation velocity than TNT. The nitrogen content of C-DHTZ-TM and P-DHTZ-TM is larger than 47%. The thermal stability of DHTz-based energetic macromolecules was found to be higher than currently used energetic polymers including GAP, polyNIMMO and polyGLYN. The ADN based compositions bonded by 60% (by weight) of P-DHTZ-HM and P-DHTZ-MB polymers have higher theoretical specific impulse than that bonded by polyGLYN. Therefore, our new compounds could be promising ingredients as energetic binders or fillers. Moreover, all of the macrocycles have potential to be used as energetic gelators in gel propellants.

A layered 2D triaminoguanidine–glyoxal polymer and its transition metal complexes as novel insensitive energetic nanomaterials

A new member of the 2D carbon–nitrogen-rich family of nanomaterials was synthesized by polycondensation of triamino-guanidine hydrochloride with glyoxal. The obtained polymer (TAGP) has a carbon-to-nitrogen ratio of 3 : 4, identical to a ratio found in carbon nitrides. Our analysis showed that TAGP has a layered 2D network-type structure. TAGP is dispersible in polar organic solvents and forms stable complexes with various transition metal ions (TAGP–Ms). TAGP and most TAGP–Ms were found to exhibit properties of insensitive Energetic Materials (EMs), where TAGP shows a very low sensitivity to impact (Im = 71.7 J) and to friction (>352.8 N). TAGP has also higher nitrogen content than all currently used energetic polymers, including glycidyl azide polymer [GAP], poly(3-nitrato-methyl-3-methyloxetane) [poly-NIMMO], and poly(glycidyl nitrate) [poly-GLYN]. Velocity of detonation of TAGP (6657 m s−1) was calculated to be significantly higher than that of azide-containing GAP and comparable to that of the nitrate ester-based poly-GLYN. In our perspective, TAGP is also an example of a modular and combinatorial approach in which high nitrogen-content aminoguanidine derivatives, reacted with amine-reactive low-carbon-content or energetic crosslinkers, can produce novel energetic polymers with tuneable properties and performance. The properties of the aminoguanidine-based EPs could be even further modified and tuned by coordination of transition metal ions. Our novel TAGP and TAGP–M energetic nanomaterials have great potential to be used in solid propellants and in energetic formulations and composites as new generation energetic binders and combustion catalysts.