Multistage Thermal Decomposition Kinetics of Glycidyl Azide Polymer-Based Thermoplastic Elastomers: A Constrained Deconvolution Approach.

Energetic thermoplastic elastomers (ETPEs) based on glycidyl azide polymer (GAP) and carboxylated GA copolymers [GAP-ETPE and poly(GA-carboxylate)-ETPEs] were synthesized using isophorone diisocyanate (IPDI), dibutyltin dilaurate (DBTDL), 1,4-butanediol (1,4-BD), and soft segment oligomers such as GAP and poly(GA-carboxylate). The synthesized GAP-ETPE and poly(GA-carboxylate)-ETPEs were characterized by Fourier transform infrared (FT-IR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), universal testing machine (UTM), calorimetry and sensitivity towards friction and impact. DSC and TGA results showed that the introduction of carboxylate group in GAP helped to have better thermal properties. Glass transition temperatures of poly(GA-carboxylate)-ETPEs decreased from -31 ℃ to -33 ℃ compared to that of GAP-ETPE (-29 ℃). The first thermal decomposition temperature in poly(GA0.8-octanoate0.2)-ETPE (242 ℃) increased in comparison to that of GAP-ETPE (227 ℃). Furthermore, from calorimetry data, poly(GA-carboxylate)-ETPEs exhibited negative formation enthalpies (-6.94 and -7.21 kJ/g) and higher heats of combustion (46713 and 46587 kJ/mol) compared to that of GAP-ETPE (42,262 kJ/mol). Overall, poly(GA-carboxylate)-ETPEs could be good candidates for a polymeric binder in solid propellant due to better energetic, mechanical and thermal properties in comparison to those of GAP-ETPE. Such properties are beneficial to application and processing of ETPE.

The energetic thermoplastic elastomers (ETPE) of glycidyl azide polymer with bonding functions were synthesized by using mixture of chain extenders including 1,4-butanediol and N-(2-cyanoethyl) diethanolamine. From FTIR results, the ability of ETPEs to form hydrogen bond weakened with the percentage of N-(2-cyanoethyl) diethanolamine increasing, which further lead to the decrease of maximum stress of ETPEs and increase of elongation at break. On the other hand, the interfacial interactions between solid ingredients and ETPEs were enhanced owing to the more –CN content. With the percentage of N-(2-cyanoethyl) diethanolamine increasing, two factors affect the adhesion between binder and fillers at the same time. The RDX/ETPE propellants were synthesized and the mechanical properties of them showed that the ETPE-50 with bonding functions can effectively prevent the dewetting, and then improve the mechanical properties of propellants. That is, when the percentage of N-(2-cyanoethyl) diethanolamine was 50 %, the synthesized ETPEs had not only binding function but also bonding interaction.

A kind of bonding functional energetic thermoplastic elastomers (ETPEs) were synthesized as the binder of solid propellants using the mixture of chain extenders including diethyl bis(hydroxymethyl) malonate (DBM). The results showed that the mechanical properties of ETPEs decreased with increasing percent of DBM in the chain extenders. On the contrary, the work of adhesion between solid ingredients hexogen (RDX) and ETPEs increased. In order to test the comprehensive impacts of two elements, the RDX/ETPE propellants were prepared. The results showed when the percent of DBM was 25%, the overall properties of the propellants were optimum.

ABSTRACTDepending upon the advantages of high efficiency, insensitivity to humidity and so on, the reaction of azide groups in glycidyl azide polymers (GAP) with alkynyl compounds has been used as a substitute of the urethane curing strategy to develop GAP‐based binder for solid propellant. In this work, an alkynyl compound of dimethyl 2,2‐di(prop‐2‐ynyl)malonate (DDPM) reacted with GAP to produce new crosslinked materials under the catalysis of Cu(I)Cl at ambient temperature, and showed great potential as a binder in composite propellant. As the feeding molar ratio of DDPM vs. GAP increased from 1 : 1 to 5 : 1, the crosslinking densities of as‐prepared materials gradually increased, together with simultaneous enhancement of Young's modulus and tensile strength. The breaking elongation showed the maximum value of ca. 82% when the feeding molar ratio of DDPM vs. GAP was 3 : 1. In addition, with an increase of the crosslinking densities, the glass transition temperatures of as‐prepared materials significantly increased from −43.9°C to −5.1°C while the mechanical loss peaks also gradually broadened and shifted up to high temperature, and even presented two peaks at the feeding molar ratio of DDPM vs. GAP higher than 4 : 1. It indicated that the formation of triazole‐based network resulted in structural heterogeneity in the as‐prepared materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40636.

As a new kind of propellant binder, energetic thermoplastic elastomer ( ETPE ) can improve propellant recyclability and environmentally friendly disposal. The rheological behavior of the ETPE binder can be beneficial to identify suitable and safe conditions for processing ETPE propellants. In this paper, ETPE /nitrocellulose ( NC ) blends with different mass ratios of NC to ETPE were prepared by the physical mixing method. The heat of explosion and the morphological, thermal, mechanical and rheological properties of the resulting blends were studied systematically. It was found that the heat of explosion of ETPE / NC blends increased with increasing NC content. SEM images showed that the NC domains in the blends changed from tiny pieces to fibers with increasing NC mass ratio, which indicates phase separation in the blends. The tensile mechanical properties of the blends had a peak value when the NC content was 10 wt%, and then increased with the increasing addition of NC . The thermal behavior made clear that the ETPE and NC were partially miscible. Rheological studies on dynamic strain sweep and frequency sweep demonstrated that the content of NC in the blends had a monotonic effect on their rheological properties at 130 °C. Rheological studies also showed that the rheology of the blends is dependent on temperature. The Cole − Cole and Han plots confirmed phase separation in the blends. © 2016 Society of Chemical Industry

Energetic thermoplastic polyurethane elastomers (ETPUs) of glycidyl azide polymer (GAP) were synthesized on GAP/poly(caprolactone)(PCL) (100/0, 50/50) as a soft segment and methylenebis(phenylisocyanate) (MDI) extended 1,5-pentanediol as a hard segment by solution polymerization in dimethyl formamide (DMF). Differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA) were used to examine the thermal decomposition behavior. Kinetic analysis was performed with model fitting and a model-free method to obtain the activation energy as a function of the extent of conversion. ETPU decomposition was divided into two stages with different activation energies. The first main weight loss step corresponds to the elimination of N2 from the decomposition of -N3 bonds within azide polymers. The activation energy of the main decomposition of GAP ETPU and GAP/PCL ETPU was approximately 190 kJ/mol. The second weight loss step coincides with the decomposition of the skeleton. The activation energy of those showed an increasing trend.

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.

Heats of combustion and formation of various energetic thermoplastic elastomers (ETPE), corresponding to linear copolyurethanes based on an energetic prepolymer and a diisocyanate, were measured by a calorimetric method. These ETPEs were synthesized from three different molecular weights of glycidyl azide polymer, from poly(3‐nitratomethyl‐3‐methyloxetane) and from poly glycidyl nitrate. The prepolymers were also analyzed for comparison with the corresponding ETPEs. A significant difference of the heats of formation was observed between the prepolymers and their ETPEs, while the heats of combustion were similar.

For years, DRDC Valcartier has invested efforts at developing energetic thermoplastic elastomers (ETPEs) based on linear glycidyl azide polymers to serve as energetic binders and replacing the thermoset matrix in insensitive explosives. It was first observed that introducing ETPEs in their melted form was not an easy task because high and nonpractical viscosities were encountered in the process. It was discovered that 2,4,6-trinitrotoluene (TNT) could be used in its melted form as an organic solvent to dissolve the ETPE and allow its incorporation into the insensitive formulations. Using these ETPEs led to the development of a greener insensitive melt-cast explosive named green insensitive munitions (GIM). This new explosive was intensely studied. The mechanical properties and proportions of ETPE in the formulations were optimized to obtain a melt cast with low viscosity while leading to an insensitive explosive formulation. Work was conducted on GIM explosives to test their performance and sensitivity, fate and behavior with regard to the environment, their recycling capability, and toxicity. This paper describes the results of all experiments conducted so far to test these aspects of GIM explosives. The preparation of the ETPEs and the GIM explosives will also be briefly described.

Glycidyl azide polymer (GAP)–energetic thermoplastic elastomer (GAP-ETPE) propellants have high development prospects as green solid propellants, but the preparation of GAP-ETPEs with excellent performance is still a challenge. Improving the performance of the adhesive system in a propellant by introducing a plasticizer is an effective approach to increasing the energy and toughness of the propellant. Herein, a novel high-strength solid propellant adhesive system was proposed with GAP-ETPEs as the adhesive skeleton, butyl nitrate ethyl nitramine (Bu-NENA) as the energetic plasticizer, and nitrocellulose (NC) as the reinforcing agent. The effects of the structural factors on its properties were studied. The results showed that the binder system would give the propellant better mechanical and safety properties. The results can provide a reference for the structure design, forming process, and parameter selection of high-performance GAP-based green solid propellants.

Poly(3,3′-bisazidomethyl oxetane-3-azidomethyl-3′-methyl oxetane) [P(BAMO/AMMO)] energetic thermoplastic elastomer (ETPE) is one of the most promising binders for the propellant and explosive formulations. It is synthesized with different content of hard segment and molar ratio of PBAMO and PAMMO. The results of mechanical test show that with higher content of hard segment and larger content of PBAMO, the ETPEs obtain higher tensile strength and lower breaking elongation. The thermal kinetics of the first decomposition stage of P(BAMO/AMMO) is investigated and the calculated apparent activation energy (E a) is about 169 kJ mol−1 by multi-heating rate method. In the single-heating rate study, f(α) = 1 − α is found to be the most probable mechanism function. Kinetic compensation effects are studied for the validation of the most probable mechanism function, and the results show that f(α) = 1 − α is quite suitable at a lower extent of conversion (α), but $$ f(\alpha ) = \frac{2}{3}\left( {1 - a} \right)\left[ { - { \ln }\left( {1 - a} \right)} \right]^{{ - \frac{1}{2}}} $$ is more fit when α is larger. P(BAMO/AMMO) ETPE was prepared, and the thermal decomposition kinetic of the first decomposition stage (mainly the thermal decomposition of –N3 group) was investigated. f(α) = 1 − α was a fitting mechanism function at a lower α, and $$ f(\alpha ) = \frac{2}{3}(1 - a)[ - \ln (1 - a)]^{{ - \frac{1}{2}}} $$ was more suitable when α was higher.

ABSTRACTEnergetic adhesives with excellent mechanical properties are of great significance for the development of solid propellant. In this paper, a small amount of graphene is used to enhance the mechanical properties of glycidyl azide polymer (GAP)‐based energetic thermoplastic elastomer (GAP‐ETPE), and an in‐depth analysis of the graphene enhancement mechanism is conducted through the structural characterization of the composite elastomer. Scanning electron microscopy (SEM) reveals that the solvent‐assisted ultrasonic dispersion method can fully disperse graphene in GAP‐ETPE, taking advantage of its high specific surface area. Fourier Transform Infrared (FT‐IR) and low‐field Nuclear Magnetic Resonance (LF‐NMR) analysis show that graphene can provide physical crosslinking sites, significantly increasing the crosslinking density of GAP‐ETPE. Dynamic mechanical analysis (DMA) indicates that the increased crosslinking density caused by graphene will restrict the segmental motion of GAP‐ETPE. Static tensile test result shows that the use of 0.1 wt% graphene can increase the tensile strength of GAP‐ETPE from 7.0 to 7.8 MPa. This work provides a basis for the application of graphene in energetic adhesives.

Synthesis and thermal decomposition of GAP–Poly(BAMO) copolymer

Glycidyl azide polymer (GAP) based binders have poor mechanical characteristics in comparison with hydroxyl terminated polybutadiene (HTPB) binders. In this study, advanced cross‐linker was used to improve the mechanical properties of GAP binder. GAP was prepared and characterized in comparison with HTPB prepolymer. Density, characteristics groups, nitrogen content, humidity, viscosity, and milligram equivalent of (OH) per binders were determined. A cross‐linker consists of trimethylol propane (TMP) and curing catalyst, dibutyltin dilaurate (DBTDL), was used as an additive to GAP polymeric matrix to enhance its functionality. Polymeric matrices based on GAP and HTPB were prepared with different curing ratio (NCO/OH) ranging from 0.7 to 1.5. Different weight percentages of cross‐linker were added to study its effect on the mechanical properties of GAP matrix. Five samples based on HTPB polymer and twenty samples based on GAP polymer were prepared. A LLOYD testing machine was used to determine the stress‐strain curves of all the studied samples. It was concluded that the cross‐linker used has significant influence on the characteristics of GAP polymeric matrix. Also the addition of 5 wt % of cross‐linker to GAP matrix at curing ratio = 1 produced optimum mechanical characteristics very close to that of HTPB matrix used in composite solid rocket propellants (CSRP). The optimum GAP polymeric matrix is candidate to replace the traditional HTPB binder in advanced CSRP.

Mass spectrometric study of combustion and thermal decomposition of GAP