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Influence of the Prepolymer Structure of Glycidyl Azide Polymer (GAP) on Binder Properties – Some Theoretical Considerations

Gettwert Volker Juergen, Keicher Thomas

Central European Journal of Energetic Materials

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2024

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Vol. 21, no. 1

53--67

EN

Glycidyl azide polymer (GAP) is a promising energetic binder for solid propellants, but it suffers from poor mechanical properties compared to hydroxyl-terminated polybutadiene (HTPB). This paper reviews the main factors affecting the mechanical properties of GAP-based binders, such as molecular weight and functionality, and discusses some possible strategies on how it could be improved. The equation of Carother is used for the theoretical consideration of the functionality of the GAP prepolymer.

2

Modification of the Physical and Thermal Properties of Glycidyl Azide Polymer Through the Formation of a Star-Shaped Polymer

Bodaghi Asghar

Central European Journal of Energetic Materials

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2022

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Vol. 19, no. 3

248--263

EN

Glycidyl azide polymer (GAP) is one of the most important binders in the preparation of propellants. One of the most important problems with this binder is its high glass transition temperature. In the present study, the physical and thermal properties of GAP were modified by the synthesis of a star shaped polymer. Dibromo end-functionalized two-arm polycaprolactone (PCL), (PCL)2-(Br)2, was synthesized by ring-opening polymerization (ROP) of ε-caprolactone monomer using 2,2-bis(bromomethyl)-1,3-propane diol as the initiator and stannous 2-ethylhexanoate as the catalyst. The bromines of the polymer were then replaced by azide groups by reaction with sodium azide (NaN3). The (PCL)2-(Br)2 was reacted with propargyl terminated polyepichlorohydrin (PTPECH) via a click reaction. Finally, (PCL)2-(PTPECH)2 was converted into (PCL)2-(GAP)2 by reaction with NaN3. 1H NMR, FT-IR and GPC studies revealed that (PCL)2-(GAP)2 was obtained. The thermal behaviour of this star polymer was investigated by thermogravimetric analysis (TGA) and derivative thermogravimetry. The results showed that (PCL)2-(GAP)2 decomposed in two stages. The first stage is related to degradation of the azide groups and the second stage was attributed to degradation of the PCL groups.

3

Study on the Thermal Stability and Decomposition Kinetics of Polypropylene Glycol – Glycidyl Azide Polymer – Polypropylene Glycol (PPG-GAP-PPG) as a Novel Triblock Copolymer Binder

Ghoroghchian Fahimeh, Bayat Yadollah, Abrishami Fatemeh

Central European Journal of Energetic Materials

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2020

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Vol. 17, no. 2

262--279

EN

In this study, the novel energetic triblock copolymer of polypropylene glycol- glycidyl azide polymer- polypropylene glycol (PPG-GAP-PPG) (Mn= 1419 g·mol–1) was synthesized by cationic ring-opening polymerization of propylene oxide using low molecular weight glycidyl azide polymer (GAP) (MMnn = 1006 g·mol–1) as the initiator and boron trifluoride etherate (BFM3·OEtM2) as the catalyst. The synthesized GAP and triblock copolymer were characterized by Fourier-transform infrared (FT-IR) spectroscopy, gel permeation chromatography (GPC), and nuclear magnetic resonance spectroscopy (1H and 13C NMR). The thermal stability of the triblock copolymer PPG-GAP-PPG was studied by differential scanning calorimetry (DSC) and thermogravimetry (TG). The DSC results showed that the glass transition temperature (TMg) of the triblock copolymer (TMg = −63 °C) was lower than that of neat low molecular weight GAP (Tg = −53 °C). Furthermore, the results indicated that this triblock copolymer is more stable than GAP. The influence of heating rate (10, 20, 30 and 40 °C·min−1) illustrated that increasing the heating rate results in an increase in the triblock copolymer’s decomposition temperature. Non-isothermal methods, proposed by ASTM E698, Flynn-Wall-Ozawa (FWO) and Kissinger, were used to calculate the kinetic parameters, such as activation energy and frequenc factor, for the thermal decomposition of the triblock copolymer PPG-GAP-PPG, using the DSC-DTG were 124.610 and 126.13 kJ·mol–1, respectively.

4

Studies on the Effect of a Covalently Bonded PGN Based Reactive Plasticizer on the Thermal Decomposition Behaviour of Glycidyl Azide Polymer

Bodaghi Asghar, Shahidzadeh Mansour

Central European Journal of Energetic Materials

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2019

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Vol. 16, no. 2

259--280

EN

Plasticizers are one of the additives that are added to polymers to increase the plasticity or decrease the viscosity of the material. Here, we have synthesized and characterized a new PGN-based reactive energetic plasticizer that has an oligomeric structure. The reactive energetic plasticizer can be grafted onto glycidyl azide polymer via a Cu-free Huisgen azide-alkyne 1,3-dipolar cycloaddition. The effect of the covalently bonded PGN-based plasticizer on the thermal properties of GAP-g-PGN copolymer has been investigated through thermogravimetric analysis and differential scanning calorimetry. The results indicate that the glass transition temperature of the prepolymer is decreased from –47.8 to –50.7 °C. Also, the kinetics of the thermal behaviour of GAP-g-PGN copolymer was determined by the application of the Kissinger and FWO kinetic models. The activation energies calculated by the Kissinger method were 165 and 188 kJ/mol for peak 1 and peak 2, respectively. Furthermore, the critical temperature (Tb) of thermal explosion for this energetic copolymer was estimated to be 182 °C.

5

Microwave Assisted Synthesis and Characterization of Glycidyl Azide Polymers Containing Different Initiating Diol Units

Kshirsagar A., Gite V., Hundiwale D., Mahulikar P.

Central European Journal of Energetic Materials

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2015

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Vol. 12, no. 4

757--767

EN

Glycidyl azide polymers (GAPs), containing different initiating diol units were prepared by treating the corresponding poly(epichlorohydrins) (PECHs) with sodium azide under microwave irradiation (600 W power) at 80 °C, during 12 min. The PECHs containing different diol units were synthesized by the polymerization of epichlorohydrin using borontrifluoride etherate as initiator in the presence of small amounts of low molecular weight diols. The synthesized PECHs and GAPs, containing different initiating diol units, were characterized by various spectroscopic techniques and by thermal analysis (DSC). These results are reported and discussed.