Pyrolysis Behavior Of Multi-Arm Azide Copolymer As Solid Rocket Fuel

A high energy for rocket fuel is one of the main goals pursued by scientists. Azido groups have a positive heat of formation and release a large amount of heat in pyrolysis. Therefore, several azide polymers (such as GAP, PBAMO, and PAMMO) are used as the fuel binder for rockets.

However, they exhibit poor low-temperature properties due to their low molecular weight and short polyether main chain.


In order to solve these problems, we have designed and synthesized a multi-arm azide copolymer (POG) which possesses a high molecular weight and low glass transition temperature. The pyrolysis behavior of POG for use as rocket fuel plays a crucial role in burning rate and safety characteristics.

Based on the complex multiple pyrolysis of POG, its decomposition kinetics and mechanism were studied in an experiment and through a detailed simulation. Mathematical function deconvolution is a simple and effective method for a multi-step reaction. The asym2sig function is beneficial for the deconvolution of POG pyrolysis curves. Trough deconvolution and kinetics analysis methods, the kinetic triplets of POG pyrolysis were successfully obtained, revealing that n-th order model and 3D diffusion model met the two different pyrolytic stages of POG (Fig.1).

Fig.1: Mechanism model of POG pyrolysis in two different stages

To further investigate the pyrolytic reaction process, the residual morphology and gaseous products are captured by SEM and TG-FTIR-MS. These results cannot get intermediate reactions, and the burning temperature of rocket fuel can reach thousands of degrees Celsius. Hence, molecular simulation is a good method for POG pyrolysis at high temperatures. Through ReaxFF-MD simulation, the intermediate reactions of -N3 decomposition were observed.


Based on these experiment and simulation results, we proposed the “crosslinked layer transition theory” of POG pyrolysis. The inter- and intramolecular crosslinking cyclization reaction of nitrenes, produced by azido group cracking, form a new crosslinked transition layer lagging the decomposition of hyperbranched polyether core. The detailed pyrolysis mechanism of POG is presented in Fig.2. The study can provide useful insights into the pyrolysis mechanism and kinetics for the efficient utilization of POG as rocket fuel.

Fig. 2: The pyrolysis mechanism of POG

These results are described in the article entitled Multistep pyrolysis behavior of core-shell type hyperbranched azide copolymer: Kinetics and reaction mechanism via experiment and simulation, recently published in the journal Fuel.

This work was conducted by Guangpu Zhang, Jinqing Li, Mengyun Zhang, Shixiong Sun and Yunjun Luo from the Beijing Institute of Technology.



Guardrails For A Sustainable Energy Future

Although a great deal of attention has rightly been paid to greenhouse gas (GHG) emissions and climate change, there are other […]

CO2 Conversion: Turning Waste Into Value

The world needs more energy. As the population continues to grow and the quality of life improves in developing economies, […]

Getting Infrared Spectrum Evaluation Straight For Biomedical Applications

Since about 40 years, the quantity absorbance, defined by the negative decadic logarithm of the transmittance or the relative reflectance, […]

Your Environment Is Part Of Your Mind

Here’s a fun experiment: Stick your finger in your eye. Well, not exactly. The experiment actually involves closing one eye, […]

Improving Tools For Quality Improvement: Crossings, Runs, And Crossrun

To maintain and improve quality in, for example, industry and healthcare, one has to understand the processes involved. All too […]

Who Invented Homework?

Roberto Nevilis invented homework in the year 1095 in Venice after being disappointed in his students. Roberto Nevilis began to give […]

A Green Method For Biomass Solubilization: Subcritical Water Process Combined With Microwave Pretreatment

Lignocellulosic biomass materials are attracting increasing attention as renewable, economical, and abundant resources to reduce dependency on petroleum resources and […]

Science Trends is a popular source of science news and education around the world. We cover everything from solar power cell technology to climate change to cancer research. We help hundreds of thousands of people every month learn about the world we live in and the latest scientific breakthroughs. Want to know more?