Preparation of Paraffin-Based Solid Combustible for Hybrid Propulsion Rocket Motor

Cardoso

Propellants Explo Pyrotec

et al. 2020

Ammonium dinitramide (ADN) has been considered the potential substitute for ammonium perchlorate in solid green propellants. However, it has also some drawbacks due to its high hygroscopicity and chemical incompatibility with some of the components present in composite propellant formulations. On the other hand, ADN melts at temperatures below degradation, which makes emulsion crystallization an important method to prepare spherical ADN particles that benefit both propellant slurry processing and casting. Spherical ADN particles were prepared by emulsion crystallization to be used for the microencapsulation studies, and whose method was assessed to better understand which parameters may affect the ADN particles formation. Microencapsulation protects ADN particles as it addresses hygroscopicity besides the given protection from chemical incompatibility. Polyurethane made of hydroxyl-terminated polybutadiene was selected as a coating material because of its common use in propellants as a binder. Also, the good performance of methylene diphenyl diisocyanate as a curing agent was such that it was used in the whole study. The number of layers and the processing time played important roles in the formation of the capsule as seen in the impermeability tests. Besides, drying at 50°C for 168 h showed to be even more beneficial on average for the capsule protective property. Chemical compatibility between the capsule and ADN was confirmed at 60°C which allows it to be used as a protective coating. However, the obtained average coating thickness of ten microns has to be reduced yet with more efficient protective coating materials.

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

ADN Recrystallization and Microencapsulation with HTPB by Simple Coacervation

Cardoso

Propellants Explo Pyrotec

et al. 2020

“…9 With the increasing attention on the trade-off between high performance and low sensitivity of energetic materials, 10,11 paraffin wax (PW) serves as a promising desensitizer and solid fuel 12 due to its low cost, controllable phase-transition temperature, chemical stability, environmentfriendliness, high heat of combustion and burning regression rate. [12][13][14][15] Jin et al 16 studied the coating and desensitization effects of PW/stearic acid (SA) composite on 2,4,6,8,10,12hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (HNIW). Kawachi et al 13 investigated the thermal and mechanical tests of a combustible grain (PW/HTPB) casted with maximum loading; the results indicated that this material could meet the criteria of performance and safety required for this type of a combustible grain.…”

Section: Introductionmentioning

confidence: 99%

“…[12][13][14][15] Jin et al 16 studied the coating and desensitization effects of PW/stearic acid (SA) composite on 2,4,6,8,10,12hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (HNIW). Kawachi et al 13 investigated the thermal and mechanical tests of a combustible grain (PW/HTPB) casted with maximum loading; the results indicated that this material could meet the criteria of performance and safety required for this type of a combustible grain. However, poor mechanical properties, diffusion and leakage of melted PW will always be an issue if the PW is directly suspended in HTPB using traditional methods.…”

Section: Introductionmentioning

confidence: 99%

Thermal and mechanical reinforcement of a novel paraffin-based hydroxyl-terminated polybutadiene (HTPB) binder containing a three-dimension (3D) diurea–paraffin wax (DU–PW) for prevention of PW leakage

et al. 2018

Propellants Explo Pyrotec

“…Paraffin-based fuels as a new solid fuel of hybrid rocket engines offer a good application potential. However, its serious disadvantage is that the mechanical property is poor [10,11]. Rocket propellants have to withstand the heavy loads during the process of ignition and launch and thus the propellants must have good mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

Mechanical Modifications of Paraffin‐based Fuels and the Effects on Combustion Performance

Tang

Chen

Zhang

et al. 2017

In order to enhance the mechanical properties, 6 kinds of additives of stearic acid, polyethylene wax (AÀC6A), ethylene vinyl acetate copolymer (EVA), low density polyethylene (LDPE), polypropylene (PP) and high density polyethylene (HDPE) were blended in the paraffin fuel. Mechanical properties of paraffin-based fuels were investigated by mixing 5 % in mass of different additives and increasing the mass percent of AÀC6A and LDPE. In addition, the combustion performance of the so modified paraffin-based fuels were tested by a 2D-radial burner at Nanjing University of Science and Technology. The effects of additives on regression rate were analyzed by thermal performance test (melting point and DSC) and viscosity measurement. Overall, all the additives can improve mechanical properties and the mechanical properties are enhanced by increasing mass% of additives. AÀC6A revealed the best for improving compressive strength (64.0 % increase by blending 5 mass %), LDPE revealed the best for improving tensile strength (105.3 % increase by blending 5 mass %). For combustion performance, the regression rates of paraffin-based fuels blended with stearic acid increased owing to the decreased melting points while the regression rates of the other five formulations decreased due to the increased melted liquid viscosity. The relationship between regression rate and viscosity is a power function which is not affected by additives at high temperature, thereby it is convenient to predict the regression rate by measuring viscosity.Keywords: Hybrid rocket propulsion · mechanical modified paraffin-based fuel · thermal and mechanical properties · melted liquid viscosity · regression rate [a] Y.