Tianfu Zhang

Fabrication and thermal decomposition of glycidyl azide polymer modified nitrocellulose double base propellants

Glycidyl azide polymer (GAP) with the advantages of non-volatility and excellent thermal stability is a candidate as a replacement for nitroglycerine (NG) in a double base propellant. The GAP-NC double base propellants were formulated with GAP and nitrocellulose (NC) fibers. Tensile test and SEM characterization indicated that GAP-NC propellants had a homogeneous structure. Thermogravimetric analysis of GAP-NC propellants revealed that the onset decomposition temperature reached a high level ranging from 192.9 to 194.6 °C, which indicated that the substitution of NG with GAP contributed to the safe storage and process operations for double base propellant. The result analysis of decomposition products of GAP-NC propellants showed that the main gas decomposition products of the propellants were NO, NO2, CO, CO2, NH3, CH4, HCN, N2, CH2O and C2H4O. The thermal decomposition process of the specimens was proposed.

Effect of hard-segment content on rheological properties of glycidyl azide polyol-based energetic thermoplastic polyurethane elastomers

A series of glycidyl azide polyol (GAP)-based ETPEs with different hard-segment contents were synthesized using GAP-diol, hexamethylene diisocyanate and 1, 4-butanediol as soft and hard segments, respectively, by prepolymerization. The synthesized GAP-based ETPEs were identified and characterized using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and rheometric spectrometry. The results of FTIR showed the forming of carbonyl hydrogen bonds in ETPEs was affected by hard-segment contents of ETPEs. DSC results showed that the glass transition temperature (Tg) of ETPEs was also affected by the percentage of hard-segment contents of ETPEs. It was shown by DMA and rheological measurements that the percentage of hard-segment contents of ETPE had a monotonic effect on the rheological properties of ETPEs.

A new strategy for the fabrication of high performance reactive microspheres via energetic polyelectrolyte assembly

Since the thermite reaction in aluminum-based nanostructured energetic materials (NEMs) is closely involved with Al and oxide nanoparticles (NPs), intimate interfacial contact between the Al and oxide NPs is widely considered to be a key parameter for the NEMs with high reactivity. With the aim to overcome the disadvantage of inert modifiers without energetic groups, used in the assembly approach, which is a cutting-edge solution to precisely organize the arrangement of the Al and oxide NPs and lead to enhanced intimacy, we successfully prepared GAP-based (GAP, glycidyl azide polymer) energetic polyelectrolytes (GEPEs) and demonstrated electrostatic assembly as a facile way to fabricate high performance, reactive Al/Fe2O3 microspheres after modification of the Al and Fe2O3 NPs with the GEPEs. The pressurization rate of the obtained reactive microspheres, a relative measurement of the reactivity, reached 410.36 MPa s−1, which is the highest value obtained so far, and is 1–2 orders of magnitude higher than that of other reported Al/Fe2O3 NEMs. The incorporated GEPEs serve three main roles: GEPEs act as a modifier by interacting strongly with the NPs, and improve the intimacy of the Al and Fe2O3 via powerful electrostatic attraction between the modified NPs; the assembly of the reactive microspheres can be achieved through the directing assembly of the GEPEs themselves; internal gas released by the decomposition of energetic sites existing inside the assembled microspheres rapidly separates the NPs to prevent adverse sintering and to weaken the nanostructure loss during the reaction, resulting in an improvement of the reactivity.

Influence of Polytetrafluorethylene on the Mechanical and Safety Properties of a Composite Modified Double Base Propellant

A novel Composite Modified Double Base (CMDB) propellant, formed by mechanically mixing aluminium/polytetrafluorethylene (Al/PTFE) powders, was prepared through a rolling process. A variety of tests, such as tensile properties, particle size analysis etc., were carried out to study the influence of PTFE on the CMDB propellant properties. The PTFE deformed from particles to fibres under a uniform shear force, forming a fibre network which greatly improved the propellant’s mechanical properties. Compared to that of the CMDB propellant without PTFE, the elongation of the propellant containing 6% PTFE was increased by 26 times, and moreover, the impact strength was enhanced by 326% at −40 °C. Significantly, the propellant friction and impact sensitivities were reduced by 75.8% and 35.6%, respectively. In addition, the presence of PTFE in the propellant resulted in fluorination of the Al. The gaseous combustion product AlF3 reduced the propellant combustion agglomeration. Consequently, PTFE significantly promoted the propellant’s mechanical performance, decreased the shock (friction, impact) sensitivity and reduced combustion agglomeration.