Energetic properties of core–shell B@PVDF/AP composite micro-units prepared by electrostatic spraying technology

Abstract

In this study, to improve the ignition and combustion performance of fuel boron (B) powder. The core–shell B@ polyvinylidene fluoride (PVDF)/ ammonium perchlorate (AP) composite micro-unit with the effect of erosion activation is successfully prepared by simple and controllable electrostatic spraying technology. The results of morphology and structural composition show that PVDF and AP are tightly wrapped on the surface of B, forming a uniform shell, which effectively prevents moisture absorption and oxidation of B during storage and transportation. The results of the thermal analysis show that the hydrofluoric acid (HF) gas generated by the decomposition of PVDF at about 100 °C in advance has a pre-ignition reaction (PIR) with the boron oxide (B2O3) film on the surface of B. The PIR generates boron fluoride (BF3) gas and breaks the B2O3 film. This reduces the initial oxidation temperature of B by 12.6 % and enhances the oxidation activity of B powder. In addition, the oxygen (O2) released by AP improves the combustion performance of B and strengthens the effect of erosion activation. It is also found that all samples can be successfully ignited and burned continuously, which improves the ignition and combustion performance of B powder. It is worth noting that the ignition delay time of the composite micro-unit sample with the stoichiometric ratio of B/PVDF/AP of 2: 1: 2 can be shortened to 0.454 s at most, which is 17 % lower than that of the physical mixed sample. Moreover, its combustion intensity and flame temperature also reach the best. These results show that the core–shell B@PVDF/AP composite micro-unit provides a great strategy for application in solid propellant and pyrotechnics.