Yi Wang, Xiaolan Song, Chongwei An and Fengsheng Li
Abstract: Three very inexpensive and readily available colour composites (red, green, and blue) with different binders were prepared by a mechanical milling method. Their micron morphology, thermal reactions, and safety characteristics were evaluated. In particular, as a focus of this work, their combustion performances were investigated by a combinatorial method using a visible light spectrometer, a thermal infrared camera, and a coloured high-speed camera. The results indicated that, although the ingredients had different particle sizes, they were mixed very homogeneously as confirmed by their SEM imaging, due to the use of ball milling. The safety characteristics of the three kinds of energetic composites were good, which implied that, in terms of safety, they act just like inert materials. DSC data showed that all composites had low reaction temperatures and activation energies, as well as higher thermal stability. Therefore, although their formulas contained large amounts of wood powder (to reduce their sensitivities),their thermal reactivity was still very high. Regarding the focus of the study, i.e., combustion performance, on the one hand, the colour effects of the red composites are excellent since its main wavelengths were 614 nm and 618 nm and its spectral purities corresponding to those main wavelengths were as high as 95.8% and 98.6%, respectively. Meanwhile, the colour effects of the green composites essentially met the practical usage requirements because their main wavelengths were located in 500～565 nm range and their chromatographic purities at the main wavelengths reached up to 74.5% and 77.2%. On the other hand, the colour effects of the blue composites were very poor. Their main wavelengths were located at 482 nm and 467 nm, barely entering the range of blue light (435～485 nm). Their chromatographic purities at those main wavelengths were only 15% and 43%, which did not meet the practical requirements. In addition, whatever the colour, the variation of binders considerably influenced the burning rates of the composites, since, with the same 20 g for each column and under the same conditions, the burning times of nitrocellulose (NC)-based composites were remarkably shorter than those of phenolic resin (POR)-based composites. However, variation of binders did not have a substantial impact on flame temperature and flame structure. These data are valuable in guiding the melioration for formulas of colour composites in the future.
Ref: JPyro 2024 (65-79)
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