Entwicklung und Untersuchung pyrotechnischer Verzögerungspellets unter Berücksichtigung der Green Chemistry

Due to the toxic and carcinogenic properties of substances used in pyrotechnic delay compositions, the aim of this work was the production and investigation of alternative pyrotechnic delay mixtures. The development process was accom-panied by the “rules of green chemistry”. The oxidizing agents CaO2, Li2O2, SrO2, KClO4, LiClO4 and SiO2 and the reducing agents Al, CaSi2, Fe, Mg, Mn, Si, pSi, Ti and Zr were used as alternative substances. The delay compositions were produced as pellets and then loaded into tubes for further investigation. In addition, the use of solvents was avoided and dry binders (HPMC, MgSt, PEG1, PEG2 and PVP) were used as adhesion promoters between the parti-cles. Furthermore, selected mixtures were subjected to an ageing simulation over 11 days at 80 °C with ambient air humidity. The delay pellets achieved combustion rates ranging from 1,1 mm s-1 to 91,4 mm s-1. The combustion rate depended on the particle size of the oxidizing agents, the pellet diameter, the binder type and content, the fuel content, the tube material and if the pellets were post pressed into the delay tubes. It was also found that the addition of binders lowers the ignition temperature of mixtures with peroxides. No reduction in the ignition temperature was determined for the perchlorates. In addition, the mechanical stability of the pellets depended on the binder content, binder type and the actual components (oxidizing agent and reducing agent). Furthermore, Raman spectroscopic investigations were carried out to examine the reaction products for residual oxidants, to characterize the two silicon powders and to investigate aging processes. No residues of oxidizing agents could be detected in the reaction products, the two silicon powders were classified as crystalline and non-porous (also using BET and grain size analysis) and indications of ag-ing processes could be detected but not fully assigned. Using DSC analyses, the earlier ignition of the peroxide mixtures with the binders could be attributed to the combustion/decomposition of the binders. Most of the mixtures were classified as impact- and friction-sensitive, but unwanted ignition with the bind-ers HPMC, PEG1, PEG2 and PVP occurred during pellet production. Even if the mixtures are classified as “gasless”, a pressure increase of up to 13 bar can be expected during the combustion of SrO2/Al/MgSt pellets. However, this de-pends on the binder content. Finally, the investigation of the aged pellets SrO2/Al/MgSt and CaO2/pSi/MgSt led to the conclusion that both mixtures are stable in the long term and can therefore be regarded as possible substitution candidates for use in delay elements.