Red pyrotechnic flames are not just used for fireworks displays.
They are important for many things, like marine distress signals and roadside flares, just to name a few.
But what many people are not aware of is that when chlorine-based compounds burn, they can transform into cancer-causing chemicals that fall to Earth.
According to Phys Org: “The characteristic red colors arise from the presence of gaseous strontium monochloride. Therefore, chlorine compounds are always added into the flare formulations although the typically added chloroorganics such as PVC form highly carcinogenic substances upon combustion.”
New Year’s 2013—Synchronized epic music:
Defense scientist Jesse Sabatini said: “New chlorine-free pyrotechnics could pave the way for a generation of red flares and fireworks that are better for the environment and for people’s health.” Sabatini is from the U.S. Army Research Laboratory in Maryland.
“These formulations typically contain a metallic fuel, such as magnesium, strontium nitrate, as the oxidizer, an organochlorine compound such as poly (vinyl chloride) (PVC), an organic binder, and sometimes auxiliary chlorine sources,” said Ernst-Christian Koch, lead author of the study.
“To make more environmentally friendly fireworks, the researchers focused on strontium monohydroxide, a compound that scientists had long believed was only a minor contributor to the red color of pyrotechnics. According to Koch, for years, scientists hadn’t realized that strontium monohydroxide also strongly flared red because its sister product, strontium oxide, produces an orange-red color that fireworks-makers try to avoid,” wrote C & EN.
“Sabatini, Koch, and coworkers formulated the new explosive by replacing polyvinyl chloride on the old ingredient list with either hexamine, a preservative in citrus washing solutions, or 5-amino-1H-tetrazole, an airbag propellant. The replacement successfully removes chlorine and helps produce strontium monohydroxide when the overall concoction is ignited, producing bright red fireworks. As an added bonus, the new formulation also avoids the production of unwanted orangey strontium oxide, Koch says.”
“The present study has shown that it is feasible to obtain both high intensity and highly saturated red flames exclusively based on SrOH with concomitant SrH emission,” the authors conclude.
Hopefully, researchers will focus on the blue and green pyrotechnics, which still use chlorine in their formulations, or at least this study may encourage other researchers to look for similar strategies.