Pyrotechnic Burn Rate Measurements: Strand Testing

Background: Burn rate is one of the most fundamentally important properties of pyrotechnic materials. While burn rate may be measured as a mass burn rate (mass of pyrotechnic composition consumed per unit time, e.g., g/s), linear burn rate is most commonly used. Linear burn rate can be defined as the distance the burning surface of a pyrotechnic composition advances inwardly (perpendicular to the burning surface) per unit time, and typically would be reported as inches per second (or mm/s). Even for a specific pyrotechnic material with a defined composition (including prescribed particle size and shape) there are a number of factors that will effect its burn rate.^[1] Generally the most important factors, ranked roughly in order of importance, are: ambient pressure, loading pressure (composition density), temperature, and burning surface area. Accordingly, for burn rate measurements to be most useful, they must take each of these additional factors into consideration.