Delay elements are used in both commercial and military items requiring a reproducible time interval between the initiation of a primary charge and the ultimate detonation or combustion of the item. The range of time required of the delay element varies from one second through a minute or more depending on the application. Delays can be gas-producing for vented applications (e.g., pyrotechnic hand-held signals) or gasless for applications that require a sealed fuze system (e.g., hand grenades).
At this time, many military pyrotechnic delay formulations contain chromates, lead, barium, and perchlorates. The U.S. Army has been successful at removing environmentally hazardous materials from gas-producing delays for pyrotechnic items however, DoD still needs an environmentally sustainable gasless delay that is highly tunable and fits in the limited space within currently fielded munitions.
Gasless delay elements are used in hundreds of thousands of items per year in a variety of applications. Examples of fuzes and end items that use gasless delay elements include, but are not limited to, the M201A1 (M18, M83 smoke grenades and M14 incendiary grenades), M208 (M8 smoke pot), M228 (M69 training grenade), M213 (M67 fragmentation grenade) and M84 (variant of the M201A1). As an example, the M201A1 fuze is used in roughly 500,000 items per year. The delay compositions used in this fuze contain environmentally objectionable materials such as barium chromate, lead chromate, and potassium perchlorate.
The environmental impacts of hexavalent chromium, lead, and perchlorate are well documented. Hexavalent chromium is a known carcinogen and is heavily controlled by environmental and occupational safety regulations. The Office of the Secretary of Defense directed the Services to reduce the use of hexavalent chromium where possible through a 2009 memorandum “Minimizing the Use of Hexavalent Chromium (Cr+6).” Lead is highly regulated in all media. A recent study by the National Research Council found that current occupational exposure levels are not protective of DoD personnel at firing ranges and shoot-houses. Perchlorate is a highly water soluble contaminant that has been shown to inhibit normal function of the thyroid. Perchlorate is regulated in drinking water in several states and EPA is developing a national regulation for perchlorate in drinking water.