Training grounds and battlefields are subject to contamination from the remains of detonated, fired or, in some cases, unexploded pyrotechnic devices. The most abundant source of contamination comes from the outer casing-housing that is usually constructed from aluminum or steel protected by a corrosion resistant coating containing hexavalent chromium and cadmium. Adverse environmental and health effects are associated with these compounds. Decommissioning training fields that are contaminated with pyrotechnic debris requires significant and costly cleanup and remediation.

The overall objective of this project was to develop an environmentally benign and economical pyrotechnics casing system consisting of a structural polymer and a degradation agent.  This casing system would be high-strength, non-corroding, highly inert, environmentally safe, have an extended/indefinite shelf life, and also be readily degraded on demand using specially tailored and safe enzymes.

Technical Approach

The rapidly degradable pyrotechnic system consists of an inert (non-corrosive) polymer as a replacement for the chromium and cadmium coated aluminum and/or steel housings. This material was combined with a unique prepackaged desiccated enzyme that will be released and activated immediately after the pyrotechnic device functions. With time, the enzyme will degrade the polymer, making the housing/container relatively unusable in the short term and in the longer term reducing it into inert and environmentally safe by-products. If needed, a secondary enzyme activating material such as water combined with environmentally safe freezing point depressant salts can be added to and kept separate from the desiccated enzyme using encapsulation technology or segregated packaging. When the pyrotechnic device is fired, the protective enzyme/additive packing fails, releasing the materials, which then begin to degrade the pyrotechnic housing/casing.

The specific goals for demonstrating the feasibility/viability of this innovative proposed material system included: demonstrating the selected structural polymer has sufficient mechanical properties to replace the presently used metallic housing/casing materials with no negative impact on pyrotechnic performance, shelf life, weight and life cycle cost and developing a specially tailored enzyme and demonstrate its ability to degrade the structural polymer.  The research team developed enzymes for LCP degradation; optimized the degradation process conditions and controls; and integrated these enzymes in the body of the pyrotechnic housing-casing.


In this SERDP feasibility study, Infoscitex Corporation and the University of Texas A&M evaluated possibility of improvement of microbial hydrolyses for biodegradation of PETbased TLCP. Based on the experimental results discussed in this report, the following conclusions were made. Several E. coli clones bearing the original and mutated genes of thermophilic hydrolase (TfH) deriving from Thermobifida fusca and exhibiting an improved total hydrolase production and excretion can be successfully generated using error-prone polymerase chain reaction to create beneficial mutations. This system could potentially degrade various polymers, including polyethylene-terephthalate (PET)-based thermotropic liquid crystalline polymer (TLCP). These bacterial strains would provide additional environmental benefits through their application for environmental clean-up. The resultant enzymes were relatively stable in solution. The potential of enzymatic biodegradation of the TLCP films was evaluated. The enzymatic exposure at 50°C resulted in significant deterioration of the mechanical properties of the TLCP film. This result needs to be replicated at ambient temperatures to achieve optimal degradation in the field.  The elevated levels of the hydrolase release from cells were successfully achieved by the lpp gene deletion.  The genetically improved hydrolases exhibited an up to 4.6-fold increase in specific enzymatic activity. The increased activity of the improved hydrolases is anticipated to dramatically increase the applied degradation to the TLCP at ambient temperatures.

The conclusions of this study clearly indicate that rapid degradation of a structural polymer is possible, thus making the rapidly degradable pyrotechnic system (RDPS) a valuable tool to reduce environmental impact from detonated ordnance casings. Future work needs to be done to further develop RDPS and eventually test in live fire validation studies.


The successful development of the RDPS will provide the following benefits for the Department of Defense (DoD): significant reduction in the release of hazardous materials into the environment from discharged pyrotechnic assemblies, excellent pyrotechnic shelf life without the need for hazardous protective corrosion-resistant coatings; significant reduction in the cleanup costs for training grounds and prevention of their closure; and equal or improved pyrotechnic performance without compromising life-cycle cost.