Development of a Sustainable Perchlorate-Free Yellow Pyrotechnic

Oct 31, 2016 - Novel yellow-light emitting pyrotechnic compositions absent perchlorate oxidizers were investigated for use in the Mk 144 marine smoke ...
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Research Article pubs.acs.org/journal/ascecg

Development of a Sustainable Perchlorate-Free Yellow Pyrotechnic Signal Flare Eric J. Miklaszewski,* Jonathan M. Dilger, and Christina M. Yamamoto Spectrum Warfare Systems Department, Naval Surface Warfare Center Crane Division, 300 Highway 361, Crane, Indiana 47522-5001, United States

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S Supporting Information *

ABSTRACT: Novel yellow-light emitting pyrotechnic compositions absent perchlorate oxidizers were investigated for use in the Mk 144 marine smoke and illumination signal. In laboratory-scale testing, three candidate formulations met or surpassed performance metrics of luminous intensity, dominant wavelength, color purity, and burn time when compared to a mock Mk 144 formulation which currently utilizes the environmentally hazardous potassium perchlorate. Also, one identified formulation does not utilize any barium compounds which may be the focus of future regulations. Furthermore, these candidate systems exhibited similar insensitivity to electrostatic, friction, and impact ignition stimuli in comparison to the mock Mk 144 formulation. Therefore, replacement formulations for the Mk 144 marine smoke and illumination signal have been identified with increased performance, environmental sustainability, and acceptable safety characteristics. KEYWORDS: Pyrotechnic, Environmentally sustainable, Perchlorate-free, Mk 144, Flare

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INTRODUCTION Perchlorate oxidizers have been widely used in military and civilian pyrotechnics due to their high reactivity, low cost, and high stability. However, the Environmental Protection Agency (EPA) has advised that concentrations as low as parts per billion can pose serious health risks through inhibition of iodine uptake by the thyroid gland.1 In response to these health concerns, the EPA has advised the permissible perchlorate levels under the Safe Drinking Water Act of 1974. These advisories have motivated costly remediation efforts on perchlorate-contaminated Department of Defense (DoD) ordnance testing sites. For example, all live fire training at Camp Edwards was suspended in 1997 due to perchlorate groundwater contamination concerns.2 Since training and testing operations are imperative to maintain military readiness, it is vital to remove perchlorate oxidizers from commonly used pyrotechnic devices to avoid further contamination and potential closures at DoD training sites. Since 2002, various efforts throughout the DoD have targeted a wide variety of commonly used KClO4-containing pyrotechnic items including perchlorate-free smoke generating formulations,3−6 time-delay compositions,7−10 and incendiary compositions.11 However, most perchlorate reformulation efforts have been focused on red- and green-light emitting signal flares such as hand-held signals (e.g., M126A1, Mk124, M195), pen flares (e.g., Mk80 and A/P25), and marine smoke and illumination signals (e.g., Mk140 and Mk141).12−19 To achieve this goal, the formulator must consider the This article not subject to U.S. Copyright. Published 2016 by the American Chemical Society

interdependence of key performance metrics (e.g., luminous intensity, burn time, and color purity) as well as the regulatory status, commercial availability, and safety of appropriate ingredients. The objective of this work was to develop a perchlorate-free yellow flare composition for use in the Mk 144 marine smoke and illumination signal. New formulations were evaluated against a mock Mk 144 flare formulation via laboratory-scale experiments to characterize luminous intensity, burn time, dominant wavelength, color purity, and ignition sensitivity.

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EXPERIMENTAL SECTION

Reactive Pyrotechnic Compositions. Table 1 summarizes the vendor information and nominal particle sizing for the commercially available powders used within the experimental compositions. All pyrotechnic compositions were hand-mixed with a metal spatula within a grounded metal beaker in relatively small quantities of 50 g or less. First, the fuel and binder were mixed until homogeneous. All other ingredients (primarily constituting oxidizers) were premixed in a separate container and added into the fuel/binder premixture. The composition was again mixed until homogeneous while maintaining proper grounding of the mixing vessel. The binder used was a two-part thermoset-epoxy consisting of 70 wt % Epon 813 and 30 wt % Versamid 140.

Received: September 19, 2016 Revised: October 28, 2016 Published: October 31, 2016 936

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Table 1. Vendor Information for Reactants powder

vendor

asphaltum Al Ba(NO3)2 KClO4 KNO3 Mg Mg0.5Al0.5 alloy Na2C2O4 NaNO3 polyvinyl chloride Sr(NO3)2

Hummel Croton, Inc. Hummel Croton, Inc. Barium & Chemicals, Inc. Barium & Chemicals, Inc. Hummel Croton, Inc. Hart Metals, Inc. READE Advanced Materials GFS Chemicals, Inc. Hummel Croton, Inc. Barium & Chemicals, Inc. Barium & Chemicals, Inc.

nominal particle size Gr C, Class 4, Type II MIL-B-162, Gr B, Class 1 MIL-P-217A, 100 μm MIL-DTL-382D, Type III −200 mesh MIL-S-210A MIL-S-322C, Gr B MIL-P-20307 MIL-S-20322B

Figure 1. Image of 15 g pyrotechnic pellet (left) and schematic of mounted and inhibited pellet (right).

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Combustion Experiments. The final composition was partially cured for 30−60 min prior to pressing into experimental pellets. Figure 1 shows a typical experimental pellet and a schematic of how samples are mounted and inhibited with Miller-Stephenson’s Epoxy 90720 to facilitate linear burning. Experimental pellets of 0.75 in. diameter were pressed utilizing a 12-ton Carver press at a load of 1500 lbs. for 10 s. Each pellet was composed of a nominal mass of 15 g of composition with 1 g of a thermite-based igniter. After mounting, samples cured in an oven at 60 °C for 24 h. A 15 g form factor was utilized for these combustion experiments due to the increased safety concerns associated with the Mk 144 form factor utilizing more than 130 g of pyrotechnic composition. Pellets (3−6) were prepared for each composition to provide statistical validity on the measurements. Pellets were ignited remotely by an electric match. Luminous intensity measurements were performed using an SED 033 silicon detector photodiode fitted with a photopic response filter (Y-filter). The average luminous intensity (ALI) is determined by averaging the steady-state intensity and therefore does not account for ignition and extinction transients. The luminous efficiency (LE) is calculated by integrating the temporal luminous intensity profile and dividing by the mass of the reacting pellet (∼15 g). The burn time (BT) is the time difference at 5% of the maximum luminous intensity over the duration of the burn of the experimental pellet. Color purity and dominant wavelength were measured using an Optroniks FMS 10 tristimulus colorimeter which referenced the standard I.C.I. Chromaticity Diagram and illuminant C as the white point.21 A StellarNet BLUE-Wave miniature spectrometer was used to evaluate qualitative differences in the spectral emissions. Sensitivity Analysis. Sensitivity testing on selected formulations was performed according to NAVSEA Instruction 8020.5C and MILSTD-1751A.22,23 Electrostatic discharge, friction, and impact sensitivities were determined in accordance with MIL-STD-1751A method 1031, method 1023, and method 1013, respectively.23 Thermochemical Predictions. Thermochemical predictions were made using the NASA CEA combustion module (hp) at a constant pressure of 1 atm.24 In these calculations, the heat of formation for polyvinyl chloride (PVC) (C 2 H 3 Cl) and Epon/Versamid (H98C83O14N4) were −22 495 and −876 278 cal mol−1, respectively.18

RESULTS AND DISCUSSION Overview of the Pyrotechnic Generation of Yellow Light. The generic chemical equation for the in-service Mk 144 yellow-light emitting flare composition is Mg + Ba(NO3)2 + Na 2C2O4 + KClO4 + hydrocarbon binders → MgO(s) + Na(g) + BaCl(g) + BaOH(g) + C(s) + others

(1)

where magnesium (Mg) is the fuel and barium nitrate (Ba(NO3)2), sodium oxalate (Na2C2O4), and potassium perchlorate (KClO4) are the oxidizers. Besides being a strong oxidizer, KClO4 also donates chlorine to produce several desired light-emitting chlorinated species upon combustion. The hydrocarbon binders include a two-part thermoset binder (Laminac 4116/Lupersol) as well as a dry binder, asphaltum. A pyrotechnic reaction will produce a variety of combustion species that emit photons over a range of spectral wavelengths. Table 2 lists the relevant light-emitting combustion products for the yellow-light emitting pyrotechnic formulations considered here. These products include the condensed-phase products of magnesium oxide (MgO) and carbon (C) as well as gas-phase products of sodium (Na), barium chloride (BaCl), Table 2. Common Emission Bands of Yellow-Light Producing Flares

a

937

species

emission wavelengths (nm)25−27

visible color

BaCl(g) BaO(g) BaOH(g) C(s) MgO(s) Na(g)

513.9, 524.1, 532.1 549.3, 564.4, 586.5, 604.0, 649.4 487.0, 512.0 blackbody 498.6, 499.7, 500.7, blackbody 589

green green, yellow, red green a greena yellow-orange

The blackbody emission profiles depend on the flame temperature. DOI: 10.1021/acssuschemeng.6b02261 ACS Sustainable Chem. Eng. 2017, 5, 936−941

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significantly lower than the 89.0% color purity of the Mk 144 formulation (see Supporting Information Table S1). It is clear from the performance evaluation that newly developed formulations are required as an Mk 144 replacement formulation. However, the high color purity of formulation 1 (93.2%) suggests that a reaction that primarily generates Na(g) in the combustion plume can yield high-purity yellow light in comparison. Hereafter, two distinctly different yellow-light emitting pyrotechnic formulation systems were evaluated: one utilizing a color-mixing strategy with the use of barium nitrate and a chlorine donor and another exploring only sodium nitrate and sodium oxalate as the oxidizers. Formulation Development: Color-Mixing with Barium Nitrate and PVC. Initial development efforts focused on simply replacing the potassium perchlorate oxidizer with sodium/barium nitrates for their oxidative potential as well as PVC as a chlorine donor. The generic form of the proposed perchlorate-free yellow-light emitting formulation is

barium hydroxide (BaOH), and barium oxide (BaO). The gaseous combustion products emit photons at specific wavelengths in the green, yellow, orange, and red portions of the visible spectrum. Thus, the pyrotechnic reaction described within eq 1 achieves its yellow color via a color-mixing strategy. The condensed-phase species [e.g., C(s) and MgO(s)] produced by the reaction also emit blackbody radiation that generally increases the luminous intensity of the flare while degrading the color purity of the flame.25 The average photopic emissions give rise to a specific color and purity as defined by the I.C.I. Chromaticity Diagram.21 Evaluation of Yellow-Light Emitting Pyrotechnic Formulations from the Literature. The initial strategy to reformulate the Mk144 was to leverage existing yellow-emitting compositions that do not contain perchlorate for their viability as replacements for the current in-service composition (Table 3).25 Sodium oxalate and nitrates of potassium and sodium Table 3. Modified Yellow-Light Emitting, Perchlorate-Free Formulations from the Literature

Mg + Mg 0.5Al 0.5 + NaNO3 + Ba(NO3)2 + Na 2C2O4

ingredient (wt %)

Mk 144

125

225

3

+ PVC + hydrocarbon binders → MgO(s) + Na(g)

Mg (Gr 17) NaNO3 Na2C2O4 Ba(NO3)2 KClO4 PVC KNO3 asphaltum epoxy

a

16.15 53.20

29.38

22 58

+ BaClg + BaOH(g) + C(s) + others

a a a

where new ingredients include the sodium nitrate (NaNO3) and magnalium (Mg0.5Al0.5), which is used as an energetic additive. Magnalium was utilized in some formulations since the nitrate salts have less oxidative potential than the previously used potassium perchlorate. By comparing eqs 1 and 2, it is shown that all of the emitting species shown in Table 2 can be produced without the use of perchlorate oxidizers. New formulations and their corresponding performance data are shown in Tables 5 and 6, respectively.16,28 As expected, the

29.38

25.65 a a

5

36.24

15

5

5

a

The exact amount of each ingredient for the current Mk 144 formulation is not approved for public release.

were utilized as the key oxidizers in these three systems. These systems were further modified with the two-part Epon 813/ Versamid 140 binder so as to mitigate other environmental safety concerns associated with other common pyrotechnic binders. Table 4 lists the combustion performance metrics for laboratory-scale samples of the mock Mk 144 and the identified

Table 5. Experimental Color-Mixed Perchlorate-Free Formulations by Weight Percent Mg (Gr 17) Mg0.5Al0.5 NaNO3 Ba(NO3)2 PVC asphaltum epoxy

Table 4. Performance Characteristics of Modified Perchlorate-Free Formulations from the Literature BT (s) Mk 144 1 2 3

42.3 61.5 40.7 41.9

± ± ± ±

0.7 0.8 0.3 0.2

ALI (cd) 1949 415 1623 3130

± ± ± ±

101 24 43 228

LE (cd s g−1)

Tad (K)

± ± ± ±

2056 2665 2471 2407

2599 553 2165 4173

135 32 57 304

(2)

4

5A

5B

6A

6B

28.10

23.00 3.60 27.40 29.00 8.10 3.95 4.95

22.50 3.52 26.81 28.38 7.93 3.86 7.0

20.10

19.67

37.00 27.05 10.90

36.20 26.47 10.66

4.95

7.0

20.00 34.10 8.90 3.95 4.95

Table 6. Performance Characteristics of the Experimental Color-Mixed Perchlorate-Free Formulations BT (s) 4 5A 5B 6A 6B

perchlorate-free formulations. Each of the perchlorate-free formulations is predicted to have moderate adiabatic combustion temperatures. As compared to the performance of the Mk 144, formulation 1 is shown to burn significantly slower with an extraordinarily lower ALI and LE. Similarly, formulation 2 displays a significantly lower (though less extreme) ALI and LE than the Mk 144. Formulation 3 was designed to have a predicted adiabatic combustion temperature similar to that of 2 while utilizing NaNO3 instead of Na2C2O4. The resulting burn time, luminous intensity, and luminous efficiency of formulation 3 was encouragingly similar or greater than that of Mk 144. However, the 77% color purity of 3 was

39.9 42.6 45.6 43.5 49.5

± ± ± ± ±

2.0 0.3 0.4 0.1 0.5

ALI (cd) 1649 1989 1888 2602 2179

± ± ± ± ±

32 49 55 72 75

LE (cd s g−1)

Tad (K)

± ± ± ± ±

2270 2542 2533 2915 2841

2198 2652 2518 3469 2905

42 65 74 96 100

predicted adiabatic combustion temperature scales proportionally with the ALI and LE. Of these formulations, 5A and 6A are most efficient with similar burn times and increased luminous intensity in comparison to the Mk 144 composition, making them suitable replacement formulations. Due to the excess ALI (650 cd) and LE (870 cd s g−1) of 6A over Mk 144, we were able to tune the burn time and intensity of formulation 6A by 938

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the luminous intensity profile (Figure 2) of 8A was excessively noisy due to the far off-stoichiometric conditions of these reactions (stoichiometry of ∼0.4). Furthermore, the ∼80% color purities of formulations 7 and 8A were lower than the 89% of the mock Mk 144 formulation (Supporting Information Table S4). Therefore, formulation 9A was developed to incorporate Na2C2O4 to reduce the MgOs species,29 thereby cooling the reaction temperature and still producing the key yellow-emitting gaseous sodium (Na(g)). Spectral intensity profiles of these formulations (Figure 3) show how the addition of Na2C2O4 increased the color purity of formulation 9B by minimizing the green MgO(s) emission described in Table 2. With the addition of Na2C2O4, formulation 9A produced a superior color purity of 90% while greatly surpassing the luminous intensity and efficiency requirements but falling short of the burn time requirement. Due to the higher than required luminous intensity and efficiency of formulations 8A and 9A, the effect of increasing the binder content to 7 wt % was again explored to balance the performance metrics. While the color purity of formulation 8B was still lacking, formulation 9B was identified as a replacement for Mk 144 due to a superior burn time, luminous intensity, luminous efficiency, and color purity while having a similar dominant wavelength to that of the Mk 144 formulation. Ignition Sensitivity Analysis. Sensitivity analysis of the most promising formulations is shown in Table 10. Here, the 50% fire energy is reported for impact sensitivity; the minimum fire energy is reported for friction sensitivity, and the maximum no-fire energy is reported for electrostatic sensitivity. All formulations tested were found to be insensitive to impact stimuli as they were not initiated at the maximum height according to MIL-STD-1751A method 1013.23 The electrostatic sensitivity of these formulations was relatively similar to that of the Mk 144 formulation except for 5A which is more sensitive to electrostatic stimuli due to its use of Mg0.5Al0.5. The data obtained from MIL-STD-1751A method 1013, the rotary friction method, can only be interpreted that each formulation is moderately sensitive to friction stimuli. A relative comparison of the friction ignition energy thresholds is not valid for this method. In summary, all of the formulations have similar ignition sensitivity to that of the Mk 144 formulation and would likely be approved for use in military items.

increasing the epoxy binder content to 7 wt % (6B). The resulting formulation achieved a more balanced performance with respect to the burn time and intensity of Mk 144. Similarly increasing the binder of formulation 5 to 7 wt % (5B) resulted in luminous intensity and efficiency below that of the Mk 144 composition. All of the colorimetric data for these formulations were similar to that of the Mk 144 composition (see Supporting Information Table S2). The burn time and intensity of formulation 5A and 6A can be further improved by changing the particle size of the magnesium fuel. Table 7 showcases this effect on performance Table 7. Effect of Mg Particle Size on Performance of Formulations 5A and 6A Mg granulation

BT (s)

Formulation 5A 37.6 ± 0.5 2308 42.6 ± 0.3 1989 Formulation 6A 29.7 ± 0.1 3960 36.7 ± 0.6 3034 43.5 ± 0.1 2602 65.1 ± 1.0 1705

Gr 15/18a Gr 17 Gr Gr Gr Gr a

15 15/18a 17 18

LE (cd s g−1)

ALI (cd) ± 100 ± 49

3077 ± 134 2652 ± 65

± ± ± ±

5279 4046 3469 2274

103 6 72 18

± ± ± ±

137 7 96 23

A mixture of Gr 15/Gr 18 Magnesium (60/40 wt %).

with the use of granulation 18 and granulation 15/18 sized magnesium powders. For each formulation, particle size scaled proportionately with burn time and luminous efficiency and inversely with luminous intensity. A granulation 17 sized magnesium fuel was found to be the optimum particle size for formulations 5A and 6A to meet or surpass the burn time and luminous intensity of the mock Mk 144 formulation. Particle size was not observed to significantly affect the colorimetric output of these formulations as shown in Supporting Information Table S3. Development of Mg/NaNO3/Na2C2O4 Formulations. In order to develop a simplistic yellow-light producing formulation, the Mg/NaNO3 was also considered. As shown in Tables 8and 9, formulations 7 and 8A were designed so that their Table 8. Mg/NaNO3/NaC2O4 Formulations by Weight Percent Mg (Gr 17) NaNO3 Na2C2O4 epoxy

7

8A

8B

9A

9B

23 72

26 69

25.5 65.6

5

5

7

26 39 30 5

25.5 38.2 29.4 7

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Table 9. Performance of Mg/NaNO3/NaC2O4 Formulations BT (s) 7 8A 8B 9A 9B

40.9 37.5 46.2 39.1 46.2

± ± ± ± ±

2.7 0.9 0.8 0.2 0.5

ALI (cd) 4106 5050 4275 4936 3101

± ± ± ± ±

164 318 80 159 122

LE (cd s g−1)

Tad (K)

± ± ± ± ±

2418 2720 2830 2310 2099

5475 6733 5700 6581 4135

219 424 106 211 163

CONCLUSIONS

Several perchlorate-free yellow-light emitting pyrotechnic compositions were developed for use in the Mk 144 marine smoke and illumination signal. In laboratory-scale testing, formulations 5A, 6B, and 9B met or surpassed the luminous intensity, dominant wavelength, color purity, and burn time of the currently used Mk 144 formulation which utilizes the environmentally hazardous potassium perchlorate. Formulation 9B does not utilize any barium salt oxidizers, which may be the focus of future regulations due to the known adverse health effects of some barium compounds. Furthermore, these candidate systems exhibit similar insensitivity to electrostatic, friction, and impact ignition stimuli, making them safe for handling. In conclusion, multiple perchlorate-free formulations which utilize commercially available ingredients have been identified for the Mk 144 marine smoke and illumination signal with increased performance, environmental sustainability, and acceptable safety characteristics.

predicted adiabatic combustion temperatures are similar to those which previously yielded promising results (i.e., 2400− 2900 K). As shown, these formulations had superior luminous efficiency in comparison to the Mk 144 formulation. However, 939

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Figure 2. Luminous intensity profiles of the Mk 144 (red) and 8A (black) formulations.

Figure 3. Raw spectral intensity profiles of Mk 144 (red), 8A (black), and 9B (blue) formulations.

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Table 10. Sensitivity Data of Yellow-Light Emitting Flare Compositions formulation

impact sensitivity (joules)

friction sensitivity (ft lbs)

electrostatic sensitivity (joules)

RDXa Mk 144 5A 6 8B 9A 9B

17.5 32.6 35.0 35.0 35.0 35.0 35.0

116.3 158.4 271.6 183.6 110.4 211.4 239.8

0.080 0.180 0.080 0.125 0.125 0.125 0.125

a

(1) United States Environmental Protection Agency. Interim Health Advisory for Perchlorate; 2008. https://nepis.epa.gov/Exe/ZyPURL. cgi?Dockey=P1004X7Q.TXT. (2) Government Accountability Office. GAO-10-769 Perchlorate Occurence Is Widespread but at Varying Levels; Federal Agencies Have Taken Some Actions To Respond to and Lessen Releases; August 2010. (3) Shaw, A. P.; Poret, J. C.; Gilbert, R. A. J.; Domanico, J. A.; Black, E. L. Development and Performance of Boron Carbide-Based Smoke Compositions. Propellants, Explos., Pyrotech. 2013, 38 (5), 622−628. (4) Chen, G.; Showalter, S.; Raibeck, G.; Wejsa, J. Environmentally Benign Battlefield Effects Black Smoke Simulator; Defense Technical Information Center, 2006; Accession Number ADA481520. (5) Moretti, J. D.; Sabatini, J. J.; Shaw, A. P.; Gilbert, R. J. Promising Properties and System Demonstration of an Environmentally Benign Yellow Smoke Formulation for Hand-Held Signals. ACS Sustainable Chem. Eng. 2014, 2 (5), 1325−1330. (6) Moretti, J. D.; Sabatini, J. J.; Shaw, A. P.; Chen, G.; Gilbert, R. A.; Oyler, K. D. Prototype Scale Development of an Environmentally Benign Yellow Smoke Hand-Held Signal Formulation Based on Solvent Yellow 33. ACS Sustainable Chem. Eng. 2013, 1 (6), 673−678. (7) Miklaszewski, E. J.; Shaw, A. P.; Poret, J. C.; Son, S. F.; Groven, L. J. Performance and Aging of Mn/MnO2 as an Environmentally Friendly Energetic Time Delay Composition. ACS Sustainable Chem. Eng. 2014, 2 (5), 1312−1317. (8) Miklaszewski, E. J.; Poret, J. C.; Shaw, A. P.; Son, S. F.; Groven, L. J. Ti/C-3Ni/Al as a Replacement Time Delay Composition. Propellants, Explos., Pyrotech. 2014, 39 (1), 138−147. (9) Poret, J. C.; Shaw, A. P.; Csernica, C. M.; Oyler, K. D.; Estes, D. P. Development and Performance of the W/Sb2O3/KIO4/Lubricant Pyrotechnic Delay in the US Army Hand-Held Signal. Propellants, Explos., Pyrotech. 2013, 38 (1), 35−40. (10) Poret, J. C.; Shaw, A. P.; Csernica, C. M.; Oyler, K. D.; Vanatta, J. A.; Chen, G. Versatile Boron Carbide-Based Energetic Time Delay Compositions. ACS Sustainable Chem. Eng. 2013, 1 (10), 1333−1338. (11) Moretti, J. D.; Sabatini, J. J.; Chen, G. Periodate Salts as Pyrotechnic Oxidizers: Development of Barium- and Perchlorate-Free Incendiary Formulations. Angew. Chem., Int. Ed. 2012, 51 (28), 6981− 6983.

RDX class 5 type II.

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ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.6b02261. Additional tables containing colorimetric performance information (PDF)

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REFERENCES

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported at NSWC Crane by the Naval Innovative Science and Engineering program as well as by the Strategic Environmental Research and Development Program under Project WP-1280. The authors gratefully thank the sponsors of this work. 940

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(12) Sabatini, J. J.; Nagori, A. V.; Chen, G. C. P.; Damavarapu, R.; Klapötke, T. M.; Chu, P. High-Nitrogen-Based Pyrotechnics: Longerand Brighter-Burning, Perchlorate-Free, Red-Light Illuminants for Military and Civilian Applications. Chem. - Eur. J. 2012, 18 (2), 628− 631. (13) Shaw, A. P.; Poret, J. C.; Grau, H. A. J.; Gilbert, R. A. J. Demonstration of the B4C/NaIO4/PTFE Delay in the U.S. Army Hand-Held Signal. ACS Sustainable Chem. Eng. 2015, 3 (7), 1558− 1563. (14) Moretti, J. D.; Sabatini, J. J.; Poret, J. C. High-Performing RedLight-Emitting Pyrotechnic Illuminants through the Use of Perchlorate-Free Materials. Chem. - Eur. J. 2014, 20 (28), 8800−8804. (15) Dye, D. F.; Shortridge, R. G.; Yamamoto, C. Y.; Chen, G. Elimination of Perchlorate Oxidizers from Pyrotechnic Flare Compositions, ESTCP WP-200730 Final Report, 2015. (16) Shortridge, R. G.; Wilharm, C. K.; Yamamoto, C. Y. Elimination of Perchlorate Oxidizers from Pyrotechnic Flare Compositions, SERDP WP-1280 Final Report, 2007. (17) Shortridge, R. G.; Wilharm, C. K.; Yamamoto, C. M.; Dreizin, E. L. Development and Testing of Perchlorate-Free Red and Green Pyrotechnic Flare Compositions. 33rd International Pyrotechnic Seminar; Fort Collins, CO, 2006; pp 281−290. (18) Sabatini, J. J.; Freeman, C. T.; Poret, J. C.; Nagori, A. V.; Chen, G. An Examination of Binder Systems and Their Influences on Burn Rates of High-Nitrogen Containing Formulations. Propellants, Explos., Pyrotech. 2011, 36 (2), 145−150. (19) Sabatini, J. J.; Raab, J. M.; Hann, R. K. J.; Damavarapu, R.; Klapotke, T. M. High-Nitrogen-Based Pyrotechnics: Development of Perchlorate-Free Green-Light Illuminants for Military and Civilian Applications. Chem. - Asian J. 2012, 7 (7), 1657−1663. (20) Two-Part Epoxy Adhesive Kit. Miller-Stephenson Chemical Company, Inc., 2015. Available online http://www.miller-stephenson. com/products/detail.aspx?ItemId=60. (21) Judd, D. B. I. C. I. Standard Observer and Coordinate System for Colorimetry. J. Opt. Soc. Am. 1933, 23 (10), 359−374. (22) Peletski, C. NAVSEAINST 8020.5C: Qualification and Final (TYPE) Qualification Procedures for Navy Explosives; Technical Report for Naval Sea Systems Command; Arlington, VA, 2000; DTIC Accession Number ADA509544. (23) Department of Defense Test Method Standard, Safety and Performance Tests for the Qualification of Explosives (High Exploxives, Propellants and Pyrotechnics); MIL-STD-1751A Technical Report for Department of Defense; 2001. (24) McBride, B. J.; Gordon, S. Computer Program for Calculations of Complex Chemical Equilibrium Compositions and Applications, II. User Manual and Program Description; NASA Reference Publication; National Aeronautics and Space Administration: Cleveland, 1996. (25) Conkling, J. A. Chemistry of Pyrotechnics: Basic Principles and Theory; CRC Press, 1985. (26) Pearse, R. W. B.; Gaydon, A. G. The Identification of Molecular Spectra, 4th ed.; Chapman and Hall, 1976. (27) Gaydon, A. G. The Spectroscopy of Flames, 2nd ed.; Springer, 1974. (28) Yamamoto, C. M.; Shortridge, R. G. Perchlorate-free yellow signal flare composition. US8,568,542 B2, Oct. 29, 2013. (29) Kosanke, K. L.; Kosanke, B. J. The Chemistry of Colored Flame. Pyrotechnic Chemistry; Journal of Pyrotechnics, Inc., 2004; Chapter 9.

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