Phase Change Materials for Enhanced Warfighter Survivability

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Advanced Materials OBJECTIVE: The Army seeks innovative solutions utilizing phase change materials tailored for thermal regulation within a Closed-Circuit Self-Contained Breathing Apparatus to reduce thermal burden, enhance operational longevity, and improve warfighter efficiency. DESCRIPTION: This STTR topic addresses the need for an advanced material solution capable of thermally regulating the microclimate of a Closed-Circuit Self-Contained Breathing Apparatus (CC-SCBA) by acting as a heat exchanger within the system. The envisioned technology would utilize phase change materials (PCMs) that are lightweight, reusable, and regenerative, with a transition temperature tailored to the unique operational demands of tactical respiratory protection devices. Current CC-SCBA systems place a significant thermal load on the operator, leading to increased fatigue and reduced mission duration and effectiveness. Additionally, the inherent heat generation compromises the CO2 scrubbing efficiency, curtailing system endurance. The integration of an optimized PCM matrix could surmount these limitations by regulating the temperature of inspired air, thereby enhancing warfighter lethality and survivability. The material must demonstrate efficacy in a composite or blend format, ensuring compatibility with existing CC-SCBA configurations and surpassing the performance of conventional ice-based systems. The developed technology should demonstrate structural stability and efficient thermal exchange within the constrained form factor of CC-SCBA units. Overall, success is defined by a phase change material that extends the operating lifetime of a CC-SCBA in terms of the thermal limitations set forth by the current NIOSH standard for CC-SCBAs (42 CFR 84.103). The ideal solution is a phase change material that can maintain an inspired air temperature below 35 C under operational flow conditions for a duration of 4 or more hours. The development process will include the optimization of encapsulation methods to prevent leakage and enhance material integration within the CC-SCBA framework. Additionally, these materials should exhibit long-term chemical stability and resistance to thermal degradation over repeated use cycles, ensuring reliability and safety in field operations. It should also be noted that the PCM will be required to operate in nearly 100% humidity in most normal conditions. PHASE I: The initial phase will focus on the synthesis and laboratory-scale characterization of PCM candidates. These materials must demonstrate a suitable phase transition at operational temperatures and possess the thermal mass necessary to sustainably absorb the heat generated during CC-SCBA operation. This phase will culminate in the delivery of a material sample along with a comprehensive analysis of its thermal performance under simulated operational airflow conditions. PHASE II: Building upon the findings of Phase I, this phase will involve the integration of the PCM into a prototype CC-SCBA system. The material's performance will be validated in a controlled environment that replicates field conditions. Key performance indicators will include the PCM's ability to maintain a target inspired air temperature below 35 C, the duration of effective thermal regulation, and the material's regenerative capabilities after thermal cycling. PHASE III DUAL USE APPLICATIONS: Collaboration with industry leaders in the CC-SCBA market will be essential to transition the PCM from a laboratory setting to a field-ready solution. This phase involves the design and production of a modular PCM component that can be seamlessly incorporated into existing CC-SCBA systems. The module must meet military specifications for durability, operational effectiveness, and ease of integration. Successful demonstration in this phase will lead to the exploration of dual-use applications, where similar thermal management challenges exist, such as in industrial respirators or high-performance athletic wear. REFERENCES: Salunkhe, P. B.; Shembekar, P. S, A review on effect of phase change material encapsulation on the thermal performance of a system. Renewable and Sustainable Energy Reviews. 2012, 16(8), p 5603-5616. https://doi.org/10.1016/j.rser.2012.05.037.; Wang, X.; Li, W.; Luo.; Wang, K.; Shah, S, A critical review on phase change materials (PCM) for sustainable and energy efficient building: Design, characteristic, performance and application. Energy and Buildings. 2022, 260, p 111923. https://doi.org/10.1016/j.enbuild.2022.111923; Mehling, H.; Brutting, M.; Haussmann, T, PCM products and their fields of application - An overview of the state in 2020/2021. Journal of Energy Storage. 2022, 51, p 104354. https://doi.org/10.1016/j.est.2022.104354; Man tests; performance requirements, 42 CFR 84.103 (2004) https://www.ecfr.gov/current/title-42/chapter-I/subchapter-G/part-84/subpart-H/section-84.103 KEYWORDS: protection, SCBA, closed circuit, phase change materials, thermal regulation, respirator