In recent years, emergency management and response have received increasing attention globally. Currently, my country's emergency management has formed a closed-loop development model encompassing "all types of disasters, the entire chain, and all aspects," representing a systemic transformation from decentralized response to comprehensive coordination, and from passive disaster relief to proactive prevention and control. This model basically covers upstream emergency material raw material supply, core technology research and development, and equipment manufacturing; midstream emergency service platforms and solutions; and downstream diverse application scenarios and services. Among these, the upstream emergency material raw material supply provides ample room for the development of high-performance emergency and response materials. Due to the specific nature of its application scenarios, emergency management and response generally require emergency materials to possess characteristics such as lightweight, high strength, flame retardancy, wear resistance, heat resistance, cold resistance, water resistance, and ease of folding and transportation.
Among various emergency response and disposal materials, polymer materials stand out as one of the most important members of the material family due to their excellent comprehensive properties. my country's Ministry of Emergency Management has created clear policy guidance and market demand, and its initiatives such as "upgrading of specialized rescue equipment," "construction of intelligent monitoring and early warning systems," and "full-risk prevention and control material reserves" have provided broad application scenarios for high-performance polymer materials (such as chemical-resistant, oil-absorbing, protective, and intelligent sensing materials). At the policy level, mechanisms such as "first-batch new material insurance compensation" and "emergency industry demonstration bases" have also provided strong support for the industrialization of high-performance polymer materials for emergency response and disposal.
High-performance polymer materials possess characteristics such as lightweight, high specific strength, high specific modulus, corrosion resistance, high insulation, good biocompatibility, and ease of modification, thus they have long been widely used in the field of emergency management and disposal. Typical applications of polymer materials in the emergency field include:
(1) High-performance lightweight structural materials. Examples include ultra-high molecular weight polyethylene (UHMW-PE) paving mats, polymer composite protective mats, and carbon fiber composite medical kits.
(2) Smart response and protective materials. Examples include thermoplastic polyurethane (TPU) composite leather (protective clothing, airbags, tents, etc.), polymer hydrogels, aramid/nanocomposite coatings (firefighting suits, etc.), and multifunctional polymer protective films (windproof, rainproof, light-blocking, heat insulation, etc.).
(3) Leak control and pollution treatment materials. Examples include polypropylene (PP) oil-absorbing cotton/absorbent felt, polyurea (PUA) grouting materials, and polymer gel sealants.
(4) Other new emergency materials. Examples include self-healing materials, conductive polymer sensor materials, smart firefighting suits, nanofiber filter materials, biodegradable polymer materials, and biocompatible medical materials.
Despite their excellent properties and numerous applications, most polymers share an undeniable drawback: they are highly flammable. To overcome this deficiency, researchers have focused on developing polymers with inherent flame-retardant properties. Polymers are generally classified into four categories based on their heat resistance (glass transition temperature, Tg): general-purpose polymers (Tg ≤ 100 ℃), engineering polymers (100-250 ℃), etc. Currently, the most widely used polymer emergency materials are mainly general-purpose and engineering polymers. However, with the continuous evolution of emergency scenarios, the demand for specialized and super-engineering polymer emergency materials is increasing. For certain special emergency scenarios, such as extreme environments like high temperatures, extreme cold, and strong radiation, conventional polymer emergency materials can no longer meet application requirements; therefore, the development of specialized polymer emergency materials is urgently needed. These polymers possess higher operating temperatures and excellent environmental stress resistance, can withstand high temperatures, and release very few flammable volatiles. The excellent overall performance of these polymer materials makes them commonly used in industries that require handling extreme conditions, such as aerospace and microelectronics, or for making fire-resistant work clothes.
Polyimide (PI) is a typical super engineering polymer material, characterized by excellent high and low temperature resistance, chemical corrosion resistance, radiation resistance, flame retardancy and smoke suppression, ease of sterilization, low biotoxicity, good mechanical and dielectric properties, diverse application forms, and flexible molecular structure designability. These excellent properties are precisely the basic performance requirements for materials in disaster prevention and emergency response, making PI materials promising for application in emergency management and response.
Although research progress on PI materials has been widely reported in the literature, systematic reports on research progress regarding PI materials as emergency management and response supplies are lacking. This article reviews the direct and indirect applications of PI materials in the emergency field from the perspective of the relationship between PI's structure and properties.
I.Properties of Polyimide and Its Impact on Emergency Response Applications
As an important type of organic polymer material, PI material is highly suitable for emergency response due to its excellent comprehensive properties, mainly reflected in the following six aspects:
(1) Temperature resistance and flame retardancy. PI material has characteristics such as high temperature resistance (thermal decomposition temperature ≥500 ℃), low temperature resistance (down to liquid helium temperature, -269 ℃), and low thermal conductivity, making it one of the polymer materials with the best temperature resistance. In addition, standard PI materials have excellent flame retardancy properties. For example, the limiting oxygen index (LOI) of Kapton® type pyromellitic PI film produced by DuPont is 37%, and the vertical burning rating is UL 94 VTM-0; the LOI value of Upilex®-S type biphenyl PI film produced by Ube Industries, Ltd. is 66%, and it also has a VTM-0 flame retardancy rating. The excellent temperature resistance and flame retardant properties of PI make it suitable as a raw material for emergency response materials such as fire suits, fire extinguishing blankets, fire blankets, and cold-weather clothing.
(2) Mechanical Properties. Strong intramolecular and intermolecular interactions endow standard PI materials with excellent mechanical properties. For example, the tensile strength of industrially produced biaxially oriented PI films is generally ≥200 MPa, with some varieties reaching over 400 MPa; elongation at break ≥50%; and tensile modulus ≥3.0 GPa. Simultaneously, PI films have a low density (~1.42 g/cm³), excellent bending resistance, and can withstand tens of thousands of folds without damage. This makes PI materials very convenient to transport and gives them promising application prospects in emergency fields such as tents, isolation belts, and protective films. Furthermore, PI-based composite materials also possess high specific strength and high specific modulus, thus showing broad application prospects in components such as disaster relief drones, helicopters, robots, and bulletproof helmets.
(3) Environmental Stability. Standard PI materials are typically insoluble and infusible, exhibiting excellent resistance to common organic solvents, mineral oils, and aviation kerosene. However, PI materials have slightly high hygroscopicity and poor resistance to high-temperature alkaline solutions. PI films demonstrate good resistance to radiation from X-rays, neutrons, charged particles, and vacuum ultraviolet light, but are susceptible to corrosion from low Earth orbit atomic oxygen. These characteristics make PI materials promising for applications in hazardous chemical emergencies and nuclear contamination emergency response.
(4) Insulation and Dielectric Properties. Standard PI materials possess excellent insulation strength (≥300 V/μm), high volume resistivity (≥10¹⁷ Ω・cm), relatively low dielectric constant (3.4~3.5 @1kHz), and dielectric loss (≤0.002 @1kHz). This makes PI materials suitable for use as high-performance insulating materials in emergency applications such as leakage current handling and insulation protection.
(5) Optical Properties. Standard PI film molecular chains exhibit strong conjugation, facilitating charge transfer within and between molecular chains, resulting in significant absorption of visible light. This gives standard PI films a typically golden-yellow to dark brown appearance. This makes them suitable for use as UV protection and light-shielding materials in certain emergency applications.
(6) Biological Properties. Conventional PI materials generally exhibit low toxicity and good biocompatibility, making them suitable for use as medical materials in emergency situations. Furthermore, the structure of PI materials is highly modifiable, allowing for flexible design to meet diverse application requirements and thus broadening its application scope. PI materials can be used as films, coatings, varnishes, adhesives, tapes, fibers, composites, and foams. Finally, PI materials are readily combined with various inorganic fillers to create a wide range of composite materials, meeting the application needs of different emergency response fields.
II.Advances in the Application of Polyimide Materials in Emergency Management and Response
2.1 Direct Emergency Materials
The main applications of polyimide (PI) in direct emergency materials include personal protective equipment (PPE) and fire-resistant and refractory materials, heat-resistant and cold-resistant materials, cut-resistant materials, radiation-resistant materials, and air filtration materials for emergency engineering.
2.2 Indirect Emergency Materials
The main applications of polyimide (PI) in indirect emergency materials include composite materials for rescue equipment and tools, life support and emergency supplies, thermal insulation and filling materials, battery materials, sensor materials, and medical treatment materials.
2.2.1 Lightweight Composite Materials
2.2.2 Battery Materials
2.2.3 Lightweight Thermal Insulation and Filling Materials
2.2.4 Specialty Fabrics
Besides the typical applications mentioned above, PI materials have also gained attention and application in fields such as explosion-proof motor insulation, medical emergency materials, air rescue, high-latitude emergency response, and underwater rescue.
"To do a good job, one must first have the right tools." Emergency management, as an independent discipline, cannot function without the support of advanced materials. Especially given the "protection-monitoring-energy-medical-infrastructure-intelligence" application matrix in modern emergency management, advanced emergency materials have become crucial support and guarantees for "all-hazard, full-chain" emergency response. As a class of advanced polymer materials with excellent comprehensive performance, the future development of PI in the emergency field shows trends such as continuous performance improvement, multi-functional intelligent integration, green and sustainable development, manufacturing process innovation, comprehensive expansion of application scenarios, and the gradual formation of an industrial ecosystem. In short, PI emergency materials are evolving from single high-performance materials to "intelligent material systems," and will fundamentally change the design concepts and application models of emergency rescue equipment in the future. Its development will follow the path of "high performance → multi-functionality → intelligence → greening → low cost and large scale", ultimately achieving the ultimate goal of "one piece of equipment to deal with multiple disaster scenarios" and providing technical support for emergency rescue.
