Preparation And Properties Of Wearable Heat-induced Fire Warning Bio-based Aerogel

Of all disasters,fire is one of the most common and widespread major threats to public safety and property security.As the front line in a fire,firefighters wear firefighting suits as the most important piece of equipment to protect them from burns.However,the overly heavy insulation of firefighting clothing makes it difficult for firefighters to keep track of temperature changes on the outside of their suits,and as a result,firefighters are extremely susceptible to high temperatures and burn damage when they are exposed to high fire temperatures（600-800℃）,thus threatening their lives.At the same time,due to the increasing environmental problems such as global warming,the use of natural renewable resources has become a current research hotspot and the direction of social development.Compared to common inorganic aerogels,organic aerogels based on polysaccharide biomass are not only lightweight,flexible,highly porous and have excellent thermal insulation properties,but also have good biocompatibility and sustainability.Therefore,fire warning materials based on biomass aerogels can not only achieve fire warning functions but also have the advantages of lightweight and thermal insulation,which have potential applications in the field of firefighting clothing.In this thesis,PEG@MW-A-CNT-CA（P@MW-A-CA）,a bio-based fire warning aerogel material for firefighting apparel,was prepared by a freeze-drying method using calcium alginate（CA）,balsa wood powder（MW）,polyethylene glycol（PEG）and aminated carbon nanotubes（A-CNT）as raw materials.Based on this,the main research elements of this thesis are as follows:（1）Biomass flame retardant and thermal insulation fire warning aerogel（P@MW-A-CA）was prepared by the freeze-drying method,using N-N-methylene bisacrylamide（MBA）as the chemical cross-linking agent and Ca²⁺provided by calcium chloride and sodium alginate exchange to achieve physical cross-linking to form an"egg-shell"structure,giving the aerogel a physical/chemical double cross-linked network.By controlling the freezing time,orientation,and temperature,the internal pore morphology of P@MW-A-CA was regulated,and the prepared aerogel showed an orderly and regular pore size structure on the microstructure,while the addition of balsa wood powder as a supporting component gave the aerogel P@MW-A-CA an orderly layered structure,forming a"reinforced concrete-like"microstructure.microstructure".The pore diameter of the aerogel P@MW-A-CA was distributed between 10 and 30 um,with a specific surface area of 1.822 m²/g and a pore volume of 0.011 cm³/g.Meanwhile,the prepared MW-A_1.0-CA demonstrated a low density of0.038 g/cm³ and a high porosity of 77.3%,which indicated that the fire warning aerogel has good lightness and wearability.wearability.（2）The role of the phase change material PEG in the prepared fire warning aerogel P@MW-A-CA system was further investigated.In this system,PEG is encapsulated in balsa wood powder mainly through the synergistic effects of hydrogen bonding interactions,capillary forces and surface tension,which can effectively prevent the potential leakage risk of the phase change thermal storage material during the phase transition process,and obtain a balsa wood powder-based shaped composite phase change thermal storage material with stable structure,low thermal conductivity,and high thermal cycling stability.The results show that the fire warning aerogel prepared in this work was heated to 90℃,but no leakage occurred.The peak melting temperature of PEG（T_m）was 64.7℃,while the maximum melting temperature of P@MW-A-CA was reduced to 63.6℃,lower than the peak of pure PEG.In addition,the prepared fire warning aerogel has an ultra-low density（0.0038 g/cm³）,thermal conductivity（0.06233±0.0012 W/m·K）,and excellent self-extinguishing properties（renewal ignition time<1.02 s and maximum heat release rate of 36.046 W/g）.（3）Thanks to the thermal resistance response of aminated carbon nanotubes（A-CNT）,the prepared fire warning aerogel P@MW-A-CA has a sensitive and reliable temperature response,triggering the fire warning system within～2.03 s under the flame.When the aerogel is exposed to high temperatures（>350℃）,its resistance rapidly and dramatically decreases from 2.25×10⁶Ωto a trend of 1.0×10⁵Ω.Meanwhile,the P@MW-A-CA exhibited good flexibility and was able to trigger the fire warning system within 2-3 s after 200 bending cycles（180°bending angle）.In addition,by using the excellent electrical conductivity of Ag NWs（silver nanowires）,the sandwich structure was constructed by spraying Ag NWs layers on the upper and lower surfaces of the aerogel,which can effectively realize the fire warning function in a large area and expand the application scope of the fire warning aerogel.The biomass fire warning aerogel with temperature response and temperature buffering function is expected to be applied to firefighting clothing to achieve real-time monitoring and warning function of the surface temperature of firefighting clothing to ensure the personal safety of firefighters during fire operations.