Development And Design Mechanism Of Temperature-Response Dynamic Thermal Protective Fabric System

High temperature staff such as fire-fighters often suffer various thermal hazards,e.g.,flash fire,radiation,convection and hot surface contact.Thermal protection provided by thermal protective clothing should meet special requirement,and thus ensure wearers'health and safety.The thermal protection and comfort properties of thermal protective clothing directly affect rescue time and efficiency.Therefore,the clothing system should not only provide basic functions but also balance thermal protection,comfort,ergonomic requirements and heat stress related issues.Owe to shape memory effect,shape memory material(SMM)can realize dynamic thermal insulation regulation of a fabric system.The placement of SMM in protective clothing will be activated when the temperature is higher than the deformation temperature of SMM.This will produce steady air layer in clothing,reducing heat transfer and increasing thermal protection.Under normal conditions,the SMM assembly is nearly flat to ensure minimum of fabric thickness,which can enlarge heat dissipation to ensure minimum thermo-physiological burden.In this study,SMM was incorporated into a typical three-layer fabric system i.e.,fireproof outer layer,moisture barrier and thermal liner,to produce a dynamic structure,The influencing factors in terms of thermal hazards,shape memory alloy(SMA)springs height,arrangement of SMA springs,placement position of SMA springs and perspiration were thoroughly investigated.The results indicated that the SMM assembly could effectively improve the protective performance of fabric combinations.Thermal hazards had an impact on thermal insulation properties of fabric system in terms of the temperature,maximum temperature difference(?Tmax)and time to reach a sensor temperature rise of 24?(ht24).Different arrangements of SMA springs exhibited significant differences,and mode one and mode 3 A showed the superior thermal protection.Additionally,the height of SMA springs affected the air gap thickness,thus determined the heat insulating property.Furthermore,the placement position of SMA springs affected thermal insulation properties of fabrics as well.The index of ht 12 and ht24 did not show significant differences in under hot surface contact whereas they showed significant differences under radiant heat exposure.Finally,the moisture has a significant impact on thermal protection,and the moisture content,i.e.,25%,50%and 100%,had a positive effect on the thermal insulation of the fabric,but had a negative effect at the cooling stage,however,the moisture would weaken the positive effect of springs height on the ht24 of fabric system.The research findings may be applied for guiding the development of intelligent thermal protective clothing with dynamic structure,balancing thermal protection and comfort.The novel thermal protective clothing will reduce clothing weight and thickness and improve thermal comfort,and thus,the physiological burden of the rescue workers will be relieved,and rescue time and efficiency will be improved.