| The environment of fire rescue scene is complex and changeable.As an important barrier to protect fire fighters from thermal disaster,the thermal protective performance of fire equipment is greatly affected by various factors.Considering the two different air layers at the open state of the neckline,cuff and other openings and the closed state far away from the opening of the fire suit,at the same time,human sweating and external fire water cause different degrees of wetting of the fire suit,and the moisture and the air layer under the clothing jointly affect the heat transfer mode of the fabric,so it is necessary to deeply explore the interaction between the air layer and the moisture layer on the thermal protection performance Ring.In addition,studies have shown that sweat can break the surface of fabric fibers and significantly affect fabric properties,so there are limitations to simulating human sweat with distilled or tap water.In this paper,based on the CSI-206 fabric thermal protection performance tester,two states of closed and open air layers of 3mm,6mm and 10 mm were added to simulate the air layers under different parts of the human body when wearing.The composite fabric was wetted from the inside and from the outside respectively with four degrees of wetness,so as to simulate the external moisture or people during the actual wearing of the fire suit Under the condition of body sweating and wetting,TPP values of each fabric under different wetting degrees and air layers were tested to explore the influence of moisture under open and closed air layers on the thermal protection performance of multilayer fabric used in fire protection.In addition,based on the different sweating conditions of human body,acidic sweat and alkaline sweat were prepared,and the sweat was used to wet the composite fabric from the inner layer at different times and at different time lengths.The TPP value of the composite fabric before and after the sweat treatment was tested,the changes in the appearance of the fabric were analyzed,and the change mechanism of the fabric performance was explored.The specific research conclusions include the following aspects:(1)Influence of moisture and air gap on thermal protection under outer wetting.The interaction of air gap and moisture has a significant impact on the thermal protection performance of fabric.When only the outer layer is wetted,the thermal protection of single-layer fabric and composite fabric increases with the increase of moisture content.The TPP value of aramid 1313 is the largest in dry condition,and with the increase of moisture degree,the TPP value of flame retardant cotton exceeds aramid 1313 at 100 % moisture degree due to its good moisture absorption.The TPP value of each fabric follows the order of open air layer > closed air layer > no air layer.The TPP values of most fabrics with air gap increase more with water content than without air layer.The addition of open and closed air layer increases the positive influence of water on the thermal protection of fabrics.(2)Influence of moisture and air layer on thermal protection under inner wettingWhen only the thermal insulation comfort layer is wetted,the TPP value decreases first and then increases with the increase of moisture content in the condition of no air layer and closed air gap,and reaches the minimum value at 15 % moisture level.With the increase of the air layer thickness,the TPP value is still less than the ten-state fabric.The air layer of 0-10 mm thickness does not offset the negative influence of moisture on the thermal protection of composite fabric,while the TPP value increases with the increase of water content and air layer thickness under open air layer.The moisture under closed air layer weakens the positive influence of increased air layer thickness on thermal protection performance,but the opposite is true under open air layer.The grey correlation analysis between air layer,moisture and TPP values shows that open/closed air layer has the greatest influence on the thermal protection of composite fabric,while the moisture content of heat insulation layer has the least influence on the thermal protection.(3)The influence of air layer on thermal protection of different fabric systems.For the two kinds of fabric systems with only waterproof layer and only heat insulation layer,the TPP value of the fabric increases after the outer layer is wetted,and the increase range of the fabric with heat insulation layer is smaller than that of the fabric with waterproof and breathable layer.When the fabric is wetted from the inner layer,the TPP value of the fabric under the no air layer and the closed air layer decreases compared with the outer layer,but it is still dry when there is no air layer Under the closed air layer,the TPP value of the fabric is lower than that of the dry fabric.Under the open air layer,the TPP value of the fabric is increased,and greater than the TPP value of the lower fabric and the outer wetted fabric.(4)The influence of sweat wetting on the thermal protection performance of fabrics.After repeated wetting by sweat for different times and single wetting for different duration,After repeated wetting for many times,someone will measure precipitates on the surface or pores of the fabric,resulting in decreased air permeability and heat insulation of the fabric.After a single wetting for a certain period of time,the fiber surface will be etched,resulting in increased air permeability,and the TPP value under acidic sweat is smaller than that under alkaline sweat. |
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