Study On The Thermal Protective Performance Of Retardant Double-laver Fabrics With Different Heat Shrinkage Rates

In actual firefighting and rescue work,firefighters are mostly in the thermal environment.The thermal shrinkage of flame retardant protective clothing fiber caused by the high temperature will change the internal air layer of clothing and directly affect the overall thermal protective performance,which will bring serious risks to the safety of firefighters and the smooth progress of their work.Therefore,it is of great significance to study the thermal shrinkage and the change of air layer in the flame retardant protective clothing fabric.This paper selects 7 kinds of retardant double-layer fabrics with different heat shrinkage rates(W1-W7)in the current market as research objects,which will produce thermal shrinkage and form a certain thickness of air layer in high temperatures.while exploring the relationship between the production of air layers and thermal shrinkage of double-layer fabrics,it studies the influence of low-radiation heat on the thermal protective performance of fabrics.Meanwhile,with 2 kinds of moisture barrier(Fl,F2),2 kinds of thermal barrier(G1,G2),2 kinds of comfort lining(S1,S2),and using orthogonal trial with mixed level designs three-layer and four-layer fabrics to study the thermal protective performance of multi-layer fabrics.The paper synthesizes multiple indicators to evaluate retardant double-layer fabrics in multi-attributes synthesis appraisal,and to evaluate multi-layer fabrics in comprehensive score method.The main conclusions are as follows:(1)Using 3D scanning and image processing techniques quantifies the average thickness of air layer generated inside the fabric and shrinkage of the projection area of the fabric,to study the relationship between them.The results show that when the fabrics are heat treated five minutes and taking temperature as a variable,in a certain temperature range,the fabric thermal shrinkage rates and the average thickness of air layer increases with temperature increases,and there is a positive correlation between them.But when the temperature continues to rise and the amount of air layer produced by the fabric is maximized,the air volume changes not obviously and the heat shrinkage continues to increase.When temperature is 260? with treated for five minutes,the thickness of the air layer is basically stable.Taking time as a variable,it shows that the average thickness of the air layer and thermal shrinkage changes not significantly with time,but both of them have an increasing trend.There is a negative correlation between them in this situation.(2)From the aspect of thermal protective performance,the thermal protection of double-layer fabrics have a positive correlation surface density,have no significant correlation with thickness and air permeability,have a negative correlation with heat shrinkage,and have a positive correlated with the average thickness of the air layer.So,the air layer produced by the fabric under heating increases the thermal protective performance.But when the air layer is produced to a certain limit and thermal shrinkage continues to increase that the positive effect of the air layer is less than the negative effect of heat shrinkage,the thermal protection will decrease.The regression relationship between TPP values and basic performance,air layer,and heat shrinkage is:Yi=-31.65+0.22X1(Y1 is TPP value,Xi is surface density),Y2=-13.587+0.124X21+1.649X22(Y2 is TPP value,X21 is surface density,X22 is the thickness of the air layer),Y3=12.896-86.538X31+2.218X32+0.006X33(Y3 is TPP value,X32 is the thickness of the air layer,X31 is thermal shrinkage rates and X33 is air permeability).Through the multi-attributes synthesis appraisal,that 7 kinds of fabrics synthesize ten indexes including thickness,surface density,air permeability,flame retardant,TPP value and the mass loss rate after testing,the discoloration degree under high temperature,thermal shrinkage rate and the average thickness of air layer are ranked as:W4>W7>W2>W5>W1>W3>W6.(3)Using the orthogonal trial with mixed level,it selects 4 kinds of better retardant double-layer fabrics for outer fabrics,to study the thermal protective performance of multi-layer fabric.The results show that the TPP value of the three-layer and four-layer fabric all reach the requirements of the industry standard.The three-layer fabrics of removing the thermal barrier achieve the purpose of weight reduction for firefighter uniform,while the three-layer fabrics of removing moisture barrier have the maximum air and moisture permeability,which can be used for the design and manufacture of thermal protective clothing in dry and high temperature workplaces.Four-layer fabrics in the primary and secondary relations of factors affecting the thermal protective performance is:comfort lining(S)>outer fabric(W)>moisture barrier(F)>thermal barrier(G),and one of the highest TPP value combinations is W2F1G2S2,in the combinations of removing the thermal barrier is W2F1S2,and in the combinations of removing moisture barrier is W7G2S2.While synthesizing ten indexes of TPP value,surface density,thickness,air and moisture permeability evaluate multi-layer fabrics,it shows that the best of four-layer fabric is W7F2G2S2,and the best of removing the thermal barrier is W2F2S2,the best of removing the moisture barrier is W7G2S2.