Estimation of the radiant performance of flame-retardant fabrics considering thermal degradation effect

Qianqian Feng,Fl Zhu,Jianfeng Hu

doi:10.1177/1558925019843615

Abstract

Specially designed thermal protective clothing is used by firefighters and furnace operators for safety against intense heat flux exposures. Radiative transfer becomes the main heat transfer mode under such high temperature conditions. This work dealt with the effects of thermal degradation on the radiant protective performance and radiative properties of Polysulfonamide and Nomex IIIA fabrics at virgin state and pyrolyzed state, respectively. Simultaneously, the thermal stability and flame retardancy of both fabrics were compared by using thermogravimetry, vertical burning test, and limit oxygen index methods. The obtained results of thermal degradation effect on radiative properties demonstrated that both of the reflectance and transmittance of the two kinds of fabrics at virgin condition are higher than those at pyrolyzed state. On the other hand, the radiant protective performance values of both fabrics at charred condition were lower as compared to those at virgin state. This study will be helpful to estimate the continuing performance of firefighters’ protective fabrics after thermal exposures during firefighting operations.

Highlights

The frequent occurrence of accidents such as fire risk increases the workload and the risk of firefighters, and protective clothing is designed to safeguard them from these fire hazards.[1,2] In a typical fire or radiant heat exposure, temperature of the outermost layer of the firefighters’ protective clothing consisting of outer shell, moisture barrier, and thermal liner may reach up to the order of 1000 K under high-intensity heat flux conditions
The TG and differential thermogravimetric (DTG) curves of PSA and Nomex IIIA fabrics in a dry nitrogen atmosphere are shown in Figures 3 and 4
The mass loss became rapid between 450°C and 600°C (Figure 3), which was attributed to the degradation of a large number of molecular chains pyrolyzed into smaller molecules

Summary

Introduction

The frequent occurrence of accidents such as fire risk increases the workload and the risk of firefighters, and protective clothing is designed to safeguard them from these fire hazards.[1,2] In a typical fire or radiant heat exposure, temperature of the outermost layer of the firefighters’ protective clothing consisting of outer shell, moisture barrier, and thermal liner may reach up to the order of 1000 K under high-intensity heat flux conditions. The mean result for three test specimens was calculated as the “heat transfer index” (HTRI12 and HTRI24).[12] The time differences HTRI24HTR12 gave a good indicator of the skin pain alarm time These fabrics will pyrolyze and form char in the period of convective heat exposure. The RPP of the pyrolyzed fabrics was tested in a modified RPP tester, developed to measure the time elapsed for a controlled radiant heat source to penetrate through a protective composite fabric system resulting in damage to human skin. The sphere is dedicated to the infrared range with a coating of infragold with reflective power of 0.95 reflectivity

Results and discussion

25 Virgin PSA

Conclusion