Pre-tension load of resistant knitted fabric influence on radiant heat transfer index

Various textile materials – woven fabrics and knitted fabrics – are used to produce special protective clothing and personal protective equipment against high temperatures. These materials differ in their raw material composition, surface density, structure, and finishing treatments. To ensure protection against high temperatures, the following quality and safety indicators are assessed: operational – tearing and tensile load, plane abrasion and the Martindale abrasion method, cut resistance, puncture resistance; technological – changes in linear dimensions after wet processing or dry cleaning, rigidity, seam breaking load; hygienic – air permeability, electrostatic field strength on the surface of the product, maximum permissible concentration of chemically hazardous substances; protective (special) – resistance to burning, open flame resistance (acting in specimen end, surface ignition and lower edge ignition), contact with surfaces heated to 250 °C, radiant heat transfer index (RHTI), convective heat transfer index. This article examines the effect of the pre-tension load value on the RHTI (Q0), transmitted heat flux density Qc and the size of the test specimen after exposure to a heat flux with a density of 20 kW/m2 for flame-resistant knitted fabrics, including three raw material compositions: modacrylic 65 % and wool 35 % with varying surface densities, and three knitted fabrics (~210.0 g/m2) with different raw material compositions. The purpose of this scientific research is to select and validate the optimal value of the pre-tension load for testing specialpurpose knitted fabrics under conditions of exposure to thermal radiation according to GOST ISO 6942-2011 at a standard incident flux density of 20 kW/m2. The article provides recommendations on the use of the optimal pre-tension load value to ensure reliable test results under GOST ISO 6942-2011.