Characterization of the Combustion Process of Flame Resistant Thermal Protective Textiles in the Presence of Oily Contaminants: Effects of Contamination and Decontamination

Abstract

This paper reports two experimental studies wherein the combustion process of flame resistant (FR) thermal protective textiles is characterized in terms of thermal decomposition and heat release parameters before and after contamination and in terms of heat release parameters after contamination and decontamination. Aramid and FR cotton/nylon decomposed at higher and aramid/FR viscose at lower temperature in the presence of oil. Oil interferes with thermally induced interactions between aramid and FR viscose, altering the thermal decomposition rates and formation of char, and thereby increasing the effectiveness of the flame retardant present in the viscose. It is apparent that oily contaminants present in FR fabrics affect the initiation of the thermal degradation and formation of char. All contaminated FR fabrics showed significantly higher peak heat release rate (PHRR), total heat release (THR) and effective heat of combustion (EHC) compared to uncontaminated ones. Oily specimens laundered with no detergent or prewash product had higher PHRR, THR and EHC compared to other treatments regardless of the fabric type or number of contamination/decontamination cycles. Heat release increased with increased number of contamination/decontamination cycles for most laundry treatments for all FR fabrics. FR cotton/nylon had the highest and aramid had the lowest PHRR and THR whether specimens were uncontaminated, contaminated or decontaminated. In this study heat release from FR fabrics increased with increased oily contamination.

Effects of oily contamination and decontamination on the flame resistance of thermal protective textiles

“…Less heat is required to vaporize the oil from the surface of the fibre than from within the fiber/oil mass. Calorimetry results showed a shorter time to ignition for Fabrics A and B than for Fabric C, again indicating that when oily contaminants were present on the surface of fibres, less time was needed to produce sufficient volatiles to make a gas mixture capable of ignition by a spark [5]. For cotton, much of the oil remains inside the fibre [16] requiring more energy to drive it from the fibre.…”

“…Each load comprised one experimental sample for FR testing, two experimental samples for LOI testing, one experimental sample for calorimetry experiments reported elsewhere [5], and a sufficient number of buffers to make the total mass of fabric in a load 784 g, equivalent to the average mass of one protective coverall. The total mass of oil in the experimental samples was approximately 34 g for each wash load.…”

“…In a two-fibre fabric, the two components are thought to react with each other thermally and chemically during burning [5,25]. In the case of Fabric C, the ability of nylon to shrink away from the flame during combustion may impart some natural FR, but this effect is assumed to be minimal here due to the small percentage of nylon present.…”

“…Of the three fabrics studied here, this unusual phenomenon seems to be peculiar to the aramid/FR viscose. Thermogravimetric studies of the combustion mechanisms for the fabrics with and without oily contaminants have shed more light on this phenomenon, indicating higher thermal decomposition temperature with contaminated aramid/FR viscose than with uncontaminated [5].…”

“…The current research was designed to study Crown et al's hypothesis further. Flammability or FR is addressed in this paper, whereas combustion characteristics are addressed in [5].…”