Thermal Protective Performance Of Fabrics Research Articles

Application of Coating Mixture Based on Silica Aerogel to Improve Thermal Protective Performance of Fabrics

Abstract The main aim of this research is to improve the protective thermal performance of fabrics. Flame-resistant fabrics characterizing comparable thermal properties were chosen, cotton fabric with a flame-retardant finish and Nomex® fabric. To improve thermal parameters the coating mixture, based on silica aerogel, was applied on one side of the sample surface. Parameters such as the thermal conductivity, resistance to contact, and radiant heat were determined based on the standards, which set high expectations for the protective clothing. Analysis of the coated fabrics surfaces was conducted based on confocal microscopy. It was found that the coating mixture caused a decrease in thermal conductivity. All the modified fabrics reached 1st efficiency level of protection against contact and radiant heat. The best sample from the point of view of protection against contact and radiant heat was modified cotton fabric with a flame-retardant finish. The coating mixture contained 45 wt% of silica aerogel. Moreover, better adhesion of the coating mixture to the cotton fabric compared with Nomex® fabric was observed.

The Effects of Multiple Flame Exposures on Thermal Shrinkage and Thermal Protective Performance of Fabrics used in Firefighter Clothing

In firefighting situations, firefighters will encounter multiple flame exposures during go through the fireground several times. In this study, the effects of multiple flame exposures on thermal shrinkage and thermal protective performance of three fabrics used in firefighting clothing were investigated. The fabric surface morphology after flame exposure was obtained by a handy scanner, and further processed in ArcGis software. The thermal shrinkage of fabrics was characterized by ten shrinkage parameters and then quantified by using principal component analysis. The results showed that flame exposure frequency had influence on the thermal shrinkage of fabrics. As compared to several short-duration exposures, a long-duration continuous exposure resulted greater thermal shrinkage. The correlation analysis showed that there was no significant correlation between thermal shrinkage of the fabric and its thermal protective performance. The findings in this study indicated that the effects of multiple flame exposures on thermal shrinkage and thermal protective performance of firefighters clothing should be considered during clothing design and performance prediction.

Investigating the Thermal-Protective Performance of Fire-Retardant Fabrics Considering Garment Aperture Structures Exposed to Flames.

The application of fire-retardant fabrics is essential for providing thermal protective function of the garments. Appropriate clothing design are beneficial for preventing the wearers from skin burn injuries and heat strains simultaneously. The intention of this work was to investigate the effects of clothing ventilation designs on its thermal protective performance by bench-scale tests. Four boundary conditions were designed to simulate the garment aperture structures on fabric level. Tests of thermal shrinkage, mass loss and time-to-second-degree-burns were performed with and without air gap under three heat-flux levels for two kinds of inherently fire-retardant fabrics. The impacts of fabric type, heat-flux level, air gap and boundary condition were analyzed. The presence of a 6.4-mm air gap could improve thermal protective performance of the fabrics, however, the garment openings would decrease this positive effects. More severe thermal aging found for spaced test configuration indicated the importance of balancing the service life and thermal protective performance of the clothing. The findings of this study implied that the characteristics of fabric type, air gap, boundary condition, and their effects on fabric thermal aging should be considered during clothing ventilation designs, to balance the thermal protection and comfort of the protective gear.

Investigation of the Thermal Protective Performance of Shape Memory Fabric System: Effect of Moisture and Position of Shape Memory Alloy

A prototype of temperature-responsive protective fabric assembly with shape memory alloy (SMA) spring was developed. The effect of moisture on the thermal protective performance of fabric was investigated under radiant heat exposure and hot surface contact. The thermal liner of fabric system was pretreated with moisture amount of 25%, 50%, and 100%. Meanwhile, the thermal protection of fabric assembly with SMA springs in different positions between the fabric layers was explored. The results showed that moisture above 25% had a positive influence on thermal protective performance of both traditional and SMA fabric assembly under two hazardous environments. The effect of moisture in SMA fabric assembly was more remarkable than that in fabric without spring. And the SMA spring located between thermal liner and moisture barrier provided better thermal protective performance. The research findings will be beneficial for manufacturing high-performance temperature-responsive fabric.

Characterization and modelling of thermal protective performance of fabrics under different levels of radiant-heat exposures

The investigation of thermal protective performance of fabrics is highly relevant in order to procure and further develop the firefighters' protective clothing. Therefore, this paper aims at investigating the thermal protective performance of fabrics used in firefighters' clothing under different levels of radiant-heat exposures. For this, properties of a set of thermal protective single- and multi-layered fabrics were measured, and these fabrics were tested under radiant-heat exposures using the Method B of ISO 6942:2002 standard. During the testing, fabrics were exposed to low (10 kW/m2), medium (40 kW/m2), and high (80 kW/m2) intensity radiant-heat exposures; and the heat transfer level (i.e., time required to increase the skin temperature of a wearer/firefighter by certain degrees) through these fabrics were calculated to measure their thermal protective performance. The effects of fabric parameters, structures, properties, and radiant-heat intensities on the protective performance were characterized, and fabric properties that significantly affected the protective performance were statistically identified at different level of radiant-heat exposures. It has been found that weight, thickness, thermal resistance, and evaporative resistance can positively affect the protective performance. Also, the significant fabric properties affecting the protective performance vary for single- and multi-layered fabrics. By using these significant properties, the protective performance of single- and multi-layered fabrics were also separately predicted by mathematical models, i.e., multiple linear regression models and multiple logarithmic regression models. As per the findings of this study, multiple linear regression models can effectively be used to predict the thermal protective performance of fabrics. This study will lead towards building a better understanding and prediction of thermal protective performance of fabrics under radiant-heat exposures.

Studies of the thermal protective performance of fabrics under fire exposure: from small-scale to hexagon tests

This study aims to investigate the thermal protective performance of fabrics used in firefighters' clothing under high-intensity fire exposure. The performance of thermal protective fabric systems with different physical properties was evaluated under laboratory simulated fire exposure. Additionally, the influence of the configuration of the fire exposure tests and modes of heat transfer through the fabrics was also thoroughly investigated. The protective performance was evaluated using the standard small-scale flame [International Organization for Standardization (ISO) 9151:1995] and radiant heat (ISO 6942:2002) exposure tests. Additionally, the protective performance was evaluated under flash-fire exposure using a newly developed hexagon test. The protective performance values obtained from the small-scale (flame and radiant heat) and hexagon (flash fire) tests were compared and discussed. It has been found that a multi-layered fabric with high weight, thickness, and thermal resistance can significantly and positively affect the protective performance. If the air permeability of this fabric is high, it can show a lower protective performance; however, the impact of air permeability on the protective performance is insignificant especially in the case of the hexagon test. Notably, the protective performance can differ under two types of small-scale tests − flame and radiant heat. Also, this protective performance value is generally higher in the case of hexagon test in comparison with the small-scale tests. These differences in protective performance are mainly due to the unique configurations of these tests and/or different modes of heat transfer through the tested fabrics. The findings from this study will guide textile or materials engineers in the design and selection of materials for high performance thermal protective clothing; in turn, it will improve the occupational health and safety for firefighters.

Test method for characterising the thermal protective performance of fabrics exposed to flammable liquid fires

SummaryPeople, such as emergency service and military personnel, require protection from fires involving flammable liquids and liquefiable solids (Class B fires) in a number of situations. Fires involving flammable liquids typically reach higher temperatures sooner when compared to other types of fuel, yet there appears to be little literature that specifically investigates the protective performance of fabrics against such fires. Therefore, a new method was developed to enable the characterisation of the protective performance of fabrics when exposed to flammable liquid fires. Fabric samples were mounted on a sample plate inclined to three different angles of incidence. Known volumes of hydrocarbon fuel were pipetted into a fuel reservoir, ignited, then tipped onto fabric samples. Ten thermocouples embedded in the sample plate measured the resultant change in temperature at the technical rear of the fabric samples throughout the exposure. Significant differences were observed between fabrics for maximum temperature, time to maximum temperature, maximum heat flux, transferred energy and estimated burn risk. Therefore, this new methodology enabled discrimination among fabrics based on the protection they provide. Differences were also observed when the volume of fuel and the angle of incidence varied and, therefore, these device settings must be controlled for repeatable results. Copyright © 2016 John Wiley & Sons, Ltd.

Effect of structural parameters on thermal protective performance and comfort characteristic of fabrics

In an attempt to understand the influence of basic structural parameters of fabrics on thermal protection and comfort, present study mainly focuses on analyzing effect of fabric weaving pattern and fabric weight. Fabric samples of three basic weaving patterns (plain, twill, and satin) and three different weights were prepared. Air permeability of the developed fabric samples was measured. Thermal protective performance of fabrics against radiant heat and flame exposures of two different intensities were measured. Spectral transmission behavior of fabrics was also studied. It was observed that for same fabric weight, protective performance and air permeability of satin woven fabrics were better as compared to the fabrics of other patterns. Protective performance increased and air permeability decreased as fabric weight increased for each type of woven structure included in this study. A new structural parameter is proposed which primarily influences the protective performance of fabrics exposed to either radiant heat, flame, or combined convective/radiant heat exposure.

Development of a test device to characterize thermal protective performance of fabrics against hot steam and thermal radiation

Steam burns severely threaten the life of firefighters in the course of their fire-ground activities. The aim of this paper was to characterize thermal protective performance of flame-retardant fabrics exposed to hot steam and low-level thermal radiation. An improved testing apparatus based on ASTM F2731-11 was developed in order to simulate the routine fire-ground conditions by controlling steam pressure, flow rate and temperature of steam box. The thermal protective performance of single-layer and multi-layer fabric system with/without an air gap was studied based on the calibrated tester. It was indicated that the new testing apparatus effectively evaluated thermal properties of fabric in hot steam and thermal radiation. Hot steam significantly exacerbated the skin burn injuries while the condensed water on the skin’s surface contributed to cool down the skin tissues during the cooling. Also, the absorbed thermal energy during the exposure and the cooling was mainly determined by the fabric’s configuration, the air gap size, the exposure time and the existence of hot steam. The research provides a effective method to characterize the thermal protection of fabric in complex conditions, which will help in optimization of thermal protection performance of clothing and reduction of steam burn.

Characterizing thermal protective fabrics of firefighters’ clothing in hot surface contact

This study characterizes the thermal protective fabrics of firefighters’ clothing under the exposure of hot surface contact. For this, thermal protective performance of different fabrics was evaluated using a laboratory-simulated hot surface contact test, and various factors affecting the performance were statistically identified. Additionally, heat transfer mechanisms during testing were analytically and mathematically modeled. It has been found that fabric’s constructional features and properties are the key factors to affect its thermal protective performance. In this study, the presence of a thicker thermal liner in a layered fabric system resulted in higher performance; in contrast, a multi-layered fabric system incorporating a moisture barrier in its outer layer displayed the lowest performance. Furthermore, it was demonstrated that a fabric’s air permeability has a minimal impact on performance, whereas weight, thickness, and thermal resistance have a significant positive impact on performance. Based on the analytical and mathematical models developed, it was apparent that conductive heat transfer mainly occurs through fabric during testing, and this conductive heat transfer depends upon the surface roughness and thermal properties (thermal conductivity, density, and specific heat) of the tested fabric. Here, thermal contact resistance between the hot surface and fabric also plays a crucial role in the heat transfer or thermal protective performance of fabric. Moreover, the heat transfer gradually decreases across fabric thickness, which can substantially affect thermal protective performance. This study can advance the theory of textile/materials science through better understanding of heat transfer in fabrics. This understanding can help in developing an integrated knowledge of fabric properties, heat transfer through fabrics, and thermal protective performance of fabrics. The findings from this study can also assist textile/material engineers with the development of a high performance thermal protective fabric for clothing to provide better occupational safety and health for firefighters.

Thermal protection retention of fire protective clothing after repeated flash fire exposure

Fire protective clothing worn by the emergency responders may be exposed to intensive heat condition time and time again during a firefighting work. In this research, the level of thermal protection retained by the fire protective clothing after repeated exposures to flash fire was investigated from bench-scale test to full-scale test. A thermal protective performance tester and an instrumented manikin with a transverse motion system device which was capable of simulating the action of running across the flame were used for the exposure test. Physical properties (mass, thickness, thermal shrinkage, tear strength) and thermal protective property of the test specimens were examined after each exposure. The results showed that repeated heat exposures resulted in continuous decrease of mechanical performance of the fabrics. The thermal protective performance of fabrics with good thermal dimensional stability such as polybenzimidazole/Kevlar and flame resistant cotton decreased after exposure. For the fabrics with severe thermal shrinkage such as Nomex IIIA and polysulfonamide, the thermal protective performance was improved due to the increase of fabric thickness induced by thermal shrinkage. However, this positive effect of thermal shrinkage diminished in the manikin test as it decreased the air gap size between the garment and flame manikin. The thermal protective property of Nomex IIIA garment exhibited continuous decrease after repeated exposures. This study was expected to provide new sights for the performance evaluation and application of fire protective clothing.

Determination of the thermal protective performance of clothing during bench-scale fire test and flame engulfment test: Evidence from a new index

The protective performance of heat- and flame-resistant materials can be studied using a bench-scale test or a full-scale instrumented manikin test. However, there are some limitations of these evaluation methods. The existing bench-scale test could not be applied entirely to assess the thermal protective performance of fabrics if the exposure duration is fixed, while the existing manikin test only provides limited information about the local difference in thermal insulation. This study developed a new index of maximum attenuation factor to second-degree burn injury (maximum attenuation factor) as an improved quantitative method of the thermal protective performance, and then investigated the use of maximum attenuation factor during the bench-scale test as well as the manikin test. It demonstrated that the calculations of maximum attenuation factor were highly repeatable. In both the bench-scale and the manikin test, strong correlations were found between the results derived from the proposed method and the measurements from the existing test method. The results between the bench-scale test and the manikin test can also be compared as a united index.

A novel protocol to characterize the thermal protective performance of fabrics in hot-water exposure

This study aims to introduce a novel protocol to characterize the thermal protective performance of fabrics used in firefighters’ clothing under hot-water exposure. For this, new and improved test methods were developed to evaluate the performance of a set of fabrics under exposure to hot-water splash and hot-water immersion with compression. The thermal energy transmission through the fabrics tested was thoroughly investigated, and the physical properties that affect the performance of fabrics were statistically identified. It has been found that mainly mass (hot-water) transfer occurs through fabrics in a hot-water splash; whereas, both conductive heat and mass transfer predominate in a hot-water immersion with compression. The compression applied in the exposure of hot-water immersion changes the physical properties of fabrics, thereby reducing fabrics’ performance. The structural configuration and physical properties (e.g., air permeability, thickness) of fabrics are crucial to their heat and mass transfer and therefore to overall fabric performance. This study’s findings may contribute to developing new fabric testing standards, as well as improved thermal protective clothing to provide better occupational safety and health for firefighters.

Investigation of automated geometry modeling process of woven fabrics based on the yarn structures

Fabric structure has a significant effect on the thermal protective performance of fabrics. Before studying the thermal performance of textiles by numerical methods, it is essential to create geometric models of textile structures. Common fabrics, such as plain weave, 2/1 twill, 3/3 twill, 5/3 satin, and double layer fabric, were modeled using TexGen software. To obtain the input data for geometry simulation of fabrics, geometric measurements were studied. Methods of modeling fabric geometries according to their yarn path function and cross-sectional shapes were introduced. The appearances of the geometric models were very close to the structures of the real fabrics when compared to their light microscopic images. The fabric models were well used to simulate the heat transfer properties of glass fiber fabrics.

Effect of an air gap on the heat transfer of protective materials upon hot liquid splashes

The thermal protective performance of fabrics against hot liquid splashes was investigated under different configurations. The air gap of 6 mm between specimen and sensor was simulated and compared with direct contact configuration. Three liquids (distilled water, canola oil, drilling mud) at 85℃ were applied as challenge hot liquid hazards. The results showed that fabric permeability significantly affected heat transfer due to the occurrence of mass transfer both with and without a spacer. The absorbed energy and second-degree burn time presented significantly negative correlation. The effect of air gap on thermal performance was investigated. The findings demonstrated that minimizing mass transfer could effectively improve thermal protection against hot liquid splashes and the existing of an air layer could improve thermal performance.

A new protocol to characterize thermal protective performance of fabrics against hot liquid splash

A hot liquid splash tester and a protocol were developed to investigate the thermal protective performance and impact penetration performance of fabrics used in protective clothing. The instrument developed could be used to characterize penetration resistance and thermal protection against hot liquid splash. Different liquids were employed to explore the effect of liquid properties on penetration performance and thermal protection. The correlation between penetration and thermal protection was discussed. The results showed that liquid viscosity and fabric surface property determined the impact penetration. Impermeable fabrics showed better protection than permeable fabrics. Increasing penetration resistance improved thermal protection of a permeable fabric. Liquid thermal diffusivity, mass transfer rate and total amount affected heat transfer through the fabric to skin simulant. The findings will provide technical data to improve protective material performance and modify test standard.

Effect of relative humidity coupled with air gap on heat transfer of flame-resistant fabrics exposed to flash fires

Relative humidity (RH) and air gap size are two characteristic indices of clothing microclimate. The current thermal protective performance (TPP) tests cannot evaluate protective performance of fabrics under a microclimate with high temperature and humidity. In this study, a newly modified TPP test apparatus was applied to investigate the effect of RH in a microclimate on heat transfer of fabrics exposed to flash fires. Air gap heights from 0 to 24 mm with increments of 3 mm were employed. Three microclimates with different RH were preconditioned respectively. The results indicate that the RH in a microclimate significantly improves thermal protection of fabric with various air gaps. Under 35% RH, the TPP obviously increases with the air gap up to 15 mm and then the increment becomes a little lower; under humidified conditions (65% or 95% RH), it becomes higher substantially with air gap height increasing until 12 mm, subsequently it decreases or increases alternatively if the size keeps increasing. The positive effect of air gap with small size on TPP of fabrics is enhanced due to the increase of the vapor in the air; however, the positive effect of air gap with large size is interfered by the RH. It is indicated that around 12–15 mm was a critical air gap size under 35% RH, while about 12 mm was a key air gap size for a damp microclimate with 65% or 95% RH.

Radiant Protective and Transport Properties of Fabrics Used by Wildland Firefighters

The radiant protective performance, thermal resistance, air permeability, and moisture evaporation of a series of fabrics made from aramid, modacrylic, polyimide, and fire resistant cotton fibers are evaluated in the laboratory. The radiant protective performance of single-layer fabrics is affected by the structure, weight, thickness, and materials, consistent with the thermal protective performance of fabrics previously discussed. A fabric's transport properties, which are closely associated with comfort performance, can be reflected by a combination of its air permeability, thermal resistance, and moisture evaporation, which are also governed by the same structural factors. Thus, it is our intention to explore the relationship between fabric structures and both radiant protective and transport properties so that we can provide the necessary information for selecting appropriate fabrics for firefighter's uniforms.