Protective Clothing Systems Research Articles

Optimizing the Performance of Phase-Change Materials in Personal Protective Clothing Systems

Phase-change materials (PCM) can be used to reduce thermal stress and improve thermal comfort for workers wearing protective clothing. The aim of this study was to investigate the effect of PCM in protective clothing used in simulated work situations. We hypothesized that it would be possible to optimize cooling performance with a design that focuses on careful positioning of PCM, minimizing total insulation and facilitating moisture transport. Thermal stress and thermal comfort were estimated through measurement of body heat production, body temperatures, sweat production, relative humidity in clothing and subjective ratings of thermal comfort, thermal sensitivity and perception of wetness. Experiments were carried out using 2 types of PCM, the crystalline dehydrate of sodium sulphate and microcapsules in fabrics. The results of 1 field and 2 laboratory experimental series were conclusive in that reduced thermal stress and improved thermal comfort were related to the amount and distribution of PCM, reduced sweat production and adequate transport of moisture.

Ergonomic comparison of a chem/bio prototype firefighter ensemble and a standard ensemble

Firefighter turnout gear and equipment protect the wearer against external hazards but, unfortunately, restrict mobility. The aim of this study was to determine the ease of mobility and comfort while wearing a new prototype firefighter ensemble (PE) with additional chemical/biological hazard protection compared to a standard ensemble (SE) by measuring static and dynamic range of motion (ROM), job-related tasks, and comfort. Eight healthy adults (five males, three females), aged 20-40 years, participated in this study. The study consisted of two repeated phases, separated by five uses of the ensembles. Subjects randomly donned either the SE or PE in either dry or wet conditions on separate days. In each phase, five tests were carried out as follows: baseline (non-ensemble), SE-dry, SE-wet, PE-dry, and PE-wet. There was a significant reduction (P < 0.05) of wrist flexion for PE-dry condition compared to the same SE-dry condition. Donning the PE took 80 s longer than the SE in phase 1, this difference disappeared in phase 2. There was a significant decrease (P < 0.05) in post-test comfort wearing the PE compared to the SE. The data collected in this study suggest that, in spite of design features to enhance chemical/biological hazard protection, the PE design does not decrease the wearer's overall functional mobility compared to the SE. However, subjects seem to be more comfortable wearing the SE compared to the PE. These overall findings support the need for a comprehensive ergonomic evaluation of protective clothing systems to ascertain human factors issues.

Effect of Moisture Management on Functional Performance of Cold Protective Clothing

This paper reports a study on the effect of moisture management in the design of cold protective clothing. In this research, two kinds of clothing systems were tested, a traditional clothing system (clothing A), and a specially designed moisture management clothing system (clothing B). Both clothing systems have the same four-layer structure (underwear, vest, coat, and outer jacket), but with use of different functional fabrics. The experiments were conducted in a climate chamber where the temperature was controlled at —15 °C. Eleven young male subjects took part in wear trial experiments, in which they were dressed in clothing A or B and walked on a treadmill. The humidities and temperatures at the skin surface and at different layers of the clothing system were measured together with measurements of thermal and moisture sensations. The experimental results showed that the moisture management property of fabrics significantly affected the moisture diffusion and temperature distributions in the cold protective clothing systems, and influenced the thermal and moisture sensations.

Use of Electrospun Nanofiber Web for Protective Textile Materials as Barriers to Liquid Penetration

To examine the potential of electrospun nanofibrous webs as barriers to liquid penetration in protective clothing systems for agricultural workers, layered fabric systems with electrospun polyurethane fiber web layered on spunbonded nonwoven were developed. Barrier performance was evaluated for the layered fabric systems with different levels of electrospun web area density, using three pesticide mixtures that represent a range of surface tension and viscosity. Effects of electrospun web density on air permeability and water vapor transmission were assessed as indications of thermal comfort performance. Pore size distribution was measured to examine the effect of electrospun fiber web layers on pore size. Penetration testing showed that a very thin layer of electrospun polyurethane web significantly improved barrier performance for challenge liquids with a range of physicochemical properties. Air permeability decreased with increasing electrospun web area density, but was still higher than most of protective clothing materials currently available. No significant change was observed in moisture vapor transport of the system from electrospun nanofibrous web layers. Pore size distribution measurements indicated the feasibility of engineering pore size via the level of electrospun web area density, hence, controlling the level of protection and thermal comfort of layered fabric systems depending on their need.

Application of Nanofiber Technology to Nonwoven Thermal Insulation

Nanofiber technology (fiber diameter less than 1 micrometer) is under development for future Army lightweight protective clothing systems. Nanofiber applications for ballistic and chemical/biological protection are being actively investigated, but the thermal properties of nanofibers and their potential protection against cold environments are relatively unknown. Previous studies have shown that radiative heat transfer in fibrous battings is minimized at fiber diameters between 5 and 10 micrometers. However, the radiative heat transfer mechanism of extremely small diameter fibers of less than 1 micrometer diameter is not well known. Previous studies were limited to glass fibers, which have a unique set of thermal radiation properties governed by the thermal emissivity properties of glass. We are investigating the thermal transfer properties of high loft nanofiber battings composed of carbon fiber and various polymeric fibers such as polyacrylonitrile, nylon, and polyurethane. Thermal insulation battings incorporating nanofibers could decrease the weight and bulk of current thermal protective clothing, and increase mobility for soldiers in the battlefield.

The Effects of Silk Screened Emblems on Thermal Protective Performance of Wildland Fire Fighter Protective Clothing Systems under Two Moisture Conditions

The objective of this study is to determine the effects of silk screened emblems on thermal protective performance of wildland fire fighter protective clothing systems under two moisture conditions. Three outerwear conditions (current emblem, new emblem, blank) were combined with both underwear conditions (emblem, blank) to produce six clothing systems. The two moisture conditions were both layers conditioned (dry) and top layer conditioned/lower layer saturated with water (wet). Both radiant protective performance (RPP) testing and thermal mannequin testing were used to evaluate the clothing systems. The data showed a decline in thermal protective properties of the clothing systems under conditions of high heat flux and wet inner layer. While both jacket emblems performed better than the blank jacket, one emblem was more protective under radiant exposure conditions while the other was found to be superior in the thermal mannequin tests.

Development of electronic textiles to support networks, communications, and medical applications in future U.S. Military protective clothing systems

The focus of this paper is on the development of textile-based wearable electronics that can be integrated into military protective clothing. A materials and manufacturing survey was conducted to determine the best performing and most durable materials to withstand the rigors of textile manufacturing and potential military use. Narrow woven technology was selected as one of the most promising textile manufacturing methods. A working wearable narrow fabric version of the Universal Serial Bus (USB), as well as a radiating conductor, were successfully developed and fabricated. A circular knit T-shirt with an integrated spiral bus was also developed. Military products developed include components of a personal area network providing data and power transport, and a body-borne antenna integrated into a load-bearing vest.

Development of Electronic Textiles to Transport Data and Power in Future U.S. Military Protective Clothing Systems

Abstract The focus of this paper is on the development of textile-based wearable electronics that can be integrated into military protective clothing. A materials and manufacturing survey was conducted to determine the best performing and most durable materials to withstand the rigors of textile manufacturing and potential military use. Narrow woven technology was selected as the most appropriate manufacturing method. A working wearable narrow fabric version of the Universal Serial Bus (USB), as well as a radiating conductor, were successfully developed and fabricated. Military products developed include components of a personal area network providing data and power transport and a body borne antenna integrated into a load-bearing vest.

Heat and water vapour transfer of protective clothing systems in a cold environment, measured with a newly developed sweating thermal manikin.

A moveable sweating thermal manikin has recently been developed. Thermal and water-vapour resistances of three kinds of cold-protective clothing ensembles, laminated with polytetrafluoroethylene, polyurethane and without a laminate were measured, with the aid of the manikin in a cold environment of 5 degrees C with a relative humidity of 70% and an air velocity of around 1.5 m s(-1). Two sweating rates of 65 and 130 g m(-2) h(-1) were employed. Supplied heat fluxes in both of the sweat rates ranged from 350 W m(-2) to 400 W m(-2). To maintain a comfortable condition, the skin wettedness (w) (mean weighted value) had to be kept at < or = 0.6. The measurements obtained from the manikin when testing the three ensembles were w=0.3 (approximately) for the low sweat rate and w > or = 0.6 for the high sweat rate, irrespective of the property differences among the ensembles. In addition, the condensation in the ensembles in comparison with those calculated from an analytical equation is discussed. Condensation mass fluxes in the ensembles obtained by experiment and those from the calculation agreed sufficiently well. Thus, distribution of the condensation in the ensembles was estimated using the equation.

Investigation and correlation of manikin and bench‐scale fire testing of clothing systems

AbstractThe US Army currently has five flame/thermal protective clothing systems to provide protection for soldiers against fire hazards. The protective performance of these clothing systems against burn injuries was investigated in full‐scale manikin tests. The protective performance of fabric layers of these clothing systems was also examined in bench‐scale tests. In addition, air gap thicknesses and distributions of the five clothing systems were determined by using a three‐dimensional laser scanning technique. In this paper, test conditions of the manikin and bench‐scale tests are compared, and the test results are correlated in light of the air gap measurements. The behavior of individual sensors on the manikin with similar test conditions to those of bench‐scale tests are compared with the bench‐scale tests. It is found that if the air gap distribution of a clothing system is known, bench‐scale tests could provide useful information for full‐scale performance, especially bench‐scale tests with zero air gap measurements. Published in 2002 by John Wiley &amp; Sons, Ltd.

Investigation of air gaps entrapped in protective clothing systems

AbstractAir gaps entrapped in protective clothing are known as one of the major factors affecting heat transfer through multiple layers of flexible clothing fabrics. The identification and quantification of the air gaps are two aspects of a multidisciplinary research effort directed toward improving the flame/thermal protective performance of the clothing. Today's three‐dimensional (3‐D) whole body digitizers, which provide accurate representations of the surface of the human body, can be a novel means for visualizing and quantifying the air gaps between the wearer and his clothing. In this paper we discuss how images from a 3‐D whole body digitizer are used to determine local and global distributions of air gaps and the quantification of air gap sizes in single and multilayer clothing systems dressed on a thermal manikin. Examples are given that show concordance between air gap distributions and burn patterns obtained from full‐scale manikin fire tests. We finish with a discussion of the application of air gap information to bench‐scale testing to improve the protective performance of current flame/thermal protective clothing. Copyright © 2002 John Wiley &amp; Sons, Ltd.

Transport properties of porous membranes based on electrospun nanofibers

Electrospinning is a process by which high voltages are used to produce an interconnected membrane-like web of small fibers (10–500 nm in diameter). This novel fiber spinning technique provides the capacity to lace together a variety of types of polymers, fibers, and particles to produce ultrathin layers. Of particular interest are electrospun membranes composed of elastomeric fibers, which are under development for several protective clothing applications. The various factors influencing electrospun nonwoven fibrous membrane structure and transport properties are discussed. Performance measurements on experimental electrospun fiber mats compare favorably with transport properties of textiles and membranes currently used in protective clothing systems. Electrospun layers present minimal impedance to moisture vapor diffusion required for evaporative cooling. There may be special considerations in the application of elastomeric membranes for protective clothing. Effects of membrane distortion upon transport behavior of the structure might be significant. Preliminary measurements have found that changes in elastomeric membrane structure under different states of biaxial strain were reflected in measurements of air flow through the membrane. Changes in membrane structure are also evident in environmental scanning electron microscope (SEM) images of the pore/fiber rearrangement as the membrane is stretched. Experimental measurements and theoretical calculations show electrospun fiber mats to be extremely efficient at trapping airborne particles. The high filtration efficiency is a direct result of the submicron-size fibers generated by the electrospinning process. Electrospun nanofiber coatings were applied directly to an open cell polyurethane foam. The air flow resistance and aerosol filtration properties correlate with the electrospun coating add-on weight. Particle penetration through the foam layer, which is normally very high, was eliminated by extremely thin layers of electrospun nanofibers sprayed on to the surface of the foam. Electrospun fiber coatings produce an exceptionally lightweight multifunctional membrane for protective clothing applications, which exhibits high breathability, elasticity, and filtration efficiency.

A Laboratory Protocol to Assess the Electrostatic Propensity of Protective-clothing Systems

The ability to predict the electrostatic propensity of textile systems has been an elusive goal for many years. Some small-scale test methods previously reported were found to be inadequate for certain conditions. One of the most serious problems is poor correlation between test measurements and the values of electrostatic discharges from a clothed person in real-life situations. This paper describes the development of a laboratory protocol to evaluate the electrostatic properties of clothing systems Four small-scale tests were evaluated and compared in order to select a protocol that could best assess the static propensity of protective-garment systems worn by workers in hazardous environments under dry conditions. Several two-layer fabric systems that included non-FR (non-fire-retardant) cotton, as well as thermal-protective fabrics of aramid fibre/carbon, aramid fibre/PBI (polybenzimidazole) fibre, aramid fibre/FR viscose, and FR cotton, were tested. Experiments were conducted at room temperature and 0% and 20% relative humidity (r.h.). Fabrics were evaluated in terms of both peak discharge potentials and charge decay. These peak potentials and charge decays were compared with data from human-body experiments, and significant coefficients of determination (R 2) of up to 0.99 were found when results from different tests were regressed on human-body data. It therefore seems that measuring peak discharge potentials and charge decays from charged-fabric systems and peak discharge potentials from a capacitor by using a battery of test methods can be sufficient to assess, with high accuracy, the static behaviour of garment systems in real-life conditions.

Benefit of heat acclimation is limited by the evaporative potential when wearing chemical protective clothing

Heat acclimation-induced sweating responses have the potential of reducing heat strain for chemical protective garment wearers. However, this potential benefit is strongly affected by the properties of the garment. If the clothing ensemble permits sufficient evaporative heat dissipation, then heat acclimation becomes helpful in reducing heat strain. On the other hand, if the garment creates an impenetrable barrier to moisture, no benefit can be gained from heat acclimation as the additional sweating cannot be evaporated. Ten subjects were studied exercising on a treadmill while wearing two different chemical protective ensembles. Skin heat flux, skin temperature, core temperature, metabolic heat production and heart rate were measured. It was found that the benefit of heat acclimation is strongly dependent on the ability of the body to dissipate an adequate amount of heat evaporatively. The evaporative potential (EP), a measure of thermal insulation modified by moisture permeability, of the clothing ensemble offers a quantitative index useful to determine, a priori, whether heat acclimation would be helpful when wearing protective clothing system. The data show that when EP is <15%, heat acclimation affords no benefit. An evaporative potential graph is created to aid in this determination.

Increased skin blood flow and enhanced sensible heat loss in humans after nicotinic acid ingestion

1. 1. A series of studies was conducted to characterize thermal and cardiovascular responses to nicotinic acid (NA) ingestion (5 mg·kg −1) in healthy subjects: (a) at rest, seated ( T a = 30°C, RH = 23%) at 0800 h and again between 1800 and 2100 h; (b) at rest and during seated exercise ( T a = 29°C, RH = 30%); and (c) during upright exercise when wearing a protective clothing system ( T a = 28°C, RH = 30%). 2. 2. (a) NA ingestion decreased esophageal ( T es) and arterial pressure and increased mean skin temperature ( T sk ), skin blood flow (SkBF), forearm blood flow (FBF), heart rate, and cutaneous vascular conductance ( P < 0.05) in the morning and evening. In the evening 2 4 subjects experienced substantial hypotension. (b) At rest, peak SkBF and peak FBF were 600% higher in NA than control while T es was 0.6°C lower and T sk was 0.6°C higher after NA ( P < 0.05). During seated exercise, SkBF and FBF were 30% higher and T es was 0.3°C lower after NA than control ( P < 0.05). (c) During upright exercise, NA increased SkBF in subjects clothed in protective clothing. 3. 3. Vascular responsiveness to NA was enhanced in the evening as shown by the increased hypotensive effect of NA in the evening. NA ingestion effectively increased sensible heat flux during rest, seated exercise and upright exercise. However, manipulation of SkBF by NA ingestion should be done cautiously, especially when NA will be used in novel circumstances.

Protective clothing systems and materials

Protective Clothing: An Overview * Design of Protective Clothing * Chemical Protective Clothing * Attitudes and Clothing Practices of Pesticide Applicators * Refurbishing Pesticide-Contaminated Clothing * Heat Transfer Through Human Body and Clothing Systems * Protective Clothing: Use of Flame-Retardant Textile Finishes * Heat- and Fire-Resistant Fibers for Protective Clothing * Biological Protective Clothing * Protective Clothing Effective Against Biohazards * Biological Test Methods for Protective Clothing.

Military Protective Clothing: Implications for Clothing and Textiles Curriculum and Research

Increased likelihood of armed forces operations occurring in hostile climatic regions have increased the need for highly specialized protective clothing systems. Protection is needed under a variety of conditions which often present conflicting requirements. Protective military clothing provides broad design possibilities and stimulates research for new textile materials and equipment. Development of protective gear provides the possibility for interdisciplinary teaching and research. Disciplines such as textile engineering, electrical engineering, industrial engineering and design, clothing design, textile science, and physiology can all be combined to provide satisfactory solutions to design problems presented by protective clothing systems. Current requirements for protective military clothing, problems with gear, and critical factors which can be addressed by clothing and textiles research are included.

Protective clothing systems: A technique for evaluating restriction of wearer mobility

To allow designers to evaluate presently available protective clothing systems (as well as aiding the development of less restrictive systems), it is necessary to develop evaluation techniques to quantify the loss of mobility associated with wearing protective clothing. Using fire fighter turnout gear, this study illustrated the application of the Leighton Flexometer ® for the measurement of restriction to body movement caused by wearing protective clothing and equipment. Statistical analyses indicated significant differences in restriction to body movement between the designs of protective clothing and equipment configurations tested. Additionally, correlation coefficients between trials established values for tes-retest reliability.

Patterning of Objective and Subjective Responses to Heat Protective Clothing Systems Part 2 Subjective Measurements of Comfort

The criteria for selection and use of protective clothing, particularly with respect to protection from high radiant heat, are both objective and subjective. Part 2 of this study examines subjective responses to clothing. Five fabrics commonly used in protective workwear were made into overalls of identical design and evaluated by adult males in a simulated work environment. Subjective evaluations of humidity sensation in the leg microclimate at set times during the exercise/rest protocol did not differ significantly with respect to the five overalls and differed significantly among subjects only after the full exercise period had elapsed. High positive correlations were found between subjective humidity sensations and objective measurements. Subjective thermal sensations taken at three different body regions did not enable discrimination among overalls. Subjects tended to rank garments similarly. Subjective thermal sensations did not pattern objective thermal data; thus when measuring two parameters (humidity and thermal responses) subjectively and objectively, discrimination among overalls was not possible.

Patterning of Objective and Subjective Responses to Heat Protective Clothing Systems

The criteria for selection and use of protective clothing, particularly with respect to protection from high radiant heat, are both objective and subjective. Part 1 of this study examines objective responses to clothing. Five fabrics commonly used in protective workwear were made into overalls of identical design and were evaluated by adult males in a simulated work environment. Microclimate humidity differences occurring during exercise and rest were significant with respect to subjects and times but not with respect to overalls. There was, however, a significant overall/time interaction. Skin temperature differences occurring during exercise and rest were significant only with respect to time and regions of the body. Thus, despite physical differences in the five overalls, particularly mass, statistically significant objective data allowing discrimination among overalls was not demonstrated.