S.F. Chou, R.A. Overfelt, W.F. Gale, 

H.S. Gale, C.G. Shannon, G. Buschle-Diller

National Air Transportation Center of Excellence for

Research in the Intermodal Transport Environment

Auburn University

Auburn, AL 36849

J. Watson

Office of Aerospace Medicine

Federal Aviation Administration

Washington, DC 20591

August 2009

Final Report

Effects of Hydrogen Peroxide 

on Common Aviation Textiles

DOT/FAA/AM-09/16

Office of Aerospace Medicine

Washington, DC 20591

OK-09-0434-JAH

Federal Aviation

Administration
NOTICE

This document is disseminated under the sponsorship 

of the U.S. Department of Transportation in the interest 

of information exchange. The United States Government 

assumes no liability for the contents thereof.

___________

This publication and all Office of Aerospace Medicine 

technical reports are available in full-text from the Civil 

Aerospace Medical Institute’s publications Web site: 

www.faa.gov/library/reports/medical/oamtechreports
i

Technical Report Documentation Page 

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. 

DOT/FAA/AM-09/16 

4. Title and Subtitle 5. Report Date 

Effects of Hydrogen Peroxide on Common Aviation Textiles August 2009 

6. Performing Organization Code 

7. Author(s) 

Chou SF, Overfelt RA, Gale WF, Gale HS, Shannon CG, 

Buschle-Diller G,1 Watson J2

8. Performing Organization Report No. 

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) 

1

National Air Transportation 

Center of Excellence for Research 

in the Intermodal Transport 

Environment 

Auburn University, AL 36849 

2

FAA Office of Aerospace Medicine 

800 Independence Avenue, S.W. 

Washington, DC 20591 

11. Contract or Grant No. 

Co-Op Agrmt No. 07-CRITE-A 

12. Sponsoring Agency name and Address 

Office of Aerospace Medicine 

Federal Aviation Administration 

800 Independence Ave., S.W. 

Washington, DC 20591 

13. Type of Report and Period Covered 

14. Sponsoring Agency Code 

15. Supplemental Notes 

Work was accomplished under Public law 108-76. 

16. Abstract 

Modern transportation systems are subject to unintentional contamination from infected passengers, as well as 

deliberate contamination from criminals and political adversaries. Hydrogen peroxide has been used for years 

as a disinfectant in the medical community and is under consideration in the dilute vapor form as a 

decontaminant/disinfectant/sterilant for transportation vehicles like aircraft, buses, subway trains, ambulances, 

etc. Although the biological efficacy of STERIS Corporation’s Vaporized Hydrogen Peroxide (VHP® 

a 

registered trademark of the STERIS Corporation, Mentor, OH.) technology has been demonstrated elsewhere, 

the compatibility of the process with typical aircraft materials has not been rigorously established. The present 

report documents a materials compatibility evaluation involving the effects of hydrogen peroxide exposure on 

the mechanical properties and flammability of the following commercial-grade textile materials: wool, nylon, 

polyester, Nomex®

, and leather. 

17. Key Words 18. Distribution Statement 

Hydrogen Peroxide, Decontamination, Materials 

Compatibility, Textiles, Technology Evaluation

Document is available to the public through the 

Defense Technical Information Center, Ft. 

Belvoir, VA 22060; and the National Technical 

Information Service, Springfield, VA 22161 

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price 

Unclassified Unclassified 26 

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized 

iii

Contents

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

METHODS AND MATERIALS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

RESULTS AND DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Changes in Flammability Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Changes in Chemical Composition and Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

v

ABBREVIATIONS

As used in this report, the following abbreviations/acronyms have the meanings indicated.

Abbreviation Meaning

ASTM ----------American Society for Testing and Materials

BI----------------Biological indicator

C ----------------Carbon, Celsius

CFU ------------Colony-forming units

DI---------------Deionized

eV ---------------Electron volt

FAA -------------Federal Aviation Administration

FAR-------------Federal Aviation Regulations

FTIR------------Fourier transform infrared

H ----------------Hydrogen

HPAI -----------Highly Pathogenic Avian Influenza

hr----------------Hour

HVFAA --------Horizontal vertical FAA flame chamber

min--------------Minute

mm--------------Millimeter

MPa-------------Megapascal

N ----------------Nitrogen

O ----------------Oxygen

psi ---------------Pounds per square inch

S -----------------Sulfur

s, sec ------------Second(s)

SARS------------Severe Acute Respiratory Syndrome

VHP ------------Vaporized hydrogen peroxide

XPS ------------X-ray photoelectron spectroscopy

1

Effects of hydrogen peroxide on common aviation textiles

INTRODUCTION

Modern outbreaks of infectious disease, such as Severe Acute Respiratory Syndrome (SARS) from China 

to Canada in 2002, Highly Pathogenic Avian Influenza 

(HPAI) in Southeast Asia in 2003, as well as possible 

future pandemic influenza, necessitate reliable clean-up 

of many elements of the transportation infrastructure 

system to alleviate impacts to human health and mitigate 

negative consequences to the global economy. Among 

all the sanitization/decontamination technologies available, vaporized hydrogen peroxide (VHP)1

 technology 

is of particular interest due to rapid sterilization, easy 

usage, intrinsic environmental friendliness (i.e., simple 

by-products composed of only water and oxygen) and 

compatibility with many materials and systems. VHP® 

technology might also be employed against deliberate 

biological/chemical attack, for instance, the 1995 Sarin 

gas attack in the Tokyo subway system (1). In fact, the 

VHP® process was utilized during the clean-up of buildings and vehicles in Washington, DC, after the 2001 

anthrax attacks (2). VHP® is generally considered to 

begin sporicidal effects at concentrations above 80 ppm.

Cycle times obviously vary based upon the size of the 

enclosed area, the capacity of the delivery system and 

the specific concentration desired. In general, VHP® 

technology shows excellent potential for application 

within the modern transportation system.

VHP® technology has been investigated for possible 

usage in aircraft applications and the process has been 

shown to be efficacious (complete kill of 106

 CFU of 

the spore forming Geobacillus stearothermophilus) in a 

narrow-body aircraft fuselage (3), as well as wide-body 

aircraft if the air in the cabin section was well mixed 

so that adequate levels of VHP® vapor were uniformly 

distributed (4,5). These studies used vaporized hydrogen 

peroxide concentrations in the range of 150 - 600 ppm 

and cycle times of 80 - 120 min. Maximum concentrations 

of hydrogen peroxide vapor were carefully controlled to 

avoid condensation in cool locations within the aircraft 

cabins. Although these previous studies did not evaluate the compatibility of the various cabin materials with 

exposure to vaporized hydrogen peroxide, it was noted 

that there were no noticeable changes to any of the cabin 

materials (4).

1

 VHP is a registered trademark of STERIS Corporation, Mentor, 

OH, USA.

Many polymeric textile materials are known to be 

susceptible to moisture sorption and, if H2

O2 vapor is 

similarly absorbed by these materials, their engineering 

properties could be seriously degraded. In considering the 

sanitization/decontamination of aircraft with vaporized 

hydrogen peroxide, cabin polymeric textiles (e.g., wool, 

nylon, polyester, Nomex2

) could be among the most 

vulnerable materials to potential hydrogen peroxide 

attack. These polymeric materials consist of long chain 

carbon-carbon backbones with side chain functional 

groups, as well as intermolecular cross-links that might 

be degraded by oxidation from the hydrogen peroxide.

Hence, it is necessary to examine and understand the 

chemical stability and mechanical response of these textiles 

after exposure to vaporized hydrogen peroxide. In this 

research, a preliminary examination of the compatibility 

of common airliner cabin textile materials with hydrogen 

peroxide has been conducted. The textile materials were 

composed of two basic categories: (i) natural materials, 

including wool and leather; and (ii) synthetic materials, 

including nylon, polyester, and Nomex®.

BACKGROUND

A typical VHP® process cycle consists of an initial 

dehumidification step, then a conditioning phase, followed by the actual sanitization/decontamination process.

Finally, an aeration phase is employed to remove residual 

hydrogen peroxide vapor. During the dehumidification 

phase, warm, dry air flows into the enclosure to lower 

the relative humidity to less than 10%, which allows a 

higher concentration of hydrogen peroxide vapor to be 

injected into the enclosure without condensation. Hydrogen peroxide liquid concentrate (35% liquid H2

O2

with a pH ~ 3) is then flash vaporized and injected into 

the enclosure during the initial conditioning phase and 

the sanitization/decontamination phase. The purpose of 

the conditioning phase is to rapidly increase the hydrogen 

peroxide concentration to minimize the overall cycle time.

During the sanitization/decontamination phase, a steady 

concentration of hydrogen peroxide vapor (typically 250 

- 450 ppm) is maintained to give the desired sanitization/decontamination cycle, as often measured by the 

6-log kill (i.e., 106

 reduction) of a commercial biological 

indicator (BI) spore population of Geobacillus stearothermophilus. Once the sanitization/decontamination phase 

is completed, the enclosure is then aerated with fresh air, 

2

 Nomex is a registered trademark of E. I. du Pont de Nemours and 

Company, Wilmington, DE, USA.
2

while any residual hydrogen peroxide vapor breaks down 

into environmentally benign water and oxygen.

Textile fabrics can be made from solutions (non-fibrous), directly from discrete fibers, or from yarns (6).

For the construction of fabrics from yarns, weft yarns are 

interweaved over and under stretched warp yarns under 

tension, as shown in Figure 1. Since warp yarns must 

withstand the tension and sometimes abrasion from the 

weaving process, warp yarns are made stronger than weft 

yarns and with more twist. Warp yarns also align straighter 

with less crimping and bending by the interlacing mechanics than the corresponding weft yarns.

The basic building blocks for either natural or synthetic 

textile yarns are the individual fibers composed of millions 

of molecular chains. The micro-mechanical properties 

of any polymer fiber are strongly dependant on the molecular weight of the polymer, the degree of crystallinity 

of the polymer, and the intrinsic intermolecular forces 

from hydrogen and van der Waals bonding, plus covalent 

cross-links, when applicable. Natural fibers can be produced from either plant (cellulose structures) or animal 

(protein structures) sources. The natural materials used 

in this research included wool and leather. The synthetic 

(man-made) fibers used in this research included nylon, 

polyester, and Nomex®.

Bleaching of textiles by hydrogen peroxide solutions 

is often accomplished during routine processing using an 

alkaline 3% hydrogen peroxide solution at a temperature 

of 80 ~ 90 oC (6). In an earlier study by Arifoglu et al. (7), 

the level of whiteness of wool after bleaching by hydrogen 

peroxide was found to be controlled by the exposure 

time, the concentration of hydrogen peroxide, the pH 

level, and the temperature of the treatment. Gacen and 

Cayuela (8) showed that when bleaching wool with an 

alkaline solution (pH = 9) of hydrogen peroxide (~5%) 

containing sodium pyrophosphate/sodium oxalate buffering medium at 55 oC for 2 hours, the whiteness index 

was greater than bleaching in an acidic solution (pH = 

4.7). Thus, chemical attack by hydrogen peroxide liquid 

concentrate was more severe in an alkaline solution than 

an acidic solution. In a more recent study by Cardamone 

et al.(9), the effect of shrinkage on wool during hydrogen peroxide bleaching was controlled by the unstable 

perhydroxy (HO2-) radicals. These authors found that 

the chemical attack of the wool disulfide cross links by 

hydrogen peroxide produced sulfonic acid and changed 

the anionic charge on the surface of wool fibers. The net 

effect was to increase the hydrophobicity, decreasing the 

electrostatic repulsion of the fibers and causing shrinkage 

in the wool fabrics.

METHODS AND MATERIALS

The specific motivation for this work was to evaluate 

the materials compatibility of textiles representative of 

those typically used in commercial aircraft. Thus, laboratory-grade textile samples of wool, nylon, polyester, 

Nomex® (Testfabrics Inc., West Pittston, PA, USA), 

and commercial-grade leather samples were acquired 

(McMaster Carr, Chicago, IL, USA).

Specimens were pre-cut and labeled according to the 

test specifications, as shown in Figure 2. Sample exposures 

to vaporized hydrogen peroxide were performed with a 

1000ED Bio-decontamination Unit (STERIS Corporation, Mentor, OH, USA) using Vaprox3

 as the sterilant 

in an enclosed chamber for 1, 10, or 25 VHP cycles. Dip 

exposure of fabric samples to 35% liquid phase hydrogen 

peroxide was carried out in opaque PVC bottles (Fisher 

Scientific, Fair Lawn, NJ, USA) for 24 hours and 168 

hours. After dip exposure, all dip specimens were rinsed 

in DI-water and then air-dried in an electrostatic film 

drying cabinet (Delta 1, CPM, Inc., Dallas, TX) for 1 

day. Sample weights were measured by an accuSeries4

accu-124 balance (Fisher Scientific, Arvada, CO, USA) 

before and after hydrogen peroxide exposures.

Changes in the various fabrics after exposures to either 

35% liquid hydrogen peroxide or vaporized hydrogen 

peroxide were initially examined via straightforward 

physical observation (i.e., appearance to the unaided 

3

 Vaprox is a registered trademark of STERIS Corporation, Mentor, 

OH, USA. 4

 accuSeries is a registered trademark of Fisher Scientific, Fair Lawn, 

NJ, USA.

Figure 1. Distinction between the warp and weft 

yarns of a common textile fabric. 
3

Figure 2. Physical dimensions of textile specimens for tensile testing and tear 

testing as well as vertical and horizontal flammability tests. 

eyes and residual post-exposure aroma), weight change, 

and observation via optical and scanning electron microscopy.

After fabric specimens were properly exposed and 

aged, mechanical testing was performed in an environmentally conditioned laboratory (21 ± 1o C, 65 ± 2% 

relative humidity) using a screw-driven Instron 4400R 

(Instron Inc., Canton, MA, USA) universal materials 

testing machine in accordance with ASTM standards D 

5034 – 95 (10) and D 2261 – 96 (11). Control specimens 

were performed regularly to confirm the stability of the 

materials, machine, and testing procedures and conditions. A calibrated 200-lb load cell was employed, and a 

12 in/min crosshead speed was used for both tensile and 

tear testing. Stress-strain curves were plotted according 

to the measurement of load and displacement.

As noted above, high-quality laboratory grade textile 

samples were procured for this study. Nevertheless, textiles 

invariably exhibit some variability of weave and anisotropy 

from batch-to-batch of sample material. These issues, 

when combined with less than exact sample alignment 

in the mechanical testing machine relative to the textile’s 

warp and weft directions, complicate the statistical interpretation of mechanical behavior due to the exposure 

conditions. A mechanical property variability study was 

conducted using wool (most variability in mechanical 

behavior, as discussed below) and Nomex® (least variability in mechanical behavior, discussed below). The 

results of this study are shown in Figures 3 and 4 for wool 

and Nomex®, respectively. It is clear that the synergistic 

influence of these experimental variabilities was small.

Flammability tests were performed in vertical and 

horizontal configurations in a HVFAA horizontal vertical 

flame chamber (ATLAS Materials Testing Technology, 

Chicago, IL, USA) in accordance with the Aircraft Materials Fire Test Handbook (12). Specimens were pre-cut 

and labeled according to the test specifications (Figure 2).

Prior to flammability testing, specimens were conditioned 

in a textile conditioning unit (Parameter Generation & 

Control, Black Mountain, NC, USA) at 21 ± 3 oC and 

50 ± 5 % relative humidity for at least 1 day. A 99% pure 

methane gas was used for burner fuel with an inlet pressure of 21⁄2 ± 1⁄4 psi, and the flame height was calibrated 

for 11⁄2 inch using a flame height indicator. A 12-second 

ignition time (length of time the flame is applied to the 

test specimen) was employed for vertical burning tests, 

whereas a 15-second ignition time was employed for 

horizontal burning tests.

Chemical analyses were performed using Fourier Transform Infrared Spectroscopy (FTIR) using an IR Prestige 

– 21 (Shimadzu Scientific Instruments, Columbia, MD, 

USA) spectrometer on pellets made of a mixture of the 

ground textile fibers and potassium bromide, over a scan 

range from 400 cm-1 to 4000 cm-1. Raman spectroscopy 
4

(a)

(b)

Figure 3. Results of batch-to-batch and day-to-day variability study of 

measured tensile strength and elongation to failure of as-received wool (13). 
5

(a)

(b)

Figure 4. Results of batch-to-batch and day-to-day variability study of measured 

tensile strength and elongation to failure of as-received Nomex®

 (13). 
6

was employed to complement the infrared spectroscopy.

Raman spectra were acquired using an Invia Confocal 

Raman Microscope (Renishaw, Wotton-under-Edge, 

Gloucestershire, UK) using a 514.5 nm wavelength and 1 

mW laser excitation source. Spectra were recorded using 

a 50X objective lens that generated a 1μm laser spot.

RESULTS AND DISCUSSION

Changes in Physical and Mechanical Properties

Warp specimens of wool, nylon, polyester, and Nomex®

intended for tear testing were weighed before and after 

hydrogen peroxide exposure, and the net weight change 

data are shown in Figure 5 (13). As seen in Figure 5, 

the weight changes observed for the polyester samples 

exhibited no statistically significant differences for the 

conditions investigated. The wool, nylon, and Nomex®

samples all gained weight after the VHP® treatments 

followed by aging in laboratory air. The wool samples 

exhibited the largest weight gains, with approximately 

1% gain after 1 VHP® treatment and 1 day of laboratory air aging, and more than 8% weight gain after 10 

VHP® cycles and 14 days aging in laboratory air. The 

weight gains of nylon and Nomex® were approximately 

half those of wool.

However, quite different results were seen for samples 

aged in a vacuum dessicator after exposure to hydrogen 

peroxide vapor. All samples exhibited weight losses after 

a single VHP® treatment, followed by aging in a vacuum 

dessicator for either 1 or 14 days. Aging samples in a vacuum 

dessicator after 10 VHP treatments showed no statistically 

significant change in weight for polyester and Nomex®, 

whereas nylon and wool exhibited reduced increases in 

weight of only about 1% and 2%, respectively. A significant 

part of the weight gains found after laboratory air aging 

were probably due to the presence of residual moisture in 

the fibers due to (i) absorption of water vapor directly from 

the environment and/or (ii) decomposition of absorbed 

hydrogen peroxide to water and oxygen.

Decreases in weight after a single VHP® treatment 

followed by vacuum aging are consistent with the weight 

gain being primarily absorbed moisture that is subsequently 

removed by the vacuum treatment. Net increases in the 

weight of wool and nylon after 10 VHP® treatments 

followed by vacuum aging are consistent with chemical 

oxidation of the polymers. In addition, the appearance of 

the wool samples after 10 VHP® cycles exhibited a slight 

discoloration from the hydrogen peroxide treatment.

Examination of the surface morphology of the synthetic fibers in the scanning electron microscope revealed 

no significant qualitative changes in surface morphology 

after VHP® and aging treatments. However, the surfaces of 

wool fibers displayed significant evidence of the hydrogen 

peroxide exposure. Secondary electron images of wool fiber 

morphology after 10 VHP® cycles are shown in Figure 6 

(13). The outer cuticle layer exhibited some separation 

from the exterior para-cell and ortho-cell cortex after 10 

VHP® cycles.

Figure 5. Percentage change in weight for wool, nylon, polyester, and Nomex®

after 1 or 10 VHP®

 cycles and 1 or 14 day post-exposure aging times in 

laboratory air or vacuum (13). 
7

The effects of VHP® exposure on the tensile strength 

and elongation to failure for samples oriented to tensile 

test either the warp or the weft fibers are shown in Figures 

7-10 for wool, nylon, polyester and Nomex®, respectively 

(13). With only laboratory aging in air, increasing VHP®

exposures lead to decreases in the tensile strength and 

increases in the elongation to failure for both orientations of wool samples. However, aging treatments in 

the vacuum dessicator after VHP® exposure made the 

wool results less conclusive. Mechanical test data for 

the nylon samples (Figure 6) yielded slight decreases in 

tensile strength (~5-10%) for almost all test conditions 

and inconclusive results for changes in the elongation 

to failure with no statistically significant trends. The 

polyester samples generally exhibited decreases in tensile 

strength (~10-20%), as well as decreases in elongation 

to failure (~10-20%) for most test conditions. Finally, 

the Nomex® samples exhibited no consistent changes in 

tensile strength for all test conditions and slight increases 

in the elongation to failure (~2-10%) for most of the 

test conditions.

The effect of exposure of the various textiles to 35% 

liquid hydrogen peroxide was investigated by leaving 

samples in the concentrated hydrogen peroxide solutions 

for periods of 1 day or 7 days (168 hours). These tests 

were undertaken because of the possibility of experiencing 

condensation of liquid hydrogen peroxide in cool sections 

of large, complex enclosures during VHP® treatment. The 

percentage changes in tensile strength and elongation to 

failure for the various textile materials (warp and weft 

orientations) are shown in Figures 11 and 12, respectively 

(13). The polyester samples exhibited minimal changes in 

tensile strength and essentially no changes in elongation 

to failure after exposure to the liquid hydrogen peroxide.

Except for the 24-hour exposure with 1 day air aging treatment, the nylon samples also exhibited minimal changes 

in tensile strength but slight increases in elongation to 

failure for most of the test conditions after exposure to 

the liquid hydrogen peroxide. The reason for the large decreases in tensile strength for the nylon samples subjected 

to a 24-hour exposure and 1 day air aging treatment is 

unclear. Wool samples generally exhibited large decreases 

in tensile strength.. Although the Nomex® samples generally exhibited large decreases in tensile strength, the 

Nomex® samples exhibited inconsistent elongation to 

failure results for these test conditions.

Stress-strain curves for representative wool samples 

are shown in Figure 13. These curves are typical of viscoelastic materials like wool and exhibit an initial low 

modulus region, followed by linear elastic deformation 

and then yielding where the modulus drops significantly.

It can be seen that the load-carrying capacity and the 

As-received After 10 VHP® cycles 

Figure 6. Secondary electron images for wool fibers (13). 
8

Figure 7. Percentage change in tensile strength and elongation to failure of wool 

after the indicated exposure conditions (13).

Figure 8. Percentage change in tensile strength and elongation to failure of nylon 

after the indicated exposure conditions (13). 
9

Figure 9. Percentage change in tensile strength and elongation to failure of 

polyester after the indicated exposure conditions (13). 

Figure 10. Percentage change in tensile strength and elongation to failure of 

Nomex®

 after the indicated exposure conditions (13). 
10

Figure 11. Percentage change in tensile strength of wool, nylon, polyester and 

Nomex®

 after 24- or 168-hour exposures to 35% liquid hydrogen peroxide for the 

indicated post-exposure laboratory air aging conditions (13).

Figure 12. Percentage change in elongation to failure of wool, nylon, polyester 

and Nomex®

 after 24 or 168 hour exposures to 35% liquid hydrogen peroxide for 

the indicated post-exposure laboratory air aging conditions (13). 
11

Figure 13. Tensile stress vs. strain curves for wool (a) as-received, (b) 

subjected to 1 VHP cycle and (c) 10 VHP cycles. 

elastic modulus of the wool materials decreased after 1 

VHP® cycle and then decreased again after 10 VHP®

cycles. The strain at which the yielding began for each 

sample decreased from about 0.13 in the as-received 

wool sample to around 0.10 for the sample subjected to 

10 cycles of VHP®.

Stress-strain curves for typical leather samples are 

shown in Figure 14. The tensile strength of the leather 

samples was seen to decrease from 22 MPa in the as-received condition to 20 MPa after 1 VHP® treatment to 

9 MPa after 10 VHP® treatments to 7 MPa for a 10-min 

dip in 35% liquid H2

O2. The elongation to failure was 

also seen to decrease from 0.6 in the as-received condition to 0.35 after 1 VHP® treatment to 0.30 after 10 

VHP® treatments. Interestingly, the 10-min dip in 35% 

liquid H2

O2 caused the measured elongation to failure 

to increase to 0.8.

Changes in Flammability Behavior

Note: These tests were designed simply to evaluate 

possible changes in the intrinsic flammability behavior of 

the various basic textile materials due to H2

O2 exposures 

and were not intended to assess compliance with any 

specific flammability requirement.

The effects of exposures to hydrogen peroxide in either 

the vapor phase (1 and 10 cycles) or liquid phase (24 or 

168 hour dips) on flammability of nylon, polyester, and 

Nomex® are shown in Figures 15, 16 and 17, respectively.

Changes in flammability test results in the vertical and 

horizontal configurations and for the warp and weft 

textile orientations due to hydrogen peroxide exposure 

are presented. The changes in flammability results for 

wool due to hydrogen peroxide exposure are shown in 

Figures 18 and 19.

Exposures of nylon (Figure 15) to 10 cycles of vaporized 

hydrogen peroxide did not produce significant changes in 

the vertical or horizontal flammability behavior in either 

the warp or weft directions. The 24-hour dip exposures 

significantly increased all measured flammability parameters for the both vertical and horizontal orientations of 

the warp weave. In contrast, 168-hour dip exposures 

produced no statistically significant changes in flammability behavior.

Polyester (Figure 16) exhibited significant increases 

in vertical flammability parameters for the weft weave 

during vertical flammability testing, whereas the warp 

weave showed no significant changes during vertical flammability testing (vapor or liquid exposures). Horizontal 

flammability testing of polyester yielded increases in burn 

length and burn time for the warp weave after exposure 

to 1 or 10 cycles of vaporized hydrogen peroxide; results 

for the weft weave were inconclusive. Dip testing of 

polyester tended to decrease the burn lengths and burn 

times during horizontal flammability testing.

Exposures of Nomex® (Figure 17) to either the vaporized or the concentrated liquid hydrogen peroxide 

did not appear to influence the measured flammability 

parameters of the material in either the vertical or horizontal flammability tests for either the warp weave or 

the weft weave.
12

Figure 13. Tensile stress vs. strain curves for wool (a) as-received, (b) 

subjected to 1 VHP cycle and (c) 10 VHP cycles. 

Figure 14. Tensile stress vs. strain curves for leather subjected to 1 

VHP cycle, 10 VHP cycles and 10-min dip in 35% liquid H2O2.
13

(a)

(b)

Figure 15. (a) Vertical and (b) horizontal flammability test results for nylon. 
14

(a)

(b)

Figure 16. (a) Vertical and (b) horizontal flammability test results for polyester. 
15

(a)

(b)

Figure 17. (a) Vertical and (b) horizontal flammability test results for Nomex.
16

(a)

(b)

Figure 18. (a) Vertical and (b) horizontal flammability test results for wool. 
17

PartiallyBurned Zone

As-received After 10 VHP cycles 

Figure 19. Appearance of wool after vertical flammability testing. 

Wool (Figure 18) exhibited a consistent trend towards 

decreases in vertical flammability parameters for all conditions (vapor exposures, dip exposures, warp and weft 

weaves). Figure 19 shows samples of wool (as-received 

and VHP® treated) after vertical flammability testing.

An expanded brownish region was observed between the 

flame decomposition product region and the unburned 

wool for the VHP® exposed specimens. During horizontal 

flammability testing of wool, VHP® treatments usually 

produced large increases in burn length and burn time, 

while dip treatments only produced minor increases in 

burn length and burn time. This can be associated with 

sample weight increases due to moisture sorption in the 

VHP® process, as well as in the conditioning unit, thus 

resulting in incomplete combustion.

As noted above, these tests were not intended to evaluate 

the compliance of any material with the materials flammability requirements, as outlined in Title 14 of the Code of 

Federal Regulations Part 25 § 853 for aircraft compartment 

interiors of transport category airplanes. None of these 

materials had any flame retardants applied.

Nevertheless, it is interesting to note that all flammability results for Nomex® — both as-received as well as 

after all exposures to hydrogen peroxide — were within 

the limits of §25.853 for both vertical and horizontal 

flammability testing.

The horizontal burn rates for nylon and polyester, 

as-received as well as after all exposures to hydrogen peroxide, met the requirements of § 25.853. The horizontal 

burn rates for wool (as-received and after all exposures to 

hydrogen peroxide) did not meet §25.853 limits.

Additionally, although the vertical flammability data 

for wool, nylon and polyester (as received and as exposed 

to hydrogen peroxide) met the limits of §25.853 for drip 

flame time, the limits of §25.853 were not met for these 

materials with respect to flame time. The vertical flammability data for nylon and polyester generally met the 

requirements of §25.853 with respect to burn length.

The vertical flammability results regarding burn length 

for wool showed no consistent trend with respect to 

meeting the limits of §25.853.(12).

Six representative samples of aviation grade, blended 

wool textiles and six samples of aviation grade leathers 

— all presumably with flame retardants applied — were 

acquired from aviation suppliers. The wool blends contained either polyamide (5 or 9% by weight) or nylon (8 

or 10% by weight) with the balance natural wool fibers.

Any specific flame retardant(s) utilized were not known 

for these preliminary tests. Vertical flammability testing 

was performed on an as-received sample from each supplier. A second sample of each was then exposed to 10 

cycles of VHP® prior to vertical flammability testing.

Weight changes due to exposure to the vaporized hydrogen 

peroxide were noted. The wool blends averaged a 3.6% 

gain in weight, whereas the leather samples averaged a 

1.9% decrease in weight. The results of this preliminary 

vertical flammability testing are shown in Table I. The 

flammability of the wool blends exhibited increases in 

burn length from 78 to 154 mm and increases in flame 

time from 1.6 to 19.6 s. The flammability of the leather 

samples exhibited increases in burn length from 46 to 

105 mm and increases in flame time from 8.8 to 13.4 
18

s. The Aircraft Materials Fire Test Handbook (12) notes 

that the average flame time will not exceed 15 seconds, 

and the average burn length will not exceed 203 mm 

for the 12-s ignition time vertical test. The 10 cycles of 

VHP® exposures caused the wool blends to exceed the 

limits of average flame time.

Changes in Chemical Composition and Structure 

FTIR and Raman spectroscopy were used to examine 

the chemical structure of all the fabrics tested. The analysis 

showed that only wool exhibited any measurably significant 

chemical structural change and the data for nylon, polyester, 

and Nomex® are not presented. Figure 20 shows the FTIR 

spectra of wool in the as-received condition and wool treated 

with either 1 or 10 VHP® cycles, followed by either 1 or 14 

days in either laboratory air or a vacuum dessicator. The usual 

characteristic bands observed in the IR spectra of wool include 

the amide I (C=O stretching), amide II (N-H stretching), 

and amide III (N-H in-plane bending and C-N stretching) 

modes at 1630-1650 cm-1, 1500-1550 cm-1 and 1200-1250 

cm-1, respectively. A distinctive new peak at around 1035 

cm-1 is seen for the VHP®-treated wool specimen. Although 

barely discernable after a single VHP® treatment, the new 

peak grows significantly and is easily seen after 10 VHP®

Table 1. 12-Second Vertical Flammability Testing of Aviation-Grade Textiles.

_________________________________________________________________________________________________________________________________________ 

 Wool Blends Leathers _______________________________________________ _________________________________________________ 

Burn Length Flame Time Burn Length Flame Time 

Treatment (mm) (s) (mm) (s)

_________________________________________________________________________________________________________________________________________ 

As-received 78 1.6 46 8.8

After 10 VHP® Cycles 154 19.6 105 13.4 

_________________________________________________________________________________________________________________________________________

Note: The Aircraft Materials Fire Test Handbook (DOT/FAA/AR-00/12, 2000) notes limits of 15 s for average flame times and 203 mm for 

average burn lengths for the 12-s vertical flammability test. 

Figure 20. FTIR spectra of wool after exposure to vaporized hydrogen 

peroxide: (i) as-received; (ii) 1 VHP cycle + 1 day vacuum desiccator; (iii) 1 

VHP cycle + 1 day laboratory air; (iv) 1 VHP cycle + 14 days vacuum 

desiccator; (v) 1 VHP cycle + days laboratory air; (vi) 10 VHP cycles + 1 day 

vacuum desiccator; (vii) 10 VHP cycles + 1 day laboratory air; (viii) 10 VHP 

cycles + 14 days vacuum; (ix) 10 VHP cycles + 14 days laboratory air. 
19

cycles. This new peak can be assigned to S=O bonds from 

the formation of sulfinite (SO3

2-) and/or sulfanite (SO42-).

Similar results were seen for the wool samples exposed to 

concentrated liquid hydrogen peroxide by dip testing.

Raman spectroscopy was then used to examine the protein 

structure of wool (i.e., amide I, II, and III). It can be seen 

from Figure 21 that the amide I and III bands corresponding 

to wavenumbers at 1630~1650 cm-1 and 1200~1250 cm-1

do not display any shift or change after 10 VHP® exposure 

cycles. The distinct peak at 1035cm-1 (due to the formation 

of S=O bonds) was also observed in the Raman spectra. In 

addition, peaks at 1450cm-1 were assigned to C-H bending 

and peaks at 890~960 cm-1 correspond with a C-C backbone 

vibration. A high wavenumber Raman spectrum of wool, 

shown in the inset of Figure 21, clearly shows C-H stretching.

To further investigate the oxidation of wool keratin 

with vapor phase hydrogen peroxide, X-ray photoelectron 

spectroscopy (XPS) was employed. Figure 22 (a) shows 

an overall scan for as-received wool, as well as VHP®

treated wool. The binding energies for carbon, nitrogen, 

and oxygen atoms remain the same. A detailed scan 

for sulfur atoms around the sulfur 2p region is shown 

in Fig. 22 (b). The binding energy for sulfur 2p in the 

as-received wool keratin was found to be 164 eV (as-received 

data, broad diffuse peak) whereas the binding energy for hydrogen peroxide-treated wool keratin was shifted to 168.7 eV 

(H2

O2 exposed data, broad diffuse peak). The shift in binding 

energy indicates a structural change from disulfide crosslink 

to sulfonic acid in the formation of sulfanite - SO4

2-.(14)

CONCLUSIONS

1. Exposures of wool, nylon, polyester and Nomex®

to vaporized or liquid phase hydrogen peroxide caused 

increases in weight, presumably due to absorption of 

water vapor from the treatment as well as decomposition of H2

O2 to oxygen and water vapor. Aging samples 

in a vacuum dessicator removed the absorbed water and 

produced net weight decreases for samples exposed to a 

single VHP® cycle. Net weight gains remained after 10 

VHP® cycles, followed by vacuum aging. Preliminary 

data with leather samples indicated a net loss of weight 

after exposure to vaporized hydrogen peroxide.

2. The tensile strength of wool was moderately degraded 

(~20-30% loss), and the elongation to failure was increased 

by exposure to vaporized hydrogen peroxide.

3. The tensile strength and the elongation to failure of 

polyester were slightly degraded (~10% loss) by exposure 

to vaporized hydrogen peroxide.

4. The tensile strength of nylon was minimally degraded 

(<10% loss) by exposure to vaporized hydrogen peroxide.

Results for the elongation to failure were inconclusive.

5. The tensile strength and the elongation to failure 

of Nomex® were unchanged by exposure to vaporized 

hydrogen peroxide.

6. The tensile strength and the elongation to failure of 

leather were severely degraded (~50% loss) by exposure 

to vaporized hydrogen peroxide.

Amide I

Amide II

Amide III

S=O

C-H

Figure 21. Raman spectra for as-received wool and VHP-treated wool. Insert 

shows high wavenumber spectra for examination of C-H stretching. 
20

7. The tensile strength of nylon and polyester generally 

were only slightly degraded (<10% loss) by exposures to 

35% concentrated liquid hydrogen peroxide.

8. The tensile strength of wool and Nomex® were severely 

degraded (~50% loss) by exposures to 35% concentrated 

liquid hydrogen peroxide.

9. All preliminary flammability results for Nomex® — 

both as-received as well as after all exposures to hydrogen 

peroxide — were within the limits of §25.853 for both 

vertical and horizontal flammability testing.

10. The preliminary flammability testing of wool, nylon, 

and polyester indicated complex effects on flame/burn 

times, burn lengths and horizontal burn rates, presumably 

due to the presence of absorbed water vapor from the 

hydrogen peroxide exposures and the pre-flammability 

 (a)

600 500 400 300 200 100 0

Relative Intensity (Counts)

Binding Energy (eV)

Wool

As‐received

10 VHP Cycles

168 HRs Dip

C1s

N1s

O1s

S2p

 (b)

171 170 169 168 167 166 165 164 163

Relative Intensity (Counts)

Binding Energy (eV)

Wool As‐received

10 VHP Cycles

168 HRs Dip

S2p

SO3 SO 2-

4

2-

Figure 22. XPS spectra for wool in the conditions indicated: (a) overview 

scan and (b) detailed scan in the sulfur atom region. 

testing conditioning treatments. Additional research into 

these effects is necessary to fully understand and rigorously characterize this important behavior.

11. The preliminary flammability testing of aviation-grade 

wool blends indicated that 10 cycles of VHP exposures 

would cause unacceptable increases in flame times. Additional research into the effects of VHP exposure to aviation 

flame retardants is necessary to characterize these effects.

12. FTIR and Raman spectroscopy indicate that the 

disulphide cross-link bonds in wool fibers are oxidized 

to sulfonic acid in the formation of sulfanite — SO4

2- by 

exposure to hydrogen peroxide. Apparently, the disulfide 

crosslinks that connect the wool’s α-helix with the keratinassociated proteins were oxidized by hydrogen peroxide 

vapor, forming the newly observed S=O bonds.
21

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