influence of nitrogen gas and oxygen scavengers on fading

14 Pages·2017·0.25 MB·English

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Faculty Publications - Textiles, Merchandising Textiles, Merchandising and Fashion Design,
and Fashion Design Department of
April 2000
IINNFFLLUUEENNCCEE OOFF NNIITTRROOGGEENN GGAASS AANNDD OOXXYYGGEENN SSCCAAVVEENNGGEERRSS OONN
FFAADDIINNGG AANNDD CCOOLLOORR CCHHAANNGGEE IINN DDYYEEDD TTEEXXTTIILLEESS
Judy J. Brott Buss
American Quilt Study Group
Patricia Cox Crews
University of Nebraska-Lincoln, [email protected]
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Buss, Judy J. Brott and Crews, Patricia Cox, "INFLUENCE OF NITROGEN GAS AND OXYGEN SCAVENGERS
ON FADING AND COLOR CHANGE IN DYED TEXTILES" (2000). Faculty Publications - Textiles,
Merchandising and Fashion Design. 15.
https://digitalcommons.unl.edu/textiles_facpub/15
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INFLUENCE OF NITROGEN GAS AND OXYGEN SCAVENGERS ON
FADING AND COLOR CHANGE IN DYED TEXTILES
JUDY J. BROTT BUSS AND PATRICIA COX CREWS
ABSTRACT—Unexpected and undesired col- phy was used to verify that no measurable oxygen
or changes in paper materials following the use of was present in the reduced-oxygen packages ini-
anoxic treatments for killing insects that infest col- tially and that less than 2% oxygen was present in
lections have been reported. Th is observation and the reduced-oxygen packages after 90 days. At the
attendant concerns prompted this research. Th is end of the exposure period, color change was eval-
study examined the infl uence of a nitrogen gas uated instrumentally using a spectrocolorimeter.
purge and oxygen scavengers on color stability of If specimens exhibited signifi cant color change ac-
dyed textiles in the presence and absence of light. cording to instrumental color measurements, visu-
Earlier studies showed that while most dyed tex- al evaluations were completed to determine wheth-
tiles exhibit less fading and color change when ox- er or not the changes were visually percepti ble.
ygen is removed from the atmosphere via a nitro-
gen purge, a small number of dyes exhibit greater Results showed that oxygen scavengers did not af-
amounts of fading and color change in the pres- fect the color of any of the dyes included in this
ence of a reduced-oxygen atmosphere. However, study, including a temperature-sensitive disperse
it was unclear whether the earlier reports of in- dye. Th is provides additional experimental fi nd-
creased fading observed in reduced-oxygen atmo- ings in support of their safety for use in anoxic
spheres were due to the presence of light or the ab- pest control treatments. Results also showed that
sence of oxygen because none of the earlier studies the low-oxygen atmospheres examined in this
included anoxic treatments conducted both in the study provided some level of protection against
presence and absence of light. fading and color change for most, but not all, dyes.
One fl uorescent dye in the presence of continuous
In recent years oxygen scavengers have been in- light exhibited signifi cantly more color change in
creasingly used for anoxic pest control measures. low-oxygen atmospheres than in ambient air. In
Th ese scavengers are known to function through the absence of light, the same fl uorescent dye did
an exothermic reaction. Th erefore, this study in- not exhibit greater color change in the low-oxygen
cluded a fabric colored with a temperature sensi- atmosphere than in ambient air. Th is suggests that
tive dye in an attempt to determine whether the the reaction is photochemical in nature and that
heat generated by oxygen scavengers was respon- the unwanted color change may be avoided during
sible for observed color changes in some dyed ma- anoxic treatments by conducting anoxic pest con-
terials rather than the low-oxygen atmosphere. trol treatments in the dark.
Selected fabrics dyed with natural dyes (turmeric TITULO—LA INFLUENCIA DEL GAS DE
and fustic on wool) and synthetic dyes (indigoid NITRÓGENO Y BARREDORES DE OXÍ-
and acid dyes on wool, a disperse dye on polyes- GENO EN LA DECOLORACIÓN Y CAM-
ter; and fl uorescent dyes on cotton) were enclosed BIOS DE COLOR EN TEXTILES TEÑI-
in transparent fi lm packages, treated with one DOS—RESUMEN. En ciertos museos se
of three reduced-oxygen atmospheres (nitrogen han reportado inesperados e indeseables cam-
purge, nitrogen purge plus oxygen scavenger, or ox- bios de color en materiales de papel, despu-
ygen scavenger alone), or ambient air (control), and es del uso de tratamientos anóxicos para matar
exposed to continuous fl uorescent light (320 lux) insectos que a veces infectan las coleccio-
or total darkness for 90 days. Gas chromatogra- nes. Esta observación y los intereses relaciona-
Textile Specialty Group Postprints 2000 55
JUDY J. BROTT BUSS AND PATRICIA COX CREWS
dos inspiran esta investigación. Este estudio exam- oscuridad total por 90 días. Se usó cromatogtaff a
inó la infl uencia de una purga de gas de nitrogeno de gases para verifi car que ningún oxígeno detect-
y barredores de oxígeno, sobre la estabilidad del able estaba presente en los paquetes con oxígeno
color de textiles tinturados en la presencia y aus- reducido después de 90 días. Al fi nal del período
encia de luz. Estudios anteriores muestran que de exposición, el cambio de color fue evaluado in-
mientras la mayoria de los textiles tenidos presen- strumentalmente usando un espectrofoto-colorí-
tan menos decoloracion y cambios de color cuan- metro. Si los especímenes mostraban cam bios de
do el oxígeno es removido de la atmósfera vía pur- color signifi cativos de acuerdo a las mediciones de
ga de nitrogenos, un reducido número de tintes color instrumentales, se completaban con evalua-
muestran cantidades mayores de decoloración y ciones visuales para determinar si los cambios eran
cambio de color en la presencia de una atmósfera o no visualmente perceptibles.
con oxígeno reducido. Sin embargo, no fue claro si
Los resultados demostraron que los barredores de
los reportes anteriores sobre el aumento de decol-
oxígeno no afectaron el color de ninguno de los tint-
oración observado en atmósferas de oxígeno redu-
es incluidos en este estudio, incluyendo un tinte dis-
cido, eran debido a la presencia de luz o a la aus-
perse sensible a la temperatura. Esto provee hal-laz-
encia de oxígeno porque ninguno de los estudios
gos experimentales adicionales en respaldo de la
anteriores incluia tratamientos anóxicos, ambos
seguridad para su uso en tratamientos de control de
conducidos en la presencia y ausencia de luz.
pestes anóxicas. Los resultados también mues tran
Adicionalmente, en años recientes el personal
que las atmósferas bajas en oxígeno exami-nadas
de museo ha aumentado el uso de barredores de
en este estudio otorgaron algún nivel de protección
oxígeno como medida de control de pestes anóxi-
contra la decoloración y el cambio de color para la
cas. Estos barredores son conocidos por funcio-
mayoría, aunque no de todos los tintes. Un tinte
nar a través de reacciones exotermicas. Por eso,
fl uorescente en presencia de luz continua mostró
este estudio incluyó una tela teñida con un tinte
signifi cativamente más cambios de color en atmós-
sensi ble al calor en un intento por determinar si
feras bajas en oxígeno que en aire ambiente. En la
el calor generado por los barredores de oxígeno
ausencia de luz, el mismo tinte fl uorescente no ex-
era respon-sable por los cambios de color obser-
hibió mayor cambio de color en la atmósfera baja
vados en algunos materiales teñidos, en lugar de
en oxígeno que en aire ambiente. Esto sugiere que la
la atmósf era baja en oxígeno.
reacción es de naturaleza fotoquímica y que el cam-
bio de color no deseado puede ser evitado durante
Telas seleccionadas teñidas con tintes naturales
los tratamientos anóxicos realizando los tratamien-
(curcuma y fustete en lana) y tintes sintéticos (indi-
tos de control de pestes anóxicas, en la oscuridad.
gos, y colorantes ácidos sobre lana, un colorante
disperse en polyester, y colorantes fl uorescentes en
1. INTRODUCTION
algodón), fueron encerrados en paquetes de fi lm
transparentes y tratados con una de tres atmós- During the 1990s reduced-oxygen atmospheres
feras de oxígeno reducido (purga de oxígeno, purga saw increased usage as an alternative to the use
de nitrógeno más barredor de oxígeno, o barredor of broad spectrum chemicals for insect control.
de oxígeno solo), o ambiente de aire controlado, y Anoxic treatments proved very eff ective in con-
expuesto a luz fl uorescente continua -320 lux- o a trolling insect pest infestations (Gilberg 1988;
56 Textile Specialty Group Postprints 2000
INFLUENCE OF NITROGEN GAS AND OXYGEN SCAVENGERS ON FADING AND COLOR
CHANGE IN DYED TEXTILES
Gilberg 1991; Valentin and Preusser 1990; Gil- colors of dyed and printed historic textiles. Sim-
berg and Roach 1992; Daniel et al. 1993; Rust ilarly, while a number of researchers have exam-
and Kennedy 1993; Selwitz and Maekawa 1998). ined the eff ects of a low-oxygen atmosphere on
In addition, low-oxygen atmospheres have been the lightfastness of dyes, none of them included
sug gested as benefi cial environments for storage the absence of light as a variable because the focus
of sensitive artifacts such as dyed textiles and wa- of their studies was lightfastness. Furthermore,
ter colors, because elimination or reduction of ox- the results of research focusing on the infl uence
ygen may slow or even arrest degradation process- of low-oxygen atmospheres on the lightfastness of
es including fi ber degradation and unwanted color dyes have been mixed. Some researchers (Amey
change or color loss (Amey et al. 1979; Daniel et al. 1979; Egerton and Morgan 1970; Padfi eld
1993; Giles et al. 1972; Giles 1965; Hansen 1998; and Landi 1966) found that a low-oxygen atmos-
Maekawa et al. 1992). Consequently, several re- phere reduced fading of some dyes; some re-
searchers have recommended using low-oxygen searchers (Egerton and Roach 1958; Schwen and
atmospheres for long-term storage environments Schmidt 1959; Giles and McKay 1963; Egerton
for selected museum objects such as textiles (Gil- and Morgan 1970; Amey et al. 1979) found low-
berg and Grattan 1994; Daniel 1993). oxygen atmospheres increased fading of selected
dyes; and some researchers (Russell and Abney
Low-oxygen atmospheres have been achieved by 1888; Giles and McKay 1963; Egerton and Mor-
creating a vacuum then fl ushing an enclosure with gan 1970) found that low-oxygen atmospheres
an inert or low reactive gas. Nitrogen gas is often neither reduced nor increased fading of dyes in
the inert gas used to achieve the low-oxygen atmo- compari son to light exposure in ambient air.
spheres by gas fl ushing. An oxygen absorber may
be inserted at the end of the nitrogen gas purge Vinod Daniel’s (1993) chapter, entitled “Stor-
and before the container is sealed to extend the age in Low-Oxygen Environments” in Storage of
oxygen-free life span of a display or storage case or Natural History Collections: A Preventive Conser-
to insure maintenance of a reduced-oxygen level vation Approach, includes observations by John
for a designated treatment period (Lambert et al.. Burke, Head Conservator of the Oakland Mu-
1992). Another method for achieving a reduced- seum Conservation Center, Oakland, Califor-
oxygen atmosphere consists of using an oxygen nia, who noted “signifi cant reduction in color
absorber alone to achieve low-oxygen levels with- fading for many colorants on paper in an envi-
in a sealed container. Th e latter method is usually ronment with less than 0.1% oxygen.” Because of
used when an institution does not have the neces- the benefi cial eff ect of a low-oxygen atmosphere
sary equipment for creating vacuums and perform- in reducing fad ing of many dyes, Daniel (1993)
ing gas purges. recommended storing museum materials in re-
duced-oxygen envir onments. At the same time,
While a number of studies have been conducted to he was aware of the sometimes negative eff ects of
verify the eff ectiveness of low-oxygen methods to reduced-oxygen atmospheres because he also ref-
kill insects and control infestations (Gilberg 1988; erences the work of Japanese scientists who ob-
Gilberg 1991; Valentin and Preusser 1990; Gil- served changes in certain artist colors subjected
berg and Roach 1992; Daniel et al. 1993; Rust and to reduced-oxygen atmospheres.
Kennedy 1993), none of the researchers examined
the eff ects of anoxic pest control treatments on the
Textile Specialty Group Postprints 2000 57
JUDY J. BROTT BUSS AND PATRICIA COX CREWS
John Burke reported in a session at the 1996 observed in some dyes. Specifi cally, the purpose of
American Association of Museums annual meet- this research was 1) to investigate the infl uence of
ing his observations of accelerated fading of select- reduced-oxygen atmosphere on the color of select-
ed colorants on paper in reduced-oxygen atmos- ed dyed textiles stored both in continuous light
pheres. In a subsequent conversation, Mr. Burke and in total darkness and 2) to determine wheth-
described especially pronounced fading of fl uores- er or not the accelerated fading observed in con-
cent colorants on self-adhesive paper labels when junction with low-oxygen atmospheres was due
exposed to a low-oxygen environment created to the heat associated with the exothermic reac-
using oxygen scavengers, but not in ambient air tions of oxygen scavengers or due to the low-oxy-
(Burke 1997). Th e light levels were not controlled gen atmosphere.
during his informal observations.
2. EXPERIMENTAL METHODS AND
Th e acceptance of oxygen scavengers as appropri- MATE RIALS
ate for anoxic pest control treatments in historic
Dyed specimens were enclosed in transparent
collections has been rapid. Some conservation sci-
fi lm packages, treated with three reduced-oxygen
entists, however, have recommended further study.
atmospheres (dry nitrogen gas, dry nitrogen gas
For example, in his conservation text, which focus-
plus oxygen scavenger, or oxygen scavenger alone),
es on photochemical and thermal aspects of accel-
plus ambient air (control), and exposed to contin-
erated aging of materials, Robert Feller, director
uous light or held in darkness for 90 days. Eight
emeritus, Carnegie Mellon Research Institute, in-
dyes, applied to the appropriate textile sub strate
cludes among his recommendations for future re-
(cotton, wool or polyester), were chosen to pro-
search, the need to study the eff ects of storing ar-
vide a selection of natural and synthetic dyes with
tifacts “under inert atmospheres or in the prese nce
a range of lightfastness properties. Th e low-oxy-
of oxygen scavengers” (Feller 1994, 168).
gen atmospheres selected and the methods used
to achieve the atmospheres were all modeled after
Confl icting reports regarding the eff ects of low-
those used by conservators and other researchers
oxygen atmosphere on dyed textiles and papers,
in experiments designed to study the eff ectiveness
particularly the unexpected and undesired fading
of anoxic methods for killing insects that some-
observed in some colored paper materials follow-
times infest museum textiles.
ing the use of anoxic treatments for insect con-
trol in museums, prompted this study. No stud-
2.1 DYES ON THE EXPERIMENTAL
ies were found in which the eff ect of a low-oxygen
TEX TILES
atmos phere on the colors of dyed textiles was ex-
amined in both the presence and absence of light. Eight dyes were selected to provide a range of light-
By fail ing to include both the absence of light, as fastness properties and included mordant dyes, vat
well as the presence of light in the experiments, dyes, fl uorescent dyes and one disperse dye. Two
several questions remained unresolved—whether AATCC Blue Wool Lightfastness Standards-L2
the absence of oxygen alone would trigger adverse and L6 (obtained from AATCC, Research Tri-
changes in color, whether the reaction was photo- angle Park, NC) were selected to represent dyes
chemical in nature and required light, and wheth- with known lightfastness qualities and fading
er or not the heat generated by oxygen scavengers rates. Blue Wool L6 has good lightfastness, where-
was the factor responsible for the rapid fading as Blue Wool L2 has poor lightfastness. Color on
58 Textile Specialty Group Postprints 2000
INFLUENCE OF NITROGEN GAS AND OXYGEN SCAVENGERS ON FADING AND COLOR
CHANGE IN DYED TEXTILES
Blue Wool Lightfastness Standards is achieved by fastness properties and was included to provide a
blending wool fi bers that were fi ber dyed using a dye likely to show the infl uences of light and po-
fugitive dye (ErioChrome Azurole B-C.I. Mor- tentially of the low-oxygen atmospheres within
dant Blue 1) with wool fi bers that were fi ber dyed the 90-day exposure period. At the University of
using lightfast dye (Indigosol Blue AGG-C.I. Sol- Nebraska—Lincoln textile labs, wool fl annel was
ubilised Vat Blue 8). Blue Wool L2, the most light mordanted with alum and subsequently dyed with
sensitive fabric in the AATCC set of lightfastness fustic or turmeric according to 19th-century prac-
standards, is made from wool fi ber dyed only with tices (Hummel 1888).
the fugi tive chrome dye.
Fluorescent dyes, known to have poor lightfastness
Th e dye used for AATCC Xenon Reference Fab- properties, were included because of noticeable
ric-1 is a temperature-sensitive disperse dye— [2,4 color changes in fl uorescent colorants on paper ex-
dinitro-6 bromo-2-amino-4-(N, N-diethy-lami- posed to low-oxygen environments as reported by
no) azobenzene], which exhibits more rapid fad- Burke (1997). Two commercially available cot ton
ing at elevated temperatures. Th e fabric sub strate fabrics dyed with fl uorescent dyes were pur chased
is polyester. According to the AATCC Technical locally (So-Fro Fabrics, Lincoln, NE). Th e specif-
Manual (1996), in the temperature range between ic fl uorescent dyes used on the purchased cotton
136-154°F an increase in temperature of 9°F re- fabrics are undetermined, but may be xanthenes,
sults in an increase in total color change (Δ E*) of possibly highly substituted acid rhodamines which
4 CIELAB units for a given period of light expo- have been developed for fi ber react ive dye applica-
sure. Xenon Reference Fabric-1 was included be- tions on cotton (Wight 1998).
cause the chemical reaction that takes place when
an oxygen scavenger absorbs oxygen is exothermic. Fluorescent dyes and synthetic fi bers are twenti-
Reasoning that if the heat generated by the oxy- eth century developments that may not be found
gen scavengers was suffi ciently high, the tempera- in great numbers in current museum collections,
ture sensitive dye used on Xenon Reference Fab- but they will become more prevalent as twentieth
ric-1 might exhibit those eff ects. cen tury textiles are added. Fluorescent dyes be-
came important during World War n when used
Indigo (C.I. Vat Blue 8) was chosen because it is on sig nal fl ags and clothing. Dyes that fl uoresce
ubiquitous in both historic and contemporary tex- have been and continue to be popular for theater
tiles. Commercially available cotton denim fabric textiles such as carpets, costumes, and scenery.
dyed with indigo was obtained from Lee Apparel In addi tion, textiles for swim wear and children’s
Company (Shawnee Mission, KS). clothing have been dyed with fl uorescent dyes.
Fustic and turmeric, yellow natural dyes, were in-
2.2. REDUCED OXYGEN ATMOSPHERES
cluded in the study because historic textiles con-
taining these two natural dyes are represented Th e low-oxygen atmospheres achieved by three
in many museum textile collections. Fustic (C.I. diff erent methods, plus an ambient air atmosphere
Natural Yellow 8 and 11) was widely used prior to (serving as the control), were included in this
the 20th century and has better light-fastness prop- study. Th e low-oxygen atmospheres were achieved
erties than does turmeric (Crews 1987). Turmeric by 1) using a nitrogen gas purge; 2) a nitrogen gas
(C.I. Natural Yellow 3) is notable for its poor light- purge with an oxygen scavenger; and 3) an oxygen
Textile Specialty Group Postprints 2000 59
JUDY J. BROTT BUSS AND PATRICIA COX CREWS
Figure 1. Th e commercial packaging machine with vacuum and nitrogen purging capacity, located in the Food Processing
Center on the University of Nebraska–Lincoln campus, used to make the reduced-oxygen enclosures.
scavenger alone. All three methods for achieving Th ree replications of each of the four atmospheres
low-oxygen atmospheres were used in an attempt for each of the eight dyes for a total of 24 replicates
to determine whether or not the absence of oxy- per atmosphere was performed. Enclosures (6” x 8”
gen or the build up of heat or some other aspect x I”) for the specimens in this research were made
of the oxygen scavenger packets was responsible using a commercial packaging machine, Multivac
for reported color changes. All three methods are M855 (Multivac, Kansas City, MO). Th e commer-
used for anoxic pest control treatments. cial packaging machine (fi g. 1) was chosen to cre-
ate our sealed enclosures, over buying ready-made
Sealed enclosures for the textile specimens neces-
fi lm packages’ .or using a hand sealing process such
sary to achieve the low-oxygen atmospheres were
as a tacking iron, because the seals formed by the
made from commercially available, transpar-
commercial packaging machine were more repro-
ent fi lm, Curlon Grade 1262, Protective Pack-
ducible, uniform and secure.
aging Film, distributed by Curwood (Oshkosh,
WI). Th e fi lm was a three-layer laminate with ny- Th e equipment possesses the capacity for creat-
lon provid ing strength for the outer layer; a co- ing a vacuum and gas fl ushing of packages as they
polymer mid dle layer of ethylene vinyl alcohol move through the machine. Gas purging occurred
(EVOH), which is a polymer with very good oxy- just prior to thermal sealing of the packages. As
gen barrier prop erties; and polyethylene, a chem- packages reached the end of the line following
ically inert poly mer with good heat sealing and thermal sealing, they were checked to make sure
adhesion properties for the inner layer. Charles ^ oxygen scavenger sachets and specimens were
Selwitz and Shin Maekawa describe EVOH in not touching. Th e gas used for this research was
their book Inert Gases in the Control of Museum dry nitrogen (99.9%). During the packaging pro-
Insect Pests (1998) as having extremely low-oxy- cess, fi lm from the bottom roller was heat molded
gen perme ability. Th ey list it among the top three to a specifi ed shape and size. Th e sealing tempera-
oxygen barrier fi lms. ture was 125°C. Th e packaging line could be start-
ed and stopped to insert dyed fabrics and oxygen
60 Textile Specialty Group Postprints 2000
INFLUENCE OF NITROGEN GAS AND OXYGEN SCAVENGERS ON FADING AND COLOR
CHANGE IN DYED TEXTILES
gen atmosphere created using a scavenger only. An
Ageless ZPT-100 sachet was placed in each pack-
age with the reduced-oxygen atmosphere cre ated
using both a nitrogen gas purge and an oxygen
scavenger.
2.3. VERIFICATION OF REDUCED
OXYGEN ATMOSPHERES
To verify that a reduced-oxygen atmosphere was
achieved initially, we used gas chromatography.
A Perkin Elmer 880 Gas Chromatograph, Mod-
el 008-0686, hot wire thermal conductivity detec-
Figure 2. Dyed specimens being randomly placed onto the
tor with Hayesep-D column for detecting nitro-
packaging machine’s conveyor belt prior to entry into the
gen and oxyg en, was used to verify that the desired
machine’s fi lm molding and heat sealing chamber.
nitrogen level (99-99.9%) and the reduced-oxygen
scavenger packets by hand according to a pre- level (less than 1%) was achieved. Gas was with-
determined work plan. Ability to stop the machine drawn from packages using a Hamilton Gas Tight
during processing allowed for randomization of #1725 syringe, 205 μl capacity.
specimens (fi g. 2).
Numerous trials on the packaging machine fol-
Ageless ZPT (Mitsubishi Gas Chemical Com- lowed by chromatographic analyses were carried
pany, New York) was the oxygen absorber se- out to ensure that the desired low-oxygen atmos-
lected for this research. As oxygen is absorbed, pheres were achieved on the packaging equipment
an exother mic chemical reaction takes place. Al- before the experimental packages were produced.
though the generated heat reportedly does not Gas chromatographic analyses were completed
produce a harm ful build-up within the enclo- on at least three randomly selected packages repre-
sure (Grattan and Gilberg 1993), the heat gener- senting each atmosphere and each of the three rep-
ated makes the pack ets quite warm to the touch lications initially. More than 36 randomly selected
and for this reason, it is recommended that the packages were analyzed on the fi rst day of the ex-
oxygen absorber sachets not be placed in con- posure period to confi rm that the level of oxygen
tact with objects to eliminate any coincidental ef- was less than 1% and that the packages with ambi-
fect (Gilberg and Grattan 1994). Calculations ent air contained 20% oxygen. Analyses confi rmed
for determining the amount of oxygen absorb- that tested packages contained no meas urable ox-
er were carried out according to the method re- ygen, except for those fi lled with air. Chromato-
ported by Daniel (1993) for a “static system” and graphic analyses were completed on another set
verifi ed by a representative of Mitsubishi (Wata- of randomly selected packages at the conclusion
nabe 1997). Th e Ageless ZPT sachets are desig- of the 90-day exposure period to con fi rm that the
nated ZPT-100, ZPT-200, ZPT-1000, etc., to desired atmospheres were maintained through-
indicate the milliliters of oxygen with which a sin- out the exposure period. To provide addi tional
gle packet will react. An Ageless ZPT-200 sachet verifi cation that the desired low-oxygen lev els
was placed in each package with the reduced-oxy- were maintained throughout the exposure peri-
Textile Specialty Group Postprints 2000 61
JUDY J. BROTT BUSS AND PATRICIA COX CREWS
od, all of the packages from the scavenger-only at- specimens in a cardboard box lined with black
mosphere (replication one) were analyzed and all polyethylene and storing them in the same room
packages were found to contain 2% or less oxy- as the other specimens.
gen at the end of the 90-day exposure period. Th e
sealed packages containing the scavenger only were
2.5. COLOR EVALUATION
thought to be the most likely to fail to main tain
Instrumental color measurement was conduct-
their low-oxygen atmosphere throughout the 90-
ed according to guidelines in AATCC Evaluation
day exposure period. For that reason, those pack-
Procedure 6, Instrumental Color Measurement,
ages were selected for additional verifi cation. It ap-
using a HunterLab LabScan® 6000 Spectro-
peared that there was some leakage, as might be
colorimeter with 0°/45° optical sensor and a one-
expected because it is virtually impossible to cre-
inch area of view. Specimens were present ed to the
ate an oxygen-free container using a fl exible barri-
colorimeter immediately as individual packages
er fi lm; however, the oxygen level remained 2% or
were opened. Specimens were backed with suffi -
less after 90 days. So the reduced-oxygen level was
cient layers of the same material until light could
maintained in the packages during the extended
no longer penetrate. Th e number of backing lay-
exposure period.
ers varied depending on the fabric— more lay-
ers were required for the cotton than for the wool
2.4. EXPOSURE CONDITIONS
specimens. Color diff erence was meas ured on all
Ninety days was selected as the time period for test specimens at the conclusion of the 90-day ex-
this experiment. While much longer than re- posure period. Total color change (Δ E*) was cal-
quired for eff ective pest control treatments, 90 culated, using the CIE 1976 L*a*b* equa tion for
days reasona bly approximates a common exhibi- total color change, with illuminant D65 and 10°
tion period for sensitive textiles. Two light condi- observer. Four repeated measurements were per-
tions were cho sen for this study—absence of light formed per specimen rotating 90° after each mea-
and presence of continuous light—to determine surement. Since there were three replicate speci-
whether or not dyed textiles responded similarly mens, the mean colorimetric value for each dye and
to low-oxygen atmospheres in both darkness and atmosphere is an average of 12 measure ments.
light. Th e light level, 320 lux, was chosen in an ef-
fort to expose specimens to a suffi cient amount When total color change, as measured instru-
of light to induce a color change during the 90- men-tally, was greater than 1 Δ E* unit (the mini-
day exposure period for comparison to the speci- mum amount of color diff erence regarded as visu-
mens exposed to the various atmospheres in dark- ally perceptible), visual evaluations of color change
ness. Additionally, 320 lux is a common light level were completed according to AATCC Evaluation
found in work rooms where objects may be kept Procedure 1, Gray Scale for Color Change. Visual
when being treat ed for pest infestations. Th e light ratings were assigned according to a scale from 1
source was over head fl uorescent lights in a win- to 5, with 5 corresponding to no visually percepti-
dowless room. Absence of light simulated object ble change and 1 corresponding to the greatest
storage in a closed container or cabinet where light overall amount of color change.
is absent even if the storage room itself is lighted at
any time. Absence of light was achieved by placing
62 Textile Specialty Group Postprints 2000
INFLUENCE OF NITROGEN GAS AND OXYGEN SCAVENGERS ON FADING AND COLOR
CHANGE IN DYED TEXTILES
3. RESULTS AND DISCUSSION Scavenger). Th erefore, it appears that the exother-
mic chemical reaction of the oxygen scavengers
Th e results of both the instrumental color measure-
did not raise the temperature of the atmosphere
ments (Δ E*) and visual evaluations (Gray Scale
sur rounding the disperse-dyed polyester fabric
Ratings) are presented in Table 1. Results showed
suffi ciently to induce a visually perceptible color
that, among those specimens exposed to light, to-
change.
tal color change (Δ E*) was lowest for those held
in a reduced-oxygen atmosphere for all dyes, ex- Among the natural dyes examined in this study,
cept the pink fl uorescent dye. Th e pink fl uorescent turmeric exhibited larger amounts of color change
dye, in contrast, exhibited greater color change in a (larger Δ E*) in all atmospheres than did fustic.
reduced-oxygen atmosphere than in air when held Th is is not surprising because the poor lightfast-
in the presence of light. ness of turmeric is well known (Crews 1987; Pad-
fi eld and Landi 1966; Society of Dyers and Co-
When the dyed specimens were held in total dark-
lourists 1971). Th e natural dyes, when exposed to
ness, none of the dyes (including the pink fl uores-
continuous light, exhibited less fading in the low-
cent dye) exhibited visually perceptible color
oxygen atmospheres than in ambient air. Th is in-
changes regardless of atmosphere. Consequently,
strumentally measured color diff erence was just
further analysis of the data are focused on the ef-
visually perceptible for the fustic exposed to air in
fects of atmosphere (ambient air versus low-oxy-
the presence of light; the color changes were more
gen) in the presence of light on the selected dyes.
noticeable in all turmeric specimens. Fustic: Gray
Scale (GS) rating = 5 (no change) for all three re-
See Table 1 on following page.
duced-oxygen atmospheres versus GS rating = 4.5
for air. Turmeric: GS rating = 4-4.5 for all three
Among the non-fl uorescent synthetic dyes exam-
reduced-oxygen atmospheres versus 3.5 for air
ined in this study, results show that all of these
(see Table 1).
dyes exhibited almost no color change at the con-
clusion of the 90-day exposure period in either the
In contrast to all other dyes included in the study,
light or the dark. Among this sub-group of dyes.
the pink fl uorescent dye exhibited larger amounts
Blue Wool Lightfastness Standard L2 and Xenon
of fading or color change in a low-oxygen atmos-
Reference Fabric exhibited the largest amounts
phere in the presence of light than in ambient air.
of color change in ambient air. Both Blue Wool
Th e accelerated fading observed in the reduced-
Lightfastness Standard L2 and Xenon Reference
oxygen atmospheres was quite noticeable with GS
Fabric exhibited slightly less color change (lower
ratings for the reduced-oxygen atmosphere rang-
Δ E* values) in a low-oxygen atmosphere than in
ing from 1.5-2.5 whereas the GS rating for air =
ambient air. However, this diff erence in amount of
4.5 (see Table 1). Th e yellow fl ourescent dye, on
total color change was not visually perceptible.
the other hand, exhibited about the same amount
of color change in the reduced-oxygen atmo-
It is interesting to note that the Xenon Reference
spheres as it did in ambient air. Th e reduced-ox-
Fabric, known to be temperature sensitive, did
ygen atmosphere neither reduced nor accelerated
not exhibit any visually perceptible color chang-
fading in the yellow fl ourescent dye.
es in the presence of Ageless oxygen absorbers (Δ
E* = 0.1-Scavenger only and 0.2-Nitrogen +
Textile Specialty Group Postprints 2000 63