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AcrylonitrilecontentasapredictorofthecaptanpermeationresistancefordisposablenitrilerubberglovesARTICLEinJOURNALOFAPPLIEDPOLYMERSCIENCEFEBRUARY2007ImpactFactor:1.64DOI:10.1002/app.25349

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Acrylonitrile Content as a Predictor of the CaptanPermeation Resistance for DisposableNitrile Rubber Gloves

R. N. Phalen,1 S. S. Que Hee,2 W. Xu,2 W. K. Wong2

1Department of Environmental Health Sciences and University of California at Los AngelesCenter for Occupational and Environmental Health, School of Public Health,650 Charles Young Jr. Drive South, Los Angeles, California 90095-17722Department of Health Science and Human Ecology, California State University San Bernardino,5500 University Parkway, San Bernardino, California 924072397

Received 29 April 2006; accepted 28 August 2006DOI 10.1002/app.25349Published online in Wiley InterScience (www.interscience.wiley.com).

ABSTRACT: The aim of this study was to determine whetherthe acrylonitrile (ACN) content inuences the permeation re-sistance of disposable nitrile rubber (NBR) gloves to aqueoussolutions of the pesticide captan. Attenuated total reectance/Fourier transform infrared (ATRFTIR) spectrophotometryat 2237 6 5 cm1 was used to measure the ACN contents ofseven different NBR gloves. The ACN contents of the glovesranged from 12.7 to 29.9%. Permeation was conductedaccording to American Society for Testing and Materials(ASTM) Method F 739-99a with a gas chromatography/massspectrometry analysis of captan in the hexane collection liq-uid. Signicant correlations were found between (1) theACN content and mass-to-area ratio and the logarithm of thesteady-state permeation rate (SSPR; Pearson correlation coef-

cient 0.9227, p 0.05), and (2) the ACN content andmass-to-area ratio and the ASTM normalized breakthroughdetection time (NBT) at 0.25 mg/cm2 (Pearson correlationcoefcient 0.9471, p 0.05). On average, the NBT increased120 min for every 5% increase in the ACN content. The aver-age SSPR ranged from 0.002 to 0.40 mg/cm2/min, a 200-folddifference. Increasing the ACN content resulted in decreasedSSPR. ATRFTIR was useful in determining the NBR poly-mer ACN content, surface homogeneity, and potential glovechemical resistance. 2006 Wiley Periodicals, Inc. J Appl PolymSci 103: 20572063, 2007

Key words: diffusion; elastomers; FTIR; infrared spectros-copy

INTRODUCTION

The selection of appropriate chemical protective cloth-ing (CPC) relies on the assumption that batch lots andsimilar materials from different manufacturers willperform in the same manner. In contrast, studies haveindicated that manufacturer and batch-lot variabilityamong similar gloves can result in marked differ-ences in chemical permeation performance in termsof the steady-state permeation rate (SSPR) and break-through time (BT).13 Mickelson and Hall1 observedup to 10-fold differences in the BT of perchloroethy-lene through chemically resistant nitrile rubber (NBR)gloves from different suppliers. Perkins and Pool2

reported considerable intermanufacturer and batch-lot variability in the permeation of 2-ethoxyethanol

acetate through similar NBR gloves. Batch-lot vari-ability resulted in up to a twofold difference in the BTand up to fourfold differences in the cumulative masspermeated at 125 min. They found no relationshipbetween the glass-transition temperature (an indica-tor of curing) and batch-lot variability in permeationthrough these gloves. Similar evidence can be foundin the Forsberg and Keiths3 compendium of permea-tion and degradation data for CPC, in which largevariations in BTs and SSPRs are reported for differentCPC brands of similar materials.Acrylonitrile (ACN) content variation in NBR gloves

has been postulated as a factor in the variability inglove BTs and SSPRs among batch lots and differentmanufacturers.2,4 The speculation has also been madein the literature that the chemical resistance of nitrilegloves increases with increasing ACN content.5,6 Morecommonly, fuel and oil resistance has been knownto increase with increasing ACN content from about15 to 50%.710 Robertson et al.11 presented preliminarydata that indicated increasing the ACN monomercontent from 26 to 39% resulted in a twofold increasein the BT of toluene through an NBR polymer. In con-trast, Mueller12 found that for the polar solventsmethanol and methyl ethyl ketone, the permeabilityrate through NBR increased when the ACN content

Correspondence to: R. N. Phalen ([email protected]).Contract grant sponsor: Southern California National

Institute for Occupational Safety and Health (NIOSH)Education and Research Center (through a NORA grant);contract grant number: T42/CCT924019.Contract grant sponsor: Association of Schools of Public

Health (through NIOSH/CDCP grants); contract grant num-bers: S1891-21/22, RO1 03754A, T42/CCT981726.

Journal of Applied Polymer Science, Vol. 103, 20572063 (2007)VVC 2006 Wiley Periodicals, Inc.

increased from 11 to 22%, although the permeabili-ty did not increase with increasing ACN content fortwo of the six organic solvents investigated. Thus,the chemical composition and properties should beconsidered when the chemical resistance of NBRgloves is evaluated. Furthermore, similar testing withaqueous pesticide formulations such as captan [i.e.,N-trichloromethylthio-4-cyclohexene-1,2-dicarboximide(CASRN 133-06-2)] has not been conducted.Common parameters of CPC chemical permeation

performance include the normalized breakthroughdetection time (NBT) and SSPR of American Societyfor Testing and Materials (ASTM) Method F 739-99a.13 The NBT is dened as the time at which themass of the chemical permeated reaches 0.25 mg/cm2

in a closed-loop test and 0.1 mg/cm2/min in an open-loop test. The SSPR is dened as the slope of thesteady-state period (mg/cm2/min).13

The ACN content can be analyzed in NBR gloveswith infrared (IR) absorption spectrometry14,15 andwith attenuated total reectance/Fourier transforminfrared (ATRFTIR) spectrometry. In the latter, IR isused at CBN NBR bond stretching from 2200 to 2400cm1.16,17 ATRFTIR has also been used to measurethe chlorine content in latex gloves.18

For ATRFTIR, the depth of evanescent wave pene-tration (dp), at which the intensity falls to about 13.5%of its value at the surface, is wavelength-dependentand can be estimated as follows:19

dp l2pn1sin2 n122 0:5

(1)

where l is the IR wavelength of radiation, n1 is the re-fractive index of the ATR crystal, n12 is the ratio of thesample refractive index to the ATR refractive index,and Y is the angle of incidence (8).The sampling depth of the evanescent wave (ds), at

which the intensity falls to about 0.25% of its value atthe surface, can be estimated as follows:19

ds 3dp (2)

With a Y value of 458 and a refractive index of 2.42for the diamond ATR crystal, dp is about 0.81.1 mm at2250 cm1 for organic polymer materials with refrac-tive indices between 1.5 and 1.6.20 The samplingdepth is therefore about 2.43.3 mm for such poly-mers. Popli and Dwivedi21 indicated the importanceof an adequate sampling depth by showing potentialpolymer nonuniformity up to a distance of 0.5 mmfrom the surface.The hypothesis of this study is that permeation re-

sistance to the fungicide captan will increase withincreasing ACN content. The specic aims were to (1)measure the ACN content in different disposableNBR glove brands and batches with ATRFTIR, (2)conduct ASTM Method F 739 permeation testing ofthe pesticide captan through each glove material todetermine the NBT and SSPR, and (3) perform multi-ple regression analysis of the ACN content, thickness,density, and mass-to-area ratio versus NBT and SSPR.

EXPERIMENTAL

Gloves and chemicals

The gloves were disposable, powder-free NBR examgloves and clean-room gloves obtained from FisherScientic (Tustin, CA) and Life Guard (City of Indus-try, CA). The glove brands tested were Ansell, BestManufacturing, Life Guard, Microex, and KimberlyClark. The tested brands were coded as gloves AF.The glove characteristics are presented in Table I. Onthe basis of previous ASTM Method F 739 permeationtests with captan, the palm regions of the gloves weretested.17 Poly(acrylonitrile-co-butadiene) reference ma-terials with ACN contents of 10, 1922, 3035, and3739% (w/w) were obtained from SigmaAldrich(St. Louis, MO). The average weight percentage of ac-rylonitrile (ave-ACN) for each reference material wasused to prepare a standard curve.Analytical grade captan (99% purity) was acquired

from Chem Service, Inc. (West Chester, PA). Captan50-WP (48.9 wt % captan, 1.1% related derivatives,

TABLE IDisposable NBR Gloves

Glove Label descriptionMeasured

thickness (mm)a

Measureddensity(g/cm3)b

A Medical nitrile exam glove, powder-free 0.126 6 0.002 0.89 6 0.03B, lot 1 Powder-free nitrile exam glove 0.113 6 0.002 1.08 6 0.03B, lot 2 Powder-free nitrile exam glove 0.119 6 0.002 1.14 6 0.04C Powder-free nitrile exam glove 0.115 6 0.002 0.99 6 0.03D Powder-free nitrile exam glove 0.109 6 0.005 0.96 6 0.03E Powder-free nitrile exam glove 0.119 6 0.004 1.07 6 0.06F Nitrile clean-room glove, powder-free 0.107 6 0.003 0.98 6 0.05

a n 60.b n 6.

2058 PHALEN ET AL.

Journal of Applied Polymer Science DOI 10.1002/app

and 50% inert ingredients) was obtained from MicroFlo Corp. (Memphis, TN). Certied ACS Plus nitricacid [used to prepare 10% (v/v) nitric acid to cleanglassware] and Optima 2-propanol were from FisherScientic. Type I water from aMillipore (Marlborough,MA) Super-Q water deionizing system was used toprepare solutions of constant relative humidity (RH).Zero air (ultrahigh purity) and helium (99.999%) werefrom Air Products (Long Beach, CA).A sodium dichromate (99.0%) saturated salt solution

was prepared in Super-Q water to generate a 55 6 1%RH atmosphere within a Pyrex vacuum desiccator(Fisher Scientic).22 RH was measured with a calibratedControl Co. ThermoHygro recorder (Fisher Scientic).

Equipment

IR spectra were obtained with a TravelIR portableATRFTIR analysis system (Smiths Detection, Dan-bury, CT), a single-beam spectrophotometer operatedwith SensIR QualID 1.40 and Omnic 6.0a softwarecontrolled by Windows XP. The crystal was a dia-mond in a single-reection, horizontal ATR mode.The unit used a zinc selenide beam splitter. The spec-tral range was 4000650 cm1. The number of scanswas optimized at 32 scans at a resolution of 4 cm1 toaccount for the effects of background carbon dioxideand water on the reectance spectra. Between eachsample scan, the ATR crystal was cleaned with ace-tone and dried for 30 s, and a new background wascollected under the same spectral conditions. A read-ing of 6 on the load pressure indicator ensured opti-mum intimate contact with the ATR crystal and wasequal to 82 6 6 kg/cm2, as measured with a modelBGI calibrated, direct-reading, portable force indica-tor with a model SBC 100 compression force sensor(Mark-10, Hicksville, NY).Permeation testing was performed with an ASTM-

type I-PTC-600 permeation cell (Pesce Lab Sales,Kennett Square, PA). The moving-tray shaker waterbath used for the simultaneous immersion of the per-meation cells was a Fisher Scientic model 127. Threecopper-metal tubes (35 cm 1.5-cm o.d. 1.3-cmi.d.) were mounted across the two rails of the shakerafter 1-mm-wide grooves were hacksawed into thebars and emery paper was used to smooth jaggededges. Three-prong clamps allowed the suspension ofthe permeation cells above and in the water asdesired. Vernier calipers (Mitutoyo, Japan) facilitatedthe measurement of the glove dimensions, as did adigital micrometer screw gauge (L.S. Starrett Co.,Athol, MA) for the glove thicknesses.

Glove density and thickness

The glove density was measured with the glove thick-ness, surface area, and mass data for 3.81-cm (1.5-in.)-

diameter disks cut from the palm region of six sam-ples for each glove. The glove samples were condi-tioned overnight at 55 6 1% RH before the thicknessand mass measurements were collected. The glovedisks were weighed with a Mettler AE 260 analyticalbalance (Fisher Scientic). Ten thickness measurementswere taken for each glove sample.

ACN content

The poly(acrylonitrile-co-butadiene) reference materi-als were sliced into thin sections, conditioned over-night at 55 6 1% RH, and analyzed by ATRFTIR. The10% ACN reference material was liquid, and a 100-mLdrop was placed on the ATR crystal and covered it,without applied pressure. At least ve measurementswere made for each reference material. IR reectanceanalysis was performed at 2237 6 5 cm1, the absorb-ance maximum for the CBNNBR bond stretching (Fig.1). As indicated in Figure 1, the CBN NBR region isfree from interference for both the glove and referencematerial. In addition, this region is free from interfer-ence fromwater and carbon dioxide in air.23,24

The outer and inner glove surfaces were measuredto assess interferences from releasing agents andexcess coagulants expected to be present on the surfa-ces. The outer surface often contained textured, roughsurfaces. Thus, the inner surface provided a smoothsurface for ATRFTIR analysis.Five gloves were selected randomly out of a box,

and the inner surfaces were rinsed with 25-mL vol-umes of hexane ve times to remove surface residues,as conrmed by an ATRFTIR analysis of the cleanedsurfaces. The palm region was cut from the gloves,air-dried, and conditioned overnight at 55 6 1% RH.Reectance spectra (Fig. 1) were collected at ve ran-

Figure 1 Sample IR reectance spectra (from 4000 to 600cm1) of glove F and the poly(acrylonitrile-co-butadiene)reference material with an ave-ACN value of 32.5%. TheCBN NBR bond stretching region is indicated by thearrows.

CAPTAN PERMEATION RESISTANCE 2059


dom locations of each sample and reference material.Mean absorbances and within-glove and between-glove precisions were compared at each of these ab-sorbance maxima.

Permeation experiments

The detailed procedure used in this study is providedelsewhere25,26 and is based on ASTM Method F 739-99a.13 In summary, glove materials were conditionedovernight in a desiccator with 55 6 1% RH. The mate-rial was held between two Teon gaskets and thePyrex chambers of the I-PTC-600 permeation cell by auniform torque as specied by the manufacturer. Avolume of 217 mg/mL of the captan formulation inwater was equilibrated to 30.0 6 0.58C for 30 min,and this was followed by vortex mixing for 30 sbefore 10 mL was pipetted into the challenge side ofeach permeation cell. The three cells were immersedin the water bath at 30.0 6 0.48C with a horizontalshaking speed of 26.1 6 0.4 cm/s to minimize theconcentration gradients. This was conrmed by priorobservation of the challenge solution opacity at differ-ent shaker speeds and permeation cell orientations.At permeation time intervals of 30, 60, 90, 120, 240,360, and 480 min, a 100-mL aliquot of the collection so-lution was removed for analysis by gas chromatogra-phy/mass spectrometry (GCMS). An analysis of thecaptan was performed with a previously describedGCMS method.20

Quality assurance procedures included tests forleaking of the assembled permeation cell and chal-lenge- and collection-side solvent back-diffusion asoutlined elsewhere.25,26

Statistical analyses

We used Student t, analysis of variance (ANOVA), cor-relation, and regression analyses in our statistical anal-yses and, when appropriate, nonparametric meth-ods. The results were deemed signicant if the p valuewas not larger than 0.05. In our study, at least triplicatesamples were used to dene arithmetic means, stand-ard deviations (SD), and coefcients of variation (CV).Linear regression analyses allowed the calculation ofslopes, y intercepts, corresponding SDs, Pearson corre-lation coefcient (r) values, and p values. Multipleregression, correlation, and ANOVA analyses wereperformed with Stata version 9 (StataCorp, CollegeStation, TX). Tests for the normal distribution of indi-vidual variables were conducted with the ShapiroWilks, ShapiroFrancia, and skewness/kurtosis nor-mality tests. When necessary, the transformation ofvariables was evaluated with ladders of powers, nor-mal quantile plots, and BoxCox regression analyses.

RESULTS AND DISCUSSION

ACN content

The IR reectance results for the poly(acrylonitrile-co-butadiene) reference materials produced a linearstandard curve between ave-ACNs of 10 and 38%with r 0.996 (p 0.05). Figure 2 shows the spectralregion between 2200 and 2240 cm1. The maximumabsorbance at 2237 6 5 cm1 was plotted versus theave-ACN (w/w). The standard curve was then usedto determine the ave-ACN within the NBR gloves.The maximum absorbance of the glove samples at

2237 6 5 cm1 was similar to that of the referencematerials, as shown in Figure 3, which uses the same

Figure 2 Sample IR reectance spectra of the CBN NBRbond stretching region for poly(acrylonitrile-co-butadiene)reference materials with specic ave-ACN values of 10,20.5, 32.5, and 38%. The IR reectance measurements weretaken at 2237 6 5 cm1.

Figure 3 Sample IR reectance spectra of the CBN NBRbond stretching region for disposable, powder-free NBRgloves A, B-1 (glove B, lot 1), B-2 (glove B, lot 2), E, and F. TheIR reectance measurements were taken at 22376 5 cm1.

2060 PHALEN ET AL.


scale (cm1) as Figure 2. The ave-ACN value wassignicantly different among all glove samples (p 0.05), including the two glove B lots (Table II). Clean-room glove F contained 3458% more ACN than theother NBR exam gloves. This glove was selectedbecause the label claim indicated that plasticizers,pigments, and llers were not present in the glove,and this increased the available ACN content.The measured ave-ACN values within the glove

samples ranged from 12.7 to 29.9% (Table II), over atwofold difference. In contrast, Perkins and Pool2

reported an ACN monomer content of 2639%, beforethe addition of plasticizers, in thicker (3.8-mm) chem-ically protective NBR gloves. Robertson et al.11 alsoreported ACN monomer contents ranging from 26 to39% for NBR lattices used for gloves of unspeciedthicknesses. The amounts of plasticizers and otheradditives were not reported in either of these studies.With the clean-room glove F excluded, the ACN con-tents of the disposable NBR exam gloves ranged from12.7 to 21%, and this indicated (1) varying ACNcontents of the NBR latex among the gloves and/or(2) variable plasticizer, pigment, and additive con-tents among these similar gloves.The within-glove CVs for ave-ACN values for dif-

ferent regions of the glove palm were less than 10%

for all gloves except glove D. The average within-glove CV for glove D was 17% (range 1.231%),and the between-glove CV was 24%. In contrast, allother between-glove CVs were less than 6%. For mul-tiple regression analyses, an F test was conducted totest the equality of variances between all gloves.27

Glove D did not meet the requirements for the homo-geneity of variances (p 0.05) and was excludedfrom the multiple regression analyses. These resultsindicated poor manufacture or lot quality for glove D.

Permeation testing

The results of the 8-h permeation tests are summarizedin Table III. In general, the NBT increased and the SSPRdecreased with increasing ACN content. Clean-roomglove F with the highest ACN content had the highestNBT at 420 6 120 min and the smallest SSPR at 0.00176 0.0015 mg/cm2/min. In contrast, glove A with thelowest ACN content had the lowest NBT at 35.9 63.6min and the largest SSPR at 0.406 0.10 mg/cm2/min.Excluded glove D had the lowest NBT value of all

the glove samples and the second highest SSPR, de-spite an ave-ACN value of about 20%. The glove qual-ity and uniformity appeared to affect the glove perme-ation performance. Previous studies have used ATR

TABLE IIACN Contents for NBR Gloves

Glove Ave-ACN (%)a

Averagewithin-gloveCV (%)a

Within-gloveCV range (%)

Between-gloveCV (%)a

A 12.7 6 0.5 3.2 0.55.9 3.9B, lot 1 14.8 6 0.7 4.2 0.88.5 4.7C 15.6 6 0.8 2.4 0.56.9 5.1B, lot 2 16.9 6 0.7 3.0 1.34.3 4.1E 18.0 6 0.7 3.4 0.69.3 3.7D 19.7 6 4.7 17 1.231 24F 29.9 6 1.1 2.0 0.55.3 3.7

a n 25.

TABLE IIIACN Contents and Captan Permeation Data for Disposable NBR Glovesa

Glove Ave-ACN (%) NBT (min)b SSPR (mg/cm2/min)c AD (g/cm2)

A 12.7 6 0.5 35.9 6 3.6 0.40 6 0.10 11.21 6 0.01B, lot 1 14.8 6 0.7 75.2 12.6 0.06 6 0.03 12.20 6 0.01C 15.6 6 0.8 59.7 6 13.4 0.10 6 0.08 13.57 6 0.01B, lot 2 16.9 6 0.7 114 6 43 0.10 6 0.04 11.38 6 0.01E 18.0 6 0.7 126.6 6 2.2 0.06 6 0.03 10.46 6 0.01D 19.7 6 4.7d 32.6 6 3.4 0.38 6 0.13 12.73 6 0.02F 29.9 6 1.1 420 6 120 0.0017 6 0.0015 10.49 6 0.01

a ASTM Method F 739 permeation testing was conducted with an aqueous-emulsion,217 mg/mL WP-50 captan formulation and with hexane as a collection solvent.

b Time at which 0.25 mg/cm2 captan was rst detected in a closed-loop permeationtest.

c Linear slope of the permeation curve.d The within-glove CV ranged from 1.2 to 31%. All other glove brands and lots had

CVs lower than 10%.



FTIR to assess the surface composition and homogene-ity of acrylate and methacrylate copolymer blends,21,28

showing that IR reectance can be used to assess poly-mer homogeneity for quality assurance. In this study,ATRFTIRwas useful in determining the uniformity ofthe ACN content within the NBR glove materials.The average SSPR ranged from 0.002 to 0.40 mg/

cm2/min, a 200-fold difference. When clean-roomglove F, with a high ACN content, was excluded,up to a sevenfold difference in the SSPR was thenobserved between the exam gloves. A 1.7-fold differ-ence in the SSPR existed between the two glove Blots. For the average NBT, the differences were 12-,3.5-, and 1.5-fold, respectively. These results werecomparable to the previously reported 10-fold differ-ences in the BT between glove brands and 2-fold dif-ferences in the BT between batch lots.1,2

Multiple regression analysis

Tests for normality indicated that the transformationof the SSPR, thickness, and density variables wasneeded to meet the assumptions for regression analy-ses. Within the BoxCox family of transformations,the log transformation of the SSPR was selected asoptimal with Stata. The resulting plot of the logarithmbase 10 of the SSPR, called here log SSPR, versus theave-ACN value was linear with r 0.9216 (p 0.05).The thickness and density variables were not easilytransformed. However, the product of the thicknessand density resulted in a measure of the mass-to-arearatio (g/cm2), called here the area density (AD), thatwas normally distributed. Thus, nal regression anal-yses were performed for both the NBT and log SSPRversus the glove ave-ACN and AD values.A signicant inverse correlation existed between

the NBT and log SSPR with r 0.9031 (p 0.05). Incomparison, a similar correlation between the NBTand log SSPR has been observed for alkylbenzene iso-mers through chemically protective NBR gloves withr 0.69 (p 0.05).29 Also, a correlation between theNBT and lag time has been reported for xylene iso-mers through chemically protective NBR gloves withr 0.748 (p 0.025).30 Similarly, these studies allused hexane as a collection solvent and closed-looppermeation tests with no indication of degradation orswelling. This type of relationship between the NBTand SSPR may not exist for other types of permeationsystems, as described in ASTM Method F 739.13

A signicant correlation was also present betweenthe thickness and log SSPR with r 0.8289 (p 0.05).Assuming Ficks rst law is obeyed, we can relate thesquare of the thickness to the lag time:31

Lag time L2=6D (3)where L is the thickness (cm) and D is the diffusioncoefcient (cm2/s). From the linear plot of the mass

permeated per unit of area (mg/cm2) versus time (s),the lag time is related to the SSPR by the following ex-pression:

Lag time b=SSPR (4)

where b is the y intercept (mg/cm2) of the linearsteady-state plot. Substituting for the lag time, theSSPR is related to the thickness:

SSPR 6bD=L2 (5)

The resulting correlation between log SSPR and theinverse square of the thickness was r 0.8374 (p 0.05), which suggests that the product of the y inter-cept and diffusion coefcient did not vary signi-cantly between the different glove permeations forcaptan. Further research is needed to evaluate therelationships between the SSPR, lag time, thickness,and diffusion coefcient.The correlation between the NBT and thickness was

r 0.6626 (p 0.05). In this model, the thickness onlyexplained 44% of the variance. The range of thicknesseswas narrow, and the thickness was not normally dis-tributed. The thickness was not used as a variable inmultiple regression analyses. No signicant correla-tions were found between the density and the parame-ters thickness, ave-ACN, NBT, and log SSPR.Multiple regression analyses resulted in signicant

correlations (p 0.05) between

1. The ave-ACN value and AD inversely with logSSPR.

2. The ave-ACN value and AD directly with theNBT.

The ave-ACN value and AD were correlated with logSSPR with r 0.9227 (p 0.05):

log SSPR 0:136 ave-ACN 0:050AD 1:71 6

When AD was excluded, the correlation between ave-ACN and log SSPR was still robust, with r 0.9216 (p 0.05). With data provided by Brun et al.32 for NBRmembranes, a correlation (r 0.9993, p 0.05) wasobserved with ACN contents ranging from 51 to 75%with the liquidgas permeation of butadiene. Compa-rable studies using liquidliquid permeation testingand lower ACN contents were not available.The ave-ACN and AD values were correlated with

the NBT with r 0.9471 (p 0.05):

NBT 24:4 ave-ACN 122AD 447 (7)

This indicated that ave-ACN and AD accounted forabout 90% of the NBT variation. On average, the NBT

2062 PHALEN ET AL.


increased by about 120 min for every 5% increase inave-ACN. Robertson et al.11 reported a twofoldincrease in the BT associated with a 13% increase inACN for the permeation of toluene through an NBRpolymer. Thus, the ACN content of an NBR polymeris an important factor and should be included in theCPC selection process when chemical permeation andbreakthrough are expected to occur.Although the ACN content and AD were shown in

this study to play signicant roles in the permeationresistance of commercial NBR gloves, with the modelaccounting for about 8590% of the variation, addi-tional factors may also affect NBR glove performance.The addition of llers, pigments, and plasticizers willreduce the ACN content. Thus, further research isneeded to determine the inuence of these parame-ters, as well as the properties of the curing process(e.g., glass-transition temperature and crosslinkingdensity)2,33 and other NBR properties that can bemeasured with standardized tests.34,35 It is to benoted, however, that Perkins and Pool23 did not nda relationship between the glass-transition tempera-ture and batch-lot variability in permeation throughchemically resistant NBR gloves.

CONCLUSIONS

Over a twofold difference in the ACN content wasobserved for the disposable NBR gloves examined.The permeation results indicate that the ACN contentplays a signicant role for both the SSPR and NBTduring captan permeation through NBR gloves.Increasing the ACN content resulted in longer NBTsand decreased the SSPR. Regression analyses alsorevealed that the ACN content explained a signicantamount of the variation in both the NBT and SSPRbetween disposable NBR glove brands and batch lots.In addition, ATRFTIR was useful in determiningNBR polymer surface homogeneity and has potentialapplication in quality assurance testing during themanufacturing process and by end users in the CPCselection process. Further research is needed to assessthe inuence of the ACN content on the permeationof different chemical classes through NBR gloves andother CPC. In addition, further research is needed toexamine the inuences of other chemical and me-chanical properties of NBR gloves on chemical per-meation.

References

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4. Forsberg, K.; Olsson, K. G.; Carlmark, B. In Performance ofProtective Clothing; Barker, R. L.; Coletta, G. C., Eds.; Ameri-can Society for Testing and Materials: Philadelphia, 1986;p 59.

5. American Dental Association. J Am Dental Assoc 2003, 134,1256.

6. Jester, R. C. Chemical Glove Selection, Document SF-1. http://www.cdc.gov/nasd, accessed August 2005.

7. Dunn, J. R.; Psterer, H. A.; Ridland, J. J. Rubber Chem Tech-nol 1979, 52, 331.

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Liquid Elastomers Conference; Rapra Technology: Shrewsbury,United Kingdom, 2001; p 61.

12. Mueller, W. J. Rubber Age 1957, 81, 982.13. Standard Test Method for Resistance of Protective Clothing

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