Ind. E n g . Chem. Res. 1994,33, 2836-2839
2836
Identification of Chemical Contamination on a Rayon Yarn Using Extraction and Infrared Spectral Subtraction Charles Q. Yangt Department
of
Textiles, Merchandising and Interiors, The University of Georgia, Athens, Georgia 30602
Chemical contamination on fibers, yarns, and fabrics is a problem commonly encountered in the textile industry. Infrared spectroscopy has been used to identify chemical contaminants on textile materials by either extracting a contaminated material with a n organic solvent and analyzing the extract or by applying a spectral subtraction technique. However, the existence of a mixture of chemicals on textile materials makes it difficult to determine the exact nature of contaminants using those methods. In this research, we extracted a contaminated 100%rayon yarn using one polar solvent and one nonpolar solvent. By subtracting the infrared spectrum of the nonpolar solvent extract from the spectrum of the polar solvent extract, we identified ethylene terephthalate oligomer as a polar chemical contaminant on the yarn. Introduction Chemical contamination on textile fibers, yarns, and fabrics frequently occurs during manufacturing, finishing, and dyeing of textile materials. Infrared spectroscopy has been one of the most widely used techniques for qualitative analysis of textile materials (O’Connor, 1968;Berni and Morris, 1983). Traditionally, chemicals on textile fibers, yarns, and fabrics have been identified by extracting a textile material with an organic solvent, followed by analyzing the extract using infrared spectroscopy (Morath, 1968; O’Connor, 1972). Spectral subtraction also has been used to identify finishes, sizing agents, and surface oxidation on textile materials (Morris et al., 1984; Koenig, 1985; Yang and Bresee, 1987; Grieble and Gardner, 1989; Morris, 1991; Yang, 1992). An infrared spectrum of the extract of a contaminated textile material or the difference spectrum between the spectrum of a contaminated textile material and the spectrum of a clean one can be used as the basis for identification of a chemical contaminant. However, chemical contamination may include more than one compound. Textile fibers, yarns, and fabrics may also contain chemical additives such as finishes. The existence of a mixture of chemicals on a contaminated textile material makes it extremely difficult to use extraction or spectral subtraction method to determine the exact nature of the contaminant. In this research, we identified a polar chemical contaminant on a rayon yarn by the combination of solvent extraction and spectral subtraction. Experimental Section Infrared Spectroscopy Analysis. A Nicolet 510 FT-IR spectrometer with a Specac “selector” diffuse reflectance accessory was used to collect the infrared spectroscopy data. The infrared spectra of the rayon yarns were collected with the diffuse reflectance access o r y and presented at absorbance mode (-log RIRo). Potassium bromide powder was used to produce a background diffuse reflectance spectrum. The transmission infrared spectra of all the extracts were obtained using a zinc selenide window. A dyed rayon yarn was first extracted with an organic solvent at room temperature for 30 min. The extract was cast on a zinc
’ E-mail address:
[email protected].
selenide window and the solvent evaporated at room temperature. The amount of the extract cast on the window was adjusted so that the most intense band in the infrared spectrum of the extract had a transmittance of approximately 20%. A transmission spectrum of ethylene terephthalate oligomer was obtained similarly after dissolving oligoester in methylene chloride. Resolution for all the infrared spectra was 4 cm-l, and there were 100 scans for each spectrum. No smoothing functions were used. A Nicolet PCAR Search software was used to perform spectral searches. Materials. A 100%single-ply high tenacity filament rayon yarn with 144 denier and 3 denier per filament (the natural yarn) was used to make a 2-ply bright filament yarn. The yarn was scoured with water at 70 “C and then dyed with a fiber reactive dye in a packagedyeing machine. The dyeing machine had previously been used to pressure-dye a polyester yarn. Both the natural yarn and the dyed yarn were industrial samples. Oligoester was collected in the dyeing machine after the dyeing machine had been used for pressure-dyeing a polyester yarn. The solvents used for extraction were reagent-grade chemicals. Results and Discussion Particles of an unknown nature were observed on the surface of a dyed rayon yarn with optical microscopy. The spectra of the natural yarn and the dyed yarn are presented in Figure 1, parts A and B, respectively. A weak carbonyl band at 1740 cm-l is shown in the spectrum of the dyed yarn (Figure 1B). The infrared spectroscopy data indicate that the particles on the dyed yarn were a chemical contamination containing carbonyl. We subtracted the spectrum of the natural yarn (Figure 1A) from the spectrum of the dyed yarn (Figure 1B). Little information was provided in the difference spectrum due to the strong absorption of cellulose. When we extracted the dyed yarn with methylene chloride, the 1740 cm-l band disappeared in the infrared spectrum (Figure lC), revealing that the chemical contamination on the yarn is soluble in methylene chloride. The infrared spectrum of the methylene chloride extract of the dyed yarn (Figure 2A) shows two strong bands at 2918 and 2849 cm-l due to the asymmetric and symmetric stretching modes of methylene and a weak band at 2957 cm-’ due to the asymmetric stretching mode of methyl. The overlapping bands
0 1994 American Chemical Society
Ind. Eng. Chem. Res., Vol. 33, No. 11, 1994 2837 9
V
n
4000
3000
2000
1000
400
WAVENUMBERS (cm-') Figure 1. Diffise reflectance infrared spectra: (A) natural yarn; (B)dyed yarn; ( C ) dyed yarn, after extraction with methylene chloride.
around 1464 cm-l are due t o the bending modes of methylene and methyl. Obviously, saturated hydrocarbon groups constitute the majority of the functionality in the methylene chloride extract. A carbonyl band at 1740 cm-l and a broad band at 1264 cm-l are also present in the spectrum (Figure 2A). A computerized spectral search to compare Figure 2A with the spectral library failed to provide meaningful information for the identification of the chemical contamination. We used hexane, a nonpolar solvent, to extract the dyed yarn. The bands a t 2957, 2918, 2849, and 1464 cm-l due to saturated hydrocarbon groups are seen in the infrared spectrum of the hexane extract (Figure 2B). However, the band a t 1265 cm-l shown in the spectrum of the methylene extract (Figure 2A) is absent in Figure 2B. We also found that the carbonyl band at 1740 cm-l is broader in Figure 2A than in Figure 2B. The differences between Figure 2A and Figure 2B reveal that the chemical contamination on the dyed yarn contains more than one chemical. The chemical with higher polarity has higher solubility in methylene chloride than in hexane, consequently has higher con-
4000
3000
2000
lo00
600
WAVENUMBERS (cm-') Figure 2. Transmissioninfrared spectra: (A) methylene chloride extract of dyed yam; (B)hexane extract of dyed yarn; (C) oligoester. centration in the methylene chloride extract than in the hexane extract. The band a t 1265 cm-l and the broadening of the carbonyl band in the spectrum of the methylene chloride extract (Figure 2A) are due to the contaminant with higher polarity. The expanded spectra of the methylene extract and the hexane extract of the dyed yarn are presented in Figure 3, parts A and B, respectively. To determine the nature of the polar chemical contamination, we subtracted the spectrum of the hexane extract (Figure 3B) from the spectrum of the methylene chloride extract (Figure 3A). The difference spectrum is presented in Figure 3C. The same difference spectrum was obtained when we extracted the dyed yarn with different polar and nonpolar solvents and performed spectral subtraction. The full-scale and expanded spectra of the oligoester are shown in Figure 2C and Figure 3D,respectively. Oligoester is usually contained in polyester fibers and
2838 Ind. Eng. Chem. Res., Vol. 33, No. 11, 1994 Scheme 1. Molecular Structure of Cyclic Ethylene Terephthalate Oligomer (Trimer)
0
-
Table 1. Comparison of the Band Frequencies (crn-l) of the Difference Infrared Spectrum (Figure 3C) and the Infrared SDectrum of Olieoester ( F i m e 3D) spectrum spectrum diff IR diff IR of oligoester spectrum of oligoester spectrum ~~~
~
1728 1572 1539 1462 1408 1368 1285 1265 1170
2000
1500
1000
600
WAVENUMBERS (crn-')
Figure 3. Expanded transmission infrared spectra: (A) methylene chloride extract of dyed yarn; (B)hexane extract of dyed yarn; (C) difference spectra, A - B; (D)oligoester.
is liable to migrate out of polyester fibers in a dyeing process a t elevated temperatures (BASF, 1976). Cyclic oligomer of ethylene terephthalate (trimer) is the major constituent of the oligoester (BASF, 1976). The molecular structure of trimer is shown in Scheme l . The band frequencies of the difference infrared spectrum (Figure 3C)and the infrared spectrum of oligoester (Figure 3D) are summarized in Table 1. All the bands in the spectrum of oligoester (Figure 3D) are present in the difference spectrum (Figure 3 0 . Comparison of the difference spectrum (Figure 3C) with the spectrum of oligoester (Figure 3D) reveals that oligoester is in the methylene chloride extract of the dyed yarn. The rayon yarn was dyed in a package-dyeing machine which had previously been used to dye a polyester yarn. Evidently, the oligoester deposit formed in the dyeing machine
1725 1572 1456 1408 1366 1286 1264 1171
1134 1124 1111 1097 1037 1017 874 727
1132 1109 1096 1038 1016 874 729
during the previous dyeing process contaminated the rayon yarn and was the major component of the polar chemical contamination on the rayon yarn. Two weak bands at 1539 and 1124 cm-' not shown in the spectrum of oligoester (Figure 3D) are probably due to a minor component of the polar contamination. The dyed yarn was also treated in a 0.5 M NaOH solution at 50 "C for 1h. After the water in the NaOH solution evaporated, the residue was extracted with methanol. The infrared spectrum of the methanol extract is presented in Figure 4. Three weak bands at 2964, 2924, and 2851 cm-' are shown in the spectrum of oligoester (Figure 2D), whereas three weak bands at 2951, 2919, and 2851 cm-l are shown in the spectrum of the methanol extract (Figure 4). The two intense bands at 1630 and 1437 cm-l in Figure 4 are associated with the asymmetric and symmetric stretching modes, respectively, of carboxylate anion. The carboxylate anion was formed as oligoester hydrolyzed during the treatment of the dyed yarn with the NaOH solution. The carbonyl band at 1728 cm-l is due to the residual eetw groups of oligoester. The bands at 868 and 837 cm-l can be attributed to the out-of-plane bending of parasubstituted aromatic hydrocarbons (Bellamy, 1975).The infrared spectroscopy data presented here indicate that the substance in the methanol extract is indeed the saponification products of oligoester. It confirms the existence of oligoester on the dyed rayon yarn. One also observes that the intense bands at 2918 and 2849 cm-' due to the stretching modes of methylene in the spectra of the methylene chloride and hexane extracts (Figure 2, parts A and B, respectively) are not present in the spectrum of the methanol extract (Figure 4). Conclusions We extracted a contaminated rayon yarn using one polar organic solvent (methylene chloride) and one
Ind. Eng. Chem. Res., Vol. 33,No. 11, 1994 2839 e c l
w
ii
E
Y
!-
4ooo
m
ZOO0
LOO0
600
WAVENUMBERS (cm.')
Figure 4. Transmission infrared spectrum of methanol extract of sodium hydroxide used to treat dyed yarn.
nonpolar organic solvent (hexane), and subtracted the infrared spectrum of the nonpolar solvent extract from the spectrum of the polar solvent extract. By combining solvent extraction with spectral subtraction, we identified ethylene terephthalate oligomer as the polar organic contaminant on the dyed rayon yarn. This simple method is useful in qualitative determination of polar organic contaminants on textile or other materials.
Berni, R. J.; Morris, N. M. Infrared spectroscopy. In Analytical Methods for a Textile Laboratory; Weaver, J.W., Ed.; American Association of Textile Chemists and Colorists: Research Triangle Park, NC, 1983;Chapter ll. Grieble, D. L.; Gardner, S. A. Applications of Infrared Microscopy to Textile Samples. Text. Chem. Color. 1989,21(81,11-13. Koenig, J. L. Recent Advances in Fourier Transform Infrared Spectroscopy of Polymers. Pure Appl. Chem. 1985,57, 971976. Morath, J. C. Identification of Textile Finishes on Fabrics. In Analytical Methods for a Textile Laboratory; Weaver, J. W., Ed.; American Association of Textile Chemists and Colorists: Research Triangle Park, NC, 1968;Chapter 4. Morris, N. M. A Comparison of Sampling Techniques for the Characterization of Cotton Textiles by Infrared Spectroscopy. Text. Chem. Color. 1991,23 (4),19-22. Morris, N. M.;Pittman, R. A.; Berni, R. J. Fourier Transform Infrared Analysis of Textiles. Text. Chem. Color. 1984,16,4347. OConner, R.T. Absorption Spectroscopy. In Analytical Methods for a Textile Laboratory; Weaver, J. W., Ed.; American Association of Textile Chemists and Colorists: Research Triangle Park, NC, 1968;Chapter 10. OConner, R. T. Infrared Spectra of Chemically Modified Cotton Cellulose. In Instrumental Analysis of Cotton Cellulose and Modified Cotton Cellulose; O'Conner, R. T., Ed.; Marcel Dekker, Inc.: New York, 1972;Chapter 8. Yang, C.Q. Infrared Spectroscopic Analysis of Textile Materials Degradation Using Photoacoustic Detection. Ind. Eng. Chem. Res. 1992,31,617-621. Yang, C. Q.;Bresee, R. R. Studies of Sized Cotton Yarns by FTIR Photoacoustic Spectroscopy. J. Coated Fabr. 1987,17,110128.
Received for review March 8 , 1994 Revised manuscript received J u n e 30, 1994 Accepted July 22, 1994@
Literature Cited BASF Corporation. Manual: Dyeing and Finishing of Polyester Fibres; BASF Corporation: Ludwigshafen, Federal Republic of Germany, 1976;pp 150-151. Bellamy, L. J. The Infrared Spectra of Complex Molecules, 3rd ed.; Chapman and Hall: London, 1975;pp 14,89.
Abstract published in Advance ACS Abstracts, October 1, 1994. @
