Well-known methods exist to evaluate the mixing of natural and synthetic chemical fibers [1]. The development of modern analytical tools has broadened the range of methods for analyzing heterogeneous fibers.

The modern method of infrared spectroscopy permits considerable shortening of the time required for testing a sample. However, the use of this method requires special preparation of the sample and the need to evaluate the interaction of IR radiation with the fiber studied [2].

In order to obtain the spectra of solids, the sample has been traditionally ground into a fine powder and placed into a matrix such as potassium bromide or Nujol since infrared spectroscopy generally involves the irradiation traversing the sample.

The use of methods of infrared irradiation reflected from the sample surface can be used for nondestructive monitoring such as attenuated total reflection (ATR), mirror, glide, and diffuse reflection [3].

The advantage of using such methods is the possibility of studying samples, which are opaque to IR radiation. Another advantage is that the analysis need not be carried out in laboratories but rather directly on site.

The study of fibers requires consideration of the quantitative and qualitative characteristics of the radiation beam after its interaction with fibers, especially in mixtures [2]. Thus, studies have been carried out to evaluate the absorption bands of wool and acrylic fiber using IR spectrometers. Since wool is a natural fiber and acrylic fiber is a synthetic material derived from a high-molecular-weight polymer, the greatest absorption is achieved in the medium-IR range from 2000 to 500 cm-1,

Figure 1 shows characteristic absorption peaks for undyed wool at 1627, 1500, and 1028 cm-1. We should also note that a factor such as dyeing of the fibres plays no role at all in the spectral analysis. Comparison of the IR spectra of undyed and dyed wools (Figs. 1 and 2) shows that their absorption peaks are identical.

Fig. 1.
figure 1

IR spectrum of undyed wool No. 69.

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Fig. 2.
figure 2

IR spectrum of dyed wool No. 64.

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For acrylic fiber with a broad range of absorption intensities, it is nevertheless possible to discern characteristic peaks at 1732 and 1450 cm-1 (Fig. 3), which are also seen for dyed acrylic fiber.

Fig. 3.
figure 3

IR spectrum of undyed acrylic fiber.

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Analysis of the spectrum of the three-component mixture shown in Fig. 4 clearly shows all the major peaks of both wool and acrylic fiber, which permits us to determine the relative component composition of the mixture.

Fig. 4.
figure 4

IR spectrum of a three•component mixture of dyed acrylic fiber, undyed acrylic fiber, and wool.

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Thus, the use of the absorption spectra of various textile fibers provides a system for analysis of the structure of mixed fibers.