Application And Study On FTIR Microspectroscopy Of Textile Fibers

Fourier transform infrared (FTIR) microspectroscopy is the coupling technique of optical microscopy and FTIR spectroscopy, and because of its unique advantage in the micro-sample analysis as well as in the micro-scale analysis on sample, there have been increasing attention and application to the field of FTIR microspectroscopy.Fiber is a fine sample, which has a diameter about 10-30 urn. The localized analyses in fiber radial and axial direction on surface layer are more microanalysis. KBr disks and direct measurement on bundle fibers have commonly been used in measuring fiber IR spectra. Using these methods, because of the fiber damage and morphological influence, IR spectrum can't show the information in high quality about fiber component and structure. By a FTIR microscopy, the IR microscope spectrum for a single fiber can be measured directly without damage. The spectrum can provide the effective information related to the fiber component and structure.In this thesis, the fundamental issues in the measurement of single fibers by FTIR microscopy were investigated systemically. Especially, the effect of fiber cross-section and testing parameters on the representative and characteristic of the FTIR microscope spectra has been discussed in detail. According to the tests, the IR microscope spectra of 28 sorts of textile fibers were collected and measured by using a Continuum microscope. The comparison of the characteristic microspectroscopic spectra to the corresponding IR spectra with ordinary measurement has been conducted. Meanwhile, the macromolecule structure of the stretched wool fibers has been analyzed by the microscope polarized FTIR spectroscopy. Several conclusions have been achieved in this study:1. A series of measurements verified that the accuracy, reproducibility and quality of fiber infrared microscope spectra rely highly on the fiber morphology and the instrument parameters, such as the aperture size and scans etc, despite of the high resolution in micrology by using the Continuum microscope. The choice of aperture sizes and scans should be matched with the analytical region on the sample. To flatten the observed fiber can eliminate the morphological influence and improve the IR spectra. The direction of fibers arrangement and the proper contact between ATR crystal and fibers are vitally important in the polarized IR and ATR measurements respectively.2. The reproducibility of the soy protein fiber spectra has also been tested bymeans of the transmission and mapping methods at high scan number. The experimental results indicate that through reasonable parameter setting and sample preparation, in fact, the IR spectra of the single fibers can be obtained quickly and reproducibly with little damaged of the fibers.3. The IR microscopic spectra have good resolution and can provide specific information about fiber component and structure. The transmissionthe integral information about the sample, while ATR spectra mainly affer the surface information of fiber structure and component The difference between transmission and ATR spectra for the same sample can characterize the distinctness between the integral and surface. In addition, ATR spectra are hardly influenced by environmental factor. For the polarized IR analysis with the Continuum microscope, the anisotropic characteristic of fiber structure can be easily tested and used in transmission, reflection and ATR microspectroscopy, However the IR reflection test has few been applied because of the low signal forthe textile fibers.4. The IR microscope spectra of the stretched wool fibers have a observable change at 1026cm-1 owing to the breakage of sulphonate bond (S-O), the evident absorbance at 1026cm-1 shows an increase as the daw ratio increases. During the slenderizing treatment, the macromolecule structure of wool fibers is changed Meanwhile, the macromolecule conformation transform from a -helix to sheet, and the sheet content get a highest value at 110% draw ratio.