No matter what kind of fiber, its structure has fixed characteristics, and this characteristic is also the essential attribute of the fiber. Different fibers have different physical and chemical properties. These properties also determine the use characteristics of the fiber. These characteristics are due to the structure and content of the fiber itself. We can form the fiber from the outer layer to the inner layer, and even from the shape of the fiber molecule. Observe the structure of the fiber and understand the interaction and arrangement of the basic units of the fiber. The internal content of the structure directly affects the properties of the fiber. To explore the basic characteristics of fibers, it has been widely used in the development of new fibers of chemical fibers, while natural fibers are rarely used. The development of fiber micro-observation: the research of fiber micro-observation structure, from the 19th century to the modern three or forty years, whether in theory, analytical methods, instrument development have made great breakthroughs, especially the birth of various new fibers, from the macro structure It has entered a new era in the field of microstructure. .With the innovation of various optical microscopes and technologies, the application of micro-observation technology in fiber identification method has become more mature.
(1) Development of microscopic optical instruments and various methods Nowadays, there are various types of optical instruments, which can meet different needs and different processes, such as:
(1) Scanning electron microscope SEM (SCANNINGELECTRONMICROSCOPE) —composed of optical system, scanning system, signal detection system, image display system, recording system, etc. After the electron beam is emitted from the electron gun, it is focused by a magnetic lens, and is deflected by two sets of scanning coils, and then projected onto the sample for a fine electron beam scanning raster, and image information is obtained on the fluorescent screen of the kinescope. The three-dimensional image is strong, and the thickness of the sample is unlimited.
(2) Transmission electron microscope TEM (TRANSMISSIONELECTRONMICROSCOPE) —composed of imaging systems such as electron guns and condensers, and image and recording systems.
(3) Scanning tunnel microscope STM (SCANNINGTUNNELLINGMICROSCOPE)
(4) AFM (ATOMICFORCEMICROSCOPE)
(5) Polarized Microscope (POLARIZEDMICROSCOPE) —A microscope that can polarize light and observe fine structures under polarization. The birefringence and degree of orientation of the fiber can be measured.
(2) Identification method of fiber structure:
(1) X-ray & Electron Diffraction (X-ray & Electron Diffraction)-The difference in diffraction images obtained when X-rays irradiate different fibers can be used to identify various types of fibers.
(2) Infrared spectroscopy (Infre-red) —Using the characteristics and chemical groups of various fibers, in the infrared spectrum, the characteristics and absorption spectra bring the identification of fibers.
(3) Ultraviolet, Fluorescence—The wavelengths of fluorescent X-rays emitted by different elements are different, and then spectrum analysis is used.
(4) Nuclear magnetic resonance NMR (Nuclearmagneticresonance)-the nuclear nucleus whose spin momentum or angular momentum is not zero, in a constant external magnetic field, the nuclear magnetic moment can take various quantized positions, at another Under the action of electromagnetic waves, the resonance transition phenomenon that occurs between the magnetic energy levels of the nucleus can analyze the order of the atomic groups or the arrangement of atoms in the molecule and the nature of the chemical bond.
(5) Others, such as Ramanspectrum, Surfaceanalysis, etc. Plus various electron microscopy (Electronmicroscopy) and so on.
Fiber can also speculate the fiber structure from physical and chemical properties, its methods:
(a) There are Thermal Analysis (Dynamic Analysis), Dynamic and Fracture Mechanics: It is a technique for measuring the relationship between the physical properties and temperature of a substance under process-controlled temperature. It is the most commonly used method in the field of chemical fibers, such as , Test quality changes include thermogravimetry (TG) and outgas analysis (EGA), test temperature changes have differential thermal analysis (DTA), test heat content changes have differential scanning calorimetry (DSC), test size changes have thermal expansion Method, test mechanical properties are thermomechanical analysis (TMA), and dynamic mechanical analysis (DTMA), test optical properties are thermooptical methods.
(b) Mass spectrometry (Massspectrometry): After the sample is ionized, a mass spectrometry analysis method is formed.
It can measure the molecular weight and structure of organic matter, as well as identify organic matter and its structure, and obtain spectral lines with different intensities through an ion sensitive plate. It is called a mass spectrum. According to the mass spectrum, the molecular weight and structure type of the substance can be rejected.
With the innovation of equipment and methods, everyone has an in-depth understanding of various fibers. Micro-observation technology is not only used in fiber identification, but also can be used to understand the characteristics of the fiber structure, so as to improve the compatibility of the subsequent process to enable Produce higher quality yarns and fabrics to further develop the textile industry.
Natural fiber is mainly cotton fiber, which accounts for a large proportion of the entire textile industry. The development of the cotton spinning industry, in addition to mechanical and technological improvements, the quality structure of cotton, directly affects the physical indicators of finished yarn. The various testing instruments, methods, and standards can only provide some data, most of which are average values. The textile mills control the production process according to the data, and often fail to understand the real situation of the batch of cotton fibers. Are the characteristics of each batch of cotton fibers close to and Matching causes problems after yarn formation.
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