The identification of cashmere and fine sheep wool is a difficult point in the detection work. Since cashmere and fine-branched sheep wool are relatively close in appearance, it is not easy to distinguish the two types of fibers using ordinary optical microscopes. Therefore, scanning electron microscopes are generally used for identification. The instrument operation of scanning electron microscopy identification is divided into two steps: sample spraying and
testing on the machine. The first step: sample spraying. First cut the representative yarn sample into short fragments of 0.5 to 1 mm, then evenly glue the sample to the conductive adhesive, place the conductive adhesive on the sample stage, cover the sample compartment, turn on the ion sputtering instrument power switch, and confirm the voltage Mode and set the spraying time (generally set to 1.5-2min, the longer the time, the greater the thickness of the film. Generally, the thickness of the coating is a little bit thicker for observation at low magnifications; the coating is thinner for observation at high magnifications), Turn the vacuum adjustment knob to adjust the pressure to 7Pa. After confirming that the instrument is ready (the ready light is on), turn on the discharge switch to start spraying, and the time indicator begins to count down. After the end, remove the sample and prepare for testing. The second step: test on the machine. Turn on the main power switch of the scanning electron microscope and the power switch of the circulating water machine, fix the prepared sample on the sample rack, and adjust each handle of the sample table to the standard position. Turn on the 'AIR' switch and wait for the pre-extraction chamber to amplify the air before installing it. sample. Push the door of the pre-extraction chamber, press the 'EVAC' key to vacuum, then turn on the 'DISPLAY POWER' power supply on the host, and enter the corresponding software operating system. Finally, add high voltage (HV) to the system, select the scan speed, adjust the magnification, focal length, pixels and other parameters until the image is clear. Use scanning electron microscope to identify difficult cashmere and wool, mainly from the thickness, density, aspect ratio, scale shape, etc. of the fiber scales to observe and make judgments (Figure 1) Scale density refers to the number of scales per unit length , The density of cashmere scales is about 60 pieces/mm, and the density of sheep hair scales is about 90 pieces/mm. The diameter-to-height ratio refers to the ratio of the fiber diameter to the scale spacing (or height). The scale spacing and diameter of cashmere are close to each other. The thicker the fiber, the greater the diameter-to-height ratio; the thickness of the scales of cashmere is about 0.35μm. The thickness of cashmere scales with a thickness of about 0.8μm tends to increase with the increase of fiber diameter, but it is not obvious. The scaly shape of cashmere mainly presents the characteristics of a ring-like uniform coating of the hair shaft, but the difficult fibers observed with a scanning electron microscope generally do not show the typical characteristics of a ring-like coating. The edge of the scales of this fiber is zigzag, similar to the scale characteristics of coarse wool, but the scales are thinner, and the other is the irregular scales, no ring characteristics, thick scales, high density, obvious brilliance on the surface of the scales, and the shape of the scales. It is also close to wool fiber. When encountering the above suspected wool fibers, a variety of characteristics must be combined to make judgments. The morphological characteristics of cashmere and wool scales are shown in Table 1.
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