What are the characteristics of wool fiber?

First, the linear density of wool

The linear density of wool fibers is highly dependent on various physical properties. Generally, the finer the wool, the more uniform the linear density, the higher the strength, the more curl, the dense scales, the softer luster, the higher the content of fat and sweat, but the shorter the length. Therefore, linear density is an important indicator to determine the quality of wool. The small linear density of the wool fiber is beneficial to the strength of the yarn and the drying of the yarn. However, it is easier to produce defects when the fine wool is spun. The linear density of wool fibers is also closely related to the quality and style of wool fabrics.

Commonly used indicators for wool thread density are average diameter, quality count, and tex number. If the fiber diameter distribution can be obtained, the coefficient of variation of the diameter can be used to indicate the uneven linear density of a batch of wool.

The diameter of the wool fibers varies widely, with the finest fluff having a diameter of about 7 μm and the thickest diameter of up to 240 μm. It is on the same wool, the diameter difference can reach 5~6μm. The reasons for the difference in wool density are complex, including the breed, age, sex, hair growth and feeding conditions of the sheep.

In the same sheep, the hair on the shoulder is the thinnest, the hair on the side of the body, the neck and the back is the second, the hair on the front neck, buttocks and abdomen is thicker, and the hair on the throat, lower leg and tail is the thickest.

The quality count is an indicator of the wool line density that has been used in the wool industry for a long time. At present, commercial transactions, the grading of the wool textile industry, and the formulation of the slivering process are all based on quality counts. In the last century, the quality of wool was historically assessed by sensory methods. At an international conference at the end of the last century, according to the requirements of the spinning equipment and spinning technology and the quality of the yarn at that time, the number of imperial combed yarns that can be spun from various linear density wools was called the quality count to represent the wool. The quality of the quality. With the development of science and technology, the improvement of spinning methods, the continuous improvement of textile quality requirements and the progress of fiber performance research, the quality of wool has gradually lost its original meaning. At present, the quality count of wool only indicates the fineness index of wool in a certain range of average diameter.

Second, the length of wool fiber

Due to the presence of natural curl, wool fibers can be divided into natural lengths and straight lengths. The fiber bundle is naturally curled, and the straight line distance between the ends is called the natural length, which is generally used to indicate the length of the pile. The wool fiber is removed from the curl and the length after straightening is called the straight length. The straightening length is used in the production of wool.

The length of wool fiber varies greatly depending on the breed, age, sex, hair growth location, feeding conditions, number of shears, and season of the sheep. Generally, the length of domestic fine wool is in the range of 5.5 to 9 cm, the length of semi-fine wool can reach 7 to 15 cm, and that of coarse wool is 6 to 40 cm. On the same sheep, the hair on the shoulders, neck and back is longer, and the hair on the head, legs and abdomen is shorter.

When the linear density of the wool fibers is the same, the wool is long and tidy, and the short-wool content of the wool, the yarn strength and the stem are good. The length of the wool is also the basis for determining the spinning number and selecting the process parameters.

Third, the curl of wool

The curl of wool fiber has a certain relationship with the shape of the hair, the density of the fiber, the elasticity, the cohesion and the fluff. Curl has a great influence on the quality of the yarn and the style of the fabric.

The crimp of wool fibers is deep and shallow. According to the depth of the curl, that is, the wave height, and the length and length, that is, the wave width, the curl shape can be classified into three types, one being weak curl. This type of crimp is characterized by less than half a circumference of the curled arc, relatively straight along the length of the fiber, and less curl. Most of the semi-fine hair curls fall into this category. 2 is a constant curl. It is characterized by a curled waveform that is approximately semi-circular. Most of the fine hair curl belongs to this type. 3 is a strong curl. It is characterized by a high amplitude of curl. More curls. Most of the fine-haired sheep's belly hair belongs to this type. Frequently crimped wool is used for combing wool and spinning yarns and fabrics that are elastic and smooth. The strong curled wool is suitable for carded woolen spinning, and the surface is full of fluffy, hand-feeling and elastic wool.

The index indicating how much the wool fiber is curled is the number of crimps; the index indicating the curling depth is the crimp ratio; and the index indicating the curl elasticity is the curl recovery ratio and the curl elastic recovery ratio. Their definitions, calculations, and test methods are described in the curl inspection of chemical fibers in Chapter 4.

Generally, the number of crimps of fine wool is 6 to 9 pieces/cm.

Fourth, the moisture absorption of wool fiber

The hygroscopicity of wool fibers is expressed by the moisture regain. The hygroscopicity of wool is the strongest of the most common fibers. Under normal atmospheric conditions, the moisture regain rate is 15% to 17%.

Fifth, the strength of wool fiber

The tensile strength of wool fiber is the lowest among the commonly used natural fibers, and its fracture length is only 9~18km. Generally, the fineness of the wool is fine, and the less the medullary layer, the higher the strength.

The elongation of wool fibers after stretching is the largest of the commonly used natural fibers. The elongation at break is up to 25% to 35%, and the wet state is up to 25% to 50%. After removing the external force, the elastic recovery ability of elongation is the best among the commonly used natural fibers, so the fabric woven with wool is used. It is not easy to produce wrinkles and has good taking properties.

6. Chemical stability of wool fiber

Wool fibers are more resistant to acids than alkalis. Short-term acid and concentrated acid have little damage to wool, so acid is often used to remove plant impurities such as grass clippings from raw wool or billet. Organic acids such as acetic acid and formic acid are important dyeing agents in wool dyeing. The alkali turns the wool yellow and dissolves.