Synthetic fibers. Synthetic polyamide fiber

Synthetic fibers began to be manufactured in an industrial way in 1938. At the moment, there are already several dozen types. For all of them, it is common that low-molecular compounds, which turn into polymers through chemical synthesis, serve as the starting material. By dissolving or melting the resulting polymers, a molding or spinning solution is prepared. They are formed from a solution or a melt, and they are then subjected to finishing.

Varieties

Depending on the characteristics that characterize the structure of macromolecules, synthetic fibers are generally divided into heterochain and carbople fibers. The first include those obtained from polymers in whose macromolecules, in addition to carbon, there are other elements - nitrogen, sulfur, oxygen and others. This includes polyester, polyurethane, polyamide and polyurea. Carbon fiber synthetic fibers are characterized by the fact that the main chain of them is built of carbon atoms. This group includes polyvinyl chloride, polyacrylonitrile, polyolefin, polyvinyl alcohol and fluorine-containing.

Polymers serving as the basis for obtaining heterochain fibers are obtained by polycondensation, and the product is molded from melts. Carbocchic are obtained by chain polymerization, and the formation occurs usually from solutions, in rare cases from melts. You can consider a single synthetic polyamide fiber, which was called a siblon.

Creation and application

Such a word as a siblon turns out to be completely unfamiliar for many, but earlier on the labels of clothes it was possible to see the abbreviation VVM, under which was hidden the viscose high modulus fiber. Then the producers thought that this name would look nicer than the siblon, which could be associated with nylon and nylon. Production of synthetic fibers of this type is carried out from the Christmas tree, no matter how fabulously it did not look.

Features

There was a siblon in the early 70-ies of the last century. It is an improved viscose. At the first stage, pulp is produced from wood, it is isolated in its pure form. The largest quantity is contained in cotton - about 98%, but cotton fibers are used to produce excellent yarn. Therefore, for the production of cellulose is more often used wood, in particular coniferous, where it contains 40-50%, and the rest are unnecessary components. They need to get rid of in the process of producing synthetic fibers.

Process of creation

Synthetic fibers are produced in stages. At the first stage, the cooking process takes place, during which all excess substances move to the solution from the wood chips, and the long polymer chains are broken down into separate fragments. Naturally, here it does not do only with hot water, additives of various reagents are produced: natron and others. Only cooking with the addition of sulphates allows the production of cellulose, which is suitable for the production of the siblon, since it retains less impurities.

When the pulp is already boiled, it is sent to bleach, dried and compacted, and then moved to where it is needed - this is the production of paper, cellophane, cardboard and fibers, that is, the main production. What's going on with it?

Post-processing

If you want to get synthetic and natural fibers, you first need to prepare a spinning solution. Cellulose is a solid that is not easy to dissolve. Therefore, it is usually converted to a water-soluble dithioureacid ester. The process of transformation into this substance is quite lengthy. First, the cellulose is treated with hot alkali, followed by spinning, while unnecessary elements are transferred to the solution. After pressing, the mass is crushed, and then placed in special chambers, where pre-ripening begins - the cellulose molecules are shortened almost twice due to oxidative degradation. Further, the reaction of alkali cellulose with carbon disulfide occurs, which makes it possible to obtain a xanthate. This is an orange-colored mass, similar to dough, an ester of dithiocarbonic acid and a starting material. This solution for its viscosity was called "viscose".

Further, filtration is carried out to remove the last impurities. Dissolved air is produced by "boiling" the ether in a vacuum. All these operations lead to the fact that the xanthate becomes like a young honey - yellow and viscous. The spinning solution is completely ready.

Preparation of fibers

The solution is forced through the spinnerets. Artificial synthetic fibers are not simply spun in the traditional way. This operation is difficult to compare with a simple textile, it will be more correct to say that it is a chemical process that allows millions of liquid viscose streams to become solid fibers. In the territory of Russia, cellulose is obtained from viscose and siblon. The second type of fiber is one and a half times stronger than the first, characterized by greater resistance to alkalis, the tissues of it differ hygroscopicity, less degree of shrinkage and creasing. And the differences in the processes of production of viscose and a siblon appear at a time when newly emerged synthetic fibers are found in the spill bath after the spinnerets.

Chemistry to the rescue

To get viscose in the bath, sulfuric acid is poured. It is designed to decompose the ether, so that pure cellulose fibers are obtained. If it is necessary to obtain a siblon, zinc sulfate is added to the bath , partially interfering with the hydrolysis of the ester, so the yarns will contain the residual xanthate. And what does this give? Then the fibers are stretched and shaped. When there are residues of xanthate in the polymer fibers, it is possible to stretch the polymer cellulose chains along the fiber axis, rather than locating them chaotically, which is typical for ordinary viscose. After drawing, the bundle of fibers is cut into spatulas 2-10 millimeters long. After a few more procedures, the fibers are compressed into bales. Tons of wood is enough to produce 500 kilograms of cellulose, from which 400 kilograms of fiber of the siblon will be released. The spinning of cellulose takes about two days.

What is next with the siblone?

In the eighties, these synthetic fibers were used as additives to cotton, so that the yarns would spin better and not break. From the siblone, substrates were made for artificial skin, and also used it for the manufacture of products from asbestos. Then the technologists were not interested in creating something new, it was required as much fiber as possible to realize what was planned.

And in the West in those days, high-modulus viscose fibers were used to produce fabrics that were cheap and durable in comparison with cotton, but at the same time absorbed moisture and breathed well. Now Russia does not have its own cotton regions, so the siblon has high hopes. Only the demand for it is not yet very large, as now almost no one buys fabrics and clothes of domestic production.

Polymer fibers

They are divided into natural, synthetic and artificial. Natural are those fibers, the formation of which is carried out in natural conditions. They are classified according to their origin, which determines their chemical composition, for animals and plant. The first consist of protein, namely carotene. It's silk and wool. The latter consist of cellulose, lignin and hemicellulose.

Artificial synthetic fibers are obtained by chemical processing of polymers existing in nature. These are commonly referred to as acetate, viscose, alginate and protein fibers. As a raw material for their production are sulfate or sulphite wood pulp. The release of artificial fibers is made in the form of textile and cord yarns, as well as in the form of staple fiber, which is processed together with other fibers in the process of manufacturing different fabrics.

Synthetic polyamide fiber is obtained from polymers that are artificially derived. As a raw material, polymeric fibers formed from flexible macromolecules of a weakly branched or linear structure with a significant mass of more than 15,000 atomic mass units and a very narrow molecular weight distribution are used in this process. Depending on the type, synthetic fibers are able to have a high degree of strength, a significant value in relation to elongation, elasticity, resistance to multiple loads, small residual deformation and rapid recovery after removal of the load. That's why, besides using it in textiles, they were used as reinforcing elements during the manufacture of composites, and all this allowed to make special properties of synthetic fibers.

Conclusion

In the past few years, there has been a very steady growth in the number of advances in the development of new polymer fibers, in particular para-aramid, polyethylene, heat-resistant, combined, core-shell, heterocyclic polymers, in which various particles are included, Silver or other metals. Now the material is nylon - this is not the height of engineering thought, since now there is a huge amount of new fibers.