What is non-woven fabric?

From fiber to fabric, generally through two steps: one is the fiber through the spinning process to form yarn, and the other is the yarn through the weaving process to form fabric. For example, woven fabrics (woven fabric) and knitted fabrics commonly used in clothing are formed by two processes: spinning and weaving. Woven fabric (woven fabric) is two groups of yarns perpendicular to each other on the loom according to a certain law of cross and cross weaving, stable structure, flat cloth. Knitted fabric is formed by a group or more groups of yarns in the knitting machine according to a certain law, the texture is soft, has greater extensibility and elasticity.

In addition, there is a part of the fabric can not be spun and woven, directly formed by the fiber, this fabric is what we usually call non-woven fabric, also known as nonwovens, nonwovens, nonwovens. Non-woven fabrics are oriented or randomly arranged fibers made by friction, holding, bonding or a combination of these methods, and the connotation is "not woven". Non-woven fabric exists in the form of fiber in the cloth, and the woven fabric is in the form of yarn in the cloth, which is also a main feature of non-woven fabric different from other fabrics, non-woven fabric is not drawn out of a thread.

What are the raw materials of non-woven fabrics?

As CNPC and Sinopec began to build mask production lines, produce and sell masks, we gradually realized that masks and oil are also inextricably linked. "From Oil to Masks" details the whole process from oil to masks step by step. Petroleum distillation cracking can get propylene, propylene through the polymerization reaction to polypropylene, polypropylene can be further made into polypropylene fiber, that is, we usually say polypropylene. Polypropylene fiber (polypropylene) is the main fiber raw material for the production of non-woven fabrics, but it is not the only raw material, polyester fiber (polyester), polyamide fiber (nylon), polyacrylonitrile fiber (acrylic fiber), viscose fiber, etc., can be used to produce non-woven fabrics.

Of course, in addition to the above chemical fibers, natural fibers such as cotton, linen, wool and silk can also be used to produce non-woven fabrics. Some people often refer to non-woven fabrics as chemical fiber products, which is actually a misunderstanding of non-woven fabrics. Like the clothing fabrics we usually wear, non-woven fabrics also have chemical fiber non-woven fabrics and natural fiber non-woven fabrics, but chemical fiber non-woven fabrics are more common. For example, the cotton towel in the following figure is a non-woven fabric made of natural fiber - cotton. (Here, I want to remind you that not all products called "cotton towels" are made of "cotton" fiber, there are also some cotton towels on the market are actually made of chemical fibers, but the feel is more like cotton, you must look at the ingredients when you buy)

How is non-woven fabric made?

Let's start by understanding where the fibers come from. Natural fibers are naturally existing in nature, chemical fibers (including man-made fibers and synthetic fibers) are dissolved into spinning solution in a solvent or heated at high temperature to melt into a melt, and then the solution or melt is extruded from the spinneret of the spinning pump, and the ejected fine stream is cooled and solidified to form a primary fiber. After the corresponding post-treatment, the primary fiber is formed into a short fiber or filament that can be used for textile.

Weaving cloth is made by spinning fibers into yarn, and then weaving the yarn into cloth by weaving or knitting. Non-woven fabrics do not require spinning and weaving, so how does it turn fibers into cloth? There are many kinds of production processes of non-woven fabrics, and the processes are different, but the core processes include fiber mesh and fiber mesh reinforcement.

Fiber mesh

"Fiber into the net" as the name suggests is to make the fiber into a network, common dry method into the net, wet method into the net, spinning into the net, melt-blown into the net and so on.

Dry netting and wet netting are more suitable for short fiber netting, and it is generally necessary to pretreat fiber raw materials, such as pulling large fiber clumps and fiber blocks into small pieces, making them loose, and removing impurities, mixing various fiber components evenly, and preparing for netting. Dry method is generally by combing the pre-treated fibers, layering into a certain thickness of the fiber network. Wet mesh is to disperse short fibers in water containing chemical additives to form a suspended slurry, and then filter out the water, and the fibers deposited on the filter network will form a fiber network.

Spinning mesh and melt-jet mesh are the use of chemical fiber spinning method, in the process of spinning forming the fiber directly laid into the net. The spinning mesh is the spinning solution or melt from the spinneret spray, after cooling, stretching to form a certain fineness of the filament, on the receiving device to form a fiber network. Melt-blown mesh uses high-speed hot air to extremely stretch the thin stream of spinnerets to form microfibers, which are then gathered on the receiving device to form a fiber network. The diameter of the fiber formed by melt-blowing method is smaller, which is conducive to improving the filtration efficiency.

Fibre-mesh reinforcement

The fiber network obtained by different methods, the connection of the internal fibers is relatively loose, the strength is relatively low, it is difficult to meet the needs of use, so it also needs to be strengthened. Common reinforcement methods include chemical bonding, thermal bonding, mechanical strengthening and so on.

Chemical bonding reinforcement method: the adhesive is applied to the fiber network by impregnating, spraying, printing and other methods, and then the water is evaporated by heat treatment, and the adhesive is solidified, so that the fiber network is reinforced to form a cloth.

Thermal bonding reinforcement method: Most of the polymer has thermoplastic, that is, after heating to a certain temperature will melt and become sticky, after cooling and re-curing, using this principle can also be used to strengthen the fiber network. Hot air bonding is commonly used - the use of hot air to heat the fiber web to make it bond and strengthen; Hot rolling bonding - Using a pair of heated steel rollers to heat the fiber web and apply a certain pressure, so that the fiber web is bonded and strengthened.

Mechanical reinforcement method: As the name suggests, it is to apply mechanical external force to strengthen the fiber network. Commonly used are acupuncture, water acupuncture method and so on. The method of acupuncture is to puncture the fiber web repeatedly with a hook thorn, so that the fibers in the fiber web intertwine with each other and play a strengthening role. Friends who have played pokes and pokes should be familiar with this method, and the fluffy fiber can be poked into a variety of shapes by needling. Spunkling is the use of high-speed and high-pressure micro-water jet into the fiber network, so that the fibers intertwined with each other to strengthen, and acupuncture method is similar, but the use of "water needle".

Complete the fiber mesh, fiber mesh reinforcement, and then after a certain post-treatment, such as drying, styling, dyeing, printing, ginning, etc., the fiber officially becomes a non-woven fabric. According to the different mesh and reinforcement processes, non-woven fabrics can be divided into many kinds, such as spunlaced non-woven fabrics, needled non-woven fabrics, spunbonded non-woven fabrics (spun into mesh), melt-blown non-woven fabrics, thermal bonded non-woven fabrics, etc., non-woven fabrics made of different raw materials and production processes also have their own different characteristics.

What are the uses of non-woven fabrics?

Compared with other textile fabrics, the non-woven fabric process is short, the production rate is fast, the output is high, and the cost is low, so the use of non-woven fabrics is very wide, and its products can be seen everywhere, it can be said that it is closely related to our daily life.

Many disposable sanitary products used in our daily life are used in non-woven fabrics, such as disposable bed sheets and pillow covers, disposable sleeping bags, disposable underwear, compressed towels, mask paper, wet wipes, cotton towels, sanitary napkins, diapers, etc. Medical industry operating clothes, isolation clothes, masks, bandages, dressings, dressing materials, etc., are also inseparable from non-woven fabrics. In addition, the wall cloth, carpet, storage boxes, vacuum cleaner filter bags, heat insulation MATS, shopping bags, clothing dust cover, etc., the floor mat in the car, the roof cloth, the door lining, the filter cloth, activated carbon packaging, seat covers, sound insulation cushioning felt, the rear window table board, etc., are also widely used non-woven fabrics.

It is believed that with the continuous innovation of non-woven fiber raw materials, production processes and equipment, more and more non-woven products with excellent performance will appear in our lives to meet our diverse needs.