Views: 0 Author: Site Editor Publish Time: 2022-06-08 Origin: Site
For masks, we just know that masks are hard to buy, but we don't know why, mainly because the supply of raw materials is in short supply. The shortage of raw materials has caused the price of masks to fluctuate again and again. So, how much do you know about non-woven fabrics and meltblown fabrics? The classification and function of non-woven fabrics of medical masks are explained in detail.
First of all, we should know that the scientific name of non-woven fabrics is non-woven fabrics, so the standards of non-woven fabrics are mostly named after non-woven fabrics. The non-woven fabrics used for mask production are mostly polypropylene spunbond non-woven fabrics, polyester non-woven fabrics, etc.
With the outbreak of pneumonia caused by the new coronavirus infection, the demand for medical materials has surged in various places, and there are two main protective materials that are most needed: one is medical protective clothing, the other is medical masks, and their main production The raw material is non-woven fabric.
Non-woven fabrics are also known as non-woven fabrics and non-woven fabrics. Traditional fabrics, whether woven or knitted or other weaving methods, go through fiber-spinning-weaving, and non-woven fabrics do not require the process of spinning, hence the name. The non-woven fabric has no warp and weft threads, so it is very convenient to cut and sew, and it is light and easy to shape. Nonwovens break through the traditional textile principles, and have the characteristics of short process flow, fast production rate, high output, low cost, wide application, and many sources of raw materials.
The main process of non-woven fabrics is, fiber forming-consolidation-post-processing, the types are mainly classified according to the method of consolidation and forming, mainly including spunbond, spunlace, dipping, needle punching, hot rolling, etc., while the production The non-woven fabric in the mask is a spunlace non-woven fabric, which sprays high-pressure fine water flow onto one or more layers of fiber webs, so that the fibers are entangled with each other, so that the fiber web is reinforced and has a certain strength.
In terms of environmental protection, the raw material of most of the non-woven fabrics used is polypropylene, while the raw material of plastic bags is polyethylene. Although the two substances have similar names, they are very different in chemical structure. The chemical molecular structure of polyethylene has strong stability and is extremely difficult to degrade, so it takes 300 years for plastic bags to decompose; while the chemical structure of polypropylene is not strong, the molecular chain can be easily broken, so it can be effectively degraded , and enter the next environmental cycle in a non-toxic form. Generally, the scraps of non-woven fabrics in processing can also be recycled and remade to generate new non-woven fabrics without any harm.
Mask non-woven fabric is a kind of surface made of pure cotton absorbent gauze or knitted fabric, with various non-woven fabrics sandwiched in the middle. The filtering effect of non-woven mask is good, but the ventilation is slightly poor. The variety of non-woven mask is non-woven material on the surface and back, and filter paper in the middle, so that the filtering effect of non-woven mask is higher. Non-woven fabrics are moisture-proof, breathable, flexible, light in weight, non-combustible, easy to decompose, non-toxic and non-irritating, rich in color, low in price, and recyclable. For example, polypropylene) pellets are used as raw materials, which are produced by a continuous one-step method of high-temperature melting, spinning, laying, and hot-pressing coiling. The non-woven fabric has no warp and weft threads, so it is very convenient to cut and sew, and it is light and easy to shape.
The core material for mask production, non-woven fabrics, is classified as industrial textiles and ranks third in the manufacturing of textile surface materials after woven and knitted fabrics. Non-woven English Non Woven Fabric, also known as non-woven fabric, is composed of directional or random fibers. It has the appearance of cloth and some cloth properties and is called non-woven fabric. Non-woven fabrics are not interwoven and woven together by traditional yarns. Non-woven fabrics are made by directly bonding fibers together by physical and chemical methods, so non-woven fabrics have no thread ends, unlike woven fabrics that can pull out thread ends.
Raw materials for non-woven production: The fibers used in non-woven production are mainly polypropylene (PP), polyester (PET), nylon (PA), viscose, acrylic, ethylene (HDPE), polyvinyl chloride (PVC), masterbatch Wait.
1. Spunlace non-woven fabric
The spunlace process is to spray high-pressure fine water flow onto one or more layers of fiber webs, so that the fibers are entangled with each other, so that the fiber webs are reinforced and have a certain strength.
Features: flexible entanglement, does not affect the original characteristics of the fiber, does not damage the fiber. The appearance is closer to traditional textiles. High strength and low fluff. High hygroscopicity, absorbs moisture quickly. Soft to the touch and good drape. The appearance is varied. The production process is long and covers a large area. The equipment is complex, the energy consumption is large, and the water quality requirements are high.
Main applications: medical curtains, surgical gowns, surgical cover cloths, medical dressing materials, wound dressings, medical gauze, aviation rags, clothing lining fabrics, coated fabrics, advanced rags in the electronics industry, cotton pads, wet wipes, mask wrapping materials, etc.
Spunbond non-woven fabric is after the polymer has been extruded and stretched to form continuous filaments, the filaments are laid into a web, and the web is then self-bonded, thermally bonded, chemically bonded or mechanically reinforced. The web becomes a non-woven fabric.
Features: The fiber web is composed of continuous filaments. Excellent tensile strength. There are many changes in the process, and various methods can be used for reinforcement. The filament fineness varies widely.
Applications: Polypropylene (PP): geotextiles, tufted carpet base fabrics, coated base fabrics, medical and health materials, covering materials for disposable products, etc. Polyester (PET): filter materials, lining materials, tufted carpet base fabrics, agricultural materials, packaging materials, etc.
2. Meltblown non-woven fabric
The process of melt-blown non-woven fabrics: polymer feeding---melt extrusion---fiber formation---fiber cooling---web formation---reinforcement into cloth. The high-speed hot air draws the thin stream of polymer melt extruded from the spinneret hole of the die, thereby forming ultra-fine fibers and condensing on the condensing screen curtain or drum, and becomes a non-woven fabric by self-bonding. principle. Features: The web consists of extremely fine shorter fibers. The uniformity of the fiber web is good, and the hand feels soft. Filtration performance and liquid absorption performance are good. The web strength is poor.
Application: filter materials, medical and health materials, clothing materials, battery separator materials, wiping materials.
3. Heat-sealed non-woven fabrics:
Fibrous or powdery hot-melt adhesive reinforcement materials are added to the fiber web, and the fiber web is then heated, melted, cooled, and consolidated into cloth.
Features: Surface-bonded hot-rolled surfaces are mostly smooth, and point-bonded hot-rolled are relatively fluffy.
Application: Production of baby diapers and women's sanitary napkin covering materials, ointment base cloth, clothing lining, masks, etc.
Pulp Airlaid Nonwoven
Airlaid non-woven fabrics can also be called clean paper and dry-laid non-woven fabrics. It uses the air-laid technology to open the wood pulp fiberboard into a single fiber state, and then uses the air-laid method to condense the fibers on the web-forming curtain, and the fiber web is then reinforced into a cloth.
Features: good bulkiness, soft hand feeling, super hygroscopic performance.
Application: Medical hygiene materials, especially disposable hygiene products with high water absorption (such as diapers, sanitary napkins, wet wipes, wipes, etc.).
4. Wet-laid non-woven fabric
Wet-laid non-woven fabrics are to open fiber raw materials placed in an aqueous medium into single fibers, and at the same time mix different fiber raw materials to make fiber suspension pulp. Reinforced into cloth.
Features: High production speed, up to 400m/min. Short fibers can be fully utilized. Product fiber uniformity is good. Large water consumption and high one-time investment.
Applications: Specialty Paper: Dust/Liquid Filter Paper, Tea Bags. Industrial use: filters, insulating materials, sound-absorbing materials. Medical use: medical backing, medical tape, surgical bag wrapping material. Civil: wallpaper, etc.
5. Needle punched non-woven fabric
Needle-punched non-woven fabric is a kind of dry-laid non-woven fabric. Needle-punched non-woven fabric uses the puncturing effect of thorn needles to reinforce the fluffy fiber web into cloth.
Features: Flexible entanglement between fibers, with good dimensional stability and elasticity. Good permeability and filtration performance. It feels plump and fluffy. Various collection patterns or three-dimensional molding products can be manufactured upon request.
Application: geotextile, geomembrane, velvet cloth, speaker blanket, electric blanket cotton, embroidery cotton, clothing cotton, Christmas crafts, artificial leather base cloth, special cloth for filter materials.
6. Stitched non-woven fabric
Stitch-bonded non-woven fabrics are a kind of dry-laid non-woven fabrics. The stitch-bonding method is to use the warp-knitted coil structure to fabricate fiber webs, yarn layers, non-woven materials (such as plastic sheets, plastic thin metal foils, etc.) or their combinations. The body is reinforced to make a non-woven fabric.
Features: Durable, Disposable. Insulating, conducting. Softness, stiffness. fineness, expansion.
Application: Garment lining, flakes, toe lining, heel lining, underwear, artificial deerskin, synthetic leather, thermal shoe lining, cloth sole lining, etc.
7. Hydrophilic non-woven fabric
Mainly used in the production of medical and sanitary materials to achieve a better feel and not scratch the skin. For example, sanitary napkins and sanitary pads use the hydrophilic function of hydrophilic non-woven fabrics.
Features: Non-woven fabrics have a certain ability to absorb moisture.
Application: medical supplies, hygiene care supplies, sanitary napkins, sanitary pads, etc.
Of course, since there is no clear standard, the previous experience in mask testing and non-woven testing is summarized, and several important testing indicators are proposed, namely filtration efficiency, respiratory resistance, hygiene indicators, and toxicology tests.
As we all know, filtration efficiency is a key indicator for the quality assessment of masks. This is also one of the important quality standards for non-woven fabrics, so referring to relevant standards, we recommend that the bacterial filtration efficiency of non-woven masks for masks should be no less than 95%, and the particle filtration efficiency for non-oily particles should be no less than 30%.
Respiratory resistance, the size of the influence on people's breathing when they wear masks. Therefore, the breathing resistance of the non-woven fabric of the mask determines the breathing comfort when wearing the mask. Here we recommend that the inhalation resistance should be ≤350Pa, and the expiratory resistance should be ≤250Pa.
Hygiene indicators are naturally another important key indicator of mask non-woven fabrics. Here we recommend testing items mainly for initial contamination bacteria, total bacterial colonies, coliforms, pathogenic pyogenic bacteria, total fungal colonies, Escherichia coli, Staphylococcus aureus, Candida albicans, ethylene oxide residues, etc.
The skin irritation test is mainly a protective test test for people allergic to some materials. Refer to the provisions in GB 15979. The skin irritation test of mask non-woven fabrics mainly uses a cross-sectional method to cut a sample of an appropriate area, soak it with physiological saline and then stick it on the skin, and then cover it with a patch for testing.
A warm reminder from Siyuan Medical Devices: In addition to providing effective protection, the wearing of masks must also take into account the comfort of the wearer and must not bring negative effects such as biological hazards. Generally speaking, the higher the protective performance of the mask, the greater the impact on the comfort performance. When people inhale while wearing a mask, the mask has a certain resistance to the air flow. When the inspiratory resistance is too large, some people will feel dizziness, chest tightness and other discomforts.
Different people have different industries and physiques, so the requirements for the sealing, protection, comfort, adaptability and other indicators of masks are also different. For some special groups, such as children, the elderly, people with respiratory diseases and cardiovascular diseases, it is necessary to choose the type of masks carefully, and under the premise of ensuring safety protection, avoid accidents such as hypoxia and dizziness when wearing for a long time.