Ramkumar and others at Texas Tech University believe that nanomaterials will be the future of nonwovens production. They believe that nonwoven products play a role in the development of nanotechnology. The 1934 patented cellulose acetate fiber electrospinning technology is widely recognized as the basis of nanotechnology.
Nanotechnology was first applied in the electronics industry, and the textile industry was adopted relatively late. Donaldson's nanofiltration equipment and Nano-Tex waterproof splash fabrics are small quantities of industrial products that enter the market. According to Donaldson, about one-third of all products contain some kind of nanomaterial. To date, more than 100 universities and industrial research units around the world are engaged in the exploration of nanofibers, textiles and polymers. Some governments have invested heavily in the research. According to the National Science Foundation, in 2005, investment in nanotechnology was invested. More than $4 billion. The United States, the European Union, and Japan are ahead of this, and there have been some interesting developments in fiber and textile nanotechnology in recent years.
Nanofibers
Nanoscale fiber products developed by the laboratory have the advantages of large specific surface area, flexibility, gas permeability, microporous structure, light weight, high Young's modulus and good functionality. Currently, there are a few successful batch applications. Such as filters, lining layers for chemically resistant fabrics, tissue scaffolds and some high-end engineering applications. Fibers having a diameter of 100-500 nm are generally considered to be nanofibers.
The electronic spinning method invented by Anton Formhals in 1934 is the pioneer of today's nonwoven nanofiber electrospinning. Electrospinning is a charged nozzle using a high-voltage electric field, spinning a polymer solution, and evaporating and drying the solvent to form a nanofiber web. In a strict sense, nanofibers are nonwoven fabrics of submicron fibers. Depending on the end use, various polymers, such as natural, synthetic and biodegradable polymers, can be conveniently fabricated into nanofiber webs using electrospinning. Thanks to the work of Professor Reneker of Akron University, a wave of nanofiber spinning emerged in the 1990s. Doshi pioneered nanotechnology company eSpin Technologies Inc. in Tennessee to mass produce electrospun nanofibers from a variety of polymers.
The Rutledge Group of the Massachusetts Institute of Technology (MIT) conducted a basic study of electrospinning, which determined the ability of a polymer to spin a terminal nozzle of the corresponding fiber diameter.
Applied to military industry
In addition to being used in filtration equipment, functional nanofibers are valued in military research and development due to their potential resistance to chemical and biological weapons. In order to protect the soldiers from poison damage and provide the necessary comfort, nanofibers can be useful. The nanofiber lining anti-biochemical military uniform is lightweight, breathable, versatile, and has good chemical resistance, and can protect against toxic liquids, vapors and smoke.
The Natick Military Center in the United States collaborates with governments, industry, and universities to explore the practical applications of nanofibers and nanoparticle materials in protective clothing. Among them are some encouraging topics, such as the electrospun fabric of thermoplastic elastomer polyurethane, which has good performance; it has high elasticity and requires no further processing or processing, and has higher strength. The current experiments and developments focus on functional melt-blown and electrospinning; mixing nano-scale aluminum and titanium materials into mesh materials, and other methods, adding reactive compounds to the fabric to obtain self-decontamination performance.
The addition of functional nanofiber webs with other materials can increase their application value. Nanofibers embedded with metal oxides can catalyze organophosphorus chemical weapons. Recently, Texas Tech University successfully buried magnesium oxide (MgO) in polymer fibers, carefully controlling the process, depositing nanoparticles on the fiber surface to maximize chemical reactivity and provide better anti-virus function. . Electrospinning technology can be effectively used to develop honeycomb filter-in-filter polyurethane nanowebs. These filter units provide filtration capabilities due to the better capture of particles by nanoscale meshes.
The National University of Singapore Ramakrishna Group and the Defense Technology Agency (DSTA) have collaborated to develop nanofiber biochemical masks that can replace nano-fiber meshes with activated carbon to capture poisons in the air. They embed nano-metal materials and cyclodextrins in nanometers. Fiber to break down chemical poisons. Preliminary experiments with chemical weapons mimants "paraoxon" have been successful. The ultimate goal is to develop nanofiber military uniforms that can be washed and durable.
At the same time, Professor Rutledge of MIT and his assistants developed super-hydrophobic electrospun nanomaterial fabrics, which are affected by the chemical and morphological properties of the fiber surface. These water-repellent nano-networks have a broad end in protective clothing and biomedical applications. use.
TANDEC et al., University of Tennessee, added nanophase Mn (VII) manganese oxide (M-7-0 agent) as a defensive material to the nonwoven fabric. M-7-0 is an environmentally friendly material and is a strong acid oxidizer for Louis. The main advantage of this type of nonwoven fabric is said to be safe to transport and can be made into materials of different shapes, flexibility, chemical weapons removal and industrial toxicity depending on the end use.
Applied to biomedicine
Professor Freg of Cornell University and his assistants have developed biodegradable polymers with high specific surface area and hydrophilic materials for biosensors for drug delivery and insecticide delivery. According to Freg, the high specific area of ​​nanofibers has more active sites of receptors in small volume fibers.
Donaldson has been at the forefront of nanofiber web biomedical applications and has been involved in the nanofiber business for more than 20 years. In 1981, its Ultra Web nanofiber filter equipment was industrially produced and expanded to new applications such as nanofiber cell culture materials and barrier smoke garments. In 2002, Donaldson established a new group to focus on new applications of nanofibers, and to encourage cooperative research partners to jointly expand batch applications; recently developed three-dimensional cell culture media to simulate in vivo extracellular matrix (ECM). Biodegradable nanowebs, because they are similar to extracellular matrices, can be used as tissue scaffolds. Such scaffolds bring cells closer together and grow into a three-dimensional organization. The key factors are mechanical stability, biocompatibility, cell proliferative capacity, and cell-matrix interaction. These determine the application of nanofibers in biomedicine.
latest progress
Recently, there has been great interest in nano-spun fused fibers, and Hills has developed a successful melt-spun fiber with a diameter of 250 nm using the sea-island method. According to the company, the fiber strength can reach 3 g / den, and can be wound for further processing in the downstream process. Hills has developed a spunbond fabric of 2-0.3 micron sea-island fiber; it has also been successfully manufactured by the island-sea method. It has been patented by forming a 300 nm diameter nanotube with a wall thickness of 50-100 nm. Hills' nanotube fibers can be used to defend against chemical weapons, drug release, micron-scale filtration and micron-scale hydraulics (hydraulics).
The Japanese power company (NEC) laboratory Sumio Ijima (pure husband island) developed multi-walled carbon nanotubes in 1991, which is characterized by light weight, high strength, electrical properties and heat resistance. Scientists at the NanoTech Institute at the University of Texas at Dallas (UTD) in collaboration with the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia have made great breakthroughs in the technology of spinning multilayer carbon nanotube yarns with high strength and toughness. Extremely soft, conductive heat transfer, can be made into "smart" clothing, storage of electricity, bulletproof, temperature regulation, porous, very comfortable to wear.
Great application prospects in nonwovens
One of the reasons why electronic spinning technology has not been widely applied and industrialized may be that it is difficult to buy industrial-scale machinery and equipment. NanoStatics of Ohio has developed nanofibers and high-yield electrospinning machinery manufacturing technologies that are industrially scalable. NanoStatics electronic spinning technology can produce 50-100 nanometer-diameter fibers, and its nano-network thickness can be in the range of 100 nanometers to 200 micrometers, with investment production conditions.
Zurich-based scientific management consulting firm ACON, AG estimates that the global nanotechnology market will reach $90 billion in 2015. The large number of nanofiber nonwoven products will help the nonwovens production and textile industry to develop a variety of high value-added applications, using nanoscience to expand its market share. Collaborative research in the basic business and industry will make the nonwovens committed to a win-win situation for future molecular-level technologies. (Textile and Apparel Weekly)
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