History of Micro fibers:


Japanese fibre manufacturing companies introduced the first 'micro-denier' products during the 1970s. Then followed the developments in Europe during the 1980s, and since the 1990s American fibre manufacturers have been following suit. At present, polyester and nylon are generally used for manufacturing microfibres. However, 'micro-denier' versions of rayon and acrylic products are on the horizon.


For as long as microfibre technology has been around, ultra-microfibre technology has existed as well. These are fibres that are less than 0.3dtex, and especially within the range of 0.1dtex. Several different processes can be used to make these fibres, all involving the splitting of a larger fibre into many smaller ones.


Micro fibers supervised as:


  • Lightweight and flexible
  • Good stability and shape retention
  • Anti-wrinkle property
  • Have a wicking ability that permits perspiration
  • Comfortable to wear as they are more spongy
  • Doesn't water stain - superior water repellency is available
  • Woven or knitted into a very high quality fabric construction
  • Formerly commenced as a polyester microfiber, today you can find nylon, rayon and acrylic microfibers too.
  • Strong and durable, water repellent and wind resistant -so tightly woven, that the fabric can't be penetrated by wind, rain or cold
  • Lightweight, resilient or resist wrinkling, have a comfortable array, preserve shape and resist pilling.
  • The positively charged microfibers draw dust; the tiny fibers are capable to enter the microscopic surface voids most materials.
  • Washable, dries quickly and also washable in at the water temperatures up to 200 degrees and their characteristics will remain intact.
  • Electrostatic effect - Hair, lint and other dust particles are attracted and grabbed by the microfibers without lifting dust.
  • The density of the material allowable it to grip six to eight times its weight in water hence high absorbing power capacity.
  • The attraction capability of the microfibers is so sound, even absorbs bacteria and germs - hence can be use as germ or bacteria free purpose.
  • The fabric consists of millions of small tiny conduits that carry oil and grease too.


Benefits of Microfibers:


  • Comfortable - very soft, texture like silk, lightweight
  • Due to its fineness and superior fiber surface area making deep, rich and bright colors achievable.
  • Less "sweaty" in warm weather than usual synthetics
  • Quickly cleanable - clean just with water
  • Highly intense and shrink-resistant
  • Presents insulation and breath ability
  • Change without help - to establish lovely drape
  • Very fine - finer than the most precise silk
  • More reusable for cleaning alternative - compared to other mops more efficient and long life.

Dyeing Properties of Polyester Micro fiber:


Sorption isotherms and dyeing rates of purified disperse dyes on polyester microfibers (fineness of 0.25-1.0 denier) from water have been measured at 95C. The isotherms are curved and well described in terms of the dual-mode sorption model: Nemst-type partitioning and Langmuir sorption are concurrently operative. The effect of a diffusion boundary layer on the dyeing rate is small under the conditions; the microfibers were dyed in the form of a bulky two-ply yarn in a well stirred bath. Dyeing rates of a commercial dye are also measured at 110 and 130C. For dyeing of a 0.32d fiber at 130C, the amount of dye sorbed by the fibers attains a maximum value at an early stage and then decreases gradually. This phenomenon is explained in terms of the aqueous solubility of very fine dye particles. The relation between dye sorption behavior and the fine structure of the microfibers is discussed.


Dyeing properties of a polyester taffeta made from ultra fine fibers (0.07 denier) with disperse dyes are clarified through an analysis of sorption isotherms and rate of dye sorption data in comparison with those for microfibers (0.25, 0.32, and 0.44 denier). Ultra fine fibers are made using sea-island-type conjugate spinning techniques, while the microfibers are made by the conventional melt spinning method. Physical properties of the ultra fine fibers relating to the dyeing properties are also measured. The sorption-diffusion behavior of purified disperse dyes in the 0.07 denier (0.07d) fibers at 95C and the physical properties of these fibers are almost the same as those of the microfibers, except for the 0.25 denier (0.25d) fiber, which contains 0.5% additives to facilitate spinning. Therefore, ultra fine fibers can be dyed by considering only the difference in the fiber radius. Two polyester taffetas are used to measure dyeing kinetics, i.e., 0.07d fibers and 0.25d fibers. Delay of dye sorption at the initial stage is appreciable for the 0.07d taffeta with purified dyes at 95C and the 0.07d and 0.25d taffetas with commercial dyes at 120C. This phenomenon is explained in terms of the presence of diffusional boundary layers around the individual filaments caused by the very slow movement of dye liquor through the taffetas. Color yields of the commercial dyes on the two taffetas are discussed.


Dyeing of Polyester Microfibers:


Due to their fineness, the total surface area of microfibre yarn or fabric is far greater than ordinary fibres. Therefore,


  1. Due to its special structure ,micro fibers has much larger quantity of size ,oil agents and wax on warp yarns.
  2. Since microfibres have very small interstitces, with consequent difficulties of size accessibility and duffusibility, desizing becomes quite difficult and costly.
  3. Microfibres have greater absorption area resulting in a dyeing rate four times higher than that of normal, which can cause unlevelness in dyeing.
  4. They also require more dyestuff than standard fibres to obtain the same depth of shade.
  5. Larger external surface means an increase in number of threads exposed to light which, on destruction of dye, is expressed as lower light fastness rating.
  6. Wash fastness and color fastness to rubbing is also poor.
  7. Staple microfibres offer difficulty in carding.

The problems in wet processing of micro fibers can be overcome by:


  1. Better knowledge about the size applied and optimum parameters during desizing operation.


To achieve satisfactory dyeing effects, desizing and refining process must be done before dyeing and after desizing and refining, there should be no impurities left such as electrolyte, antistatic finishing agent, spin finishes and blot.


  1. Pre-setting


Suitable pre setting conditions (time, temperature and tension) helps not only in stable dimensional stability, softness but also better dyeing results.


  1. Alkali weight reduction


Alkali weight reductions to treat the fabric with concentrated alkali at high temperature. Fiber molecule hydrolyse under this condition and lose some weight with change in properties, thus space occurs between crossing points and rubbing resistance relative to slippage among yarns becomes small. Alkali weight reduction makes fabric soft, liveliness, limber and improved absorption.


Proper dye selection for micro fiber dyeing:


  • Compatible
  • Having same exhaustion rates
  • Having high wash fastness properties.
  • Good migration and leveling properties
  • Eliminates problems regarding build-up and fastness properties.
  • Disperse dyes for polyester microfibers


Proper selection of dye bath additives such as:


Leveling agents: A strong leveling agent which shall start working at lower temperatures.


Dispersing agents: Higher quantities of dispersing agents are needed because amount of dyes required are more to produce the desired depth.


Chelating agents: Ant creasing agents, Dye bath softeners/Lubricants because micro fiber textiles are prone to creasing, therefore use off dye bath lubricants is must.


Soaping: In order to obtain satisfactory color effect, fabric should be soaped after dyeing .Soaping is the key process to achieve satisfactory dyeing results especially on polyester / nylon micro denier fabric.


Reduction clear: Good reduction clear process is needed to achieve satisfactory washing, rubbing and light fastness properties.


Washing: Is required for neutralizing and removing alkali after reduction clear treatment.

Application of Microfibers dyed good:


Microfibers are most commonly found in polyester and nylon. Some rayon and acrylic micros are in production and available to consumers. Micros can be used alone or blended with conventional denier man-made fibers as well as with natural fibers such as cotton, wool, and silk.


In textiles,


Microfibers are used in a variety of fabrics, but most commonly in dress and blouse weight garments. Suit jackets and bottom weights are becoming available. Look for micros in lingerie, rainwear, outdoor fleece and wind-resistant sportswear, as well as tents, sleeping bags, track and jogging suits. The strength of microfibers make them particularly adaptable to sueded or sandwashed finishes because of their extensive fiber surface area and the use of strong fibers like polyester and nylon. As a result, many microfibers simulate the appearance of sandwashed silk.


Other Main products for which micro fiber are ideally suited:


  • Micro fiber Glass Cloth
  • Duster/Multi-purpose Micro fiber Cleaning Cloth
  • Micro fiber Scrubber
  • Micro fiber Kitchen Cloth
  • Micro fiber Optical & CD Cloth
  • Micro fiber Mops
  • Micro fiber Cleaning Sponge
  • Micro fiber Cleaning Cloths Terry Cloths, Suede Cloths, Waffle-Weave Cloths


Procedure:


  1. The substrate (polyester/nylon) is treated in a bath containing a carrier and pH-adjusting agent at 50C for about 10 minutes.
  2. Dispersing agent and disperse dye solution are then added and the temperature is raised to 110C to carry out dyeing under the high-temperature conditions for dyeing with the use of a carrier.
  3. Reduction cleaning is carried out after dyeing so that disperse dye staining on nylon can be stripped as much as possible.
  4. The dyeing of the nylon component is carried out under the usual dyeing conditions for 100% nylon.
  5. Fixing is carried out for improved wet fastness, if necessary.


Dyeing auxiliary used Carrier:


  • Carriers for polyester are used, mainly those which are methylnaphthalene-based.
  • Dispersing agents that produce superior effects at high temperatures are used rather than dispersing/leveling agents.
  • Reduction clearing agent
  • Nonionic/amphoteric-type surfactants for reduction clearing of 100% polyester are used.
  • Leveling agents for 100% nylon are used.
  • Fixing agent for nylon.
  • Selection should be made mainly focusing on acid dye fixing properties.

Some examples of general and spectacular applications of microfibres:


  1. Automotive application to improve air oil filtration, allowing improved engine performance and extended life;
  2. Perfect for asthma and allergy sufferers, removing dust mites without chemicals;
  3. Used extensively for hair transplantation, this works to conceal thinning hair.
  4. Microfibres are also used in sports applications such as sports wear, sports materials, etc.
  5. Microfibres are extensively used as a luxurious apparel wear.
  6. Microfibres as swing threads.
  7. Microfibres for production of synthetic leather.
  8. Use in the technical textile sector, as well as outside the clothing industry.
  9. Computer mouse pads, along which the mouse can slide easily, keeping the mouse ball clean at the same time.
  10. Polishing cloths for wafers and hard disks, acoustic insulation, high performance sound absorption panels and concert hall seat covers, among other products.


Conclusion:


Microfibres are a completely new generation of ultra-fine synthetic yarns, which have not yet reached their peak of development. There are still a wide range of possibilities to be explored in the design, production, processing and use of this type of fibre. In addition to the common raw materials, PES, PA, and PAC, this specialty range will in future include other raw materials such as cellulose.


References:


  1. Polyester microfibre fabric by Prof. (Dr.) M.D. Teli.J.T.A. Mar-April 1999, 295-299.
  2. Microfibre Production, Properties & Application, by S .K. Pal. Textile ASIA, Vol. 24, Jan. 1993, 53-58.
  3. Production of Microfibres, by Dr. (Ms.) S. Thiel J.T.A. Jan-Feb 1997, 213-216.
  4. Microfibres, by Prof. D.B. Ajgaonkar. M.M.T.T., Sept. 1992, 327-337.
  5. Micro Denier Yarns, by K. L. Vidur. NCM, March 1997, 9-16.
  6. Microfibres, The New Man-Made Fibre Image, by Jurg Rupp & Akira Yonenaga. I.T.B.Vol.46, (4th Issue) April 2000, 12-24.


Image Courtesy:


  1. Tradekorea.com


This article was originally published in Textile learner blog run by Mazharul Islam Kiron.