FUNCTIONAL NANOFINISING OF FABRICS
Nanotechnology (NT) deals with materials 1 to 100 nm in length. At the National Nanotechnology Initiative (NNI), NT is defined as the understanding, manipulation, and control of matter at the above stated length, such that the physical, chemical, and biological properties of the materials (individual atoms, molecules, and bulk matter) can be engineered, synthesized, and altered to develop the next generation of improved materials, devices, structures, and systems. Textiles or textile structures are abundantly used in high-performance technical applications starting from furnishing, food packaging, protective textiles, automotive to aerospace and medical textiles. In order to enhance the performance of these functional textiles, nanotechnology is considered the futuristic approach superseding the conventional chemical, physical or physiochemical modifications. NT at the molecular level can be used to develop desired textile characteristics, such as high tensile strength, unique surface structure, soft hand, durability, water repellency, fire retardancy, antimicrobial properties, etc. Indeed, advances in NT have created enormous opportunities and challenges for the textile industry, including the cotton industry. The focus of this article is to summarize applications of NT in textile finishing process which adds functionality in fabrics. 2.
Textile finishing becomes more thorough, even and precise with innovative techniques of nanotechnology. Nanofinishing or the finishing using nanotechnology can be broadly classified into two major areas – one is the use of nanoparticles in conventional finishing composition, and the other is to use a finishing composition that can develop nanostructures on the surface of the fabric. Both nanoparticles and in situ nanostructures exhibit functionality or multi-functionality with exceptional fastness and without any change in feel and comfort of the fabric. Most of the nanofinishes are in the form of nanoemulsions or nanosols.
NANOEMULSIONS or NANO SOLS:
Nanoemulsions can be defined as emulsions with mean droplet diameters ranging from 50 to 1000 nm. Usually, the average droplet size in nanoemulsions is between 100 and 500 nm, which is smaller compared to conventional emulsion, where the size is in micron range. Nanomicelles, nanosols and nanocapsules produced 1
through nanoscale emulsification can more evenly adhere to textile substrate. The preparation of nanoemulsions requires high-pressure homogenization. Although dispersion or high-energy emulsification methods are traditionally used for nanoemulsion formation, these are also efficiently formed by condensation or lowenergy methods. The droplet sizes in the range of 20–200 nm and narrow size distributions can be obtained in both the methods.
The small droplet size, high kinetic stability and optical transparency o f nanoemulsions, compared to conventional emulsions, give them advantages for their use in many technological applications. Nanoemulsions, as nonequilibrium systems, present characteristics and properties that depend not only on the composition but also on the method of preparation. Nanoemulsions are obtained by the phase inversion temperature method, phase inversion composition method or self-emulsifying method. Due to the limitations in stability of nanoemulsions, these are prepared just before their use.
Depending on the functionality required, one-sided two-sided or bulk application of nanosols can be carried out by using conventional methods of finish application such as dipping, padding or spraying. A disadvantage of nanosol is that films formed by this process is relatively thick( >100nm).
The main application for nanoemulsions is in the preparation of...
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