Nano Finishing of Textiles-AN INCIPIENT TECHNOLOGY

Overview:• Introduction• Nanotechnology• Textile finishing• Introduction of Nano finishes in textiles• Characteristics of Nano finishing in garments• Synthesis of Nano phase materials• Nano particles used according to properties• Nanotechnology applications in textiles.• Conclusion

Introduction:• The term Nano in Nano technology comes from a Greek word

« Nanos » which means ‘dwarf’. The dictionary meaning of dwarf is abnormally small. On a scale of 10-9 having or involving dimensions of less than 100 nanometer.

• Today, the use of nanotechnology is allowing textiles to become multifunctional. The emergence of a reality to create, alter and improve textiles at the molecular level, and to enhance their durability and performance beyond those of existing textile products, is already apparent due to applications of nanotechnology.

Nanotechnology:• Nanotechnology is the engineering of functional systems at the

molecular scale. • It is the design characterization, production and application

structures, devices and system by controlling shape & size at Nano scale.

• This technology that can work at the molecular level, atom by atom to create large structures with improved molecular organization.

Nanotechnology:A NANO SIZE PARTICLES NORMAL 0.03 MICRON SIZE

PARTICLES

Textile finishing:• A finish is done to a fabric after weaving

or knitting to change its appearance, handle & performance.

• Textile finishing is a term commonly applied to different process that the textile material undergoes after pretreatments (singeing, desizing, scouring, bleaching), dyeing & printing to enhance their attractiveness and sale appeal as well as comfort & useful finish.

Introduction of Nano finishes in textiles:

The first commercial application of Nano tech in textile and clothing industry is found in the form of Nano particle (sometimes called Nano bead) through a finishing process, which is generally known as Nano finishing. The impact of Nano technology in the textile finishing area has brought up innovative finishing as well as new application technique.

Characteristics of Nano finishing in apparels:• Nano-processed garments have protective coating, which is water

and beverage repellent.• Their protective layer is difficult to detect with the naked eye.• When a substance is manipulated at sizes of approximately 100

nm, the structure of the processed clothing becomes more compressed. This makes clothing stain- and dirt-resistant.

• Saving time and laundering cost.• This technology embraces environmental friendly properties.

Characteristics of Nano finishing in apparels:• Nano-materials allow good ventilation and reduce moisture

absorption, resulting in enhanced breathability while maintaining the good hand feel of ordinary material.

• The crease resistant feature keeps clothing neat.• Nano-processed products are toxic free.• Garments stay bright, fresh looking and are more durable than

ordinary materials.• Manufacturing cost is low, adding value to the products

Synthesis of Nano phase materials:

• A large number of methods exist for the synthesis of Nano phase materials.

• They include synthesis from atomic or molecular precursors (chemical or physical vapor deposition; gas- condensation; chemical precipitation; aerosol reactions; biological templating), from processing of bulk precursors (mechanical attrition; crystallization from the amorphous state; phase separation), and from nature.

• It is generally preferable to synthesize nanostructured materials from atomic or molecular precursors, in order to gain the greatest control over a variety of microscopic aspects of the condensed ensemble, but other methodologies can often yield very useful results.

Chemical vapor deposition:• Chemical vapor deposition (CVD) is a chemical process used to

produce high-purity, high-performance solid materials.• Chemical Vapor Deposition is the formation of a non-volatile solid film on a

substrate by the reaction of vapor phase chemicals (reactants) that contain the required constituents.

• The reactant gases are introduced into a reaction chamber and are decomposed and reacted at a heated surface to form the thin film.

Plasma deposition:

Plasma deposition:• Plasma polymerization (or glow discharge polymerization)

uses plasma sources to generate a gas discharge that provides energy to activate or fragment gaseous or liquid monomer, often containing a vinyl group, in order to initiate polymerization. 

• Polymers formed from this technique are generally highly branched and highly cross-linked, and adhere to solid surfaces well.

• The biggest advantage to this process is that polymers can be directly attached to a desired surface while the chains are growing, which reduces steps necessary for other coating processes such as grafting.

• This is very useful for pinhole-free coatings of 100 Pico meters to 1 micrometer thickness with insoluble polymers.

Plasma Polymerization Mechanism and Species:

Nanoparticles Used according to Properties:

SL No Nano particles Properties 01 Silver Nano particles Anti-bacterial finishing02 Fe Nano-Particles Conductive magnetic properties, remote heating.

 03 ZnO and TiO2 UV protection, fiber protection, oxidative catalysis04 TiO2 and MgO Chemical and biological protective performance,

provide self-sterilizing function.05 SiO2 or Al2O3 Nano-particles with PP or

PE coatingSuper water repellent finishing.

06 Indium-tin oxide Nano-Particles EM / IR protective clothing.07 Ceramic Nano-Particles Increasing resistance to abrasion08 Carbon black Nano-Particles Increasing resistance to abrasion, chemical resistance

and impart electrical conductivity, coloration of some textiles.

09 Clay Nano-particles High electrical, heat and chemical resistance.10 Cellulose Nano-whiskers Wrinkle resistance, stain resistance, and water

repellency. 

Nanotechnology applications in textiles:• Due to the advancement of

nanotechnology in the manufacturing of fibers/yarns including the development of fabric finishes, the applications and scopes are widespread in the area of textiles for the last few decades.

• By combining the nanoparticles with the organic and inorganic compounds, the surfaces of the fabrics treated with abrasion resistant, water repellent, ultraviolet (UV), electromagnetic and infrared protection finishes can be appreciably modified.

Water repellence:• The water-repellent property of fabric can be improved by creating

Nano-whiskers, which are hydrocarbons and 1/1000 of the size of a typical cotton fiber, that are added to the fabric to create a peach fuzz effect without lowering the strength of cotton.

• The spaces between the whiskers on the fabric are smaller than the typical drop of water, but still larger than water molecules; water thus remains on the top of the whiskers and above the surface of the fabric.

• The performance is permanent while maintaining breathability. This can be developed also by the Nano Sphere impregnation involves a three-dimensional surface structure with Gel-forming additives which repel water and prevent dirt particles from attaching themselves.

Water repellence:The mechanism is similar to the lotus effect occurring in nature, as demonstrated in Figure 1. Lotus plants have super hydrophobic surfaces which are rough and textured.

Self-cleaning textiles:• Super hydrophobic surfaces have considerable technological

potential for textile applications due to their extreme water-repellent properties.

• Finished surfaces with a high contact angle can also exhibit a self-cleaning effect. Extremely water-repellent super hydrophobic surfaces can be produced using roughness of nanoparticles combined with hydrophobicity of polymer matrix.

• By adopting such methods, the contact angle of the resultant surface can easily reach as high as 120°.

Self-cleaning textiles:The textile surface modification methods mainly include sol-gel methods to fabricate a fluorinated inorganic organic coating on polyamide 6.6 textiles, grafting poly(acrylic acid) on a polyamide polymer surface and then chains.

Cotton-based super hydrophobic surfaces can be fabricated mainly by modification of hierarchical Nano scale structure that can confer super hydrophobicity on the cotton substrates.

UV-protective finish:• The UV-blocking property of a fabric is enhanced when a dye,

pigment, de-lust rant, or ultraviolet absorber finish is present that absorbs ultraviolet radiation and blocks its transmission through a fabric to the skin.

• To impart UV- protection, several Nano compounds or nanoparticles can be applied on textile material. Inorganic UV-blockers are more preferable to organic UV-blockers as they are non-toxic and chemically stable under exposure to both high temperatures and UV.

• Inorganic UV-blockers are usually certain semiconductor oxides such as TiO2, ZnO, SiO2 and Al2O3

UV-protective finish:• Titanium dioxide is a photo catalyst; once it

is illuminated by light with energy higher than its band gaps, the electrons in TiO2 will jump from the valence band to the conduction band, and the electron (e-) and electric hole (h+) pairs will form on the surface of the photo catalyst.

• The negative electrons and oxygen will combine into O2 the positive electric holes and water will generate hydroxyl radicals.

• Since both are unstable chemical substances, when the organic compound falls on the surface of the photo catalyst it will combine with O2 and OH- respectively, and turn into carbon dioxide (CO2) and water (H2O).

Anti-bacterial finish:• For imparting anti-bacterial properties, Nano-sized

silver, titanium dioxide and zinc oxide have been used so far.

• With the use of Nano-sized particles, the number of particles per unit area is increased, and thus anti-bacterial effects can be maximized.

• Nano silver particles have an extremely large relative surface area, thus increasing their contact with bacteria or fungi, and vastly improving their bactericidal and fungicidal effectiveness.

Anti-bacterial finish:• Nano-silver is very reactive with

proteins. • When contacting bacteria and fungus,

it will adversely affect cellular metabolism and inhibit cell growth.

• It also suppresses respiration, the basal metabolism of the electron transfer system, and the transport of the substrate into the microbial cell membrane

• Hence, Nano silver particles are widely applied to socks in order to prohibit the growth of bacteria.

Anti-bacterial finish:• In addition, nano-siIver can be applied to a large range of other

healthcare products such as dressings for burns, scald, skin donor and recipient sites.

• It has been established that a fabric treated with nano-TiO2, could provide effective protection against bacteria and the discoloration of stains, due to the photo catalytic activity of nano-TiO2.

• ZnO nanoparticle can also provide effective photo catalytic properties once it is illuminated by light, by the way it can be employed to impart anti-bacterial properties to textiles.

Anti-static finish:• ZnO nanoparticles have been used for various applications like UV

protection, mechanical, antibacterial finishes in textiles as discussed earlier. Another area of application of ZnO is antistatic finishing agent in textiles.

• Nano ZnO with amphoteric surfactant was used to prepare nanometer antistatic finishing agent and the effect of Nano ZnO concentration, ratio of reactants and reaction temperature were analyzed by Fan and Junling .

• The cotton fabric and the polyester fabric were both finished by pad-dry-cure process with the above antistatic finishing agent.

• They found that the charge density of the treated fabric decreased significantly in comparison with the original piece, showing that the fabric finished with the antistatic finishing agent was compounded with Nano ZnO producing antistatic performance.

Anti-static finish:• It was found that a low concentration of finishing agent is able to

achieve a better antistatic effect.• Increasing the amount of ZnO nanoparticles added decreases the

fabric antistatic property, because of the declined dispersion and increased agglomeration of Nano ZnO finishing agent. The increased amount of nanoparticles results in the limitation of characteristics of nanoZnO.

• Through comparison between cotton and polyester treated fabrics, it was observed that the decline rate of charge density of the latter is more obvious than the former, revealing that the antistatic effect of polyester fabric finished with nanometer antistatic finishing agent is better.

Wrinkle free finish:

• To impart wrinkle resistance to fabric, resin is commonly used in conventional methods. However, there are limitations to applying resin, including a decrease in the tensile strength of fiber, abrasion resistance, water absorbency and dye ability, as well as breathability.

• To overcome the limitations of using resin, some researchers employed nano-titaniumdioxide and Nano-silica to improve the wrinkle resistance of cotton and silk respectively.

• Nano-titanium dioxide was employed with carboxylic acid as a catalyst under UV irradiation to catalyze the cross-linking reaction between the cellulose molecule and the acid.

• On the other hand, Nano-silica was applied with maleic anhydride as a catalyst; the results showed that the application of Nano-silica with maleic anhydride could successfully improve the wrinkle resistance of silk.

Anti pollen finish:• A few marketing companies around the world have introduced anti-

pollen fabrics and garments.• It is claimed that particles of 30 nm sizes are attached to the

surface of yarns thus the smoothness of the finish on the surface and the anti-static effect does not let pollen or dust come close.

• This is achieved by using the polymer which has antistatic or electro conductive composition e.g. Fluro alkyl – methacrylate polymers).

• It is used in coats, blouses, hats, gloves, arm covers, bedding covers, etc.

Flame retardant finish:• NYACOL Nanotechnologies TM has

been developed colloidal antimony pent oxide which has been applied for flame retardant finish in textile.

• Colloidal antimony pent oxide has been offered as fine particle dispersion, for use as a flame retardant synergist with halogenated flame-retardants (the ratio of halogen to antimony is 5:1 to 2:1).

• Nano antimony pent oxide is used with halogenated flame-retardants for a flame retardant finish to the garments.

Conclusion:• Nano finishes being developed for textile substrates are at their infantile stage. • Nanotechnology is an emerging technology, which is no longer just a vision for

the future as it was generally seen at the end of 20th century. Instead, nanotechnology is a ubiquitous technology with a lot of potential to impact on every aspect of modern technology.

• Nanotechnology, with all its challenges and opportunities, is an unavoidable part of our future. The possibilities with nanotechnology are immense and numerous .

• The researches are filled with technology are beginning to make their mark. The new concepts exploited for the development of Nano finishes have opened up exciting opportunities for further R&D.

• In future, one can expect to see many more developments in textiles based on Nano technology. At last “Nano-Finishing” can be described as a “Synonyms for Innovation”.