Chapter 1
Functional Finishing of Textiles via Nanomaterials

Azadeh Bashari*, Mina Shakeri, Anahita Rouhani Shirvan and Seyyed Abbas Noorian Najafabadi

Textile Engineering Department, Amirkabir University of Technology, Tehran, Iran

*Corresponding author: bashari@aut.ac.ir

Abstract

The unique properties of nanomaterials have real commercial potential for the textile industry. In recent years, fine materials that are produced using nanotechnology have been used in the textile production process. Production of functional textiles is the main purpose of using nanomaterials or nanocomponents on natural fibers such as cotton, wool, silk and synthetic fibers such as polyester, nylon, and acrylic, as they possess various properties such as light resistance, antimicrobial, self-cleaning, fire retardant, etc.

Different kinds of nanostructures are used in textiles. For example, carbon and copper nanoparticles or polymeric nanostructures such as polypyrrol and polyaniline as electro conductive agents; aluminum, zinc oxides, and carbon nanotubes (CNTs) for increasing durability of fibers; antimicrobial agents such as silver, zinc oxide, and titanium dioxide (TiO2); moisture absorbent agents such as TiO2; self-cleaning nanostructures such as CNT, TiO2, and fluoroacrylates; UV protection agents as TiO2 and ZnO; nano porous structures such as silicon dioxide or carbon black in order to improve dye ability of fibers; and many advanced properties such as heat conducting or insulating or electromagnetic shielding via introducing CNT or vanadium dioxide and indium tin oxide to fibers, respectively.

In this chapter, the development of using nanostructures to improve the properties of textiles is discussed. For this reason, nanostructures used in finishing processes are presented, separately.

Keywords: Nanotechnology, functional finishing, antibacterial, anti-odor, deodorant, UV-protective, water repellent, self-cleaning, flame-retardant, wrinkle-resistance

1.1 Introduction

Textiles play a major role in the development and industrialization of countries. The increasing demand for modern functional textiles has led to the usage of new materials and technology. Therefore, high-tech materials and well thought-out fabric constructions can improve the wearing comfort and provide unique properties. Antimicrobial effects, UV-protection, flame retardancy, stain and water repellency features, and others are the most important requirements of textiles. Since textiles are now widely used in different application sectors such as clothing, pharmaceutical, medical, engineering, agricultural, and food industries, imparting these characteristics into textiles can increase their potential for different applications.

Nowadays, there is a new revolution in the textile industry with the apparition of new technologies, which could add special functions and prominent features to the fabrics. For example, there has been notable improvement in technologies for natural and synthetic textile finishing, smart fabrics, and high performance functional textiles. In this sense, nanomaterials play a vital role in technological evolution since they show interesting surface properties that allow increasing their effect in comparison with bulky traditional additives and materials. For instance, using conventional nanomaterials such as metal oxide agents, carbon-based materials, host-guest compounds, and so on are examples of nanostructured materials used in antimicrobial, deodorant, UV-protection, self-cleaning, and other common finishing methods. In addition, in view of the rising environmental awareness, using environment-friendly methods and materials is necessary in the finishing process. Therefore, using alternative materials with high environmental safety is preferred.

This chapter reviews the most relevant contributions of the use of nanoparticles for functionalize textile materials. In fact, in this section, the use of nanomaterials for providing new properties such as antibacterial activity, anti-odor properties, UV-protection, self-cleaning, crease resistance, and others is explained.

1.2 Antibacterial Textiles

With increasing population in recent years, the bacterial infection problems are becoming more and more serious in comparison to the past. Many microorganisms live in human's environment. The presence of these microorganisms on textiles can lead to unwanted consequences such as paling, staining, decrease in mechanical properties, and decaying of the textile. In addition, some environmental factors such as temperature and humidity and chemical materials that are used in textile finishing can provide an appropriate media for the microorganisms to grow and multiply [1].

Some species of bacteria have a covering capsule, which surround them and keep them from drying out and other external factors. Each bacterium is enclosed by a rigid cell wall composed of peptidoglycan, a protein-sugar (polysaccharide) molecule. The wall gives the cell its shape and surrounds the cytoplasmic membrane, protecting it from the environment. The most important role of antibacterial agents is to penetrate in the cell wall and inhibit the bacteria's living.

The best way to prevent growth and multiplication of bacteria is to destroy their appropriate conditions for living. Several factors provide an acceptable media for bacteria to live such as nutritional requirements, water, oxygen, and heat. These factors are easy to find in textiles due to their contact with the human body. That is why the human body can be a good place for the microorganisms to live and multiply [2].

Antibacterial modification of textiles prevents the growth of bacteria, fungi, alga, and other microorganisms on them. One or more chemical agents that can destroy the microorganism's structure are used in this process [3].

Antibacterial materials are divided into two main groups called bacteriostatic and bactericide.

• Bacteriostatic can link to the amino acids of the DNA in the bacterial structures and prevent the multiplication of the bacteria.
• On the other hand, bactericides can disrupt the routine metabolism of the bacteria and completely destroy them [4].

A practical antibacterial agent must be easy to use in textile finishing methods, stable and durable in different treatments, compatible with other finishing materials, and non-toxic for end users and environment [3].

The antibacterial finishing of textiles has recently become a very active research field and has a great significance among the other methods of modification of textiles. Several metal nanoparticles have been suggested for antibacterial finishing of textiles such as silver, zinc, and titanium. There are also some biopolymers like chitosan, alginate, and starch that are used extensively in the textile industry.

Metal nanoparticles are more effective in comparison to biopolymers due to their multi-targeted mechanism of action, high surface area-to-volume ratio, and unique properties of these nanoparticles. A large surface area of the nanoparticles increases the contact of the antibacterial agent with bacteria and fungi, which is an important advantage of nanoparticles. Among all the materials with antibacterial properties such as copper, zinc, silver, titanium, gold, chitosan, and alginate, silver have proved to be the most effective against bacteria in antibacterial textile finishing [5].

Metal nanoparticles can be induced into textile by sol-gel technique, magnetron sputter coating, plasma sputtering, layer-by-layer coating, and other methods. One of the widely used techniques for coating textile substrates is the combination of the sol-gel synthetic procedure with the "pad-dry-cure" method [1, 6].

Some of the nanostructures that can be used in antibacterial finishing of textiles are mentioned as follows.

1.2.1 Antibacterial Organic and Non-Organic Nanostructures

These nanostructures can be applied directly on the fabric or can be loaded on the textile via a chemical carrier. There are following two groups in this category.

• Non-organic and metal nanostructures and nano composites: As mentioned before, some nanoparticles such as metal oxides, copper nano crystals, carbon nanotubes (CNTs), and nano clay can be used for antibacterial finishing of textiles.
• Nanostructure-loaded carriers: In this method, several chemical materials such as nano spheres, nano/microcapsules, dendrimers, liposomes, and nano tubes can be used for loading of the antibacterial agent and delivering it to the surface of the fabric.

Some of the mentioned nanostructures are explained briefly as follows.

1.2.1.1 TiO2 Nanoparticles

When the titanium dioxide (TiO2) catalyst is irradiated with light of energy greater than or equal to its band gap energy, electron-hole pairs are generated that can induce redox reactions at the surface of TiO2 [7]. The general scheme for the photocatalytic damage of microorganism cells by TiO2 photocatalytic properties involves several steps:

1. The photo-excited TiO2 catalyst produces electron-hole pairs that migrate to the TiO2 surface.
2. Photo-generated holes in TiO2 can react with adsorbed H2O or OH- at the catalyst/water interface to produce highly reactive hydroxyl radicals and the electrons can react with oxygen vacancies to form superoxide ions.
3. Finally, the various highly active oxygen species generated can oxidize organic compounds/cells adsorbed on the TiO2 surface, resulting in the death of the...