Nanomaterials in the Wet Processing of Textiles

Preface

Nanotechnology has been booming in many areas, including materials science, mechanics, electronics, optics, medicine, plastics, energy, electronics, and aerospace. Nowadays, it is playing an extraordinary role in the functional finishing of textiles and polymers. It has sought to improve existing material performances and develop fibers, composites, and novel finishing methods. Application of nanoparticles has imparted novel characteristics to textiles such as flame retardation, UV-blocking, water repellence, self-cleaning, and antimicrobial properties. This book on Nanomaterials in the Wet Processing of Textiles presents diverse aspects of nanomaterial application in the textile industry, approaches used for synthesis and application, as well as strategies to remove toxic effluents from wastewaters employing state-of-the-art nanoadsorbents. We have no doubt that the readers will benefit from this book which covers latest developmental work pertaining to functionalization of textiles using diverse nanomaterials. We would also like to thank all the authors who contributed the chapters and provided their valuable ideas and knowledge in this book. We are also very thankful to the editorial board, and in particular to Martin Scrivener for the generous cooperation at every stage of the book production.

Shahid-ul-Islam

B.S. Butola

Indian Institute of Technology Delhi

(IITD), Hauz Khas, New Delhi, India

December 15, 2017

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: [email protected]

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:

The photo-excited TiO2 catalyst produces electron–hole pairs that migrate to the TiO2 surface.

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.

Finally, the various highly active oxygen species generated can oxidize organic compounds/cells adsorbed on the TiO2 surface, resulting in the death of the microorganisms [8].

By the combination of electron and electron hole with oxygen, carbon dioxide and water will form in an oxidation-reduction reaction (Figure 1.1).

Figure 1.1 Photocatalysis mechanism of titanium dioxide [9].

Through this reaction, TiO2 nanoparticles can destroy the cell wall of the bacteria and provide an effective protection against them [9, 10].

1.2.1.2 Silver Nanoparticles

Silver is a nontoxic inorganic metal, which is not harmful for the human body. Several studies have shown that silver has a broad antibacterial activity toward bacteria and fungi. It is believed that the antibacterial effect of silver nanoparticles comes from their strong affinity toward phosphorus or sulfur. Since the cell wall of the bacteria contains amounts of sulfur-containing proteins, silver nanoparticles can react with these groups and affect the bacteria performance [11, 12]. It was also reported that the released silver ions (particularly Ag+) from silver nanoparticles can interact with phosphorus moieties in DNA, leading to inactivation of DNA replication, or react with sulfur-containing proteins, resulting in the inhibition of enzyme functions [13].

Silver nanoparticles have attracted many researchers due to their effective performance against bacteria and fungi. These nanostructures can be very reactive with proteins and will inhibit the growth of the bacteria completely (Figure 1.2) [9].

Figure 1.2 Close-up of the TEM image of silver nanoparticles in different shapes and sizes [5].

Scientists suggest the following three main mechanisms for antibacterial effect of silver nanoparticles:

Decomposing of the bacterial cell wall

Reacting with the S–H group in the enzymes and inhibiting the metabolism of the microorganism

Creating the active oxygen groups [14].

In recent years, researchers have been studying on the usage of silver nanoparticles in nano composites with polypropylene fibers and other metal oxides [15].

1.2.1.3 ZnO Nanoparticles

Zinc oxide nanostructures are also photocatalyst materials, which has the same mechanism as TiO2 nanoparticles. ZnO nanoparticles are widely used now in antibacterial textiles due to their effective photocatalytic properties [9].

Recent studies indicate that the ZnO nanostructure show better antibacterial properties when doped with CuO molecules. It can be due to the narrower band gap of Zn structures when doped with copper and better photocatalysis activity in this condition [16].

In another study, antibacterial behavior of suspensions of zinc oxide nanoparticles has been investigated against E. coli. It was deducted that the effects of particle size, concentration, and the use of dispersants are large on the antibacterial behavior. The results show that the ZnO nano fluids have bacteriostatic activity against E. coli. It was also deducted that the antibacterial activity increases with increasing nanoparticle concentration and with decreasing particle size, while it turned out that particle concentration is more important than particle size. SEM analyses of the bacteria before and after treatment with ZnO nano fluids show that the presence of ZnO nanoparticles damages the membrane wall of the bacteria. Electrochemical measurements also show some direct interaction between ZnO nanoparticles and the bacterial membrane at high ZnO concentrations [17].

1.2.1.4 Chitosan

Chitosan is one of the natural biopolymers that has attracted researchers’ attention due to the environmental and toxicological concerns about the use of heavy metals for the production of nanoparticles (Figure 1.3). It is assumed that the antibacterial effect of chitosan is because of the presence of amino groups, which gives chitosan a significant characteristic in decomposing the bacteria and fungi [5].

Figure 1.3 Chemical structure of a chitosan [6].

Chitosan’s molecular weight is an important object in researches, which has a significant effect on the antibacterial activity of the textiles. Recent studies on the antibacterial activity of chitosan and chitosan oligomers have revealed that chitosan is more effective in inhibiting the growth of bacteria than chitosan oligomers. Furthermore, the antibacterial effect of chitosan and chitosan oligomers is reported to be dependent on its molecular weight [18].

In a study, the molecular weight of chitosan and chitosan oligomers has been investigated. It was shown that chitosan has a better antibacterial activity in comparison to chitosan oligomers [19].

1.3 Anti-Odor Textiles

Anti-odor textiles are one of the main sectors of the textile industry, which have increased considerably over the last few years due to rising consumer health awareness. Especially in the main parts of the textile industry such as sportswear, underwear, socks, and shoes, using anti-odor textiles have received much attention and nanotechnology plays a vital role in this issue.

There are various types of unpleasant odors in our daily life, such as body odor caused by metabolism and aging, and odors of garbage and cigarettes. In terms of chemical structures, unpleasant odors are divided into the following three main groups:

Fatty acids such as body odor, sweat odor, etc.

Nitrogen compounds such as urine, the smell of fish, etc.

Sulfur-containing compounds, such as excreta, etc.

Therefore, deodorant technology has attracted worldwide attention in different fields of applications. Among the various approaches, physical methods (absorption of odors by activated carbon), chemical methods (turning the odor into a common smell), and using aromatic compounds have been proposed to eliminate unpleasant odors [20]. Therefore, with the increasing number of people being sensitive to odors, using anti-odor technology is an obligation for textile producers.

1.3.1 Odor-Control Methods

In general, there are two different mechanisms for controlling the odors in textiles:

Absorption: simple capture of the offending molecules. No change is made to the process of decomposition.

Prevention: bacteria are prevented from multiplication; the offending molecules are not generated [21, 22].

1.3.1.1 Absorption Mechanism

According to the absorption mechanism, several types of nanostructured materials are used for deodorizing textiles, which is shown in Figure 1.4.

1.3.1.1.1 Cyclodextrins

Cyclodextrins (CDs) are a family of cyclic oligosaccharides with 6–8 gluco-pyranoside units which are known as α, β, and γ-CD [23]. Among different types of CDs, β-CD has a wide range of applications in the textile industry due to its low cost, ease of production, and ease of attachment to surfaces. Also, the size of pores makes it suitable for trapping a range of odor molecules [24]. One of the natural properties of CD is stacking the molecules on top of each other that increases the probability of absorption of odorous compounds. On the other hand, when the scent molecules are absorbed by CDs, the conical structure provides the effective possibility of maintaining the odor molecules. However, CDs as anti-odor agents have some problems. Since different odor compounds have various sizes and shapes, small molecules pass easily through the pores but large molecules cannot enter the inner structure of CDs. Therefore, CDs just maintain specific odor molecules with certain size [25]. CDs have been extensively used for the absorption of various odors in different applications such as controlling the odors caused by chronic wounds. For example, CDs can be incorporated into various materials used for wound healing such as hydrogels. They are used in applications outside of wound care for the control of foul odors. However, there are some limitations in the absorption process by CDs like slow diffusion rate and water deficiency. It seems that these problems can be solved by using the combination of CDs and conventional hydrocolloids, such as sodium carboxymethyl cellulose for effective elimination of wound malodor. This technology has been already introduced as Exuderm Odorshield brand (Medline Industries Inc, Mundelein, IL, USA) [26].

Figure 1.4 Odor-absorbing nanostructured materials.

In a research, Narayanan et al. introduced an efficient wound odor removal by β-cyclodextrin-functionalized poly (ε-caprolactone) nanofibers. According to the results, the PCL/β-CD nanocomposites, by virtue of having their β-CD cavities free and unthreaded by PCL, could potentially be an ideal substrate for removing wound odors through the formation of inclusion compounds with odorants [27]. In the same study, Lipman et al. developed a new series of hydrocolloid adhesives based on CDs to provide an alternative technology for the adsorption of chronic wound odors. Their results showed that CD materials provide a new method of controlling the malodor associated with various types of wounds [28].

1.3.1.1.2 Activated Carbon Nanoparticles

Activated carbon is one of the most widely investigated absorbents in various fields such as water treatment, food industry, medicine, and the environment. It is considered as the most effective method for deodorizing in textiles. The mechanism of odor absorption by activated carbon is physical entrapment and it is capable to trap small molecules of body odors due to the high porous structure. Then, in order to eliminate the trapped scent molecules from a textile, a scouring treatment is required. In addition, activated carbon has an incredibly large surface area per unit volume and good potential to absorb a large quantity of odor molecules.

Another amazing property of activated carbon nanoparticles is their ability to absorb a wide range of odor compounds with various sizes. According to the research by Dr. Don Thompson from North Carolina State University, there are different types of odor compounds in the shoes due to the foot sweat. So, the diversity of odor compounds produced by body sweat creates a serious requirement to use materials such as carbon nanoparticles [29]. In a patent, Quincy et al. invented a dual-element odor control in personal care products. Their products comprised two portions with a formulation of activated carbon and silver nanoparticles. The obtained layer is disposed in a personal care product selected from the group consisting of diapers, training pants, absorbent underpants, adult incontinence products, and feminine hygiene products [30].

1.3.1.1.3 Bamboo Charcoal Nanoparticles

Bamboo is an Asian plant that is found in diverse climates from cold mountains to tropical or subtropical regions. Bamboo is one of the most notable natural resources because it is a fast-growing plant and used for various applications such as preparation of cellulose nanofibers and enhancing properties of synthetic fibers such as polyester.

Bamboo charcoal is prepared by five years of pyrolysis process of bamboo at high temperatures of about 800–1200 °C (Figure 1.5) and obtained from two different resources:

Figure 1.5 The production process of a bamboo nanoparticle.

Stems, leaves, and roots of the bamboo plant

Bamboo wastes.

Therefore, the bamboo charcoal nanoparticles act like a sponge, catching any odor inside its fine pores. These nanoparticles are considered as a good candidate for odor absorption of textiles and the environment [31, 32]. Organic bamboo charcoal is 100% safe to use in fabrics, which are directly in touch to our skin. Therefore, bamboo charcoal nanoparticles have already been widely used with great success in different applications such as beauty products, water filters, foods, and medicines.

Bamboo charcoal powder’s ultra-fine structure contains millions of tiny gaps, which allows 1 gram of bamboo charcoal powder to cover a surface area of 600 square meters. This super porous structure of bamboo charcoal powder absorbs bacteria, unwanted odor, and wicks away sweat up to 50% quicker than cotton.

According to the literatures, bamboo charcoal can absorb formaldehyde, benzene, toluene, ammonia, and chloroform at a rate of 16–19.39%, 8.69–10.08%, 5.65–8.42%, 22.73–30.65%, and 40.68%, respectively. Also, bamboo charcoal fiber effectively decomposes the microorganisms attached to its surface and in the air around it. Recently, Ettitude Company has introduced its new product, Bacteria and Odor Control Bamboo Charcoal Bedding. In this product, bamboo charcoal’s ultra-fine structure powder is added in the bamboo lyocell fabrication process to create the antimicrobial and anti-odor bedding fabric [33]. In addition, Greenyarn Company has exposed their fabrics that contain bamboo charcoal nanoparticles for use in products such as socks and underwear. These bamboo charcoal nanoparticles have antibacterial and deodorizing properties [34].

1.3.1.1.4 Dandelion-like polymers

A novel method of producing an odor-controlling textile is using a polymer with odor-trapping ability (Figure 1.6). Milliken Company first developed this technology in 1865 as a housekeeping and cleanliness technology to control the unpleasant odor of carpets and furniture. This method was inspired by a dandelion structure as a polymer mass containing very small branches. When, a person wears such a textile with an odor-trapping technology, the small scent molecules released from the body are trapped by the dandelion structure. Following the odor-capturing process, the conventional scouring method is utilized to remove the odor compounds from the polymer. So, these kinds of textiles have reusability, which is the most important characteristic of dandelion-like polymers. However, short lifetime and absorption of a low range of odor compounds are the main drawbacks of these polymers [35].

Figure 1.6 Odor-captured textiles with dandelion polymers.

1.3.1.1.5 Activated alumina nanoparticles

Activated alumina is prepared by de-hydroxylation of aluminum hydroxide. It is a highly porous material with a large surface area-to-volume ratio due to the many tunnel like pores. Activated alumina is used as an effective odor absorbent in a wide range of applications such as wastewater, anti-odor textile, and others via trapping the odor molecules in their pores [36]. In some researches, activated alumina nanoparticles with their tunnel-like pores have been used as an effective absorbent for different applications. For example, Jenkins et al. produced an absorbent composition with improved odor control suitable for use as an animal litter, comprising an absorbent material, activated alumina, and optional additives [37]. Furio et al. proposed an absorbent structure with odor-control material consisting of activated alumina, carbon, silica gel, zeolite, siliceous molecular sieve, and their mixtures for an adult incontinence garment, absorbent pad, or diaper [38].

1.3.1.1.6 Nano Silica Gel

Silica gel is a hard, granular, and porous substance made by precipitation from sodium silicate solutions treated with an acid. The main properties of nano silica gel such as porous structure and large specific surface area play a vital role in the odor absorption process [39]. However, nano silica gel is not commonly used as an odor absorbent in comparison with other odor absorption agents in different applications.

1.3.1.2 Prevention Mechanism

This approach is based on preventing proliferation of the odor-causing bacteria by different types of antimicrobial agents such as silver, titanium, zinc oxide nanoparticles, and so on, which are described in section 1.3.

1.4 Deodorant Textiles

Smelling a delightful aroma can be a very pleasurable experience and have physiological and emotional effects. Fragrance finishing of textiles has been greatly expanded in recent years and enhanced the benefit of the products.

The most natural aromatic substances are essential oils that are extracted from different parts especially aerial parts of plants such as leaves and flowers. These compounds are produced due to complex metabolic reactions in plant in order to protect the plant against various pathogens and insects and also reduce the tendency of some herbivorous animals [40]. Some of the biological activities of natural aromas such as antimicrobial, antiviral, anti-inflammatory, anti-mutation, anti-cancer, and antioxidant effects have been proven [41].

1.4.1 Aromatic Textiles with Nanocarriers

Although the aromatic textiles concept is not new, recently great progress has been made on the textile-finishing process in order to produce effective and long-lasting aromatic textiles. In the past, the aromatic extracts usually have been used via direct spraying on the surface of textiles. Today, encapsulation has been known as an effective method to increase the lifetime of odors on textiles. Micro/nano encapsulated fragrances are coated on textiles and released due to pressure or abrasion of textiles or garments [42].

For many years, researchers are seeking a new formulation for gradual release of drugs in the body. Today, drug delivery systems (DDS) such as lipid- or polymer-based nanostructures are characterized having great benefits in comparison with conventional methods of drug delivery [43]. In order to control the release rating, improve the efficiency, reduce the toxicity, and lower the side effects of aromatic compounds, the same DDS are used for essential oils [44].

Nanocarriers such as lipid carriers, nano emulsions, and biocompatible polymer nanostructures are able to protect aromatic compounds against oxidation or evaporation. Some types of nanocarriers are shown in Figure 1.7.

Figure 1.7 Aroma nanocarriers.

In the 1970s, researchers used nanoparticles for delivering and releasing vaccines and anticancer drugs for the first time. Recently, in addition to pharmaceutical compositions, the nanoparticles have been utilized to carry the aromatic compounds and protect them from optical and thermal decompositions and increase the lifetime and efficiency of these active materials.

1.4.1.1 Polymeric Nanocarriers

Polymeric nanocarriers include nanocapsules and nano sphere systems. Nanocapsules are nanoscale core/shell systems made from a polymer in which aroma is confined into the core surrounded by a polymer membrane, while nano spheres are matrix systems in which the aroma is physically dispersed.

Biocompatible natural or synthetic polymers are suggested for producing polymeric nanocarriers. The most common natural and man-made polymers in preparation of polymeric nanocarriers are chitosan, gelatin, alginate, polylactides (PLA), poly (lactide co-glycolides) (PLGA), and poly acrylamide [45].

1.4.1.1.1 Methods of Producing Nanocapsules

This group of nanostructures can be prepared with different physical, chemical, physicochemical, and mechanical techniques, which are effective on size, particle-size distribution, thickness of shell, morphology, and other characteristics of the nanocapsules [46]. Different types of such methods are summarized in Figure 1.8.

Figure 1.8 Nanocapsule production methods [46].

Many methods have been developed for preparing polymeric nanocarriers containing aromatic compounds. The usage of a non-solvent compound to fabricate nanostructured deposition and solvent exchange are the most widely used methods. In this technique, polymer and aroma are dissolved in a suitable organic solvent or a mixture of several solvents, and then this organic solution, in the presence or absence of a surfactant, is introduced to water with applied shearing stress. The organic solvents are separated from the polymer via evaporation and a polymeric film or powder is made [47].

Corzani prepared a fragrance delivery system consiting of a mixture of 50% poly(tetramethylene glycol) having an a number average molecular weight (Mn) of approximately 2000 Da with 25 wt% of a rosin ester plasticizer and 25 wt% benzyl acetate with a selcted perfume.

Yang prepared a fragrance delivery system consiting of 20% limonene and 3% γ-terpinene compounded with an ionic stabilizer, dihydropropyltrimonium chloride, fatty esters, and a silicob fluid.

A fragrance delivery system consisting of a nanostructure microcapsule shell of urea-formaldehyde or melamine-formaldehyde and containing an olfactive component was prepeared by Lie and had at least a 6-month shelf life when stored at 37 °C [48].

Encapsulating rose fragrance in nanoparticles in order to reduce the evaporation of volatile compounds and prepare the long-term fragrance-releasing textile has been proposed by Hu et al. Chitosan nanocapsules loaded with fragrance were prepared via the ionic gelification in acetic acid, Tween 80 as a surfactant, and sodium tripolyphosphate as a gelation compound under ultrasonication. Aroma-loaded nanocapsules were incorporated into the cotton fibers via immersion in nanoemulsion under vacuum [49]. The SEM micrographs of untreated cotton