**3. Bulk modification of synthetic textiles using nanomaterials**

In recent years, synthetic polymer-nanometric filler composites have generated significant attention in diverse applications such as transportation vehicles, construction materials, electronics, sporting goods, packaging, household and textile industries (Sinha Ray & Okamoto, 2003; Leszczy´nska et al., 2007a). The aim is to enhance a wide range of properties including mechanical properties (modulus, stiffness and strength), barrier, flame retardancy, solvent and heat resistance, biodegradability, chemical and thermal stability as well as improvement in dyeability relative to a virgin polymer (Leszczy´nska et al., 2007b, Pesetskii et al., 2007). In order to obtain these specifications, fillers such as cellulose, clay, calcium carbonate, carbon, metal oxides and various forms of silica have been developed by different researchers. In this regard, the geometrical shape of the particles plays an important role in determining the properties of composites (Bhat et al., 2008; Njuguna et al., 2008; Ma et al., 2003).

Processing of such polymeric nanocomposites are more difficult compared to the corresponding pure polymers since such inorganic nanoparticles have strong tendencies to agglomerate. To overcome such difficulties, the sol-gel method, LbL deposition, in situ polymerization and melt processing are put into practice. The last method is still the most cost effective, simple, feasible and environmentally benign process for the mass production of polymeric nanocomposite (Burgentzle´ et al., 2004; Modestia et al., 2007).

Considerable efforts have been devoted to improve various physical, mechanical and barrier properties of PET through mixing it with nanoclays (Phang et al., 2004; Chang et al., 2004; Chang et al., 2005; Jawahar et al., 2005). The layered clays used are mica, fluoro-mica, hectorite, saponite, etc., but one of the most commercially interesting clay is bentonite belonging to a structural family known as the 2:1 phyllosilicates (Calcagno et al., 2007). It is well known that the clay minerals have also been used as adsorbent for removal of acid, reactive, disperse and basic dyes from aqueous solutions due to the fact that they are globally abundant and inexpensive (Xiao et al., 2005). Their inner layers comprise an octahedral sheet, which is situated between two tetrahedral sheets. The substitutions of Al3+ for Si4+ in the tetrahedral layer and Mg2+ or Zn2+ for Al3+ in the octahedral layers result in a net negative surface charge ion in water which cause the repulsion interaction with anionic dyes (Parvinzadeh & Eslami, 2011).

The dyeability of synthetic fibers depends on their physical and chemical structure. Dyeing process consist of three steps including the diffusion of dye through the aqueous dye bath on to the fiber, the adsorption of dye into the outer layer of the fiber and the diffusion of dye from the adsorbed surface into the fiber interior. It was shown by researchers that functional groups of PET and water molecules play a great role in this process. The terminal carboxylic and hydroxyl groups in PET chains interact with water molecules. This makes a swelled fiber resulting to increase the attraction of disperse dye by these functional groups of fiber (Kirk–Othmer, 1998).

The proportion of crystalline and amorphous regions of polymer is another factor influencing the dyeability. Researchers are concerned with the development and implementation of new techniques in order to fulfill improvement in dyeability of various polymers. Blending of polymeric fibers with nanoclays as inexpensive materials is still claimed as cost effective method to enhance dyeability (Geoghegan & Krausch, 2003). Up to now, only two research articles are focused on dyeing properties of polypropylene- and polyamide 6- layered clay incorporated nanocomposites prepared by melt compounding

Gu, 2007).

(Froehling, 2001)

**4. Remarks and outlook** 

producers for the next textile industry revolution.

Surface and Bulk Modification of Synthetic Textiles to Improve Dyeability 287

Another applicable nanofiller is silica nanoparticle which impacts high stiffness, tensile strength, modulus, toughening, crystallinity, viscosity, creep resistance, coefficient of friction, wear resistance, toughness and interfacial adhesion in various polymer nanocomposites (Xanthos, 2005, Parvinzadeh et al., 2010b). Recently, a research program to explain dyeability of PET/silica nanocomposite was done by Yang and Gu. They used *in situ* polymerization to prepare PET/SiO2 nanocomposites. According to the results, the color strength of the dyeing increased with increasing SiO2 content in polymer (Yang &

Over the last 20 years polymer chemistry has created a non-linear polymeric structure coined dendritic polymers. Their architecture arises from the introduction of a large number

of branches with many functional end groups (Froehling, 2001).

Fig. 16. Incorporation of hyperbranched polymers into the fiber structure

and the lower crystallinity of the polymers (Khatibzadeh et al., 2010).

Two classes of these polymers are dendrimers with a perfectly branched uniform structure and hyperbranched polymers with non-uniform ones. It was already suggested by different authors that highly branched molecules should be able to act as a host for the encapsulation of guest molecules of dyes or a dendritic box. This structure can lead to industrial development of dyeable poly(propylene) fiber (Froehling, 2001) (.*cf* **Figure 16**). Other authors suggested that an improvement in dyeability of the polymeric- hyperbranched additive nanocomposites can be attributed to the decrease in glass transition temperature

Various types of physical and chemical finishing methods have been described in this chapter. Most of them are developed to solve problems with synthetic fibers to expand their usefulness. Examples of such problems are their insufficient fabric softness, low absorbency of water, flammability, and pilling, low dyeability, slipping and static problems during production and usage. New finishing processes using physical and chemical methods can solve these problems and restrictions. Both the improved and the newly developed finishes based on nano-science are valuable tools that can project an enhanced image of the finish

(Razafimahefa et al., 2005; Toshniwal et al., 2007). Toshniwal et al. suggested that polypropylene fibers could be made dyeable with disperse dyes by addition of nanoclay particles in polymer matrix (Toshniwal et al., 2007). Another research work done by Razafimahefa and her colleagues showed that the introduction of the nanoclay improves the dyeing ability of nylon with disperse dyes. Nevertheless, because of the interactions between the anions in montmorillonite and the amino groups on the polyamide, the dyeing sites are occupied with the nanoclay. This led to inferior dyeing with acid or metal complex dyes than in the case of the unfilled polymer (Razafimahefa et al., 2005).

Our previous study on dyeability of PET/clay nanocomposites stated the following type of interactions between the disperse dye and clay surfaces:


The second reason for improving disperse dye absorption of PET/clay nanocomposites could be the relatively large voids between clay platelets after modification with quaternary ammonium salts (Parvinzadeh et al., 2010a; Parvinzadeh et al., 2011). It was shown that the surface morphology of PET/clay nanocomposites has great influence on water contact angle of the resultant nanocomposite (*.cf* **Figure 15**).

Fig. 15. 3d topographic images of atomic force microscopy for various composites: (a) Pure PET, (b) PET=15A, (c) PET=30B, (d) PET=Na+ (Parvinzadeh et al., 2010a).

(Razafimahefa et al., 2005; Toshniwal et al., 2007). Toshniwal et al. suggested that polypropylene fibers could be made dyeable with disperse dyes by addition of nanoclay particles in polymer matrix (Toshniwal et al., 2007). Another research work done by Razafimahefa and her colleagues showed that the introduction of the nanoclay improves the dyeing ability of nylon with disperse dyes. Nevertheless, because of the interactions between the anions in montmorillonite and the amino groups on the polyamide, the dyeing sites are occupied with the nanoclay. This led to inferior dyeing with acid or metal complex

Our previous study on dyeability of PET/clay nanocomposites stated the following type of




The second reason for improving disperse dye absorption of PET/clay nanocomposites could be the relatively large voids between clay platelets after modification with quaternary ammonium salts (Parvinzadeh et al., 2010a; Parvinzadeh et al., 2011). It was shown that the surface morphology of PET/clay nanocomposites has great influence on water contact angle

Fig. 15. 3d topographic images of atomic force microscopy for various composites:

(a) Pure PET, (b) PET=15A, (c) PET=30B, (d) PET=Na+

(Parvinzadeh et al., 2010a).

dyes than in the case of the unfilled polymer (Razafimahefa et al., 2005).

interactions between the disperse dye and clay surfaces:

of disperse dye molecules.

molecule on the other hand.

ammonium salt in modified clays.

of the resultant nanocomposite (*.cf* **Figure 15**).

Another applicable nanofiller is silica nanoparticle which impacts high stiffness, tensile strength, modulus, toughening, crystallinity, viscosity, creep resistance, coefficient of friction, wear resistance, toughness and interfacial adhesion in various polymer nanocomposites (Xanthos, 2005, Parvinzadeh et al., 2010b). Recently, a research program to explain dyeability of PET/silica nanocomposite was done by Yang and Gu. They used *in situ* polymerization to prepare PET/SiO2 nanocomposites. According to the results, the color strength of the dyeing increased with increasing SiO2 content in polymer (Yang & Gu, 2007).

Over the last 20 years polymer chemistry has created a non-linear polymeric structure coined dendritic polymers. Their architecture arises from the introduction of a large number of branches with many functional end groups (Froehling, 2001).

Fig. 16. Incorporation of hyperbranched polymers into the fiber structure (Froehling, 2001)

Two classes of these polymers are dendrimers with a perfectly branched uniform structure and hyperbranched polymers with non-uniform ones. It was already suggested by different authors that highly branched molecules should be able to act as a host for the encapsulation of guest molecules of dyes or a dendritic box. This structure can lead to industrial development of dyeable poly(propylene) fiber (Froehling, 2001) (.*cf* **Figure 16**). Other authors suggested that an improvement in dyeability of the polymeric- hyperbranched additive nanocomposites can be attributed to the decrease in glass transition temperature and the lower crystallinity of the polymers (Khatibzadeh et al., 2010).
