Abstract: Excessive exposure to solar ultraviolet (UV) radiation causes human health damages, such as sunburns and skin cancer. Thus, the use of sun-protective clothing is a simple, easy, and practical method for UV protection of the human organism. In this perspective, incorporation, coating, and anchorage of UV-protective compounds in textile fibers have been employed to enhance the UV-blocking ability and/or promote functional finishings to smart fabrics. This review describes recent research efforts on the development of UV-protective compound-containing smart fabrics highlighting the UV-blocking properties and multifunctional activities. Different compound class examples and discussions are presented in order to contribute to new insights into sun-protective clothing and future applications of multifunctional textiles.
Keywords: smart fabrics, textile properties, different UV-protective compound classes, UV-blocking ability, ultraviolet protection factor.
UV-protective compound-containing smart textiles: A brief overview
Universidade Estadual Paulista Júlio de Mesquita Filho
Recepción: 29 Marzo 2022
Aprobación: 12 Diciembre 2022
Publicación: 01 Enero 2023
The sun is essential for the Earth’s life and its environment (Powers and Murphy, 2019); consequently, solar radiation effects provide human health benefits, such as physical and mental well-being (Flor et al., 2007) and the stimulation of melanin (Serre et al., 2018) and vitamin D biosynthesis (Baker et al., 2017). However, the excessive solar radiation exposure cause sunburns (Sambandan and Ratner, 2011), irregular skin pigmentation, immune system depression, premature aging (Kockler et al., 2012) and skin cancer (Bagde et al., 2018). Among electromagnetic radiations emitted by the sun that reach the Earth’s surface, the ultraviolet (UV) radiation is the main responsible for photochemical reactions in the human organism (Baker et al., 2017). UV radiation may be subdivided into following regions: UVC (200–290 nm), UVB (290–320 nm) and UVA (320–400 nm) (Velasco et al., 2008). Stratospheric ozone layer blocks a high percentage of the incident UVC radiation (Baker et al., 2017); therefore, a combination of UVB and UVA radiation reaches the terrestrial surface (Fourtanier et al., 2012). UV radiation penetrates in the upper and deeper layers on the skin causing cellular damages and immune system function modifications (Kockler et al., 2012). Thus, sunscreens and UV-blocking fabrics can be used to minimize the human health risks induced by excessive UVB and UVA radiation exposure. According to the literature, UV blocking (Faure et al., 2013) and UV shielding (Parwaiz et al., 2019) are scientific terms commonly used to express the solar UV protection performance of photoprotective materials. However, UV blocking term is more used than UV shielding to designate the photoprotective capacity of textiles (Mondal, 2022).
The main constituents of photoprotective products are organic and inorganic filters, which are chemical compounds that absorb and/or scatter UV radiation without changes in their physicochemical properties (Saito et al., 2021). Organic filters are organic molecules composed by chromophore groups that commonly exhibit high degree of the π-conjugated system (Saito et al., 2021). The UV absorption capacity of organic filters depends on both the energy differences from electronic transitions between frontier orbitals and molar absorption coefficient (ε). In general, π→π* and/or n→π* transitions give rise the UV absorption mechanism of organic filters (Baker et al., 2017; Flor et al., 2007). Some examples of organic filters are beta-diketones and organic compounds derived from: benzophenone, anthranilate, salicylic acid, cinnamic acid, p-aminobenzoic acid and camphor (Antoniou et al., 2008). Organic filters are widely used in sunscreen applications due to their UVB and/or UVA absorption capacity (Kockler et al., 2012). Furthermore, these organic compounds show solubility in different dispersion mediums, which facilitates the use of them in the manufacturing process of photoprotective products (Forestier, 2008; Morabito et al., 2011).
Organic filter decomposition under high temperature and/or oxidizing environment exposure results in changes and/or loss of the UV shielding ability and induces the free radical’s production that could cause DNA, elastin and/or collagen damages (S. Jain and N. Jain, 2010).
Inorganic filters are inorganic compounds that exhibit UV-visible (UV-VIS) absorption capacity and, depending on the refractive index and/or particle size of them, can scatter UV radiation (Abuçafy et al., 2016; Seixas and Serra, 2014). In general, UV-VIS absorption process in metal oxides (e.g., ZnO and TiO2) involves electronic transitions between valence band and conduction band (VB→CB). The main advantages of inorganic filters are thermal stability, broad spectrum absorption (Seixas and Serra, 2014) and low toxicity to the human body (S. Wang et al., 2010). For these reasons, inorganic filters are widely incorporated in cosmetic formulations and/or UV-blocking products intended for children and people with skin diseases or sensitive skin (Serpone et al., 2007). However, these inorganic compounds can promote photocatalytic reactions (L. Wang et al., 2018) that decompose cosmetic ingredients affecting on the UV shielding ability of photoprotective products.
The growing concern about deleterious effects of the UV radiation exposure combined with the negative aspects related to the use of commercial inorganic and organic filters has significantly promoted the development of photostable compounds with high UV protection and low toxicity to the human organism and the environment, i.e., UV-protective compounds (Saito et al., 2018). In this perspective, UV-protective compounds have been obtained by the coordination of organic filters with transition metals (Ahmedova et al., 2002; Pettinari et al., 2016), association between inorganic and organic filters (Parisi et al., 2016), encapsulation of organic (Morabito et al., 2011) or inorganic filters (Frizzo et al., 2019), and intercalation of organic filters into inorganic layered matrices (Franco et al., 2020; Saito et al., 2021).
One of the most important manufacturing steps of photoprotective products is the dispersion or incorporation of organic and/or inorganic filters in sunscreens, polymer matrices or textile fibers. Sunscreens are emulsions and/or particle dispersions, whose main purpose is to protect the human skin from UV damages (Saito et al., 2019). However, these cosmetic formulations can cause skin allergies depending on the ingredients present in their composition (Giokas et al., 2007). Thus, the sun-protective clothing is a viable alternative for UV protection due to the lower occurrence of allergic reactions by skin contact and its simple, easy, and practical use. It is important to emphasize that the global smart fabrics market, which includes the promoting and selling of self-cleaning, flame retardant, antibacterial and UV-blocking fabrics, was estimated at US$ 289.5 million in 2012. Before the COVID-19 pandemic, smart fabrics market projections for 2020 was quoted at US$ 361.9 million, keeping similar growth rates and correcting inflation (SEBRAE, 2014).
The UV shielding ability of the sun-protective clothing is directly related to the physical and chemical properties of the fabric used in its manufacture. Therefore, the chemical composition, weave pattern and optical properties are the main factors that should be considered when making sun UV-blocking fabrics (Alebeid and Zhao, 2017).
In the last decades, several kinds of textile fibers or fiber blends have been used to fabric manufacturing (Jabbar and Shaker, 2016). Polyethylene terephthalate (PET), commonly named polyester, and cotton fibers are the most employed to produce sun-protective fabrics. Generally, PET (Fig. 1) is obtained by the condensation polymerization process of terephthalic acid and ethylene glycol under specific synthetic conditions (Jaffe et al., 2020). In the first step of the PET polymerization, the bis(hydroxyethyl)terephthalate (BHET) monomer is produced by esterification of terephthalic acid. It is important to highlight that the esterification reaction produces a mixture of PET oligomers and BHET; consequently, water and impurity removal is essential to the ultimate achievement of the PET polymer. The next step of the PET polymerization consists in the ester interchange reaction between two BHET molecules to split off a glycol molecule, building polymer molecular weight. This condensation reaction must be catalyzed, being the antimony trioxide (Sb2O3) the catalyzer most used. Moreover, the melt-polymerization temperatures at or above 285°C are used to promote the uniform stirring of the reactional medium. In the last step, PET polymer is pelletized for melt spinning or putted on a spinning machine and transformed to fiber (Jaffe et al., 2020). The main reasons for the using of PET fibers in sun-protective clothing are the low cost, ease of blending with natural fibers and UVB absorption capacity (Curtzwiler et al., 2017). Its UVB absorption ability is directly related to the presence of aromatic rings and carboxyl groups, i.e., chromophores groups in the polymeric structure.
Figure 1.
Polyethylene terephthalate (PET) monomer structure.
Cotton is a natural fiber formed by dried cell walls of formerly living cells of Gossypium genus plants (Ioelovich and Leykin, 2008; Liu, 2018). The cotton fiber formation starts in an ovary of the cotton flower and proceeds in a mature seed-containing cotton bowl (or fruit). Thus, fiber development includes initiation, primary cell wall formation for fiber elongation, secondary cell wall biosynthesis for cellulose deposition and cell wall thickening, and maturation. Cotton fibers are composed by cellulose (88.0–96.5%), proteins (1.0–1.9%), waxes (0.4–1.2%), pectins (0.4–1.2%), inorganic compounds (0.7–1.6%), and other substances (0.5–8.0%). It is important to emphasize that the chemical composition of cotton fibers depends on the cotton cultivar, growing environment and degree of fiber maturity (Liu, 2018). Cellulose, major chemical component of cotton fibers, consists in linear β-1,-4-linked chains of D-glucopyranose (Fig. 2) produced by photosynthesis process (Yue et al., 2012). In the cloth manufacturing, cotton fibers are widely used due to their low cost, softness, high air permeability, moisture-absorptive features, high thermal resistance, and hypoallergenic properties (H. Wang and Memon, 2020).
Figure 2.
Schematic representation of the simplified cellulose structure.
Different weft types can be used in weaving stage of the sun-protective fabrics. The weft is the arrangement of intertwined threads that gives rise to fabric. This thread arrangement is classified into plain weave fabric and mesh (Pezzolo, 2007). In the plain weave fabric, the thread interweaving turns it more difficult to deform in shear. (Mohammed et al., 2000; Pezzolo, 2007). While the mesh allows the stretching of the fabric because there are no fixed thread loops in its weft (Pezzolo, 2007).
Plain fabric’s frames are commonly classified in taffeta, twill or satin. The taffeta has a weft design that looks like a chessboard (Fig. 3a), which provides a higher mechanical resistant due to its homogeneous shape. Twill has a diagonal pattern (Fig. 3b), offering less dirt adhesion and easier cleaning, because its weft pattern provides more empty spaces among the plain weave fabric. Satin weft presents larger heels between the threads than other plain weave designs (Fig. 3c), consequently, this weft design influence on the fabric brightness (Pezzolo, 2007).
Figure 3.
Schematic representations of plain fabric’s frames: (a) taffeta, (b) twill and (c) satin.
After the weaving process, fabrics are submitted to the finishing stages (1st, 2nd, and 3rd stage) of the textile processing. The 1st finishing stage is mainly composed by the brushing, shaving, singeing and scouring processes. In the 2nd finishing stage, also known as dyeing and printing, pigments and/or dyes are adsorbed and/or anchored in the surface of textile fibers. Finally, the 3rd finishing stage consists in chemical processes used to generate specific physical-chemical properties in fabrics, e.g., waterproofing ability (Pezzolo, 2007). Among these chemical processes, the incorporation of nanoparticles in textile fibers has been widely used (Chau et al., 2007; Costa, 2012; Ferreira et al., 2014; Sánchez, 2006) in order to create smart fabrics, i.e., fabric with self-cleaning, antibacterial or even flame-retardant properties. It is important to point that the 2nd stage can provide textile benefits similar to 3rd stage depending on the physical and chemical properties of pigments and/or dyes used. Thus, 2nd and 3rd stage can be understood as the same finishing stage of the textile processing.
UV protection on fabrics depends on the fiber type, weft design, fabric thickness, yarn linear density, and the optical properties of pigments or dyes. For example, the solar transmittance decreases, and the diffuse reflectance increases when yarn linear density, i.e., the number of weft yarns per unit length increases (Yildirim et al., 2018). Besides textile properties, UV shielding capacity can be enhanced by incorporation, coating, or anchorage of UV-protective compounds in the textile fiber surface (Table 1a–d). Thus, the purpose of this review is to report scientific results about UV-protective compound-containing smart fabrics in the period from 2010 to 2021.
It is known that the incorporation, coating and/or anchorage of UV-protective compounds in smart fabrics protects human skin against excessive UV radiation exposure and reduces the photodecomposition percentage of textile fibers. Nevertheless, this brief review focused in showing the main scientific results and potential applications of UV-blocking fabrics used to minimize the human health hazards.
Examples of UV-protective compound-containing textile fibers described in scientific literature between 2010 and 2012.
PET: Polyethylene terephthalate.
Examples of UV-protective compound-containing textile fibers described in scientific literature between 2013-2016.
PET: Polyethylene terephthalate.
Examples of UV-protective compound-containing textile fibers described in scientific literature between 2017 and 2018.
PET: Polyethylene terephthalate. * MIL: Materials Institute Lavoisier. MOF: metal-organic framework. # Natural herbal nanoparticles prepared from shade-dried Aloe vera plant.
Examples of UV-protective compound-containing textile fibers described in scientific literature between 2019 and 2021.
PET: Polyethylene terephthalate. MOF: metal-organic framework.
The growing request for UV-protective textiles, especially for clothes manufacturing, has driven scientific studies about textile fibers with UV shielding properties. Therefore, incorporation, coating and/or anchorage of metal oxides, dyes, organic filters, graphene compounds, metal-organic frameworks (MOFs), coordination compounds, metal nanoparticles or composites in the fiber surface are widely related in the recent literature (Table 1a–d). Several different synthetic methods have been used to produce these textile fibers, including pad-dry-cure (Z. Chen and Yin, 2010), electrospinning (Pant et al. 2011), hydrothermal (Y. Li et al., 2011), microwave (Y. Li et al., 2012; Thi and Lee, 2017), microwave assisted hydrothermal (Ates and Unalan, 2012), simple spray coating (Rana et al., 2016), electrostatic layer-by-layer self-assembly approach (Zhao et al., 2013), solid-phase hot-pressing procedure (G.-P. Li et al., 2020) and dip-pad-cure (Ibrahim et al., 2010b). Among them, the pad-dry-cure method is the most used due to the easier synthetic procedures and high-efficiency fiber coating. In the pad-dry-cure process, fabrics are soaked in UV-protective compound solution or suspension under specific conditions, e.g., liquor to fabric ratio. Then, fabric specimens are padded through two dips and two nips using a padding machine. After padding step, fabrics are dried and cured at specific temperatures and times, which are based on fabric properties. Regardless of experimental method and/or fiber type used, UV-protective compounds incorporated, coated and/or anchored improve UV-blocking properties of textile fabrics (Fig. 4) as proven by UV-VIS spectroscopic measurements, e.g., in vitro UV protection factor (UPF) assessment. Moreover, these UV-protective compounds can promote other beneficial functions to textile fibers such as antibacterial and self-cleaning properties (Table 1a–d). In so many cases, a superhydrophobic coating in the textile fibers is also made to provides waterproofing (Table 1a–d). It is important to highlight that multifunctional textile fibers give rise smart fabrics, which offer new insights to clothing manufacturing.
Figure 4.
Schematic representation of a UV-protective compound-containing smart fabric.
Titanium oxide is a commercial inorganic filter commonly used in skin care products due to its UV absorption capacity (Abuçafy et al., 2016; Seixas and Serra, 2014) and low skin toxicity (Abuçafy et al., 2016). Besides UV shielding ability, TiO2 exhibits photocatalytic activity that enable its use in self-cleaning systems (Banerjee et al., 2015). According to the literature (Yadav et al., 2016), this metal oxide also has antibacterial properties. For these reasons, TiO2-containing textile fibers have attracted considerable interest in the field of smart fabrics.
Mihailović et al. (2010; 2011), in two different scientific research publications, investigated the multifunctional properties of polyethersulfone (PES) fabrics loaded with TiO2 prepared by oxygen, argon or air RF plasma or corona discharge pretreatment and subsequent dip-pad-cure process with titanium oxide. On both studies, oxygen, argon or air RF plasma and corona discharge pretreatments of PES fibers induced the enhanced deposition of TiO2 nanoparticles ensuring excellent self-cleaning properties, UV protection and antibacterial activity. Considering UV blocking efficiency of PES fabrics obtained, high UPF values (UPF > 66) were reached and retained after five laundering cycles. The washing procedure used in the laundering durability test can be summarized as follows: the PES fabrics were washed in the bath containing 0.5% Felosan RG-N (Bezema) at liquor-to-fabric ratio of 40:1. After 30 min of washing at 40 °C, fabrics were rinsed once with warm water (40 °C) for 3 min and three times (3 min) with cold water. Subsequently, fabrics were dried at 70 °C.
Montazer and Pakdel (2010) reported the UV-blocking ability of TiO2-containing wool textiles obtained by ultrasonic bath method. The TiO2-protective layer on fabric surface provided higher UV absorption in the 300-350 nm region. Moreover, the increase of the amount of TiO2 on wool surface enhanced the UVB blocking capacity and decreased the UV photodegradation of wool fibers, i.e., photoyellowing of wool textile. In other scientific publication, Montazer and Seifollahzadeh (2011) prepared multifunctional textiles through enzymatic pretreatment of polyester/wool blend followed by the fiber coating with TiO2 nanoparticles. These textile materials also exhibited higher UVB blocking ability and showed self-cleaning and antibacterial properties.
Pant et al. (2011) successfully prepared an electrospun nylon-6 spider-net like nanofiber mats containing TiO2 nanoparticles. The addition of a small amount of TiO2 NPs improved the hydrophilicity and mechanical strength of nylon-6 nanofiber mats and gave rise to antibacterial and UV blocking properties.
Nazari et al. (2013) developed UV-blocking polyester fabrics using TiO2 as inorganic filter and polysiloxane as cross-linkable agent. The polysiloxane agent promoted the enhance of TiO2 nanoparticles absorption and stabilized them on the polyester fiber surface. Consequently, the nano-TiO2/polysiloxane coating improved the UV-blocking features of polyester fabrics as seen in UV-VIS transmission spectra.
Zhou et al. (2017) reported a facile and eco-friendly way to prepare a novel hybrid polyamine/nano TiO2 fabric by a combination of UV irradiation and ultrasonic bath method. The research results indicated that TiO2 were fixed on the fiber surface providing photocatalytic, antibacterial, UV blocking and superhydrophobic properties to polyamine fabrics. UPF values equal to 56 and 1123 were obtained.
Sadr and Montazer (2014), Emam and Bechtold (2015), D. Chen et al. (2018), Morshed et al. (2018), Suryaprabha and Sethuraman (2021) and Riaz et al. (2021) investigated the UV blocking properties of TiO2-containing cotton fabrics. Sadr and Montazer (2014) reported the multifunctional features of TiO2 nanoparticles coated cotton fabrics obtained by in situ sonosynthesis method. The sonochemical method had no negative influence on cotton fabric fibers and provided the formation of the nano-TiO. coating on the textile surface that led to UV-blocking and self-cleaning properties. Moreover, UV-protection rating of these cotton fabrics maintained even after 25 home launderings indicating an excellent washing durability. Emam and Bechtold (2015) immobilized TiO2, ZnO or CuO particles into cotton and oxidized cotton fabrics by using pad-dry-cure method. The surface interactions between carboxylate groups of cotton fibers and metal oxides, mainly TiO2, provided the enhancement of the UV shielding capacity of cotton fabrics as seen in UV-VIS transmittance spectra and in vitro UPF values. D. Chen et al. (2018) developed UV-blocking, superhydrophobic and robust cotton fabrics by combination of polyvinylsilsesquioxane (PVS) and nano-TiO2. Based on structural, thermal, mechanical, and spectroscopic results, the improvement on the UV protection, water repellency and rigidity of the fabrics were attributed to the synergism between the PVS polymer and nano-TiO2. Morshed et al. (2018) reported to sonochemical synthesis of TiO2 nanoparticles in cotton fibers via low temperature sol-gel technique. Ultrasonication time, ultrasonic power, and concentration of tetrabutyl titanate affected on UPF values of cotton fabrics. Suryaprabha and Sethuraman (2021) prepared multifunctional cotton fabrics based on the deposition of TiO2 sol followed by surface modification using stearic acid (STA). STA-TiO2 cotton fabrics exhibited UV-blocking ability and self-cleaning properties. Moreover, these superhydrophobic fabrics showed chemical durability and mechanical stability. Finally, Riaz et al. (2021) reported to the fabrication of cotton fabrics with TiO2 nanoparticles modified with two different silane coupling agents using pad-dry-cure method. The presence of modified nanoparticles in the fiber surface improved the UV-blocking performance causing minimum effect on inherent properties of cotton textiles, e.g., sensorial comfort.
Fakin et al. (2012) investigated the SiO2 coated TiO2 particles performance in reactive dyeing of cotton fabrics. The incorporation of synthesized particles into the dyeing with reactive dyes brought about an outstanding UV blocking ability of the dyed fabrics even after 15 laundering cycles without considerable negative impact on color and comfortable properties. Washing process was performed according to the BS EN ISO 105-C06:2010 (2010) standard. UV protection, comfort, and dyeing properties of cotton fabrics were directly associated to dyeing temperature and amount of dye and SiO2 coated TiO2 particles.
S. Li et al. (2017) reported to the development of multifunctional cotton fabrics obtained by hydrothermal deposition of TiO2 particles onto fiber surface followed by in situ deposition of Ag nanoparticles via reduction method. These fabrics exhibited high antibacterial activity with an inhibition rate higher than 99% against Staphylococcus aureus and Escherichia coli bacteria. Moreover, UPF values between 35 and 57 confirmed the UV-blocking capacity of them. Using a different two-step coating approach, Pakdel et al. (2020) prepared cotton fabrics coated with TiO2 and hollow glass microspheres (HGMs). The presence of TiO2 layer on cotton fibers gave rise to an excellent UV-blocking activity as proved by UPF values higher than 190. In addition, HGMs coating reduced the inflammability of cotton fabrics and improved their thermal resistance and sound absorption capacity. Therefore, these TiO2 + HGMs coated cotton fabrics exhibited multifunctional properties, i.e., UV-blocking ability, thermal insulation, flame retardancy and acoustic performance. It is important to highlighting that noise is considered a health hazard (Münzel et al., 2020) and it is required to be eliminated for a better performance of humans in different areas (Pakdel et al., 2020).
In different scientific publications, Dastjerdia et al. (2010), Rana et al. (2016), Chimeh and Montazer (2016), Xu et al. (2018), Bouazizi et al. (2020) and Zohoori et al. (2021) reported the development of UV-protective fabrics with different nanocomposites based on TiO2. Dastjerdia et al. (2010) investigated the multifunctional properties of Ag/TiO2 nanocomposite coated polyester fabrics prepared by pad-dry-cure method. The results revealed that the nanocomposite coating gives a considerable antibacterial, self-cleaning, anti-staining and UV-blocking capacity to polyester textiles. In this scientific paper, authors focused on showing the main results of characterization techniques without in-depth discussions about physic-chemical phenomena involved. In similar scientific research, Rana et al. (2016) reported the preparation of multifunctional cotton fabrics with Ag/AgBr-TiO2 nanocomposite coating by simple spray coating process. The results showed that the nanocomposite coating onto cotton fabrics improved textile mechanical properties and gave rise to antibacterial and UV-blocking abilities.
Chimeh and Montazer (2016) prepared polyester fabrics with nano-TiO2/carbon nanotubes or nano-TiO2/nanocarbon black composites through exhaustion method and post-curing. The composite coating increased the UV blocking capacity of PET textiles as seen in UV-VIS reflectance spectra. Furthermore, nano-TiO2/carbon composites imparted photocatalytic activity and electrical conductivity to fabrics. Also, Xu et al. (2018) successfully prepared superhydrophobic and UV-protective cotton fabrics by the incorporation of TiO2/SiO2 composite nanoparticles followed by hydrophilization with hexadecyltrimethoxysilane. TiO2/SiO2 composite nanostructures onto fibers made the textiles rougher, which contributed to the formation of superhydrophobic surfaces, and decreased the UV transmittance of cotton fabrics promoting UPF values higher than 80.
Bouazizi et al. (2020) reported the design and functionalization of new composite-based PET fibers with UV protection. The fixation of MOx/polyvinylidene fluoride/Chitosan composite (MOx = TiO2, ZnO or SiO2) into PET fibers improved both the thermal stability and UV protection of textiles. High UPF values (80.5 – 113.4) of textiles indicated their excellent UV-blocking capacity.
Zohoori et al. (2021) prepared wool fabrics coated with TiO2/Ce or ZnO/Ce nanocomposite coated wool fabrics by ultrasonic method. XRD, EDX and SEM results showed the formation of nanocomposites and indicated a good distribution of them on the wool surface. The wool fabrics coated with TiO2/Ce or ZnO/Ce nanocomposites showed lower UV transmission percentage than raw wool fabric indicating an improvement on the UV protection. Also, these fabrics exhibited antibacterial and self-cleaning activity.
Zinc oxide is also a commercial inorganic filter widely used in cosmetic formulations and/or self-cleaning systems. Like TiO2, zinc oxide has UVB absorption capacity (Flor et al., 2007; Seixas and Serra, 2014), low skin toxicity (Abuçafy et al., 2016), photocatalytic and antibacterial ability (Qi et al., 2017). Consequently, fabric fibers with zinc oxide or nanocomposite based on ZnO have been investigated to provide new insights in UV-protective textile manufacturing.
Y. Li et al. (2011) reported the preparation of cotton fabric with ZnO, in which ZnO particles were in situ synthesized inside of textile fibers, via two-step hydrothermal method. The results showed that zinc oxide particles were successfully assembled into the lumen and the mesoporous cotton fibers. Therefore, UV-blocking ability of the cotton fabric was significantly improved by assembling ZnO inside the fibers.
Ates and Unalan (2012) investigated to self-cleaning, superhydrophobic and UV-blocking properties of zinc oxide nanowire-containing cotton fabric prepared by microwave assisted hydrothermal method and subsequently functionalized with stearic acid. The results showed the superhydrophobic nature of textile fibers, the decrease of the transmission intensity in UV spectral region and considerable degradation of methylene blue under UV light irradiation, one of the main photodegradation methods to investigate self-cleaning properties.
Çakir et al. (2012) successfully prepared ZnO coated cotton fabrics that exhibit UV-blocking, self-cleaning and antibacterial properties. It is important to emphasize that ZnO nanoparticles were synthesized in reverse micelle cores of PS(10912)-b-PAA(3638) copolymer obtained by atom transfer radical polymerization. The ZnO nanoparticles coating onto textile fibers provided photocatalytic activity on degradation of methylene blue and antibacterial activity against Escherichia coli and Staphylococcus aureus bacteria. Moreover, ZnO coated cotton fabrics exhibited UPF values greater than 60.
Y. Li et al. (2012) investigated UV blocking property and water-wash durability of nano-ZnO assembled cotton fibers obtained by microwave assisted precipitation and crystallization process synchronously in situ for the first time. UV-VIS transmission spectra showed an excellent UV-blocking activity in the 225–380 nm region. The water-washing process of nano-ZnO assembled cotton fibers did not change their UV absorption capacity as seen in UV transmission measurements. The water-washing durability test was carried out in a domestic washer (XQB45-846B National, Panasonic), where nano-ZnO assembled cotton textiles were washed with water (v = 33 L) for 20, 40 and, 60 min.
Shateri-Khalilabad and Yazdanshenas (2013b) and Zhang et al. (2013) successfully prepared smart fabrics via in situ synthesis of ZnO on the cotton fiber surface. In both publications, ZnO coated cotton fabric exhibited high UV-blocking ability as proven in UPF values (105.61 [Shateri-Khalilabad and Yazdanshenas, 2013b] and 136 [Zhang et al., 2013]). Moreover, it showed bacterial inhibition (Shateri-Khalilabad and Yazdanshenas, 2013b) or antibacterial (Zhang et al., 2013) activity.
The pad-dry-cure method was used by Raza et al. (2016) and El-Naggar et al. (2018) in the preparation of cotton fabrics coated with chitosan/ZnO nanocomposites and ZnO nanoparticles, respectively. Nanocomposite (Raza et al. 2016) and ZnO (El-Naggar et al., 2018) coated cotton fabrics exhibited antibacterial activity and UV-blocking capacity.
Thi and Lee (2017) reported the development of self-cleaning and UV-blocking cotton fabric with modification of photoactive ZnO coating via microwave method. ZnO coated cotton fabrics synthesized at pH range equal 6–7, 8–9 and 10–11 showed UPF values of 222.52, 162.68 and 202.57, respectively. In addition, these cotton fabrics exhibited excellent self-cleaning ability proved by high removal degree of the coffee stains under UV irradiation at different air humidity levels.
Subbiah et al. (2018) successfully prepared nanostructured ZnO modified cotton fabrics via sol-gel and sputter seed layer-coated sol-gel techniques. All modified cotton fabrics exhibited greater UPF values than raw fabric, but the seed layer-initiated sol-gel modified cotton fabric showed the highest UPF value (378). Moreover, these modified cotton fabrics showed room temperature gas sensing response towards volatile organic compounds enabling their use as gas sensor.
Mai et al. (2018) reported the development of multifunctional polyvinylsilsesquioxane/ZnO coated cotton fabrics. Composite coatings improved UV-blocking, superhydrophobic and antimicrobial properties of cotton fabrics compared to the reference textiles. In addition, polyvinylsilsesquioxane/ZnO coatings enhanced the mechanical properties of cotton fabrics and did not compromise their thermal stability.
X. Wang et al. (2019) successfully prepared UV-protective fabrics via grafted polymer brushes for in situ growth of ZnO on modified cotton fiber using the electroless deposition method. According to the results, the functionalized fabrics exhibited UV blocking properties and wash durability due to the presence of the ZnO on the inner wall of cotton fibers and the polymer-tethered structure.
Khan et al. (2020) reported a novel microwave hydrothermal method to grow aligned ZnO nanorods on cotton fibers. The ZnO coated cotton fabrics obtained showed greater UPF values than pristine cotton fabric, which indicated that ZnO nanorods improved the UV protection of cotton textile. Moreover, the functionalization of ZnO coated cotton fabrics with non-fluorinated silane provided superhydrophobic properties and oil–water separation performance.
Noorian et al. (2020) prepared antibacterial and UV-blocking fabrics by pretreatment of cotton fibers with 4-aminobenzoic acid (PABA) followed by in situ sonochemical synthesis of ZnO nanoparticles. The PABA treatment provided significant sites for the growth of the ZnO nanoparticles and maintained cross-linking property between oxidized cellulosic fibers and the ZnO nanoparticles. Synergistic effects from ZnO and PABA association imparted UPF values higher than 65 and antibacterial activity against E. coli and S. aureus to the cotton fabrics.
Xue et al. (2011; 2013), in two different scientific research publications, investigated the superhydrophobic and UV-blocking properties of PET fabrics coated with ZnO/SiO2 core/shell particles and hexadecyltrimethoxysilane. The coated PET textiles exhibited superhydrophobic surface and UV-blocking ability as seen in water contact angle and UV-VIS spectroscopy results. In addition, the SiO2 shell inhibited the photocatalytic activity of ZnO ensuring the superhydrophobicity of PET surfaces when exposure to UV radiation. Huang et al. (2019) also investigated the superhydrophobic and UV-blocking properties of silk fabrics prepared by combining a one-step in situ synthesis of ZnO nanorods on fiber surface and hydrophobic treatment with n-octadecanethiol. The presence of ZnO nanorods in the silk fibers increased surface roughness and induced a rise in UPF values of fabrics indicating the improvement of UV-blocking ability. Also, obtained superhydrophobic surface showed mechanical and chemical stability.
Singular properties of graphene compounds described in the recent literature (Tiwari et al., 2018) explain their several multifunctional applications in different systems and/or devices. In the smart fabric field, UV-blocking, electrical conductivity and/or antibacterial activity are mainly graphene compound properties investigated in the last scientific publications (Babaahmadi and Montazer, 2016; Hasani and Montazer, 2017a; b; Hu et al., 2015; Mirjalili, 2016; Tian et al., 2016; S.-D. Wang et al., 2020). Electrically conducting textiles produce clothes with static dissipation, anti-spark and electromagnetic interference shielding (Varesano and Tonin, 2008) that can be used in the smart clothing design, e.g., innovative sportswear.
Hu et al. (2015) prepared multifunctional cotton fabrics coated with graphene and waterborne anionic aliphatic polyurethane composites by pad-dry-cure method. Graphene/polyurethane coatings significantly enhanced the UPF values indicating high UV-blocking capacity of cotton fabrics. In addition, graphene/polyurethane coated cotton fabrics exhibited far-infrared emissivity up to 0.911 in the wavelength range of 4–18 μm and lower electrical resistivity than pristine cotton fabric. Far-infrared emitting fabrics are commonly used in health care and therapeutic clothing manufacturing because the far-infrared radiation (6–15 μm) promotes the enhancement of blood microcirculation and metabolism (Vatansever and Hamblin, 2012).
Mirjalili (2016) investigated the UV-blocking, electrical conductivity, magnetic and antibacterial properties of the reduced graphene oxide/Fe3O4 nanocomposite coated cotton fabric. UV-blocking ability of the nanocomposite coated cotton fabric was proved by the increase of the UPF value compared to raw cotton textile. This fabric also displayed a low electrical resistivity, antibacterial activity, and magnetic properties.
Tian et al. (2016) successfully prepared cotton fabrics coated with graphene oxide and chitosan by the electrostatic layer-by-layer self-assembly approach. These fabrics showed higher UPF values than control cotton fabric and washing durability even after 10 times water laundering. It is important to emphasize that the water laundering durability test of cotton fabrics was performed by following the American Association of Textile Chemists and Colorists AATCC 61 (2006).
Babaahmadi and Montazer (2016) investigated electrical conductivity and UV-blocking properties of reduced graphene oxide/SnO2 nanocomposite coated PET textile obtained by modified exhaustion method. Electrical resistivity decreased and UPF value increased with reduced graphene oxide/SnO2 nanocomposite coating of PET fibers, which indicated the formation of an electroconductive and UV blocking textile. Moreover, electrical resistivity and UV-blocking results demonstrated the good durability of nanocomposites on surface of PET fabrics after 10 washes with deionized water.
In different scientific papers, Hasani and Montazer (2017a; b) reported the multifunctional properties of reduced graphene oxide-coated cotton/nylon fabrics. According to the UV-VIS reflectance results, textile materials showed high UV absorption in the 200–400 nm region indicating their potential as UV-protective fabrics. These fabrics also exhibited lower electrical resistance, antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Enterococcus faecalis bacteria and antifungal activity against eukaryotic fungus C. albicans.
S.-D. Wang et al. (2020) successfully prepared a multifunctional silk fabric by grafting graphene oxide (GO) nanosheet dispersion onto the fabric surface. The silk fabrics modified with GO showed higher UPF values than control silk, which indicated the enhancement of UV-blocking properties. Furthermore, modified silk fabrics exhibited excellent antibacterial activity against Escherichia coli and Staphylococcus aureus bacteria.
Zhang et al. (2020) developed a series of multifunctional textiles prepared via in situ modified MOFs nanocrystals on the cotton surface. Based on structural and spectroscopic characterizations, it was confirmed the existence of chemical bonds between MOFs and hydroxyl and/or carboxyl groups belonging to cotton fibers. In addition, a uniform distribution of MOFs nanocrystals in textile surface was observed. The MOFs/cotton textiles exhibited greater UV blocking activity and acoustic absorption performance than blank cotton that demonstrated their potential use as fabrics for UV protection and noise reduction. According to the literature (Münzel et al., 2020), excessive exposure to the noise environment induces adverse cardiovascular effects and mental annoyance.
Emam et al. (2020) investigated the multifunctional properties of cotton fabrics with zeolitic imidazole frameworks (ZIFs). ZIF(Ni), ZIF-8(Zn) and ZIF-67(Co) were in situ synthesized into cotton fabrics before or after silicate modification on the fiber surface. When silicate functionalization was performed before the ZIFs formation, the silicate acted as cross-linker between ZIFs and cotton fibers providing the increment of MOFs amount in the fabric surface. Modified cotton fabrics showed higher UPF values than pristine cotton textile and washing durability (AATCC M6, 2010). Also, they exhibited antibacterial activity against Staphylococcus aureus, Bacillus cereus, Escherichia coli, and Candida albicans bacteria.
Emam and Abdelhameed (2017) reported the incorporation of MIL-68(In)-NH. or MIL-125(Ti)-NH. (MIL = Matériaux de I′Institut Lavoisier) into cotton or silk textiles using quite simple and one-pot process to produce UV-blocking textiles. All MIL-MOFs incorporated textiles exhibited UV-blocking activity; however, MIL-MOFs and metal contents in natural fibers influenced on the UPF values obtained. After five washing cycles (AATCC M6, 2010), these textiles showed a slight decrease of UPF values, which proved their laundering durability.
G.-P. Li et al. (2020) investigated the UV-blocking properties of InOF-1 coated cotton, polyester or aramid textiles prepared by hot-pressing method. Regardless of textile fiber type used, InOF-1 coating provided a significantly increasing in the UV-blocking performance. Moreover, the interactions between InOF-1 and textile fibers, as proven in FTIR results, enhanced the tensile strength and elongation at break of MOF coated textiles.
Ibrahim et al. (2010a) investigated the transfer printability and UV blocking properties of polyester-based textiles obtained by pretreatment of polyester fibers and polyester/wool, polyester/cotton, and polyester/viscose blend fibers with monochlorotriazinyl β-cyclodextrin (MCT-β-CD), chitosan or ethylenediamine followed by transfer printing with sublimable disperse dyes. Hydrophobic cavities generated via grafting of MCT-β-CD, amine functional groups incorporated via aminolysis of the polyester and/or chitosan fixed onto textile matrix afforded an improvement of UV-blocking capacity, transfer printing and fastness properties of modified post-printed fabric samples. In other scientific publication, Ibrahim et al. (2011) reported the development of multifunctional cotton and viscose fabrics printed with reactive dyes through combined reactive printing and MCT-β-CD loading in one-step followed by subsequent treatment with Neem oil. The post-treatment with Neem oil provided the improvement of the antibacterial activity of the treated reactive prints without adversely affecting the UV-blocking properties of the final products.
Subramani et al. (2017) investigated multifunctional properties of the Aloe vera-chitosan nanocomposite coated cotton fabric prepared by pad-dry-cure method. Cotton fabric coated with herbal nanocomposite exhibited excellent UV-blocking ability (UPF > 52), superhydrophobicity, and antibacterial activity against Escherichia coli and Staphylococcus aureus bacteria.
In different scientific publications, Khan et al. (2018) and Shabbir et al. (2018) reported the development of UV-blocking fabrics from natural plant extracts. Khan et al. (2018) successfully prepared UV-blocking and antibacterial fabric by wool treatment with aqueous and alkali extracts of Cinnamomum camphora leaves. Camphor leaves extract imparted dyeing, UV-blocking and antibacterial properties to wool fabric. Shabbir et al. (2018) reported UV-protective and antioxidant finishing of wool fabric dyed with marigold (Tagetes erecta) flower extract. Carotenoid compounds of marigold extract are main responsible for UV-blocking and antioxidant properties of this organic dye. Marigold dyed wool fabrics showed UPF values higher than 30 and capacity to capture peroxide reactive species; therefore, dyed fabrics can be used as potential UV-blocking and antioxidant textiles.
Z. Chen and Yin (2010) investigated the UV-blocking capacity of Eu(III) complex-containing cotton fabrics prepared by pad-dry-cure method. Based on spectroscopic results, Eu(III) complex-cotton fabrics showed higher UPF values than blank cotton fabric and red-light emission. These results are similar to the Eu(III) doped LDH intercalated with cinnamate anions reported by. The Eu(III) doped LDH material exhibited UV-shielding ability and low-intensity red emission that could be inducing collagen production (Saito et al., 2018). Thus, Eu(III) complex-containing cotton fabrics can be able to induce the collagen biosynthesis depending on its intensity emission.
Ibrahim et al. (2010b) prepared functional finishes of linen-containing fabrics by fiber surface modifications using oxygen or nitrogen plasma followed by subsequent dip-pad-cure process with metal salts, nano-scale metal or metal oxides, ionic dyes, quaternary ammonium salt or antibiotics. The linen-based textile results indicated the loading of metal salts, nano-scale metal or metal oxides or ionic dyes onto the plasma treated substrates provided antibacterial activity and a remarkable improvement in UV blocking capacity. Moreover, these functional properties were retained even after 10 laundering cycles (AATCC 124, 1996). In other scientific publication, Ibrahim et al. (2018) reported the multifunctional properties of PET fibers obtained via premodification with sodium hydroxide followed by coating with SiO2, TiO2, ZnO or ZrO. nanoparticles using gelatin as a green binding agent. The results showed an improvement on antibacterial, UV blocking, self-cleaning and softness properties of PET fabrics, which are maintained after 15 laundering cycles (AATCC 135, 2000).
In a series of scientific papers (Rezaie et al., 2017a; b; c) Rezaie and coworkers reported the multifunctional properties of CuO-containing wool and/or polyester fabrics. Based on the results of the UV protection enhancement (%) method described by Noorian et al. (2015) CuO-containing fabrics exhibited higher UV-blocking ability and self-cleaning activity. In addition, these fabrics showed antibacterial activities toward two pathogen bacteria including Staphylococcus aureus as Gram-positive and Escherichia coli as Gram-negative bacteria with no adverse effects on human dermal fibroblasts based on MMT cytotoxicity test (Montazer et al., 2015). The CuO-containing PET fabrics also exhibited a rapid and effective colorimetric response for ammonia detection indicating their potential as ammonia sensing.
Zhao et al. (2013) successfully prepared cotton fabrics coated with amino-functionalized Mg.Al-HMBS-LDH (HMBS = 2-hydroxy-4-methoxybenzophenone-5-sulfonate anions) by electrostatic layer-by-layer assembly technique. Based on thermal analyses, intercalated HMBS showed higher thermal stability than HMBS pristine due to host-guest interactions in the interlayer region. All cotton fabrics assembled with amino-functionalized Mg.Al-HMBS-LDH showed water contact angles greater than 150° suggesting superhydrophobic ability. In addition, these superhydrophobic fabrics exhibited the enhancement of UPF values compared to untreated cotton textile demonstrating UV-blocking capacity.
Sedighi et al. (2018) investigated the multifunctional properties of 3,4‑ethylene dioxythiophene polymer (PEDOT)/magnetite nanoparticles coated PET fabrics. PEDOT/magnetite nanoparticles coating improved the UV-blocking capacity of PET fabric especially in UVB and UVC regions. This nanoparticle coating also provided significant antibacterial activity against S. aureus bacteria, electromagnetic interference (EMI) shielding behavior and superparamagnetic properties. In this paper, EMI shielding corresponds to microwave attenuation ability of these multifunctional PET fabrics.
N. Li et al. (2018) reported a novel coating technique involving in situ self-assembly of the polyoxotitanate (POT) cage [Ti18Mn.O30(OEt)20Phen3] to fabricate multifunctional cotton fabrics in a single step. The POT cage coating imparted excellent UV-blocking performance (89% blocked at 350 nm), hydrophobicity (water contact angle > 148°) and antibacterial activity (Escherichia coli, Staphylococcus epidermidis, and Staphylococcus aureus bacteria) to cotton fabrics.
Jin et al. (2019) successfully prepared bismuth phosphate (BiPO2) nanorods coated cotton fabrics by two-dip-two-nip technique. Chitosan and acetic acid acted as cross-linking agents between BiPO2 and cotton fibers as seen in UV-VIS absorption and FTIR results. The coated fabrics exhibited UV-blocking ability confirmed by UPF values greater than blank cotton fabric and self-cleaning activity.
A series of scientific publications (Čuk et al., 2021; Nateghi and Shateri-Khalilabad, 2015; Pan et al., 2012; Razmkhah et al., 2021; Shateri-Khalilabad and Yazdanshenas, 2013a; Tang et al., 2017) reported multifunctional features of metal nanoparticles coated smart fabrics. In this perspective, silver nanoparticles had widely used due to their antibacterial ability. Shateri-Khalilabad and Yazdanshenas (2013a) investigated superhydrophobic, antibacterial, and UV-blocking properties of the silver nanoparticles (AgNPs) coated cotton fabric. AgNPs coating was formed on the cotton surface through an alkali preactivation followed by in situ reduction of silver nitrate. Then, AgNPs coated cotton fibers were subjected to superhydrophobic treatment with octyltriethoxysilane (OTES). AgNPs coated cotton fabric showed UPF value equal to 266, water contact angle greater than 150° and shedding angle equal to 8°. Also, coated fabric exhibited antibacterial activity against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria.
Nateghi and Shateri-Khalilabad (2015) also investigated multifunctional properties of the silver nanowires (AgNWs) coated cotton fabric prepared by dip-dry method followed by superhydrophobic treatment with Danasylan F 8815. SEM/EDX results indicated a thin and uniform AgNWs coating on the cotton fibers. AgNWs coated cotton fabric also exhibited UV-blocking (UPF > 113), superhydrophobic (water contact angle > 150° and shedding angle < 10°) and antibacterial properties. In other scientific paper about Ag nanoparticles coated textiles, Čuk et al. (2021) reported the development of multifunctional fabrics using plant food waste (green tea leaves, avocado seed and pomegranate peel) and alien invasive plant extracts (Japanese knotweed rhizome, goldenrod flowers and staghorn sumac fruit) as reducing agents for the in-situ synthesis of silver nanoparticles in cotton fibers. Regardless of the reducing agent used, all silver nanoparticles containing cotton fabrics showed UPF values above 50 and antibacterial activity against E. coli and S. aureus bacteria.
Pan et al. (2012) successfully prepared a superhydrophobic and UV blocking cotton fabric via sol-gel method and self-assembly using inexpensive and ordinary reagents, aluminum nitrate and sodium stearate. The interactions between aluminum coating and sodium stearate in cotton fabrics was confirmed by XPS results. Cotton fabric treated with 1.5% Al sol and 20 mmol L–1 sodium stearate exhibited excellent hydrophobic properties (water contact angle > 146°) and UV blocking ability (UPF = 164).
In other scientific publication about nanoparticle-containing cotton fabrics, Tang et al. (2017) reported the development of gold nanoparticles (AuNPs) coated cotton fabrics prepared by in situ synthesis of AuNPs onto fiber surface using a heating method. The localized surface plasmon resonance of the AuNPs imparted the cotton fabric with colors, showing good colorfastness to washing and rubbing. It is important to highlight that the colorfastness to washing and rubbing were evaluated in accordance with Australian Standard AS 2001.4.15–2006 and Australian Standard AS 2001.4.3–1995, respectively. The AuNPs coating improved the UV-blocking ability of cotton textiles and resulted in UV-protective fabrics with remarkable antibacterial activity. In addition, AuNPs coated cotton fabrics exhibited catalytic activity, which did not influence on their dyeing with reactive dyes.
Razmkhah et al. (2021) reported the UV-blocking and antibacterial properties of selenium nanoparticles coated wool fabrics. Based on the results of the UV protection enhancement (%) method (Noorian et al., 2015), the coated fabrics exhibited UV-blocking ability. In addition, these fabrics showed reasonable bactericidal and fungicidal performances toward Escherichia coli, Staphylococcus aureus and Candida albicans.
For comparative purposes, Fig. 5 and 6 were made to analyze and discuss the main scientific information of UV-protective compound-containing smart fabrics described above. Thus, Fig. 5 shows the number of scientific publications for each UV-protective compound class presented in the chemical composition of smart fabrics and Fig. 6 illustrates the UV-blocking range of UV-protective compound-containing fabrics. It is important to highlight that UV-blocking range corresponds to the UV-shielding performance of compound class including specific UV spectral region of each compound.
Analyzing the number of scientific publications about UV-protective compound-containing smart fabrics in the period from 2010 to 2021 (Fig. 5), it is observed that TiO2, ZnO and nanocomposites based on TiO2 or ZnO were the most used in the development of UV-blocking fabrics. Probably, low human skin toxicity (Abuçafy et al., 2016) and UV-shielding (Abuçafy et al., 2016; Flor et al., 2007; Seixas and Serra, 2014), self-cleaning (Banerjee et al., 2015; Qi et al., 2017) and antibacterial (Qi et al., 2017; Yadav et al., 2016) properties of these oxides and/or nanocomposites combined with several synthetic methods used to obtain them (Montazer and Pakdel, 2011; Montazer and Amiri, 2014) encouraged this great number of scientific studies. In general, synthetic approaches use low-cost and easy-to-obtain reagents and, depending on the synthetic route, allow to control the morphology, surface, and particle size of TiO2, ZnO and/or nanocomposites based on TiO2 or ZnO. Despite the smaller number of scientific papers, other UV-protective compounds, mainly LDH, MOFs and Graphene compounds, demonstrate growing potential to be used in the development of novel smart fabrics due to their new multifunctional features, increasingly reported in the recent literature. Thus, a promise increasing of scientific publications about this type of smart fabrics could be expected.
Figure 5.
Number of scientific publications of the UV-protective compound-containing smart fabrics per UV-protective compound class in the period from 2010 to 2021.
Another relevant aspect to be considered is that the smart fabrics with LDH, MOFs or graphene compounds exhibited UV-blocking range situated in the UVB and UVA regions (Fig. 6) indicating broad-spectrum action, i.e., capacity to protect the human skin from both UVB and UVA radiation. Organic compounds or metal nanoparticles containing smart fabrics also had same broad-spectrum behavior, while other fabrics showed UVB-blocking capacity (Fig. 6). Therefore, UV-protective compound presented in the textile composition determines the UV radiation region that smart fabrics have higher protection efficiency.
Although organic compounds can undergo decomposition under certain conditions, e.g., high temperature and/or oxidizing environment, the synergistic effects from interactions between these compounds and textile fibers improve their thermal, chemical and/or photochemical stability. Moreover, synergistic properties reduce the fiber photodegradation of smart fabrics. In this perspective, molecular interactions between textile fibers and UV-protective compounds provide specific physicochemical properties to textile materials and ensure lower occurrence of skin allergies by fabric contact.
Figure 6.
UV-blocking range of the UV-protective compound-containing smart fabrics per compound class.
Besides the UV-blocking range, UPF values are commonly used to indicate the UV protection of smart fabrics. Analogous to sun protection factor (SPF) of sunscreens, UPF is a parameter defined as the ratio of the average effective UV irradiance calculated for unprotected skin to the average effective UV irradiance calculated for skin protected by the smart fabric (Hoffmann et al., 2001). Many scientific publications have shown that UV-VIS spectroscopic measurements are accurate and reproducible in vitro test method to determining UPF (Montazer and Amiri, 2014), which is obtained by Eq. 1:
(1)where E. is the relative erythemal spectral effectiveness and S. is the solar spectral irradiance of the source. The Tλ corresponds to spectral transmission of the test fabric as a function of wavelength (λ) and the wavelength integration limits refers to the combined UVB and UVA wavelength range.
According to Hoffmann et al. (2001), UPF values between 15 to 24 (ratings 15 and 20, respectively) indicate a good UV-protection, UPFs of 25 to 39 (ratings 20, 30 and 35, respectively) demonstrate a very good UV-protection, and UPFs ≥ 40 correspond to an excellent UV-protection (ratings 40, 45, 50 and 50+). Analyzing the UPF values of scientific publications cited in this review, it is observed that more than 90% of them exhibited UPF values higher than 40. Therefore, smart fabrics had an excellent UV-protection regardless on the UV-protective compound presented in the textile fibers. However, some precautions must be considered in the analysis and interpretation of these UPF results. One of the most important aspects is the UV-VIS transmission measurements, which undergo spectral changes and/or deviations depending on the experimental conditions used and/or optical properties of smart fabrics. In this perspective, opaque and translucent smart fabrics, which exhibit nonlinear behavior of Lambert–Beer law, must be carefully analyzed to avoid mistakes in the interpretation of UPF results.
In this review, recent literature on UV-blocking textiles have been reported to give an overview of their importance and prospects in sun-protective methods. UV-protective compounds incorporated, anchored, or coated textile fibers compose a useful class of UV-blocking materials for the development of smart fabrics as proved by the large number of scientific publications in the last years. Different UV-protective compounds, mainly TiO. and ZnO, are used to improve UV-blocking ability of fabrics and, often, they also impart to additional fabric properties, e.g., antibacterial, and self-cleaning activities. Analyzing from spectroscopic point of view, the elucidation of UV-blocking mechanisms gives an important information about electronic structure and optical properties of UV-protective textiles; therefore, it can be more investigated and discussed in the literature. A remarkable point is the reduced number of scientific papers that reported the use of organic filters in smart fabrics although these UV-protective compounds have high UV absorption capacity and, depending on their molecular structure, can interact to fiber surface without the presence of cross-linker compounds. UPF is a good parameter to indicate the UV-blocking ability of UV-protective compound-containing smart fabrics, however, some aspects must be considered in the analyses and interpretation of UPF results. Among them, (i) the amount of the UV-protective compound per textile area, (ii) textile thickness, and (iii) textile properties changed by the incorporation, coating and/or anchorage with UV-protective compounds, e.g., textile roughness. In this perspective, new scientific studies need to be undertaken to know the effective contribution of UV-protective compounds in the UPF values. Considering the growing requirement for simple, cheap, and practical sun-protective products, UV-blocking textiles are one of the best alternatives. Thus, scientific research in the field of smart fabric and/or UV-blocking textile, especially UV-protective compounds incorporated, anchored, or coated textile fibers, must be encourage in order to promote new insights in sun-protective clothing and future applications of multifunctional textiles.
Conceptualization: Lupino, J. H. B.; Saito, G. P.; Cebim, M. A.; Davolos, M. R.
Data curation: Lupino, J. H. B.; Saito, G. P.; Cebim, M. A.; Davolos, M. R.
Formal Analysis: Not applicable.
Funding acquisition: Davolos, M. R.
Investigation: Not applicable.
Methodology: Not applicable.
Project administration: Not applicable.
Resources: Not applicable.
Software: Not applicable.
Supervision: Davolos, M. R.
Validation: Lupino, J. H. B.; Saito, G. P.; Cebim, M. A.; Davolos, M. R.
Visualization: Lupino, J. H. B.; Saito, G. P.; Cebim, M. A.; Davolos, M. R.
Writing – original draft: Lupino, J. H. B.
Writing – review & editing: Saito, G. P.; Cebim, M. A.; Davolos, M. R.
Data sharing is not applicable. In this review, all scientific publications reported were found in the Web of ScienceTM database (https://www-webofscience.ez87.periodicos.capes.gov.br).
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). Grant No: 317610/2021.
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) - Programa Institucional de Bolsas de Iniciação Científica (PIBIC). J.H.B.L Scholarship No: 1127 – Edital 01/2020.
The authors acknowledge the Instituto de Química - Universidade Estadual Paulista (Unesp) for the institutional infrastructure and technical support.
marian.davolos@unesp.br
Figure 1.
Polyethylene terephthalate (PET) monomer structure.
Figure 2.
Schematic representation of the simplified cellulose structure.
Figure 3.
Schematic representations of plain fabric’s frames: (a) taffeta, (b) twill and (c) satin.
Examples of UV-protective compound-containing textile fibers described in scientific literature between 2010 and 2012.
PET: Polyethylene terephthalate.
Examples of UV-protective compound-containing textile fibers described in scientific literature between 2013-2016.
PET: Polyethylene terephthalate.
Examples of UV-protective compound-containing textile fibers described in scientific literature between 2017 and 2018.
PET: Polyethylene terephthalate. * MIL: Materials Institute Lavoisier. MOF: metal-organic framework. # Natural herbal nanoparticles prepared from shade-dried Aloe vera plant.
Examples of UV-protective compound-containing textile fibers described in scientific literature between 2019 and 2021.
PET: Polyethylene terephthalate. MOF: metal-organic framework.
Figure 4.
Schematic representation of a UV-protective compound-containing smart fabric.
Figure 5.
Number of scientific publications of the UV-protective compound-containing smart fabrics per UV-protective compound class in the period from 2010 to 2021.
Figure 6.
UV-blocking range of the UV-protective compound-containing smart fabrics per compound class.
