Functional cotton fabric using hollow glass microspheres: Focus on thermal insulation, flame retardancy, UV-protection and acoustic performance

https://doi.org/10.1016/j.porgcoat.2020.105553Get rights and content

Highlights

  • Bi-layer coatings based on TiO2 nanoparticles and HGMs were developed on cotton fabrics.

  • The effects of HGMs on flame retardancy and thermal insulation of cotton fabrics were analysed.

  • HGMs resulted in an acoustic performance over the frequency range of 0−3500 Hz.

  • Cotton fabrics possessed excellent UV protection.

  • The impact of coating process on mechanical properties of fabrics was investigated.

Abstract

This research aims at developing novel multifunctional coatings on cotton fabrics using titanium dioxide (TiO2) nanoparticles and hollow glass microspheres (HGMs) (2−20 wt%). Different properties of fabrics including thermal insulation, flame retardancy, and acoustic performance were studied. In addition, the impact of the coating process on UV-protection and mechanical properties of fabrics was also explored. The thermal insulation of fabrics was characterized based on thermal infrared (IR) imaging and sweating guarded hot plate testing system. The findings demonstrated that the presence of HGMs on the surface of cotton improved the thermal resistance by 78% highlighting their superior thermal insulation. The thermal stability and flame retardancy of samples were tested using thermogravimetric analysis (TGA), limiting oxygen index (LOI), and vertical flame testing. The obtained results confirmed the protective role of the developed coatings in increasing the thermal stability and lowering the flammability of samples. The presence of a thin layer of titanium dioxide (TiO2) nanoparticles on cotton fabrics gave rise to an excellent UV-protection where the UPF level increased by 2.8 fold compared with the uncoated sample. In addition, fabrics coated with HGMs showed superior sound absorption behavior over the frequency range of 0−3500 Hz. The developed multifunctional fabrics can be of potential applications as new generation of curtains, protective clothing, and even automotive interior parts.

Introduction

Developing energy saving technologies especially for buildings has attracted significant attention in recent years [1,2]. Space conditioning the indoor environment for residential and commercial buildings takes approximately 20–40% of the overall consumed energy bills [1]. Among different parts of a building envelope, windows play a significant role by being responsible for around 20–40% of energy waste. This has encouraged researchers to develop energy-efficient windows [3,4]. One of the practical methods for achieving this goal is developing functional thermal coatings on curtain fabrics to regulate heat gain and loss [5]. The main functionalities of these products would be reducing the heat flux from outside to inside in summer days and also preventing the heat loss from warm indoor space to the environment in winter. This can significantly contribute to reducing the overall energy required for indoor heating and cooling [5].

In addition to thermal protection, curtain fabrics should also be flame retardant and UV-protective to minimize any risk of injury and health hazards for users in indoor space. These properties can be achieved through developing functional coatings on fabrics [6]. Incorporation of different types of organic and inorganic flame retardants in coating formulations has been effective in introducing flame retardancy to the coated fabrics [7,8]. Halogenated and boron-containing additives have been used in lowering the flammability of textiles; however, their use has been restricted due to their potential toxicity and low durability [9]. Also, different types of nanomaterials such as nanoclays [9], carbon nanotubes (CNTs) [[10], [11], [12]], TiO2 [13,14], graphene oxide [15], and silica [16] were utilized in the textile treatments. These materials can reduce the flammability of fabrics by forming a char layer on fabrics acting as a heat barrier on the substrate [6,17]. However, to achieve an effective flame retardancy, a high loading of nanomaterials and developing thick coatings are required [17]. Also, some of these nanofillers particularly the carbon-based nanomaterials can negatively impact the natural color of fabrics. Furthermore, coatings should be able to block the incoming ultraviolet (UV) light from the solar spectrum. Among different wavelengths, UVA (320–400 nm) can pass through the window glasses causing damage to both human body and household furniture. Although some factors such as color and weaving structure are effective in the overall UV-protection of fabrics, applying functional coatings containing UV absorbers can significantly improve UV-protection [18,19]. Some nanocoatings containing TiO2 and zinc oxide (ZnO) have been recognized as efficient UV absorbers which can be applied to different surfaces such as textiles [20].

Hollow glass microspheres (HGMs) have been used in fabricating products with thermal insulation property in different fields such as aerospace, coatings, plastics, and building materials [21,22]. These are inorganic hollow microscopic spheres (1−1000 mm) with a thin shell (1–8% of diameter), which possess some unique properties such as light weight, inertness, low thermal conductivity, excellent dispersion and low density [23]. Their hollow inner space contains some gases such as CO2 or N2 leading to superior heat and sound insulation properties. The positive impacts of HGMs addition on lowering the thermal conductivity and flammability of composite structures have been demonstrated [24,25]. For instance, the addition of HGM along with specific concentrations of carbon nanofibres (CNFs) to high-temperature resins, led to producing composites with low thermal and high electrical conductivities [26]. Moreover, the effects of HGMs on mechanical, thermal properties and flammability of different compositions such as HGM/phenolic resin (PR) composites [21], HGM/phosphate adhesive (Syntactic foam) [27], HGMs/high density polyethylene (HDPE) [28], and HGM/polypropylene [29], to name but a few, have been explored. In addition, the synergetic role of HGMs in improving the acoustic performance of syntactic foams has been reported [30]. Some works have focused on incorporating HGMs in the coating formulations of textiles. For instance, coatings containing Ag-modified HGMs were applied to the surface of cotton and PET/cotton fabrics using different binders such as printing paste and water-borne polyurethane [31,32]. Modifying HGMs surface with silver nanoparticles through the electroless plating method led to a core-shell structure of Ag/HGM [31]. This material was applied along with aluminum powder to cotton where the coating provided an electromagnetic shielding effect because of its conductive nature. Also, coated fabrics showed a low surface emissivity which was suitable for IR-stealth applications [31]. Increasing the content of Ag/HGM (5–20%) improved the heat radiation resistance of PET/cotton fabrics [32]. However, other aspects of the fabrics such as flammability and acoustic performance have not been investigated.

Although there are many published research papers on the application of HGMs in developing polymer composite structures, there is not much work done on using this insulating material in textiles. This research develops a facile strategy to incorporate the superior features of HGMs in conventional textile products. To this end, bilayer coatings consisting of TiO2 nanoparticles and HGMs were developed on cotton fabrics. TiO2 is a semiconductor material that has widely been used in surface functionalizing textiles to achieve different features such as self-cleaning [[33], [34], [35], [36]], UV-protection [37], antimicrobial activity [38,39] and photocatalytic performance [40,41]. Therefore, its unique features such as intrinsic UV absorption along with low thermal conductivity of HGMs can be combined to develop a multifunctional coating layer on textiles. In this article, a comprehensive analysis on the coated cotton fabrics is carried out to investigate the thermal performance, flame retardancy, sound absorption, UV-protection, and mechanical properties.

Section snippets

Materials

100% natural cotton fabric (50 cm × 50 cm) was used as substrate in this study. Titanium tetra isopropoxide (TTIP) 97% was purchased from the Sigma-Aldrich Company as the precursor of TiO2 nanoparticles. Hollow glass microspheres (3M™ Glass Bubbles iM30 K) with an average diameter of 18 μm were purchased from 3M™ Company. Self-cross-linking acrylic-based emulsion (ACRYSOL RM-8W) and rheology modifier (ACRYSOL™ RM-8W) were used as the binder and thickener, respectively and were provided by Dow

Characterization of TiO2 and HGMs

The prepared materials were characterized in terms of their crystallinity and elemental composition. The TEM image of TiO2 nanoparticles showed the parallel arrays of a crystalline structure with the distance of n = 0.35 nm indicating the presence of anatase TiO2 nanoparticles. This was further confirmed by the XRD pattern where the peaks at 2θ of 25.2°, 37.92°, 47.62°, 54.25°, 62.35°, 69.7° and 75.2° represented the lattice parameters of 3.51(101), 2.37(004), 1.88(200), 1.66(211), 1.48(204),

Conclusion

This study investigated the applicability of hollow glass microspheres (HGMs) in conjunction with TiO2 nanoparticles in developing flame retardant, UV-protective, thermally insulating, and acoustic textiles. Different concentrations (2−20 wt%) of HGMs were incorporated in the acrylic-based formulations and then applied to the fabric surface using a blade coating approach. Prior to applying HGMs to fabrics, the samples were treated with 5% colloid of TiO2 nanoparticles to achieve excellent

Data availability

The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.

CRediT authorship contribution statement

Esfandiar Pakdel: Conceptualization, Methodology, Investigation, Writing - original draft, Data curation. Maryam Naebe: Writing - review & editing, Data curation, Resources. Sima Kashi: Investigation. Zengxiao Cai: Investigation. Wanjie Xie: Investigation. Anthony Chun Yin Yuen: Investigation. Majid Montazer: Writing - review & editing, Resources. Lu Sun: Supervision, Conceptualization, Writing - review & editing. Xungai Wang: Supervision, Writing - review & editing.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

The 1st author acknowledges the support of Alfred Deakin Postdoctoral Research Fellowship provided by Deakin University. We would also like to acknowledge support from the Australian Research Council World Class Future Fiber Industry Transformation Research Hub (IH140100018). Deakin University’s Advanced Characterization Facility is also acknowledged for using SEM and TEM facilities.

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