Facile fabrication of fluoro-polymer self-assembled ZnO nanoparticles mediated, durable and robust omniphobic surfaces on polyester fabrics

https://doi.org/10.1016/j.jfluchem.2020.109565Get rights and content

Highlights

  • Fluoro-monomer was polymerized on ZnO seed layer grown polyester fabric.

  • Omniphobic polyester was fabricated.

  • ZnO nanoparticles seed layer acts as intermediate to combine both polymers.

  • Final omniphobic product is mechanically robust and withstanding washing cycles.

Abstract

Omniphobic surfaces have been widely used in many applications, especially owing to their self-cleaning property. In this work, polyester fabric was modified to be super-omniphobic with a water contact angle (WCA) of 152° by reducing the surface free energy of the fabric surface via the polymerization of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl methacrylate (TDM) on a ZnO seed layer grown on polyester which acts as intermediate in combining polymerized TDM into polyester. Two types of fabrics, one with and the other without the seed layer, were characterized using various analytical techniques. The WCA of the fabric with the seed layer was measured to be 153° compared to 142° of the fabric without the seed layer. The modified omniphobic fabric with the seed layer made a contact angle of 132° with SAE 40 motor oil indicating its oleophobicity while non-treated fabric made no measurable contact angle. In addition to that, the treated fabric is omniphobic against milk tea, coffee, coconut oil, and ethanol. The morphological analysis using scanning electron microscopy (SEM) of the treated and non-treated fabrics revealed that the particle size of the seed layer applied fabric was ranging from 100−300 nm and upon the TDM application it became less than 100 nm. Elemental analysis by EDS showed the presence of fluorine in the composite and FT-IR analysis confirmed that the polymerization of TDM has indeed taken place. The polymerization of fluoropolymer was further confirmed by TGA and DSC analyses. The durability of the fabrics was tested and the contact angle of the surface-modified fabric remained unchanged even after 1.5 h washing and 50 cycles of abrasion. The modified fabric is robust and no change was observed in the color of the fabric during the process. More importantly, the fabric modification method in this work is simple, low cost and quick.

Introduction

Omniphobic surfaces have gained great deal of attention due to their special properties such as oil-water separation [1], self-cleaning [2], anti-corrosion [3,4], water repellency [5] and mechanical robustness [6]. Omniphobic property can be used especially with textile materials for various functional applications such as coats, rainwear, shoes, umbrellas and table clothes. Generally, a surface with a static water contact angle>150° is defined as a superhydrophobic surface [7]. The water contact angle (WCA) of a surface depends on two major properties: 1) surface roughness and 2) low surface energy [3,[7], [8], [9]]. The surface roughness can be achieved by fabricating a micro and nano-structured layer on the surface [10]. The low surface free energy can be realized by applying a low surface free energy substance on top of the nanostructured layer [10]. There are various reported methods available to fabricate superhydrophobic surfaces such as electrochemical deposition [11], self-assembly layer by layer method [2], hydrothermal synthesis [12], chemical vapor deposition, phase separation, wet chemical reaction [13], dip coating [7], spin coating, electrospinning and sol-gel processing [14]. Most of these methods are multi-step processes that require special equipment or chemicals, moreover they are expensive to implement at large scale and even the coatings are not transparent. As water has high surface tension (72.1 mN/m), superhydrophobic surfaces can be produced easily and also available in nature. However to repel low surface tension-liquids such as ethanol, a surface with lower surface free energy is usually required.

Fluoropolymers have lower surface free energy, high chemical and thermal stability, outstanding adhesive and oil-repellent properties, low refractive indices and low dielectric constants. These properties can be attributed to the high electronegativity of fluorine, strong fluorine-carbon bond and large Van der Waals radii [[15], [16], [17], [18], [19]]. Omniphobic textiles have been prepared using various fluoropolymers such as 1H, 1H, 2H, 2H-perfluorodecanethiol [13], 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane and perfluorododecyl -1H, 1H, 2H, 2H-triethoxysilane [14]. However, these methods are highly time consuming and the modifications therein change the fabric color or leave a slippery surface.

In our work, we developed a method to modify polyester fabric to make it omniphobic. The method involves first depositing a seed layer on the fabric followed by a polymer layer. In a typical experiment, the polyester fabric is first coated with ZnO seed layer and the low surface free energy was realized using TDM. First ZnO and TiO2 both were used to deposit the seed layer as they are less expensive, easily available, easy to handle and environment-friendly. Out of the two, ZnO turned out to be the best as the TiO2 seed layer detached from the fabric during fluoropolymer application indicating weak interaction with the fabric compared to ZnO. When the most optimized method is used, interestingly no color change or slippery surfaces were observed. More importantly this method is less time-consuming, low cost and easy to process [18,19].

Section snippets

Materials and characterization techniques used

3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctyl methacrylate(C12H19F13O2, 98%), sodium hydroxide (NaOH, 98%), sodium persulfate (Na2S2O8, 98%), zinc nitrate hexahydrate ((Zn(NO3)2.6H2O, 99%), titanium(IVI isopropoxide (Ti[OCH(CH3)2]4, 97%) (TTIP), hexamethylene tetraamine (HMT) (C6H12N4, 99%) and absolute ethanol (100%) were purchased from Sigma-Aldrich and used without further purification. Polyester fabric was purchased from a local store (Technical parameters of the fabric: Fabric type- woven,

Morphological and elemental characteristics

Achieving the omniphobic property, as described before, mainly depends on the careful construction of the modified surface. In this regard, surface morphological characterization is very important. SEM characterization was carried out to analyze the surface morphology of the non-treated polyester fabric (NT) (Fig. 1a), fluoropolymer applied fabric without any seed layer (FP) (Fig. 1b), ZnO seed layer applied fabric (ZO) (Fig. 1c), fluoropolymer applied fabric on top of the ZnO seed layer (Fig. 1

Conclusions

Polyester fabric surface was successfully modified to achieve robust omniphobic property using a novel and simple method. The fabric with the ZnO seed layer showed better superhydrophobicity (WCA 152°) compared to the fabric without a seed layer (142°). The modified omniphobic fabric showed higher durability over 50 cycles of abrasion and over 1.5 h of washing (three washing cycles). The treated fabric also made contact angle of 132° with oil and even after 50 cycles of abrasion the contact

Declaration of Competing Interest

The authors declare that there is no conflict of interest. All authors have reviewed and agreed to publish the manuscript in the Journal of Fluorine Chemistry.

Acknowledgements

The authors are grateful to Ms. A. Senthilnathan and Ms. G. T. D. Chandrakumara for their kind support during this research.

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