Improving Hydrophobicity Properties of Water-Based Paints in the Construction Sector

 

Abstract

In this study, red rose petals were added to water-based paint formulation to enhance its hydrophobic properties. Red rose petals were dried and ground into powder form. Boron chemicals, talc, and red rose petals were added to water-based interior paint at varying ratios, representing 0-6% by weight of the paint. The Taguchi experimental design method was employed, selecting three levels and three parameters for the experiments. Nine paint samples with different formulations were prepared and homogeneously mixed with the additives, then applied to specially prepared panels. After the coatings dried on the panels, samples were subjected to testing. The additives incorporated into the paint were found to enhance not only the hydrophobic properties of water-based interior paint but also other characteristics.

Introduction

With advancing technology and changing expectations, paint coatings used on materials are expected to develop enhanced properties. In conducted studies, natural and synthetic additive materials have been incorporated into paint. Researchers have examined the effects of these additions on paint performance. Environmental factors, raw material costs and quality have also been considered. As an important property of chemistry, the wettability of a surface holds great significance in fundamental and industrial applications [1]. Control of surface wettability is valuable for self-cleaning glass in aviation and automotive industries, wear-resistant structures in the construction sector, water-repellent textiles, non-fouling surfaces for optical instruments and mobile phones, membrane applications, cell and antibacterial adhesion, and cookware coatings. To determine surface wettability, equilibrium contact angle measurements must be performed [2]. When a liquid droplet contacts a solid surface, a surface is wettable if the contact angle is less than 90°, while a surface is non-wettable if the contact angle is greater than 90°. Wettable surfaces are called hydrophilic and non-wettable surfaces are called hydrophobic [3]. Although superhydrophobicity has been known since the 1940s, it has gained greater importance in recent years following research by Barthlott and Neinhus in 1997 into the surface structure of various natural plant leaves, including lotus leaves [4].

Superhydrophobic surfaces possess properties such as non-adhesiveness, non-soiling and self-cleaning, and are expected to be used in many biological and industrial applications due to these characteristics [5].

Surfaces on which a liquid droplet has a contact angle greater than 150° are called superhydrophobic surfaces [4]. For a surface to exhibit superhydrophobic properties, two basic factors are required: low surface energy and surface roughness [3]. These two basic factors have led to two methods for synthesizing superhydrophobic surfaces. In the first method, a rough surface can be synthesized from a hydrophobic material. In the second method, a rough hydrophilic surface can be chemically modified or a hydrophobic material can be applied to it [5]. Numerous different methods can be used to create surface roughness at the scale needed to impart superhydrophobic properties, including plasma etching, laser etching, chemical etching, electrochemical reaction and deposition, electrospinning, chemical vapor deposition, lithography, sol-gel processing, solution casting, layer-by-layer and colloidal assembly [3]. The water-repellent and self-cleaning properties found on the surfaces of certain organisms such as lotus and rice leaves, butterfly and dragonfly wings, mosquito eyes, gecko feet and rose petals have been the subject of research for years. The lotus flower, also known as the water lily, which grows in wetlands, is the best example of a surface capable of self-cleaning and hydrophobic properties [6]. The leaves of the lotus plant contain randomly distributed micro and nano roughness. Though not apparent from the outside, the nano protrusions provide the structure with superhydrophobicity and impart a high contact angle [7]. Water droplets rest on the highest points of the nano protrusions because the cavity structures beneath the droplet are filled with air pockets. The reason lotus flower leaves exhibit superhydrophobic properties stems from the presence of air pockets [5]. Due to the hydrophobic character of the surface, water droplets cannot make complete contact with the surface and roll downward under their own weight, removing all dirt particles on the surface in the process, an occurrence known as the self-cleaning property. The self-cleaning property of surfaces, also known as the "lotus effect," is providing new applications and developments in many industrial sectors today, particularly in textiles and coatings [7]. In this study, using the Taguchi Method, an optimization technique, the hydrophobic properties of water-based paint were improved through additives incorporated into the paint, and positive results were obtained in the tests performed.

Experimental Work

Boron chemicals (B), red rose petals (RP), and talc (T) were prepared in specific proportions by weight in the 0-6% (w/w) range and added to white-colored, water-based, interior paint, then homogeneously mixed with a mechanical stirrer. Following completion of the mixing process, paints with 9 different content ratios were prepared according to the Taguchi optimization method. Viscosity values of each of these paints were measured. Viscosity results were used in the Taguchi optimization method to determine optimum experimental parameters (Table 1).

Table 1. Taguchi L-9 orthogonal array

These paints containing materials in specific proportions were applied to panels measuring 26x26 cm². Paint mixtures prepared according to the Taguchi optimization method were applied to the panels at a draw-down thickness of 150 μm with the aid of an applicator (Figure 1). After a drying time of 24 hours, the hydrophobicity values of the paints were determined using a contact angle measurement device.

Figure 1. Panel sample with paint mixtures applied

Results and Discussion

Viscosity values for the paints prepared according to the Taguchi optimization method are presented in Table 2.  

Table 2. Viscosity values of prepared paints

In the prepared paint set, experiment no. 9, which used the third level for the boron chemicals and red rose petal parameters and the second level for talc, yielded the most optimum result (Figure 2).

Figure 2. Main effects plot for S/N ratio

In the hydrophobicity test, a water droplet was first applied to the dried paint on the panels using a pipette. The panels were slowly brought to a vertical position to observe the flow of the water droplet over the paint. No adverse effects such as softening, deterioration, peeling or color change were observed on the surface of the paint samples (Figure 3).

Figure 3. Hydrophobicity test of reference paint and optimum paint

A contact angle measurement device is a computer-controlled instrument based on video image capture and automatic image analysis used to measure liquid absorption in porous materials, surface and interfacial tensions of liquids, surface free energies, and static or dynamic contact angles. Drop shape analysis is used to determine surface/interfacial tension, absorption and static or dynamic contact angles of liquids. The camera feature in its structure enables image capture at time intervals ranging from 10 ms to 1000 s. After images are positioned by appropriate methods, contact angles between 5° and 180° and surface tension between 0.01 and 999 mN/m can be obtained [8]. Using a contact angle measurement device, contact angles of the reference paint and optimum paint samples from both sets were measured to determine the degree of hydrophobic properties they exhibited. Measurement results are shown in Figures 4 and 5.

Figure 4. Contact angle image of reference paint

The contact angle measurement result of the prepared optimum paint sample is 81.25°. It was observed that by adding red rose petals, which possess hydrophobic properties, as an additive, the paint's contact angle value increased and approached 90°, thereby improving the hydrophobic properties of the paint.

Figure 5. Contact angle image of optimum paint

Conclusion

In conclusion, parameters that can minimize the adverse effects water will exert on the paint structure while imparting hydrophobic properties have been evaluated. Contact angles of the reference paint and the prepared optimum paint samples were determined using a contact angle measurement device. While the reference paint had a contact angle value of 61.64°, the optimum paint sample prepared with additives had a contact angle value of 81.25°. While the reference paint exhibited hydrophilic properties, it was observed that the addition of red rose petals brought the contact angle closer to 90°. It was concluded that the rose petals made a positive contribution to the hydrophobic properties of the optimum paint samples. Assistant Professor Nil Acaralı - Department of Chemical Engineering Yıldız Technical University Master of Chemical Engineering Merve Bağcı - Department of Chemical Engineering Yıldız Technical University

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