Paints and Coatings: From Past to Present

The history of paint goes back as far as human civilization itself. Early humans began using colorants of plant, mineral, or animal origin found in nature for purposes such as protective coating, decoration, and marking. It was also common practice for people to apply these colorants to their bodies as a means of attractiveness, intimidation of enemies, markers of special occasions, or signs of belonging to a group or tribe. The increase in types of colors and manual skills led people to use paints to depict what they saw around them and to create artistic works. Examples of these works that have survived to the present day can be seen in different parts of the world. For instance, approximately 600 images containing nature scenes found in the Lascaux cave in southwestern France are estimated to date back around 17,000 years [1], Figure 1. [caption id="attachment_104448" align="aligncenter"] Figure 1. An example of animal drawings found in Lascaux cave [1][/caption] Today, paints are used widely in much larger quantities and with an increased number of color tones. Protection of the surface to which they are applied, beautification, coloring, differentiation, or warning against a danger are a few examples of the uses of paints.

Paints are generally liquid mixtures consisting of basic components serving different purposes: solvent, binder, filler, and pigment which provides coloring.

Based on the type of solvent used, they are divided into two groups: water-based and oil-based [2]. Paints are applied as a thin layer to the desired surface and form a solid film there. [caption id="attachment_104449" align="aligncenter"] Figure 2. Painting of the mask surface can reduce air flow[/caption] The importance of issues such as paint composition, ease of application, the potential of a painted surface to harbor microorganisms, and the safety of such surfaces for users and the environment is increasing day by day. The practice of painting certain products that were previously used with a plain surface color to increase their visual appeal has brought discussions in its wake. A current example of this is the widespread, and even mandatory, use of masks for protection against the coronavirus causing Covid-19. It is observed that the addition of colored patterns and drawings to these types of masks, which traditionally have mostly been white, has become widespread. A significant part of this change is achieved by painting existing mask surfaces, which has led to discussions about potential health problems.

Some of the related discussions concern allergic reactions caused by the paint used and color staining on the face. Another important issue is the closure or expansion of mask pores due to physical stress on the mask and the paint applied.

In a study being conducted on factors negatively affecting mask use, this problem was also mentioned, and preliminary data observed that some masks have a high potential for negative impact on air flow [3]. [caption id="attachment_104450" align="aligncenter"] Figure 3. Unrecycled disposable plastic bags are waste that is difficult to break down in nature[/caption] Due to the rapid depletion of natural resources and increasing environmental pollution, the European Union and most developed countries are implementing increasingly stringent regulations and providing incentives to ensure that industrial products are long-lasting, preferably multi-use, recyclable, and easily biodegradable in nature. For example, today's automobiles are much lighter than those from fifty years ago, can travel 2-3 times farther on a liter of fuel, and pollute the environment less. Similar considerations would apply to paints. When applied paint is long-lasting, it will prevent the same surfaces from being painted frequently. Paint intended to remain on a surface for only a short time should be designed to be easily removable and to decompose quickly and harmlessly to nature.

In designing such paints, various applications and principles used for other types of products can be utilized. Plastic shopping bags and packaging materials are petroleum-derived, synthetic, polymeric products.

In the natural environment where they are abandoned after use, in waste disposal areas, or in the sea, their breakdown takes a very long time. Adding biodegradation-assisting substances, such as starch, to such plastics during the production stage helps them break down quickly and harmlessly in nature. Similarly, adjusting suitable substances added to paint or the proportions of basic components can result in short-lived, environmentally harmful substances breaking down. Binders used in perfumes are liquids with very high boiling points (generally above 300°C), meaning they evaporate very slowly. Fragrantly scented compounds mixed homogeneously with these binders also gain the property of being effective very slowly, for days, weeks, or even months. Adding tiny amounts of these mixtures to paints will keep painted areas pleasantly scented for long periods. Another application of the same method is adding scents that insects and flies dislike and find repellent to paint through a suitable binder, allowing the painted area to remain free of pests for long periods [4].

Another important issue concerning paints is the waste generated. As a general definition, "anything that has completed its useful life or is left over from use is waste."

Waste can be hazardous (containing at least one of the properties of being toxic, corrosive, reactive, or flammable) or non-hazardous. Additionally, waste that one person wants to dispose of can be a valuable material for another. Paint waste is a type of waste that cannot be recycled for the same purpose. Processes conducted for paint waste generally involve incineration or disposal in waste storage areas. Another possible process is to use them as raw material for other types of products. The addition of paints that do not meet quality standards during production and are removed from surfaces after their useful life to ceramic raw materials creates the potential for these types of waste to have another use [5]. During the firing of ceramics at temperatures around 1200°C or higher, porous structures are created due to voids resulting from the combustion of paint components (Figure 4). These porous ceramics will find very wide applications due to their low density and high sound and thermal insulation properties. [caption id="attachment_104451" align="aligncenter"] Figure 4. A mixture of powdered pumice (a) and oil-based paint removed from walls (b) was molded with water and then fired to produce porous bricks.[/caption]

References 1. Depiction of aurochs, horses, and deer in the Lascaux Caves. Prof saxx/Wikimedia Commons/Public Domain, https://en.wikipedia.org/wiki/Lascaux. 2. Kuzugüdenli, Ö.E., Ülgen, A., "Determination of Surface Properties before Painting," 8th International Paint Congress. 23-26 Sept. 2010, İstanbul. 3. Kuzugüdenli, S., "Maske Yapıları ve Koruyuculuğunu Etkileyen Faktörler," unpublished experimental study, 2020. 4. Kuzugudenli, O.E., Kuzugudenli, S. and Kuzugudenli, I.O., "Combining Long-Lasting Fragrance with Textiles," UTIB VII. International R&D Brokerage Event), Bursa, April 26-29, 2015. 5. Kuzugüdenli, Ö.E., "the Utilization of Paint Wastes in the Production of Porous Ceramics," pending publication article, 2020.

Dr. Sevgi Kuzugüdenli Cerrahpaşa Medical Faculty, Istanbul University-Cerrahpaşa İnci Oya Kuzugüdenli European Commission Budget Directorate/Brussels Dr. Ömer Edip Kuzugüdenli Specialist Surfaces and Colloidal Systems