The color of the materials that make up a product is an indicator of its quality. However, very often discoloration processes occur due to environmental factors or production failures, showing a sensation of fragility of the product. In today’s post, we show you why these discoloration processes occur and how to solve them. Do not miss it!

The importance of color

The color of an object can be defined as its ability to absorb or reflect light from a body. People observe the light that a body reflects, allowing us to perceive its color. Therefore, the existence of colors is due to the presence of light.

The colors of a final product are more important than we can imagine. Color is used as a visual tool that interacts directly with our visual-cognitive system, giving us crucial information for our perception, which allows us to create a first impression that brings us closer to or away from a product. According to the Institute for Color Research, consumers create an opinion about a product in less than 90 seconds after first contact with it, and between 62% and 90% of that opinion is based solely on the color of the product.

Numerous investigations of psychology have concluded that the color can be a crucial aspect to make the difference between the choice of one product or another. Color influences people from an emotional point of view, attracting them in the event that the color of a product inspires them with security or distancing them from it if it inspires distrust.

For this reason, many highly successful products associate their colors with a characteristic feature that differentiates them from the rest. Also, all colors have a purpose or meaning. For example, Google’s first three colors (blue, red, yellow) could be defined as a pattern. However, in the following letters when the pattern is started again, the color green is included after the blue. According to Ruth Kedar, the designer who created the logo, the goal of the design was to work with the primary colors, then inserting a secondary color (green), with the goal that Google would convey the message that “everything is a game, where no follow the rules and regulations ”.

Discoloration of materials

Have you ever wondered if Coca-Cola products would have been so successful if they had not managed to keep their red color so vivid or if the black color degraded when the cans were stored in the refrigerator?

As we have seen in the previous section, color directly influences its quality and its differentiation from other products on the market. However, the influence of color on people is double-edged, since if the color of a product deteriorates, the perception of it by people will also deteriorate.

One of the most significant examples is the discoloration that occurs in food, more specifically in apples. The oxidation process that apples undergo when the skin that surrounds them is removed is known throughout the world. Apples contain polyphenols in their composition that act as protection against fungi and bacteria. When an apple is exposed to air, the polyphenol oxidizes and triggers a chemical reaction that produces a brown pigment, forming a layer that acts as a barrier against fungal attack. However, if we only focus our attention on its physical appearance, the color that the apple acquires is much less attractive than its original color.

Another of the cases most analyzed by the ATRIA materials team is that experienced by certain plastic products when exposed to stressful environmental conditions, such as long exposure to ultraviolet light or when immersed in solutions with aggressive pH values. The cause of the degradation can lie from modifications in the pigments of its formulation to modifications in the injection parameters. Either way, the discoloration of a plastic product gives rise to a sensation of fragility in relation to its application, whatever it may be, and, therefore, it should be avoided and solved as soon as possible.

Mechanisms of discoloration of materials with real cases

Next, we tell you the main causes and mechanisms that can lead to discoloration of a product. As you can see, some of them are very common processes in our daily lives.

  • Light discoloration: There are a large number of products with sensitivity to light, such as some plastics, paper or fabrics. When these products are exposed to light for long periods of time, they experience a deterioration of their color. This is because light and ultraviolet radiation trigger a series of successive chemical reactions in the pigments of materials that cause them to discolor. In the project that you see in the image, the polymer was degraded by an inadequate selection of the anti-ultraviolet additive that had been made.
  • Discoloration from smoke and elevated temperatures: on many occasions, when we are in high temperature environments, the air comes into contact with hot surfaces and inorganic oxides such as nitrogen oxide or sulfur oxides can be generated. These oxides are capable of reacting with the dyes and pigments of the products, frequently those with acetate or nylon, thus giving rise to a color change and discoloration. In the Project that you see in the image, the nylon was degraded by exposure to the exhaust gases of an equipment.
  • Discoloration due to the action of water: in some products, whose formulation has hygroscopic materials, that is, they attract water in the form of vapor or liquid, discoloration of the same can be caused. This is because the water molecules “swell” the monomer chains that make up the product material, changing their conformational structure. This color change can be temporary, if the water can come out of the material, or permanent, if the inclusion of water molecules modifies the chemical composition of the product. In the project image you can see color changes due to this cause.
  • Discoloration due to pH: we can frequently observe color changes and discoloration of many products due to pH. In fact, the simplest and most comfortable way to analyze the pH of a solution is to use pH indicator paper, which changes color depending on the pH range of the solution. The main mechanism by which this process occurs is due to the oxidation or reduction of the pigment when it is found in acidic or basic environments. Depending on the type of pigment that the product has, it can be observed that its application is adequate for a certain pH range. This fact is very important since the discoloration produced by the pH can deteriorate the pigment and decrease its resistance to other factors such as heat or humidity.
  • Discoloration by cleaning agents: one of the most characteristic examples of this section is the one that occurs when we use an alcohol-based cleaning product and, to our surprise, apart from cleaning the surface of a product, discoloration occurs. Another very significant case would be the discoloration of the clothes when using colognes or perfumes that contain alcohols in their composition. The main cause of this process is that there are numerous pigments and dyes that have a high solubility in alcohol, so that when they come into contact with it, they dissolve and decompose, causing a permanent loss of color.

    Finally, another of the most characteristic cases and with which we must pay special attention, is with the use of bleach, which is a strongly oxidizing product and contains bleaches such as chlorine. All this as a whole is capable of reacting with the pigments of the products and giving rise to a deterioration of their color. In the image of the project you can check the tests carried out to determine the maximum concentration of oxidizing agent that these fibers supported.

Real case examples of material discoloration analysis

At ATRIA we have extensive experience in analyzing material failures. These failures often manifest as changes in the color of the product. Here is the strategy to follow to solve the problems of discoloration of materials:
  1. Definition of the problem. Location of the defect, time point where it is observed in the process, environmental conditions that produce its appearance, etc.
  2. Simulation of the problem. Simulation tests to evaluate the hypothetical causes of the appearance of the problem.
  3. Study and analysis of results. Research on the composition, production parameters and properties of the material under study and contrast with the experimental results obtained.
  4. Conclusions and proposal for improvements. Evaluation of the key points of the results and proposal of modifications to solve the problem.
To better understand the process, we show you a series of projects that have been investigated and solved by the ATRIA materials team.
  • Improved resistance to sun exposure of colored polymers. In this project, the client informed the ATRIA team of materials experts that their current materials were not capable of passing a sun exposure test, not knowing if the cause was a deterioration of the pigment, the additive or the base material. The solution proposed by the ATRIA team was the search for new pigments with protection against ultraviolet radiation. In addition, accelerated aging tests were carried out for its validation. Finally, those that had shown the best performance were sectioned and real samples were developed for subsequent validation with the test carried out by the client, giving rise to satisfactory results since they met the requirements demanded by the client.
  • Study of irreversible stains in synthetic fabrics. In this case, the client presented the ATRIA team with a type of whitish stain that appeared on their textile products. After analyzing when the stain occurred, a set of validation tests were defined, evaluating different environmental variables. In addition, the experimental study was complemented with the analysis of the spots by means of scanning electron microscopy (SEM). Finally, differences in the composition of the product were observed when spots appeared, evidencing the presence of chemical reactions. After knowing what kind of reactions were happening, ATRIA advised the client to use a type of cleaning agent that would reverse the appearance of the stain.
  • Improved resistance to UV wear. In this project, the client presented the ATRIA team with problems about the resistance of their final product to UV radiation. In this case, after an evaluation of the case, it was observed that the pigment was suitable for applications with long exposure periods with UV light, however, the additive did not offer sufficient compatibility with the base polymer to protect it from radiation. In the same way as the previous view, new additives were selected and validated by accelerated aging tests, selecting those that met the requirements demanded by the client.
  • Study of stains on plastic products. In this case, the customer reported to the ATRIA team stains that appeared on their product after being washed in the dishwasher. After analyzing the problem and simulating it, the possible sources of the problem were detected. The results were complemented with an analysis of the chemical composition of the stain by means of scanning electron microscopy (SEM), the problem being defined. Finally, ATRIA proposed the cleaning agent that removed the stain.

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