To ensure the correct functioning of a product, it must go through a strict quality control before being put on the market. For this, numerous quality tests are carried out, both on raw materials and on the finished product.

On some occasions, despite the fact that all the raw materials have passed their quality control correctly, unexpected failures are detected during the quality tests of the finished product. These failures, commonly generated by contamination during the production process, make the product, already manufactured, not marketable. For this reason, it is very important to detect them in time and know their origin.

Types of pollution or contamination

Contamination, sometimes undetectable, can cause serious aesthetic and quality problems in finished products. To solve these problems it is very important to detect the type of contamination that has occurred. Once the type of contamination has been detected, it is possible to locate the source and identify its origin. Next, we indicate the most frequent types of contamination:

  • Particle contamination

    Particulate contamination is one of the most common situations we face in this type of project. These particles, which can be dust or other elements, adhere to the surface of the material at some point in the product process. The presence of this type of contamination can affect the later stages of the process, deteriorating the quality of the product. A clear example is the deposition of dust particles before applying a coating on a plastic part, these particles generate aesthetic defects and areas where the coating has not been properly deposited.

  • Chemical contamination

    In other cases, cross contamination with a chemical compound, such as cleaning products or washing water, can lead to a chemical reaction in certain areas of the product. Next, we show you a composition mapping, carried out using SEM + EDX, of a plastic where a reaction has occurred that has changed its surface composition.

  • Silicone contamination

    Silicone contamination could be included within chemical contamination, however, this type of contamination has a very particular behavior, so we treat it separately. In processes where silicones are used, it is very common to find traces of this compound in products where it should not be. It usually results in severe adhesion failures. In the following image you can see a metallic sample with paint adhesion problems as a result of silicone contamination

  • Biological contamination

    Finally, biological contamination is less frequent than the previous ones, but it can also take place. A clear example of this type of contamination is the presence of mold in wood products, deteriorating their mechanical properties and appearance. In addition, on some occasions, this type of contamination, in addition to damaging the product, can be dangerous for humans. Next, we show you an image of a mold taken from a conglomerate.

Problems that contamination can generate

In most cases, contamination is detected because a quality quality problem has previously been observed in a product that must be studied to solve it. Thanks to our experience in this type of project, many failures can be directly correlated with a contamination problem during the production process. Here are some of the problems that pollution can cause: Paint or coating adhesion problems Aesthetic problems Loss of mechanical properties Loss of surface functionality:
 
  • Paint or coating adhesion problems
  • Aesthetic problems
  • Loss of mechanical properties
  • Loss of surface functionality

How to detect contamination?

As we anticipated in the previous section, contamination is usually detected during the study of a failure that has occurred in the product. As it occurs on a very small scale, to detect certain types of contamination it is necessary to use specific equipment. In our case we use the following characterization techniques to study the type of contamination that has occurred:

  • SEM + EDX

    Scanning electron microscopy (SEM) allows us to observe the surface where the problem has occurred, study its morphology, detect possible intruders or any type of imperfection that helps us better understand the failure that has occurred. Thanks to its ability to take images with large magnifications, it allows us to detect even the smallest particles, such as dust or other elements.

    Additionally, this equipment has the possibility of characterizing the surface by means of X-ray spectroscopy (EDX). In this way, in addition to obtaining images of the defect, it is possible to analyze its composition and detect elements that should not be present. This complement is very interesting to know the origin of the contamination.

  • FIBSEM + EDX

    In the event that the problem occurs in the internal layers of the product, before performing the observation with scanning electron microscopy, it is necessary to perform a cross section of the product to observe the internal state. To do this, a FIBSEM equipment is used, which is capable of cross-cutting using an ion beam. Once the cross section is isolated, it is possible to study its morphology and composition following the same methodology as the SEM + EDX.

  • XPS

    In case that the contamination is found in very low concentrations or in the first nanometers of the surface, the most suitable equipment to detect the composition of the contaminant is X-ray photoelectron spectroscopy (XPS). This equipment allows us to detect compositional differences between good and bad samples.

  • FTIR

    Fourier Transform Infrared Spectroscopy is a very useful technique to study those contaminations that occur in larger quantities. Using this technique, it is possible to detect compositional differences between contaminated samples and uncontaminated samples.

Projects carried out by ATRIA

At ATRIA we have experience in studying this type of failure caused by contamination. Here are some cases where we have found the source of the failure and proposed a solution for our clients:

  • Detection of contamination in paint

    In this project, our client reported a crosslinking problem in the paint. Analyzing it with scanning electron microscopy we observed the presence of small fibers that produced the failure. The contamination was then characterized with Infrared Spectroscopy. This result was compared with all the elements that participated in the production chain until the cause was found. In this way the problem could be solved.

  • Characterization of dust particles in plastic pieces

    In this case, our client observed problems in the adhesion of the coating that he deposited on a plastic. To do this, we conducted a failure study where the presence of dust between the coating and the plastic was observed. This powder, which was characterized to determine its composition, was generating point defects that gave rise to larger failures, visible to the naked eye.

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