“What’s that stain?”
This is a question that many quality assurance specialists in the manufacturing industry will need to answer at some point in their careers. Stains on products often signal a quality issue that can compromise the safety or function of the product. Fortunately, materials testing can help QA specialists answer that question.
Materials testing is a broad term that refers to the use of analytical testing techniques to identify the chemical composition or characteristics of a sample. Below are some of the techniques that can be used to not only identify surface stains, but also help manufacturers trace the source of the contamination.
Auger Electron Spectroscopy
Auger Electron Spectroscopy (AES) is a surface analysis technique that is often used to determine surface composition, identify stains and contaminants, and analyze passivation layers on conductive and semi-conductive materials. Typically, this technique is particularly useful for electronic and medical device manufacturers who’ve encountered unknown stains on products or product parts.
How Auger Electron Spectroscopy Works
AES uses an incident electron beam to excite a solid sample and release electron emissions. Then an energy analysis of the electrons is conducted to reveal the analytical information about the sample. The main advantage of AES is its high spatial resolution, which is needed for identifying stains that appear in a very thin film.
AES in Action
A medical device manufacturer discovered a thin stain on a titanium electrode. Suspecting that the stain was caused by hard water used in the rinse cycle, AES was used to map several different species from the stained area. The map showed there were high levels of calcium, chlorine and potassium, which can all be found in hard water. Armed with the test results, the manufacturer was able to change the water in the rinse cycle and resolve the issue.
Electron Spectroscopy for Chemical Analysis (ESCA) is used to identify elemental and binding information about a material’s surfaces and interfaces. Like AES, this technique is often used to identify thin layers of contamination on the surface of a material and evaluate passivation of stainless steels. But ESCA can also be used to study the surface chemistry of polymers, glasses, plastics and other insulators. Generally speaking, this technique is a useful analysis tool for electronics, medical device and plastics manufacturers.
How Electron Spectroscopy for Chemical Analysis Works
ESCA analysis uses an x-ray beam to excite the molecules on a solid sample, resulting in the emission of photoelectrons. An energy analysis of the photoelectrons then provides the elemental and chemical bonding information about the sample’s surface.
ESCA in Action
A plastics manufacturer found a brown-colored contaminant on a polyethylene part and identified a rusty piece of steel that had been in contact with the part as the potential culprit. ESCA analysis was used to analyze the contamination spot. Test results revealed the presence of iron, magnesium, silicon, sodium, nitrogen, fluorine and oxygen, which are all consistent with rust, thereby confirming the rusty steel as the source of the stain
Fourier Transform Infrared Spectroscopy (FTIR) analysis is used to identify unknown organic compounds in solid, liquid, or gas samples and quantify known organic compounds. FTIR analysis is often the first step in the materials testing process because of its sensitivity, simplicity and speed. This technique has a variety of applications, and can be a useful quality assurance tool for manufacturers of electronics, medical devices, toys and food service items.
How Fourier Transform Infrared Spectroscopy Works
FTIR analysis identifies the composition and structure of a material by applying infrared light and measuring how the unique light spectra is absorbed by the material. Using a simple device called an interferometer, an optical signal is produced with all the IR frequencies encoded into it. The signal is then decoded by applying Fourier transformation and the computer-generated process produces a map of the spectral information. The map is then compared to samples in reference libraries for identification.
FTIR in Action
A manufacturer found a white residue in the crevices of a molded plastic part. Unsure of where the contamination came from, FTIR analysis was enlisted to help. As a result, the spectrum obtained through testing suggested that the material was a surfactant that had not been completely removed during the manufacturing process.
For more information on materials testing services from Innovatech Labs, get in touch with us today.