PORTABLE FTIR SPECTROMETERS continued
Figure 2 – Handheld FTIR is used to measure regions of composite-based aircraft that show potential thermal, UV, or chemical overexposure. Prior to composite repair, the handheld FTIR utilizes the diffuse reflectance sampling interface and tracks the carbonyl region of the infrared spectrum as an indicator of oxidation caused by thermal overexposure. Mapping intensity of the 1725 cm–1 and boundaries of the oxidized portions of the composite.
with diffuse reflectance sampling interface can guide the process by eluci- dating the condition of the composite as the laminate layers are exposed by the sanding process.
Polymers Carbon black-filled polymers are found in a wide variety of products. Examples include automobile tires, in which carbon black and silica are added to the rubber to provide extra wear protection; plastics used in the electronics industry, in which the carbon black acts as an antistatic agent; and rubber gaskets, O-rings, and seals, for which the addition of carbon black adds strength to the polymer material. Because carbon black absorbs and scatters infrared radiation, the mid-IR spectra of carbon black-filled polymers are often compromised and have strongly skewed baselines as well as low absorbance-to-noise for the polymer infrared absorbance bands. For this reason, the ExoScan system uses a germanium internal reflection sampling interface to obtain high-quality spectra of carbon black-filled polymers. As a result of the index of refraction of germanium, infrared radiation does not penetrate as deeply into the polymer material, and the presence of carbon black has less of an effect on the resultant polymer spectrum.
In the ExoScan system, the germanium ATR sensor is spherical in design to optimize contact with the polymer, as well as to allow flexibility of the contact angle with the polymeric material to provide quality spectra. For noncarbon black-filled polymers, the ExoScan employs a spherical diamond attenuated total reflection (ATR) sampling interface.
The analysis of automobile tires is simplified using the ExoScan equipped with the spherical germanium ATR sampling interface. For example, the handheld system has been used to determine if racecar tires have been af- fected by high-speed use or contaminants on the race course, or have been purposely adulterated to improve traction. Changes in the rubber composi- tion at the surface of the tire as well as the presence of foreign substances are elucidated by measurement with the handheld FTIR system (Figure 3).
In electronic industry scrap recycling, the handheld system equipped with the germanium ATR is used to identify the composition of the carbon black-filled plastic so that it can be appropriately reclaimed and recycled.
carbonyl band as a function of position defines the shape
Figure 3 – Handheld FTIR equipped with the spherical germanium ATR was used at the 2011 Deutsche Tourenwagen-Meisterschaft (DTM) races to analyze tires. Changes in polymer composition and/or the effect of track contaminants on the tire were measured. Unintentional or intentional adulteration or contamination of the tire surface by oil, brake fluid, softening agents, etc., is quickly detected and analyzed by the FTIR system.
By matching the spectra of an unknown plastic scrap with reference spectra contained in an on-board library, the identity of the unknown is determined in less than 1 min.
Coatings Correct composition, thickness, and uniformity of coatings on metal substrates are essential to the performance of the coated metal in a variety of applications (Figure 4). The handheld FTIR system equipped with external reflectance sampling interface is well-suited for verifying the quality of polymer coatings. Similarly, the system is used for the analysis of paints and primers on a variety of substrates for a range of commercial applications. The curing of polymer film on a metal surface is another important application for handheld FTIR. Furthermore, the ExoScan system equipped with specular reflectance sampling technol- ogy measures the thickness of metal oxide layers on metal substrates in anodization processes.
Contaminants In the manufacture of aerospace, automobile, metal, and biomedi- cal products, as well as in other industries, surface contaminants are
AMERICAN LABORATORY • 18 • JUNE/JULY 2013
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46