ABSTRACT

This paper/presentation will discuss and demonstrate some uses for several analytical tools/instruments related to troubleshooting problems associated with industrial coatings.

This paper will highlight several analytical techniques and instruments used to evaluate industrial coatings. I will cover methods used for research and development, manufacturing, quality control and failure analysis. The material will likely be less exciting and glamorous than an episode of CSI but there are some similarities in the equipment used. A toolbox full of good analytical equipment and the knowledge of how to use it can make a big difference in the determination of why a product failed or did not perform as intended. Many things can go wrong on the best job or manufacturing site. Knowing how to evaluate for a root cause of a problem and having the tools to do so can make a big difference in the trouble resolution process.

PURPOSE

There are several useful analytical tools/instruments out there that can help identify problems related to industrial coatings. Having a good understanding of these tools and what they can be used for, will help identify and troubleshoot problems.

The focus of this paper will be on the following instrumentation:

• FT-IR (Fourier Transform Infrared Spectroscopy) – ASTM E1252

• TGA (Thermal Gravimetric Analysis) – ASTM E1131

• DSC (Differential Scanning Calorimetry) – ASTM D3418

• EIS (Electrical Impedance Spectroscopy) – ASTM G106

• DMA (Dynamic Mechanical Analysis) – D5026

• GC-MS (Gas Chromatography – Mass Spectrometry) – ASTM D6420

• 3D Microscope with digital imaging

Each instrument/methodology will be briefly described as to how they can be used for evaluating industrial coatings. A few practical examples of each will be also discussed.

METHODOLOGY

Fourier Transform Infrared Spectroscopy (FT-IR)1 is an analytical technique and instrument that can be used to identify organic, inorganic to some degree, and polymeric materials utilizing infrared light for scanning samples. This technique is fast and powerful and can be used for several things associated with industrial coatings. Including but not limited to; comparing functional groups of material, quick chemical comparisons, accuracy of mix ratios in multi-component mixed products, identify contaminants, and measure surface degradation changes. It is a great tool for quick comparisons of raw materials, intermediate and finished products alike. It is important to be aware that methods of collecting FT-IR spectra can vary and not all infrared spectra should be compared to one another. Spectra of the same material collected with different collection methods can vary considerably. Therefore, it is best to compare things using the same collection method. With the use of different collection methods, the instrument can be used to collect spectra of most everything from liquid resins to powdered fillers, pigments, and other solid materials. It is also a great tool for generically identifying unknown materials of interest. A spectrum of an unknown material can be collected and compared to a reference library containing spectra of thousands of materials. With todays’ volatile supply chain issues an FT-IR can be a very valuable tool to compare potential chemical equivalents. To determine if two materials are chemically equivalent FT-IR is a good place to start. If the infrared spectra of two materials match such as in Figure 1. it does not mean they are chemically identical. However, it is a good start in proving the functional groups of the materials are the same. Other things like viscosity and molecular weight of materials can differ while having very similar infrared spectra. Differences in two materials’ infrared spectra collected with the same method represent differences in the materials’ composition and functional groups. As seen in Figure 2. the differences in the appearance intensity of the peaks/IR absorptions represent differences in the amounts of similar materials between the products. The interpretation of the two spectra suggests the two materials most likely contain the same ingredients but at different amounts. With the right sample preparation and/or separation techniques there are numerous ways to compare materials by IR.

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