Material characterization is commonly undertaken across many industries, including the plastic, ceramic, minerals coating and chemical industries, enabling scientists to identify the internal structure and properties of a material. This technique helps scientists to understand the function of the various material components and verify whether the material under investigation meets contamination specifications.
Fourier Transform Infrared (FT-IR) spectroscopy has been established as a powerful tool for precise and reliable material characterization. When combined with Attenuated Total Reflectance (ATR) spectroscopy or Thermal Gravimetric Analysis (TGA), the technique provides valuable information about the composition of a material, degradation, contaminants and treatments.
FT-IR spectroscopy facilitates rapid material characterization with maximum confidence. Shorter analytical cycles are enabled, resulting in significant process improvements and enhanced quality assurance. Advanced FT-IR spectrometers are capable of measuring all IR frequencies simultaneously, helping investigators to easily and quickly identify, quantify and verify materials. Combining modern high-sensitivity FT-IR spectrometers with robust ATR accessories provides a fast, reliable and non-destructive technique to characterize a broad range of materials. A high quality spectrum from many materials can be acquired in less than a minute by simply pressing the sample against the optical crystal of the ATR accessory and starting the scan.
FT-IR spectroscopy can also be used in conjunction with TGA, which is a powerful deformulation technique commonly used in material analysis. TGA works by placing a small amount of sample on a pan which is then inserted into a furnace. While the pan is hanging on a sensitive microbalance, a slow temperature ramp is applied and the sample is bathed in an inert purge gas. As the temperature increases, various components of the material are forced into the vapor phase, resulting in weight loss.
The key benefit offered by TGA is the generation of high quality quantitative information about weight losses as a function of temperature. Coupling the TGA to an FT-IR spectrometer provides a powerful technique that can identify the vapors that are being produced.
Application examples
Minerals and Inorganic Materials
ATR accessories are equipped with rugged diamond crystals, which are designed for heavy use and are thus ideal for simple and rapid characterization of minerals and inorganic materials. Using a diamond ATR crystal accessory in FT-IR allows for precise identification of small differences in composition of minerals and inorganic materials. The efficiency of the technique for this type of analysis was demonstrated a number of years ago, when several homeowners in Florida and other communities in the southeast United States reported severe corrosion of the copper electrical and plumbing hardware in their houses. The use of imported drywall in those houses was blamed for the corrosion. A series of drywall sample analyses were performed in an attempt to understand the possible cause of the corrosion. Some of the samples that were analyzed had been manufactured outside of the U.S.
Small pieces of drywall of less than 2 mm in diameter were pressed onto the diamond ATR crystal of an FT-IR spectrometer (Nicolet™ iS™10, Thermo Scientific) and low noise spectra were acquired in less than a minute. The analysis revealed clear differences between the spectra generated from samples of domestic drywall and those generated from samples of the imported drywall (Figure 1). It was concluded that the presence of small amounts of carbonate in the samples was the causing factor of the major spectral differences. The carbonate concentrations were compared to the strontium concentrations measured by XRF to identify whether the component was strontium carbonate. While it was unlikely that the presence of carbonate had contributed to the corrosion, it did indicate that the gypsum used in the drywall was less pure and might contain other naturally occurring minerals that could have led to the corrosion.
Epoxy
The combination of FT-IR spectroscopy with TGA forms a competent solution for accurate characterization of both the components in material and the thermal degradation components evolving from the sample during the heating cycle. The combined technique is also suitable for identifying residual solvents or other volatiles that might be trapped in a material. The vapors released from the material pass through a gas cell placed in the FT-IR instrument, where the spectrum is obtained. The vapors are subsequently identified through spectral searching. The chemistry of the sample is effectively analyzed using the joint powers of FT-IR spectroscopy and TGA, namely the weight loss data generated by TGA, the time efficiency and increased sensitivity of FT-IR spectroscopy and the spectral searching capability of the combined method.
An experiment was performed using an FT-IR spectrometer (Nicolet 6700, Thermo Scientific) featuring an in-sample compartment TGA accessory equipped with a double pass gas cell heated to 220°C. This system was coupled to a TGA instrument (Q5000, TA Instruments) with a heated transfer line. A single drop of a freshly mixed two-part epoxy (normal 12 hour cure time) was placed on a TGA sample pan. The temperature was raised from ambient to 500°C at the rate of 15°C/min.
The FT-IR data were reported via the system’s software platform (OMNIC Series, Thermo Scientific) as shown in Figure 2. The upper trace represents the evolution of the overall IR signal in time (the GS plot), while the lower trace is the IR spectrum present at the time point indicated by the scroll bar in the upper window. The small signals in the GS plot around 11-12 minutes (190-210°C) result from CO2 and water bubbles evolving from the sample. The larger peak rising after 15 minutes (about 250°C) is associated with many features in the IR and the leading edge of the peak contains different components than those observed later in the weight loss.
Identifying the different components of an epoxy sample has been a challenging task due to the fact that gases evolve simultaneously. TGA does not discriminate between simple and complex gas evolutions; instead, the instantaneous IR spectra are summations of all gases being driven off at a given time. Complexity is considerably increased with the need to use multiple search regions to selectively extract individual components. In addition, many investigators are unfamiliar with the look of gas phase spectra, further jeopardizing analytical efficiency. Modern analytical software (OMNIC Specta, Thermo Scientific) helps overcome these disadvantages, enabling scientists to perform multi-component searches at a single click.
In this experiment, the first gases to emerge were clearly from the unreacted base materials of the epoxy and hardener, including the common epoxy ingredient bisphenol-A. With the increasing temperature, ester peaks appeared, indicating the accelerated curing. As the epoxy broke down, methane evolution and low levels of bisphenol-A became evident. A multicomponent search from one of the spectra acquired during the run was then performed, confirming the presence of several major components. The results of this multi-component search are shown in Figure 3. The upper trace is the sample spectrum and the spectrum below this is a weighted sum of the four spectra that provided the best fit to the sample. The individual spectra are shown in the lower part of the figure. Bisphenol-A was identified as the reference spectrum contributing the most to the sample spectrum.
Plastics
The plastics industry relies heavily on FT-IR spectroscopy for material characterization, using the technique to obtain critical data to facilitate understanding of the base polymer and its morphology. FT-IR spectroscopy is also extensively used for the analysis of the complex additive packages found in many plastics formulations. This is a particularly important application, given that plastics manufacturers around the world are required by legislation to have documentation verifying the chemical composition of many consumer products. FT-IR spectroscopy can efficiently and reliably identify material contamination or degradation issues, while also verifying that materials are meeting specifications.
For example, it is mandatory to confirm that children’s toys are free from phthalate plasticizers, subsequent to recent evidence demonstrating that these compounds may cause health problems. An experiment was performed, whereby an FT-IR spectrometer (Nicolet iS10, Thermo Fisher Scientific), equipped with an ATR accessory (Smart iTR, Thermo Fisher Scientific), was used to confirm that a children’s PVC plastic toy did not contain phthalate plasticizers. The toy was placed on the ATR accessory and pressed down upon the optical crystal using the pressure controller. The spectrum, which was acquired within less than 10 seconds, was automatically analyzed using several of the multivariate statistical techniques provided with the system’s software platform (OMNIC, Thermo Fisher Scientific).
The material was screened using an automatic two-step process. The sample was initially verified by comparing the peaks in a specific region of the spectrum to those in a reference spectrum. The peaks were then examined in a region specific to phthalates (1620-1560 cm-1) and provided that a good match was identified, it was possible to generate a report similar to the one shown in Figure 4. In cases when the match was poor, the ATR analysis was reported inconclusive and further work was required to test for phthalates at lower levels. The depth of penetration of the infrared light into the sample influences and can limit the sensitivity of the ATR technique. This shortcoming can be overcome by increasing the optical pathlength.
This can be done by pressing a piece of the material into a film using a hot press and acquiring an infrared transmission spectrum through the film. In that way, the method’s detection limits can be considerably improved.
FT-IR spectroscopy is a proven technique for rapid and dependable characterization of a wide variety of multicomponent materials, including plastics, epoxy, minerals and inorganic materials. The technique can be used with ATR sampling accessories or TGA technology for additional reliability, time efficiencies and productivity gains.
Large IR reference spectra databases are currently available, allowing investigators to easily draw comparisons with sample “fingerprints” in order to identify the most similar compounds. As a result, key information can be obtained about the chemical composition of unknown materials.l
www.thermofisher.com
Fourier Transform Infrared (FT-IR) spectroscopy has been established as a powerful tool for precise and reliable material characterization. When combined with Attenuated Total Reflectance (ATR) spectroscopy or Thermal Gravimetric Analysis (TGA), the technique provides valuable information about the composition of a material, degradation, contaminants and treatments.
FT-IR spectroscopy facilitates rapid material characterization with maximum confidence. Shorter analytical cycles are enabled, resulting in significant process improvements and enhanced quality assurance. Advanced FT-IR spectrometers are capable of measuring all IR frequencies simultaneously, helping investigators to easily and quickly identify, quantify and verify materials. Combining modern high-sensitivity FT-IR spectrometers with robust ATR accessories provides a fast, reliable and non-destructive technique to characterize a broad range of materials. A high quality spectrum from many materials can be acquired in less than a minute by simply pressing the sample against the optical crystal of the ATR accessory and starting the scan.
FT-IR spectroscopy can also be used in conjunction with TGA, which is a powerful deformulation technique commonly used in material analysis. TGA works by placing a small amount of sample on a pan which is then inserted into a furnace. While the pan is hanging on a sensitive microbalance, a slow temperature ramp is applied and the sample is bathed in an inert purge gas. As the temperature increases, various components of the material are forced into the vapor phase, resulting in weight loss.
The key benefit offered by TGA is the generation of high quality quantitative information about weight losses as a function of temperature. Coupling the TGA to an FT-IR spectrometer provides a powerful technique that can identify the vapors that are being produced.
Application examples
Minerals and Inorganic Materials
ATR accessories are equipped with rugged diamond crystals, which are designed for heavy use and are thus ideal for simple and rapid characterization of minerals and inorganic materials. Using a diamond ATR crystal accessory in FT-IR allows for precise identification of small differences in composition of minerals and inorganic materials. The efficiency of the technique for this type of analysis was demonstrated a number of years ago, when several homeowners in Florida and other communities in the southeast United States reported severe corrosion of the copper electrical and plumbing hardware in their houses. The use of imported drywall in those houses was blamed for the corrosion. A series of drywall sample analyses were performed in an attempt to understand the possible cause of the corrosion. Some of the samples that were analyzed had been manufactured outside of the U.S.
Small pieces of drywall of less than 2 mm in diameter were pressed onto the diamond ATR crystal of an FT-IR spectrometer (Nicolet™ iS™10, Thermo Scientific) and low noise spectra were acquired in less than a minute. The analysis revealed clear differences between the spectra generated from samples of domestic drywall and those generated from samples of the imported drywall (Figure 1). It was concluded that the presence of small amounts of carbonate in the samples was the causing factor of the major spectral differences. The carbonate concentrations were compared to the strontium concentrations measured by XRF to identify whether the component was strontium carbonate. While it was unlikely that the presence of carbonate had contributed to the corrosion, it did indicate that the gypsum used in the drywall was less pure and might contain other naturally occurring minerals that could have led to the corrosion.
Epoxy
The combination of FT-IR spectroscopy with TGA forms a competent solution for accurate characterization of both the components in material and the thermal degradation components evolving from the sample during the heating cycle. The combined technique is also suitable for identifying residual solvents or other volatiles that might be trapped in a material. The vapors released from the material pass through a gas cell placed in the FT-IR instrument, where the spectrum is obtained. The vapors are subsequently identified through spectral searching. The chemistry of the sample is effectively analyzed using the joint powers of FT-IR spectroscopy and TGA, namely the weight loss data generated by TGA, the time efficiency and increased sensitivity of FT-IR spectroscopy and the spectral searching capability of the combined method.
An experiment was performed using an FT-IR spectrometer (Nicolet 6700, Thermo Scientific) featuring an in-sample compartment TGA accessory equipped with a double pass gas cell heated to 220°C. This system was coupled to a TGA instrument (Q5000, TA Instruments) with a heated transfer line. A single drop of a freshly mixed two-part epoxy (normal 12 hour cure time) was placed on a TGA sample pan. The temperature was raised from ambient to 500°C at the rate of 15°C/min.
The FT-IR data were reported via the system’s software platform (OMNIC Series, Thermo Scientific) as shown in Figure 2. The upper trace represents the evolution of the overall IR signal in time (the GS plot), while the lower trace is the IR spectrum present at the time point indicated by the scroll bar in the upper window. The small signals in the GS plot around 11-12 minutes (190-210°C) result from CO2 and water bubbles evolving from the sample. The larger peak rising after 15 minutes (about 250°C) is associated with many features in the IR and the leading edge of the peak contains different components than those observed later in the weight loss.
Identifying the different components of an epoxy sample has been a challenging task due to the fact that gases evolve simultaneously. TGA does not discriminate between simple and complex gas evolutions; instead, the instantaneous IR spectra are summations of all gases being driven off at a given time. Complexity is considerably increased with the need to use multiple search regions to selectively extract individual components. In addition, many investigators are unfamiliar with the look of gas phase spectra, further jeopardizing analytical efficiency. Modern analytical software (OMNIC Specta, Thermo Scientific) helps overcome these disadvantages, enabling scientists to perform multi-component searches at a single click.
In this experiment, the first gases to emerge were clearly from the unreacted base materials of the epoxy and hardener, including the common epoxy ingredient bisphenol-A. With the increasing temperature, ester peaks appeared, indicating the accelerated curing. As the epoxy broke down, methane evolution and low levels of bisphenol-A became evident. A multicomponent search from one of the spectra acquired during the run was then performed, confirming the presence of several major components. The results of this multi-component search are shown in Figure 3. The upper trace is the sample spectrum and the spectrum below this is a weighted sum of the four spectra that provided the best fit to the sample. The individual spectra are shown in the lower part of the figure. Bisphenol-A was identified as the reference spectrum contributing the most to the sample spectrum.
Plastics
The plastics industry relies heavily on FT-IR spectroscopy for material characterization, using the technique to obtain critical data to facilitate understanding of the base polymer and its morphology. FT-IR spectroscopy is also extensively used for the analysis of the complex additive packages found in many plastics formulations. This is a particularly important application, given that plastics manufacturers around the world are required by legislation to have documentation verifying the chemical composition of many consumer products. FT-IR spectroscopy can efficiently and reliably identify material contamination or degradation issues, while also verifying that materials are meeting specifications.
For example, it is mandatory to confirm that children’s toys are free from phthalate plasticizers, subsequent to recent evidence demonstrating that these compounds may cause health problems. An experiment was performed, whereby an FT-IR spectrometer (Nicolet iS10, Thermo Fisher Scientific), equipped with an ATR accessory (Smart iTR, Thermo Fisher Scientific), was used to confirm that a children’s PVC plastic toy did not contain phthalate plasticizers. The toy was placed on the ATR accessory and pressed down upon the optical crystal using the pressure controller. The spectrum, which was acquired within less than 10 seconds, was automatically analyzed using several of the multivariate statistical techniques provided with the system’s software platform (OMNIC, Thermo Fisher Scientific).
The material was screened using an automatic two-step process. The sample was initially verified by comparing the peaks in a specific region of the spectrum to those in a reference spectrum. The peaks were then examined in a region specific to phthalates (1620-1560 cm-1) and provided that a good match was identified, it was possible to generate a report similar to the one shown in Figure 4. In cases when the match was poor, the ATR analysis was reported inconclusive and further work was required to test for phthalates at lower levels. The depth of penetration of the infrared light into the sample influences and can limit the sensitivity of the ATR technique. This shortcoming can be overcome by increasing the optical pathlength.
This can be done by pressing a piece of the material into a film using a hot press and acquiring an infrared transmission spectrum through the film. In that way, the method’s detection limits can be considerably improved.
FT-IR spectroscopy is a proven technique for rapid and dependable characterization of a wide variety of multicomponent materials, including plastics, epoxy, minerals and inorganic materials. The technique can be used with ATR sampling accessories or TGA technology for additional reliability, time efficiencies and productivity gains.
Large IR reference spectra databases are currently available, allowing investigators to easily draw comparisons with sample “fingerprints” in order to identify the most similar compounds. As a result, key information can be obtained about the chemical composition of unknown materials.l
www.thermofisher.com
