Polymers FTIR microscopy

Figure 3 FTIR microscopy absorbance spectra (100 pm aperture) recorded from a microtomed section through a defect area of a PES film. The upper spectrum is characteristic of the base film the lower spectrum is representative of the defect area. The difference in relative intensity of the band at 760 cm 1 can be clearly seen this band is attributable to the aryl-Cl end group. The consequence of this difference was the aryl-Cl end group deficient material processed differently giving rise to a gel-like feature in the polymer film. Reproduced with permission from Chalmers and Everall [1]. Copyright Wiley-VCH Verlag GmbH Co. KGaA.

A prime example of the use of FTIR microscopy is in the examination of polymers, a very important class of engineering materials. The physical properties of polymers are very dependent on their molecular structure. The presence of impurities, residual monomers, degree of crystallinity, size, and orientation of crystalline regions (the microstructure of a polymer) greatly affects their mechanical behavior. FTIR microscopy can identify polymers, additives, and determine the presence of impurities. 

When it is necessary to characterize the heterogeneity of a polymer film or a composite film both along and across the surface, FTIR microscopy is used [724, 725] (see also Section 4.3). For example, the degradation of an acrylic polymer automotive coating that had been subjected to Florida sun for 3 years was studies with a FTIR microscope using synchrotron radiation [726],... 

TLC remains one of the most widely used techniques for a simple and rapid qualitative separation. The combination of TLC with spectroscopic detection techniques, such as FTIR or nuclear magnetic resonance (NMR), is a very attractive approach to analyze polymer additives. Infrared microscopy is a powerful technique that combines the imaging capabUities of optical microscopy with the chemical analysis abilities of infrared spectroscopy. FTIR microscopy allows obtaining of infrared spectra from microsized samples. Offline TLC-FTIR microscopy was used to analyze a variety of commercial antioxidants and light stabilizers. Transferring operation and identification procedure by FTIR takes about 20 min. However, the main drawbacks of TLC-FTIR are that TLC is a time-consuming technique and usually needs solvent mixtures, which makes TLC environmentally unsound, analytes must be transferred for FTIR analysis, and TLC-FTIR cannot be used for quantifying purposes. 

IR spectra obtained. LC-FTIR and SFC-FTIR microscopy have been used to identify additives extracted from polymer samples (cfr. Chps. 7.3.3.1 and 7.3.2.1 of ref. [77a]). 

On-line/in-line technology for monitoring extrusion processes, including FTIR microscopy, near-IR spectroscopy and optical microscopy was reviewed [500]. Several reviews describe uFTIR applications to polymers [458,501]. Line map applications of /U.FTIR have been discussed [491]. A recent review [502] refers to a large number of FTIR mi-crospectroscopic studies as an important source of structural and spatial information for polymer-based articles. A monograph describes applications of FTIR microspectroscopy to polymers [393]. ASTM E 334 (1990) describes the general techniques of infrared microanalysis. 

Analytical investigations may be undertaken to identify the presence of an ABS polymer, characterize the polymer, or identify nonpolymeric ingredients. Fourier transform infrared (ftir) spectroscopy is the method of choice to identify the presence of an ABS polymer and determine the acrylonitrile—butadiene—styrene ratio of the composite polymer (89,90). Confirmation of the presence of mbber domains is achieved by electron microscopy. Comparison with available physical property data serves to increase confidence in the identification or indicate the presence of unexpected stmctural features. Identification of ABS via pyrolysis gas chromatography (91) and dsc ((92) has also been reported. 

Combination techniques such as microscopy—ftir and pyrolysis—ir have helped solve some particularly difficult separations and complex identifications. Microscopy—ftir has been used to determine the composition of copolymer fibers (22) polyacrylonitrile, methyl acrylate, and a dye-receptive organic sulfonate trimer have been identified in acryHc fiber. Both normal and grazing angle modes can be used to identify components (23). Pyrolysis—ir has been used to study polymer decomposition (24) and to determine the degree of cross-linking of sulfonated divinylbenzene—styrene copolymer (25) and ethylene or propylene levels and ratios in ethylene—propylene copolymers (26). 

Applications The general applications of XRD comprise routine phase identification, quantitative analysis, compositional studies of crystalline solid compounds, texture and residual stress analysis, high-and low-temperature studies, low-angle analysis, films, etc. Single-crystal X-ray diffraction has been used for detailed structural analysis of many pure polymer additives (antioxidants, flame retardants, plasticisers, fillers, pigments and dyes, etc.) and for conformational analysis. A variety of analytical techniques are used to identify and classify different crystal polymorphs, notably XRD, microscopy, DSC, FTIR and NIRS. A comprehensive review of the analytical techniques employed for the analysis of polymorphs has been compiled [324]. The Rietveld method has been used to model a mineral-filled PPS compound [325]. 

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