Polymer blends infrared spectroscopy

Keywords Focal Plane Array FTIR Imaging Infrared spectroscopy Polymer blends... 

Kanis, L.A., Viel, F.C., Crespo, J.S., Bertolino, J.R., Pires, A.T.N., and Soldi, V. (2000) Study of poly (ethylene oxide)/ carbopol blends through thermal analysis and infrared spectroscopy. Polymer, 41, 3303-3309. 

The role of specific interactions in the plasticization of PVC has been proposed from work on specific interactions of esters in solvents (eg, hydrogenated chlorocarbons) (13), work on blends of polyesters with PVC (14—19), and work on plasticized PVC itself (20—23). Modes of iateraction between the carbonyl functionaHty of the plasticizer ester or polyester were proposed, mostly on the basis of results from Fourier transform infrared spectroscopy (ftir). Shifts in the absorption frequency of the carbonyl group of the plasticizer ester to lower wave number, indicative of a reduction in polarity (ie, some iateraction between this functionaHty and the polymer) have been reported (20—22). Work performed with dibutyl phthalate (22) suggests an optimum concentration at which such iateractions are maximized. Spectral shifts are in the range 3—8 cm . Similar shifts have also been reported in blends of PVC with polyesters (14—20), again showing a concentration dependence of the shift to lower wave number of the ester carbonyl absorption frequency. 

As already indicated above, what one may consider a surface depends on the property under consideration. Adhesion is very much an outer atomic layer issue, unless one is dealing with materials like fibreboard in which the polymer resin may also be involved in mechanical anchoring onto the wood particles. Gloss and other optical properties are related to the penetration depth of optical radiation. The latter depends on the optical properties of the material, but in general involves more than a few micrometer thickness and therewith much more than the outer atomic layers only. It is thus the penetration depth of the probing technique that needs to be suitably selected with respect to the surface problem under investigation. Examples selected for various depths (< 10 nm, 10 s of nm, 100 nm, micrometer scale) have been presented in Chapter 10 of the book by Garton on Infrared Spectroscopy of Polymer Blends, Composites and Surfaces... 

A. Garton, Infrared Spectroscopy of Polymer Blends, Composites and Surfaces, Hanser, Munich (1992)... 

Many studies use infrared spectroscopy for quality control and quality analysis in polymer production. It is particularly used for the determination of the composition of copolymers and polymer blends and also for determination of additive and filler contents [90, 91, 92]. 

It is concluded that IR spectroscopy provides information on qualitative as well quantitative analyses of rubbery materials, apart from their microstructures (that is, whether cis or trans, syndiotactic, atactic or isotactic). Different types of rubber blends (compatibilised or self-crosslinked) can be identified by the infrared spectroscopy. Synthesis, and degradation of polymers can also be followed by IR spectra. Mechanism of interaction between rubbers and fillers, can also be studied by IR-spectra. Different types of chemical reactions like the milling behaviour of rubbers, mechanism of adhesion and degradation can also be studied with the help of IR spectroscopy. The technique plays a great role in the product analysis under reverse engineering. 

Practical problems associated with infrared dichroism measurements include the requirement of a band absorbance lower than 0.7 in the general case, in order to use the Beer-Lambert law in addition infrared bands should be sufficently well assigned and free of overlap with other bands. The specificity of infrared absorption bands to particular chemical functional groups makes infrared dichroism especially attractive for a detailed study of submolecular orientations of materials such as polymers. For instance, information on the orientation of both crystalline and amorphous phases in semicrystalline polymers may be obtained if absorption bands specific of each phase can be found. Polarized infrared spectroscopy can also yield detailed information on the orientational behavior of each component of a pol3mier blend or of the different chemical sequences of a copoljnner. Infrar dichroism studies do not require any chain labelling but owing to the mass dependence of the vibrational frequency, pronounced shifts result upon isotopic substitution. It is therefore possible to study binary mixtures of deuterated and normal polymers as well as isotopically-labelled block copolymers and thus obtain information simultaneously on the two t3q>es of units. 

Up-to-date compendiums on applications of infrared spectroscopy in applied polymer science are as follows. "An Infrared Spectroscopy Atlas for the Coatings Industry" (95) describes techniques, has liberal references to specific methods, and contains high-quality grating reference spectra on paint components and blended compositions. "Atlas of Polymer and Plastics Analysis," 2nd ed., by Hummel and Scholl (96), has issued two volumes Vol. 1, Polymers Vol. 3, on Additives and Processing Aids Vol. 2, on Plastics, Fibers, Rubbers, Resins, is in press. "Infrared Spectra of Plasticizers and Other Additives," 2nd ed., published by The Coblentz Society, Inc., is a high-quality IR reference spectrum collection (97). 

Garton A (1992) Infrared Spectroscopy of polymer blends, composites and surfaces. Hanser, Munich... 

For the studies of interactions in polymer blends the nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FTIR) are of principal significance. 

The use of infrared spectroscopy for the characterization of polymer blends is extensive [Olabisi et al, 1979 Coleman and Painter, 1984 Utracki, 1989 Coleman et al, 1991]. The applicability,... 

Infrared Spectroscopy of Polymer Blends, Composites and Surfaces. 

Infrared spectroscopy is frequently used to study blends. As explained in section 2.6.4, the infrared spectrum of a mixture of substances can be used to determine the concentrations of the various components, provided that there is no change in the spectrnm of either component on mixing. This will be the case for a polymer blend when the components are immiscible. Miscibility nsnally involves some strong interaction between the two polymers, so the spectrnm of the blend is then not simply a weighted sum of the spectra of the individual polymers. One of the most important types of interaction in polymer blends is hydrogen-bonding, particularly when one of the polymers contains carbonyl groups, >C=0. 

Fourier transform infrared (FT-IR) spectroscopy can be used to characterize drug substances, polymer blends, polymer complexes, dynamics, surfaces, and interfaces, as well as chromatographic effluents and degradation products. It provides information about the complexation and interactions between the various constituents in the PECs. It is capable of qualitative identification of the structure of unknown materials as well as the quantitative measurement of the components in a complex mixture. FT-IR spectra of physical mixture and PEC can be determined by FT-IR spectrophotometer using KBr disc method in the range of 4000 to 250 cm h Since the stability and drug substance is very important in several applications, determination of their physicochemical stability is crucial. The FTIR spectra of polyacrylic acid, PVP, metformin hydrochloride, and PEC microparticles of metformin were shown in Figure 56.8. The FTIR spectra of polyacrylic acid and PVP have shown... 

Rubbers have physical characteristics and a chemical composition that precludes their successful identification by infrared spectroscopy due to their inherent elasticity and highly filled composition. In contrast, no such difficulties are encountered with Py-GC. Crime scene rubber evidence from automotive tires and rubber vehicle components is found in hit-and-run cases and in soles of shoes worn by offenders in offenses against property. Discrimination of vehicle bumper rubbers by Py-GC has been reported. Volatile and polymeric components of rubbers and other polymers have been analyzed by Py-GC and the inorganic residue recovered for subsequent analysis. The technique may also be used to quantitate rubber blends by measuring the ratios of characteristic pyrolysis products. Figure 8.8 shows examples of the pyrograms of three common types of rubber. 

Polymer blends are mixtures of polymeric materials and consist of at least two polymers or copolymers. Infrared spectroscopy is now quite a commonly used technique for examination of the interactions in polymer blends [9, 10]. If two polymers are immiscible, the infrared spectrum should be the sum of the spectra of the two components. Phase-separation implies that the component polymers in the blend will have an environment similar to the pure polymers. If the polymers are miscible, there is the possibility of chemical interactions between the individual polymer chains. Such interactions may lead to differences between the spectra of the polymers in the blend and the pure components. Generally, wavenumber shifts and band broadening are taken as evidence of chemical interactions between the components in a blend and are indicative of miscibility. 

Hydrogen bonding is readily examined by nsing infrared spectroscopy, as described earlier in Chapter 3, and is of interest in polymer blends where it may be nsed to understand polymer compatibility [5, 9]. Hydrogen bonding is also an issne for polyurethanes (PUs), which have the general structure, -CO-O-R-O-CO-NH-R-NH-. The major infrared modes common to PUs are hsted in Table 6.5. PUs are extensively hydrogen bonded, with the proton donor... 

---