Oxidative stability infrared spectroscopy

As part of a multi-technique investigation (see also discussion under mid-infrared spectroscopy later), Corrales et al. [13] plotted the carbonyl index for films prepared from three grades of polyethylenes a high-density PE (HDPE), a linear low-density PE (LLDPE) and a metallocene PE (mPE) (see Figure 5). In this study, the data trend shown in Figure 5 correlated well with activation energies derived from the thermal analysis, which showed that the thermal-oxidative stability followed the order LLDPE > mPE > HDPE, whereas the trend... 

CO is an excellent probe molecule for probing the electronic environment of metals atoms either supported or exchanged in zeolites. Hadjiivanov and Vayssilov have published an extensive review of the characteristics and use of CO as a probe molecule for infrared spectroscopy [80]. The oxidation and coordination state of the metal atoms can be determined by the spectral features, stability and other characteristics of the metal-carbonyls that are formed. Depending on the electronic environment of the metal atoms, the vibrational frequency of the C-O bond can shift. When a CO molecule reacts with a metal atom, the metal can back-donate electron density into the anti-bonding pi-orbital. This weakens the C-O bond which results in a shift to lower vibrational frequencies (bathochromic) compared to the unperturbed gas phase CO value (2143 cm ) [62]. These carbonyls form and are stable at room temperature and low CO partial pressures, so low temperature capabilities are not necessary to make these measurements. 

The chemistry of difluoramines of the type X—NF has been studied to gain an understanding of the nature of the N—F and N—X bonds, to obtain a picture of the relative electron distributions in X—NFg compounds, and to determine the existence and stabilities of N—F radicals and ions. These compounds have been studied using electrochemistry, com-plexation, infrared spectroscopy, and theoretical calculations. Oxidation-reduction reactions have been carried out, and the effects of various environments on the N—F and N—X bonds have been investigated. The results of these studies emphasize the chemistry of difluoramine and the existence and stability of NFf+, NFg, NFg, and HgNFg+. 

In summary, NO Os can be formed via totally different paths with different starting nitrogen oxides. However, unambiguous interpretation of the structure, stability and transformation mechanism involving this peculiar ionic species is unavailable. Therefore, comprehensive experimental means, including x-ray diffraction measurement, Raman and Infrared spectroscopy were employed to understand the fundamental properties of NO Os synthesized via the last path mentioned above. While the diffraction measurements established the P-V equation of state, the optical spectra, especially the low-temperature Raman data, elucidate important aspects of the transformation, thermodynamic properties, and stability diagram of NO Os. ... 

Mesoporous alumina samples have been synthesized using poly(ethylene oxide)-based nonionic surfactants. The effect that the addition of n-alkylamines to the synthesis gel has on the texture and thermal stability of mesoporous aluminas is studied. Textural and structural characterization using nitrogen adsorption, powder X-ray diffraction, a1 nuclear magnetic resonance and Fourier Transform infrared spectroscopy, as well as catalytic n-hexane hydroisomerization tests are performed. 

Among chemical analysis methods are gas chromatography, infrared spectroscopy, and mass spectroscopy for example, a TGA apparatus may be coupled with a Fourier Transform Infrared (FTIR) spectrophotometer to measure the thermal oxidative stabilities of several fluorinated polyimides." ... 

Platinum and palladium are effective catalysts for alcohol oxidation when used alone however, significant stability and selectivity improvements have been observed on incorporation of a second (usually less active) metal promoter such as Bi, Pb, and Sn [63-65]. These observations are common to aerobic selox of allyhc and benzylic alcohols, as well as polyols such as propylene glycol [64] and glycerol [66]. In the case of Bi, in situ X-ray absorption spectroscopy (XAS) and attenuated total reflection infrared spectroscopy (ATR-IR) indicate that the promoter protects Pt against deactivation by overoxidation and prevents site blocking by, for example, aromatic solvents [67]. 

Infrared spectroscopy is used in the paint industry for quality control, product improvement and failure analysis, and for forensic identification purposes [8, 18-21], Paints are mainly comprised of polymeric binders and pigments in a dispersive medium. The binders are commonly alkyds (oil-modified polyesters), acrylics and vinyl polymers. Titanium oxide is the most commonly used pigment, while water or organic solvents are used as the medium. Paints may also contain other additives such as fillers (e.g. calcium carbonate) and stabilizers (e.g. lead oxide). 

Usami T, Itoh T, Ohtani H, Tsuge S, Structural study of polyacrylonitrile fibers during oxidative thermal degradation by pyrolysis- gas chromatography, solid-state C nuclear magnetic resonance and Fourier transform infrared spectroscopy. Macromolecules, 23, 2460 465, 1990. Bhat GS, Cook FL, Abhiraman AS, Peebles LH Jr., New aspects in the stabilization of acrylic fibers for carbon fibers. Carbon, 28(2,3), 377-385, 1990. 

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