卷 48, 编号 2 (2017)

The swelling processes of rubbers on the basis of ethylene–propylene SKEPT-40, butadiene–nitrile SKN-18, and fluorine SKF-26 caoutchoucs in transformer oil GK were investigated by ¹H nuclear magnetic resonance spectroscopy and ¹H NMR relaxation techniques. The main rubber-swelling singularities were developed. It was shown that polymeric affinity to oil decreases in the next rubber row—ethylene–propylene, fluorine, and butadiene–nitrile. The oil molecular mobility is on the contrary increased in the same row. The surface NMR probe express test of oil amount in real production was introduced.

The behavior of electron paramagnetic resonance spectra due to ¹⁵N and ¹⁴N nitroxide free radicals undergoing spin exchange in liquids at frequencies \(\omega_{\text{ex}}\) that are high, of the same order of magnitude as the nitrogen hyperfine coupling constant \(A_{0}\), is investigated. The well-known features are reconfirmed: (1) at low values of \(\omega_{\text{ex}}\) where the lines broaden, shift toward the center of the spectrum, and change shape due to the introduction of a resonance of the form of a dispersion component; (2) at values of \(\omega_{\text{ex}}\) comparable to \(A_{0}\), where the lines merge into one; and (3) at values much larger than \(A_{0}\), where the merged line narrows. It is found that each line of a spectrum may be decomposed into an admixture of a single absorption and a single dispersion component of Lorentzian shape. These two- or three-line absorption–dispersion admixtures, for ¹⁵N and ¹⁴N, respectively, retain their individual identities even after the spectrum has merged and has begun to narrow. For both isotopes, the average broadening and integrated intensities are equal to the predictions of perturbation theory although, in the case of ¹⁴N, the outer lines broaden faster than the central line and intensity moves from the outer lines to the central line. In fact, the outer line intensity becomes zero and then negative at higher values of \(\omega_{\text{ex}}\) which is compensated by the central line becoming more intense than the overall integrated intensity. For both isotopes, the dispersion components and the line shifts depart from the perturbation predictions. The results are presented in terms of measurable quantities normalized to \(A_{0}\) so that they may be applied to any two- or three-line spectrum.

Radicals in mainstream cigarette smoke (MCS) have been proposed to contribute to the harm caused by cigarette smoking. In the present study, we used natural antioxidant, squalene, to treat cigarette filters and tobacco for scavenging gas- and particulate-phase free radicals in MCS. The scavenging activities of cigarette filter and tobacco containing squalene against gas and particulate-phase free radicals were detected and quantified using spin-trapping or directly electron spin resonance spectroscopy method. The results revealed that squalene could significantly scavenge gas- and particulate-phase free radicals in MCS in a dose-dependent manner. The radical-scavenging activity of cigarette filter treatment was higher than that of tobacco treatment, irrespective of either gas-phase free radicals, or particulate-phase free radicals in MCS. Among them, 3 mg squalene/filter treatment showed that the highest scavenging effects against gas- and particulate-phase free radicals were 35.9 and 35.4%, respectively. The use of squalene as potential scavenger for reducing free radicals in cigarette smoke is discussed.