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电子自旋共振(ESR)是一个可行而灵敏地确定分子结构以及有机自由基寿命或稳定性的波谱技术。因此,ESR波谱仪提供了一个判断自由基在防老剂稳定橡胶过程中所起的作用的合乎逻辑的方法。我们用ESR波谱仪测定了十二种酚防老剂所获得的一系列苯氧自由基的分子结构。我们也用ESR测定了自由基的相对浓度并评论了十二种酚防老剂的相对效率。我们发现ESR测定的自由基相对浓度是自由基相对稳定性的度量,而自由基的相对稳定性与温度有关。根据自由基相对浓度与温度的函数关系图,我们能够将这十二种防老剂的相互顺序排列起来。这种排列顺序与这些防老剂在乙丙胶中的活性非常一致。这些数据在防老剂的机理的有关部分讨论了。
Electron Spin Resonance (ESR) is a spectroscopic technique that is feasible and sensitive to determine the molecular structure and the life span or stability of organic radicals. Therefore, the ESR spectrometer provides a logical way to judge the role of free radicals in stabilizing rubbers. We measured the molecular structure of a series of phenoxy free radicals obtained with twelve phenol antioxidants by ESR spectroscopy. We also measured the relative concentrations of free radicals by ESR and commented on the relative efficiencies of the twelve phenolic antioxidants. We found that the relative concentration of free radicals measured by ESR is a measure of the relative stability of free radicals, whereas the relative stability of free radicals is temperature dependent. According to the relative concentration of free radicals and temperature as a function of the relationship between the twelve antioxidant we can order the mutual order. This arrangement is in good agreement with the activity of these antioxidants in ethylene-propylene rubber. These data are discussed in the relevant part of the mechanism of antioxidants.