Electron Paramagnetic Resonance of Radicals Formed during Milling

Abstract

It is well known that during the mechanical degradation of polymers there takes place scission of molecular chains and the formation of macroradicals. It is of considerable interest to study the electron paramagnetic resonance (EPR) spectra of the macroradicals produced by milling, and to compare them with the spectra of the macroradicals formed in the process of polymerization, and also during the irradiation of polymers by gamma rays and neutrons. We may endeavor to compare the amount of macroradicals formed with the extent of mechanical destruction (for instance with the area of the new interface which is formed). In addition, as was found by experience, the macroradicals formed by mechanical scission are good models for the investigation of reactivity since practically all of them are in the newly formed surface layers and are therefore very accessible to various chemical influences. They enter easily into reaction with various agents present in the medium since in this process diffusion from the surface is found in practice not to be a predominating factor. In the present communication we give the first EPR results obtained on mechanically degraded polymers.

ESR Spectroscopy in Polymer Research

“…ESR spectroscopy was successfully applied for study of free radicals generated during fracture in rubber45, 46,306,307,320,321,371,536,537,546,1100,1453,1578,1765,1822,1839,1878,2400) and especially in ozone atmosphere 537,539,544,545,548). The results obtained were reviewed in detail by DeVries 537 ).…”

The Effect of Thermal Processing History on the Photooxidation of Polymers

“…They showed that most polymers, particularly in plasticized form, undergo a rapid reduction in molecular weight on cold mastication and that the macroradicals produced by shear initiate conventional free radical processes. In the presence of air the macroradicals are converted rapidly to alkylperoxy radicals (3,8). The change in applied torque with time during the processing of PVC in a typical mixer (RAPRA torque rheometer) at two temperatures is shown in Figure 1.…”