γ辐照 聚全氟乙丙烯(F46)的电子自旋共振研究 I.真空中俘获自由基的定量研究

A method for determining respectively the concentration of free radicials...CF2-CF2.(RI), ...CF2-CF-CF2...(RII)and...CF2- C(CF3)-CF2...(RIII) trapped in γ-irradiated F46 in vacuum at room temperature by analysing the ESR overlapping spectra is proposed. A quantitative relation between the concentration of free readicals and the total dose of γ-irradiation has been studied. The generating rate o free radicals caused by irradiation, i.e. G-value, has been calculated; it is 2.0 for RIII, 1.2 for RI, and 0.59 for RII. the magnitude of G value of free radicals is in the reverse order of their stability. Hence, we assume that the G value of free radicals in F46 mainly depends on the escaping rate of F2 and other fluorine-containing small molecules from surface of polymer into space. Therefore the looser the molecular chain, the larger becomes the G value of free radical. From that, we consider that both unstable free radicals RIII and RI with larger G-value mainly locate in the amorphous region, and the stable free radical RII with lower G-value is in the crystalline region. Recombinations between free radicals RII and RIII, or between RII and RI are forbidden at the temperature lower than 80C. An explanation for the saturation phenomenon of concentration of free radicals is given.