Radiation effects of paraffins as polymer model compounds—II. Crosslinking determination by liquid chromatography

Abstract

The G-values of crosslinking and chain scission of normal paraffins (C 20H 42, C 21H 44, C 23H 48 and C 24H 50) and squalane (C 30H 62) as the model compounds of polymers were determined by the measurements with a liquid chromatography (LC) after Co-60 γ-rays irradiation in solid and in liquid phases at -77, 25 and 55°C. The crosslinking products as dimer, trimer and the more polymeric products were well resolved and the relative yield of polymeric products increased with increasing dose. The G(cross-linking) of n-paraffins was 1.0 in the crystalline at -77°C and 1.15 in the crystalline at 25°C, and 1.7–1.8 in the liquid phase at 55°C of irradiation temperature. The G(crosslinking) of squalane was 1.3 in the glassy phase at -77°C and 1.6 in the liquid phase at 25 and 55°C. However, the chain scission products were too small to detect by the LC measurement, that is, the yield was estimated to be less than 1/10 of the crosslinking products. The unsaturations which appeared in u.v. detector of LC spectrum were observed in monomer, dimer, trimer and the more polymeric products, and the relative concentration was the higher in the more polymeric products, especially in liquid phase. So the molecules with unsaturation would react preferentially with other molecules as monomer or dimer to produce the polymeric products including the unsaturation.