Electron beam treatment of polyacrylonitrile copolymer above the glass transition temperature in air and nitrogen atmosphere

The electron beam (EB) modification of polymers belongs to the group of chemical modification of polymers and bases on polymer radicals formed during the spatial and temporal precise input of electron energy. The radical induced chemical modification of polymers strongly depends on the constitution of polymer and the processing conditions during the EB treatment. For the first time, the present study reports the EB treatment of polyacrylonitrile copolymer (Co-PAN) powder in air and nitrogen atmosphere at an average temperature of 125 °C in order to study the electron-induced reactions of Co-PAN above the glass transition temperature, but still below the initiation temperature of the thermal induced chemical reactions. The gas atmosphere during the EB treatment of Co-PAN powder strongly influenced the number of trapped radicals, the ratio of chain scission density to density of crosslinked units, the level of fluorescence, the EB induced functional groups, the extent of cyclization and the residual mass at a temperature of 800 °C. The nitrogen atmosphere during the EB modification of Co-PAN led to reduced cyclization and reduced residual mass at 800 °C with increasing gel content. [Display omitted] •Cyclization of Co-PAN can be induced by an EB treatment at 125 °C.•Maximum extent of cyclization was achieved by EB treatment in air.•Strong Co-PAN network led to reduced values of residual mass at 800 °C.•Cyclization and residual mass are controlled by chain scission to crosslinking ratio.