THERMOLUMINESCENCE OF POLYMERS IRRADIATED AT ROOM-TEMPERATURE AND UNDER HIGH-PRESSURE

Influence of the pressure up to 2.3 GPa on thermoluminescence of PE, PP and PTFE irradiated at room temperature has been studied. Thermoluminescence of polymers irradiated without pressure is a slight glow above 300 K with a maximum at 330-350 K. Irradiation under pressure results in increase of intensity and decrease of temperature of this maximum. The maximum is displaced down to the position of the phase or relaxational transitions (approximately 300 K for PTFE, 255 K for PP, 225 K for PE), then temperature of the maximum becomes constant and its intensity begins to fall. With increase of pressure the initial part of the luminescence curve continues to displace in the low temperatures region resulting in formation of additional 2-3 maxima in the 150-200 K range for pressure above 1.7 GPa. The appearance of thermoluminescence maxima after irradiation at room temperature under pressure points out that for irradiation below the relaxational transition temperature the molecular mobility is retarded by pressure, and charges are stabilized. The different number of maxima and different rates of displacement of the initial part of the curve with increase of pressure are related with the difference in the values of the free volume and compressibility for different polymers.