PARTICLE TRACK DETECTION AND RELAXATION TRANSITIONS IN POLYMER

The sensitivity of polymeric track detectors is influenced by the regi stration temperature, i.e. the temperature of the polymer at the momen t of the particle impact. Here, temperature effects on registration we re considered in terms of molecular mobility and relaxation transition s. An attempt was made to find a correlation between the formation of heavy particle tracks in polypropylene (PP) and known transitions in t his polymer. The track etch rate was measured as function of temperatu re in the range between 77 and 373 K. The obtained results were compar ed with radiothermoluminescence curves and thermally stimulated curren ts used for detecting charges in molecular mobility. It was found that the increase of the track etch rate with decreasing registration temp erature seems to correlate with gamma and glass transitions. The decre ase of the track etch rate at the irradiation temperatures below 130 K can be assigned to the situation when oxidation is prohibited but som e structure reparation reactions still take place. The heating of irra diated PP samples at the temperatures above ca. 340 K leads to a drama tic increase of damage in heavy ion tracks which can be associated wit h another transition occurring in semicrystalline polyolefins.