Influence of aging on the crystallization phenomenon of isotactic polystyrene

The crystallization from the glassy state of different samples of isotactic polystyrene (iPS) was investigated with different techniques, such as differential scanning calorimetry, infrared analysis, and polarized optical microscopy. The different samples of iPS were obtained by aging the glassy iPS films at room temperature and at 70°C; the behavior of the aged films was compared with that of a fresh sample, brought to the crystallization temperature as soon as prepared. The temperature of crystallization was 140°C. All the techniques investigated to follow the crystallization phenomenon show that the fresh sample crystallizes much later than the others; the sample aged at 70°C takes the shortest time to crystallize, whereas intermediate behavior is shown by the sample aged at room temperature. This result was correlated with the initial structural organization of the glassy amorphous samples.