The morphology and temperature dependence of the lateral growth rate G are reported for isotactic polystyrene crystallized from 0.1% dimethyl phthalate solution at high supercoolings. The outline of a lamella is a rounded hexagon for the highest temperature and a ragged circle for lower temperatures. The edges of the lamellae become ragged and overgrowth is pronounced with decreasing temperature. A linear relationship is found between log(G/r/) and 1~TAT over a wide range of supercooling (AT= T~a - T) from 70 to 170 K, where r/is a retardation factor of Arrhenius form with an activation energy of 8400 K, and ~ is the equilibrium dissolution temperature. The value of ~d is determined to be 200°C by differential scanning calorimetry. In these high supercoolings, the nucleation theory of polymer crystallization loses its validity; in fact, the slope of the plot of log(G/r/) versus I/TAT is four times as large as the value predicted by nucleation theory. Possible growth mechanisms at high supercoolings are discussed on the basis of the morphology
Посилання на статтю:
Growth rate and morphology of isotactic polystyrene crystals in solution at high supercoolings / Yasutoshi Tanzawa* // Polymer. – 1992. – Vol 33. – P. 2659-2665.