Spherulite morphology and growth kinetics of poly(octamethylene terephthalate) (POT), cast on single-side glass or confined between two slides in thin-film forms, were characterized using polarized versus nonpolarized optical microscopy, scanning electron microscopy (SEM), and wide-angle X-ray (WAXD) analysis. POT can simultaneously display solely one type of spherulite or dual types of spherulites (double-ring-banded and ringless ones), depending on TC or Tmax imposed. Fractions of these two types depend on Tc when quenched from a fixed Tmax = 160 °C. At lower 7c's, POT exhibits higher crystallization rates leading to higher fractions of ringless spherulites; at higher Tc's, POT exhibits lower crystallization rates leading to ring-banded spherulites. At intermediate to high Tc's where the growth kinetics of POT could be monitored, the ring-band type dominates and the fraction of ringless spherulites is insignificantly small. Both ringless and ring-banded spherulites can be seen in regime III (Tc = 70-110 °C), with fractions of ringless type of spherulites decreasing with temperature. Thus, growth kinetics for POT was mainly focused on the regime of ring-banded spherulites. In regime III, the ring-band pattern is more orderly concentric with smaller inter-ring spacing (1-2 μm) for lower Tc's but intermediately larger spacing (3-5 μm) for higher Tc's. The orderly lamellar orientation in the ring-bands in contrast with the inter-ring valley region is discussed. In regime II (115 °C and above), the ring-band pattern is first distorted to highly zigzag irregularity at higher Tc's and then eventually disappears at extremely high Tc, with the lamellar crystals eventually turning dendritic with no rings. Apparently, the types of spherulites in polymers are more influenced by the growth rates as determined by Tc and slightly less by Tmax, but not by the substrate surface nucleation.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Surfaces and Interfaces