Ring-Banded Spherulites in PCL and PCL/MWCNT Solution-Casting Films and Effect of Compressed CO2 on Them

The ring-banded spherulites in poly(epsilon-caprolactone) (PCL) solution-casting films in the absence and presence of multi-walled carbon nanotube (MWCNT) are studied by atomic force microscopy (AFM), polarized optical microscopy (POM), transmission electron microscopy (TEM), and scanning electronic microscopy (SEM). The results indicate that birefringent ring-banded spherulites of PCL can grow from solution below 50 degrees C, and the temperature is much lower than that from pure PCL melt. We also find out that the presence of MWCNT apparently widen the temperature range of forming ring-banded structure. Furthermore, the mechanism for the ring-banded structure forming is studied, and it is attributed to the twisting of lamellae crystals, and the driving force is suggested including the deflexion of lamellae bundles. In addition, effect of compressed CO2 on the morphology of PCL and PCL/MWCNT solution-casting film is also investigated, and the results reveal that both PCL and PCL/MWCNT films undergo recrystallization with the treatment of compressed CO2 and accordingly, the related properties can be adjusted. (C) 2009 Wiley Periodicals, Inc. J Polyrn Sci Part B: Polyrn Phys 47: 784-792, 2009