Isothermal and nonisothermal crystallization kinetics of poly(ε‐caprolactone)/multi‐walled carbon nanotube composites

Abstract

Abstract Differential scanning calorimeter (DSC) and polarized optical microscopy (POM) have been used to investigate the isothermal and nonisothermal crystallization behavior of poly(ε‐caprolactone) (PCL)/multi‐walled carbon nanotube (MWNT) composites. PCL/MWNT composites have been prepared by mixing the PCL polymer with carboxylic groups containing multi‐walled carbon nanotubes (c‐MWNTs) in tetrahydrofuran solution. Raman spectrum of c‐MWNT indicated the possible presence of carboxylic acid groups at both ends and on the sidewalls of the MWNTs. The TEM micrograph showed that the c‐MWNT is well separated and uniformly dispersed in the PCL matrix. DSC isothermal results showed that the introduction of c‐MWNT into the PCL initiates strongly heterogeneous nucleation, which induced a change of the crystal growth process. The activation energy of PCL significantly decreases by adding 0.25 wt% c‐MWNT into PCL/c‐MWNT composites and then increases as c‐MWNT content increases. The result demonstrates that the addition of c‐MWNT into PCL induces the heterogeneous nucleation at lower c‐MWNT content and then inhibits the polymer chain transportation ability during crystallization at higher c‐MWNT content. In this study, we have also studied the nonisothermal crystallization kinetics and melting behavior of PCL/c‐MWNT composites at various cooling rates. The correlation among isothermal and nonisothermal crystallization kinetics and melting behavior of PCL/c‐MWNT composites can be also discussed. POLYM. ENG. SCI., 46:1309–1317, 2006. © 2006 Society of Plastics Engineers