Non-isothermal Crystallization Behaviors of HDPE/MWCNT Nanocomposites

摘要

Thermal properties and non-isothermal crystallization kinetics of polyolefin nanocomposites (high-density polyethylene/multi-walled carbon nanotubes) were characterized by differential scanning calorimetry and thermogravimetric analysis. In situ metallocence polymerization was used to prepare nanocomposites of multi-walled carbon nanotubes (MWCNTs) and high-density polyethylene (HDPE). This polymerization method consists of attaching a metallocene catalyst complex onto the surface of the MWCNTs followed by surface-initiated polymerization to generate polymer brushes on the surface. A kinetic equation for the non-isothermal crystallization was employed to analyze the crystallization characteristics of the nanocomposites. The Avramic exponent, n, can be reasonably well determined from the non-isothermal crystallization exotherm. The polarized optical microscopy showed that neat polyethylene possessed a well developed spherulite morphology: whereas, the nanocomposites displayed elongated entities that subsequently developed as bundle-like entities. Non-isothermal analysis implicitly provides clues about the morphological development history and HDPE molecular ordering around the carbon nanotubes.