(336e) Nucleating Effect of Expanded Graphite Nanoplatelets on Poly(Hydroxybutyrate)

Expanded graphite nanoplatelets (xGnP) were investigated as possible nucleating agents for poly(hydroxybutyrate) (PHB). It was found that xGnP efficiently induce the crystallization of PHB, leading to increased nucleation density, smaller spherulites, increased crystallization temperature, higher crystallization rate, and lower degree of supercooling. The kinetics of nonisothermal crystallization from the melt was studied by means of differential scanning calorimetry, and the process was described using modified Avrami equation, and Ozawa analysis. The activation energy for PHB crystallization from melt dropped from -60 kJ/mol to -214 kJ/mol after addition of 1% xGnP, indicating that the crystallization of PHB/xGnP was thermodynamically more favorable than that of pure PHB. Optical microscopy and atomic force microscopy were used to observe the changes in size and number of the PHB spherulites upon addition of xGnP, and to investigate the nucleation mechanism. This research is financially supported by EPA?STAR 2002 award # R830904.