Science / Technology - Colloquium
Monday, November 19, 2012
4:00 PM-5:00 PM
Modulated Differential Scanning Calorimetry (MDSC) was used to measure the complex specific heat over a wide temperature range on crystallization and melting for polypropylene(iPP)/carbon nanotube (CNT) composites as function of CNT content. In the last few years, great attention has been paid to the preparation of polypropylene(iPP) nanocomposites using the carbon nanotubes(CNTs) due to the tremendous enhancement of the thermal and structural properties of iPP. On cooling for weight fraction of CNT in iPP/CNT samples up to 1%, considerable heterogeneous nucleation is observed that scales with the CNT surface area. Saturation occurs for above 1 wt.% of at higher loadings of CNTs, reaching a plateau value for the crystallization onset that is 8 K higher than in the neat polymer. Upon subsequent heating, an increase in the melting temperature is observed likely due to enhanced crystalline order in the presence of CNTs. A complex multiple melting behavior is observed with multiple specific heat signatures that are discussed. Varying heating and cooling rates reveal the effect of CNTs on the chain segment mobility of the polymer matrix and recrystallization upon heating is largely suppressed for scan rates factor than 4 K/min. Observations further show that the total enthalpy of the iPP/CNT sample increase strongly with increasing CNT wt.%, saturating for CNT concentrations above 2 wt.%. These results are interpreted as the CNTs acting as nucleation sites for iPP crystal formation from the melt.
Refreshments will be served in Olin Hall 118 at 3:30 P.M.
Sponsored by: WPI Physics Department
Suggested Audiences: College
Last Modified: October 30, 2012 at 9:27 AM