期刊
POLYMER ENGINEERING AND SCIENCE
卷 62, 期 9, 页码 2977-2985出版社
WILEY
DOI: 10.1002/pen.26078
关键词
absolute heat capacity; fast scanning Chip calorimetry; glass transition; nanocomposites; polystyrene
资金
- National Science Foundation [DMR-2141221, DMR2004960]
The absolute heat capacity of a matrix-free polystyrene grafted silica nanocomposite system was investigated using Flash DSC and compared to a neat polystyrene sample. The results showed that the heat capacity of the polymer in the nanocomposite was 8% lower than that of the neat polystyrene, and there was a 15% lower change in heat capacity at the glass transition temperature. Moreover, there was a 2 nm-thick immobile layer of polymer around the nanoparticles, and the glassy layer remained immobile up to 300 degrees C.
The absolute heat capacity of a matrix-free polystyrene grafted silica nanocomposite system is investigated using ultrafast Flash differential scanning calorimetry (Flash DSC) and compared to results for a neat polystyrene sample of similar molecular weight. The heat capacity of the polymer in the nanocomposite is 8% lower than that of the neat polystyrene. In addition, the step change in heat capacity at the glass transition T-g is 15% lower, indicating a 2 nm-thick immobile layer of polymer around the nanoparticles. There is neither an increase in the nanocomposite heat capacity towards that of the neat material nor any additional increment C-p steps, indicating that the glassy layer around the nanoparticles remains immobile up to 300 degrees C. In addition to the analysis of the absolute heat capacity, the dynamic temperature gradient in the Flash DSC sample increases linearly with increasing rate of measurement, whereas the noise in the heat capacity data increases linearly with the reciprocal of the scanning rate; the optimum rate for measurements lies between 300 and 1000 K/s for the samples studied here and will depend on the sample thickness.
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