Bioreneweable polymer nanocomposites: A study of the design space available for cellulose nanocrystal/poly(3-hydroxybutyrate) nanocomposites
Lin, Stephanie J.
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This research is directed toward determining the design space that is available for cellulose nanocrystals /poly(3-hydroxybutyrate)(CNC/PHB) composites. In order to develop this understanding, the processing-structure-properties relationships of CNC/PHB nanocomposites were examined at several different steps in a stepwise processing method. The as-processed morphology of solvent cast (SC) and anti-solvent compression molded (ASCM) samples were examined using DSC, optical microscopy and ATR-FTIR and the effect of processing and CNC addition on the isothermal and nonisothermal crystallization was examined using DSC, hot stage microscopy, and a novel fast scanning chip calorimeter, the Flash DSC. Results show that the addition of water during SC processing significantly reduced the rate of crystallization at both isothermal and nonisothermal conditions. This reduction in crystallization rate was due to the presence of water suppressed the intramolecular hydrogen bonding. Results from the experimenters performed also indicated CNCs act as a nucleating agent. Even though the overall kinetics of crystallization was increased with CNC addition, the growth rate of the spherulites was reduced with the addition of CNCs. Mechanical characterization of the ASCM and SC-EtOH samples showed that the differences in viscoelastic behavior with CNC addition for the ASCM samples but not the SC-EtOH samples. Also the strain to failure of both processing methods was increased with CNC addition. The knowledge that was obtained from this work can be used when designing processing protocols and heat treatments for PHB-based nanocomposites materials to allow greater control over crystallization processes and mechanical properties expanding opportunities for materials design.