Date of Award
Master of Science (MS)
The effect of dispersion and interphase properties on the elastic behavior of cellulose nanocomposites was investigated using a number of composite models, experimental data and a thorough literature review. Cellulose nanocomposites consisting of soy protein isolate (SPI) and cellulose nanocrystals (CNC) or polydopamine coated cellulose nanocrystals (PD-CNC) were prepared via solution casting method and tested for mechanical stiffness. These outcomes were compared to standard composite models as well as novel methods adapted from the literature that incorporate data regarding dispersion quality and interphase properties. The literature review verified that both dispersion and interphase properties are highly dependent on interfacial chemistry between constituent phases. A comparison of the elastic modulus among 11 similar CNC-polymer systems revealed that CNC functionalization directly leads to improved mechanical stiffness. All analytical models demonstrated that the quality of dispersion in composites drastically affects their overall modulus, and this was verified by the literature. Although the high stiffness of the interphase was shown to be a somewhat misleading basis for analytical predictions, the possibility of a secondary percolation threshold due to high interphase volume merits further investigation. Due to these results, the enhanced stiffness seen for PD-CNC-SPI films relative to unmodifed CNC-SPI films was attributed to improved dispersion through increased chemical compatibility with the surrounding matrix. Characterizing dispersion as a function of CNC loading and interfacial characteristics is the current focus of our lab, and updated results will be published in the near future which incorporate these findings.
Guy Genin Srikanth Singamaneni
Available for download on Thursday, April 18, 2024