Processing and characterization of nanocomposites prepared by high torque melt mixing, 2017
Cross, Lionel W.
2010-2019
The rapid development of polymer nanocomposites has received extensive attention over the last few decades. The ability to alter functionalities of composites, dramatically improving properties and performance at low filler content creates flexibility in designing materials for advanced applications in various industrial fields. This work focuses on nanocomposites relevant to the packaging and aerospace industries. This work evaluated the ability to homogeneously distribute nanomaterials into a polymer matrix, understand the effects on rheological properties, understand changes to microstructure and effects, and characterize properties of resulting nanocomposite. High torque melt mixing was used to disperse surface modified cellulose nanocrystals in a poly(lactic acid) (PLA) resin and graphene in a phenylethynyl terminated imide resin, PETI 298, using bulk graphite. Rheology, Raman spectroscopy, and X-Ray powder diffraction were applied for the understanding of changes to the microstructure and location of optimum loading by the determination of the percolation threshold. Thermomechanical performance was evaluated through TGA, DMA, and DSC. It was determined that graphene and short stacks of graphene could be dispersed and distributed at low loadings in PETI 298. As expected, the addition of graphitic material led to an increase in viscosity, but also caused a retardation of the cure which could be attributed to increased viscosity or quenching of free radicals. Changes to the microstructure were difficult to evaluate because of the competing chemistry occurring in the system but it could be determined that something significant occurs around 1 wt % at which the melt rheology and the microstructure behavior was different from other composites. It was further determined that the melt mixing process led to the formation of an ordered structured. Modification of the cellulose nanocrystals (m-CNC) with Cardura, glycidyl ester, provided no improvement to mechanical properties of PLA composites. However, m-CNCs were found to nucleate the crystallization of PLA. Lack of improvement to mechanical properties could be attributed to the degradation of polymer during processing. KEY TERMS: Nanocomposite, Polyimide, Graphite, Cellulose, Lactide, Chemistry, Materials Chemistry, Polymer Chemistry
text
application/pdf
2017-05-22
dissertation
Doctor of Philosophy (PhD)
Clark Atlanta University
Chemistry
Mintz, Eric A. Schueneman, Greg Parker, Cass D.
Georgia--Atlanta
http://hdl.handle.net/20.500.12322/cau.td:2017_cross_lionel_w
