Date of Award
2008
Degree Type
Thesis
Degree Name
Doctor of Philosophy
Program
Mechanical and Materials Engineering
Supervisor
Professor D. M. Shinozaki
Second Advisor
Professor R. Klassen
Third Advisor
Nanocomposites consisting of montmorillonite in polyethylene have been prepared by melt mixing, followed by injection molding or channel-die forming. Polarized optical microscopy, SEM, X-ray diffraction and FTIR have been used to characterize the morphology of average particle size and spatial dispersion which developed during the post-mixing molding process. The crystallization kinetics was measured by means of differential scanning calorimetry (DSC). Differences were shown between exfoliation and intercalation dominated nanocomposites by mechanical tests and theoretical modeling. The orientation of clay in the forming process was studied in detail by using a controlled strain/strain rate channel die forming process. Synchrotron radiation X-ray diffraction at the SUNY Stony beam line X27C at Brookhaven has been used to obtain high resolution small angle and wide angle patterns to demonstrate the distribution of nanoparticles orientation. Factors affecting orientation mechanisms were investigated based on WAXD and the preferred orientation of the clay platelets was found to influence the orientation of PE lamellae which was found to epitaxially grow on the platelet surface. This orientation effect can also be confirmed by the reverse orientation examination by remelting the oriented composite plaques. The skin-core structure of injection molded nanocomposites was illustrated through micromorphology characterization. The relationship between the particle structure and orientation and the mechanical properties was measured point to point using displacement controlled micro-indentation. The testing results were compared with tensile testing and standard dynamic mechanical thermal analysis (DMTA) and good agreement and superior accuracy was achieved. The anisotropy of clay particles affected by clay dispersion and orientation was illustrated using the Arridge and Ward analysis. The heterogeneity in mechanical properties as a function of orientation in the molded part can thus be concluded as the result of anisotropic property of clay tactoids and non-uniform orientation. The Halpin-Tsai equation and Mori-Tanaka model were fitted to predict the modulus with the change of clay modulus, matrix modulus, aspect ii ratio and orientation. Finite element modeling results were compared with tensile tests along axial direction and indentation measurements along the normal direction. The theoretical models were shown to give reasonable predictions compared with the experimental results.
Abstract
Nanocomposites consisting of montmorillonite in polyethylene have been prepared by melt mixing, followed by injection molding or channel-die forming. Polarized optical microscopy, SEM, X-ray diffraction and FTIR have been used to characterize the morphology of average particle size and spatial dispersion which developed during the post-mixing molding process. The crystallization kinetics was measured by means of differential scanning calorimetry (DSC). Differences were shown between exfoliation and intercalation dominated nanocomposites by mechanical tests and theoretical modeling. The orientation of clay in the forming process was studied in detail by using a controlled strain/strain rate channel die forming process. Synchrotron radiation X-ray diffraction at the SUNY Stony beam line X27C at Brookhaven has been used to obtain high resolution small angle and wide angle patterns to demonstrate the distribution of nanoparticles orientation. Factors affecting orientation mechanisms were investigated based on WAXD and the preferred orientation of the clay platelets was found to influence the orientation of PE lamellae which was found to epitaxially grow on the platelet surface. This orientation effect can also be confirmed by the reverse orientation examination by remelting the oriented composite plaques. The skin-core structure of injection molded nanocomposites was illustrated through micromorphology characterization. The relationship between the particle structure and orientation and the mechanical properties was measured point to point using displacement controlled micro-indentation. The testing results were compared with tensile testing and standard dynamic mechanical thermal analysis (DMTA) and good agreement and superior accuracy was achieved. The anisotropy of clay particles affected by clay dispersion and orientation was illustrated using the Arridge and Ward analysis. The heterogeneity in mechanical properties as a function of orientation in the molded part can thus be concluded as the result of anisotropic property of clay tactoids and non-uniform orientation. The Halpin-Tsai equation and Mori-Tanaka model were fitted to predict the modulus with the change of clay modulus, matrix modulus, aspect ii ratio and orientation. Finite element modeling results were compared with tensile tests along axial direction and indentation measurements along the normal direction. The theoretical models were shown to give reasonable predictions compared with the experimental results.
Recommended Citation
Fan, Ying, "MICROSTRUCTURE AND PROPERTIES OF POLYMER NANOCOMPOSITES" (2008). Digitized Theses. 4873.
https://ir.lib.uwo.ca/digitizedtheses/4873