Morphology and compatibilization of multicomponent polymer blends.

Abstract

The goal of this research was to develop a thorough understanding of the morphology and compatibilization of multicomponent polymer blends. The first part, an experimental study of ternary polymer blends with non-reactive copolymer compatibilizers, provided an understanding of the relationships between component concentrations, mechanical properties, and morphologies. The effects of the compatibilizers on the corresponding binary blends and on the matrix properties were also investigated. The mechanical testing indicated that compatibilization of each dispersed phase was necessary for significant property improvements, that the results from testing binary systems can be used to estimate the requirements for ternary systems, and that excess compatibilizers can have significant effects on matrix properties. The resulting morphologies were that of complete wetting, partial wetting, and separate particles, with partial wetting dominant in compatibilized systems. The investigations of binary systems showed that additional compatibilizers did not significantly affect the particle size distributions. In the second part of this investigation, the thermodynamics governing the morphology of the dispersed components in ternary blends were examined. Two wetting models were developed based on minimizing the Gibbs energy. The first model predicted the geometry of a system where one dispersed phase consisted of non-deformable spherical particles and the other dispersed phase consisted of deformable particles. The second model predicted the geometry of a system where both dispersed phases were deformable particles. The relationships between morphology, particle size ratios, and interfacial energies were determined. The models showed that the type of spatial configuration, i.e., complete wetting, partial wetting, or separate particles, depended only on the interfacial energies. For partial wetting, the geometry itself depended on both the interfacial energies and the size of the interacting particles. These models provide a basis to alter the interfacial energies to achieve desired morphologies. A separate model was developed to establish the relationships between the three-dimensional partial wetting morphologies and the two-dimensional observable geometries generated from random slicing, and the most probable observed two-dimensional geometry was the same as the actual three-dimensional geometry. Finally, the wetting models were validated by showing agreement between the morphology predicted by the model and experimental observations.