Date of Award
Doctor of Philosophy (PhD)
Biobased polymers have attracted significant attention since the 1990s. Research has focused on the conversion of biomass, such as crop oils, into useful polymeric materials. The Departments of Chemical Engineering and Chemistry at the University of North Dakota have developed a process to convert crop oils into jetfuel and a suite of other chemicals including fatty acids with a variety of molecular weights. This dissertation focuses on the preparation and property measurements of thermoplastics using monomers, especially linear vinyl esters (LVEs), which originate from cracked oil-based fatty acids. Commercial LVEs were used in this dissertation study in order to explore some key properties of the resultant copolymers using current polymer synthesis and characterization technology.
Copolymers of LVEs with a variety of monomers, including styrene, methyl methacrylate, acrylic acid, and ethylene, have been successfully synthesized using bulk or solution copolymerizations. The LVE compositions were varied by adjusted the feed ratio. The average molecular weights (MWs) decreased with increasing LVE composition.
Thermomechanical property measurements showed that the glass transition temperatures of the resultant copolymers decreased with increasing LVE compositions. This indicates the side chains of LVEs resulted in easier segmental movements. When the MWs and LVE compositions of the copolymers were similar, the glass transition temperatures decreased for copolymers that had longer side chains. This shows LVEs with longer chains had a greater reduction on the energy required for segmental diffusion. At the same time, the storage moduli (E') of the resultant copolymers decreased with increasing LVE compositions. Therefore, the rigidity of the copolymers could be reduced by incorporation of LVEs. Copolymers with longer side chains but similar MWs and LVE compositions exhibited lower storage moduli (E'), which indicates LVEs with longer chains had a greater impact on the storage moduli (E') than lower molecular weight LVEs.
The rheological property measurements showed that the shear storage moduli (G'), shear loss moduli (G"), and complex viscosity of resultant copolymers were mostly determined by the MWs. The effects of side chains on the shear flow behaviors of LVE based copolymer melts were not significant.
Wang, Hai, "The Study Of Vinyl Ester Copolymers Derived From Bio-Sourced Fatty Acids" (2012). Theses and Dissertations. 1386.