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Articles 1 - 5 of 5
Full-Text Articles in Engineering
Evaluating Effects Of Molecular Heterogeneity On The Non-Linear Mechanical Behavior Of Epoxy Networks, Zhan Hang Yang
Evaluating Effects Of Molecular Heterogeneity On The Non-Linear Mechanical Behavior Of Epoxy Networks, Zhan Hang Yang
Doctoral Dissertations
This thesis describes synthetic and processing strategies to formulate epoxies resins with molecular heterogeneity to achieve enhanced engineering properties. The network heterogeneities include chemical differences in stiffness and crosslink density, as well as mechanical difference in baseline energy state. The focus is to understand the fundamental structure-process-property relationships in these unusual network polymers, especially the post-yield responses and fracture toughness. The main characterization techniques to probe the complex network architectures are dynamic mechanical spectroscopy and compression tests. Ductility and governing parameters are also proposed to describe the relationships between molecular structures and physical properties. Three different staged fabrication strategies are …
Structure Of Nearly Ideal And Multi-Component Polymeric Biomaterials, Erika Saffer
Structure Of Nearly Ideal And Multi-Component Polymeric Biomaterials, Erika Saffer
Doctoral Dissertations
Hydrogels have long been considered ideal candidates for biomaterial and tissue engineering applications due to their many desirable properties, such as high water content and tunable gelation conditions. Although these materials have undergone extensive research and development, some mechanical and physical properties are still difficult to achieve. The reason for this is often related to the structure of the hydrogel network. Understanding how network structures are influenced by changes in formulation parameters (i.e. polymer molecular weight, initial polymer concentration, ratio of hydrophilic to hydrophobic polymer), and correlating these results to known mechanical and physical properties would yield well characterized systems …
Composition Dependence Of The Flory-Huggins Interaction Parameter In Polymer Blends: Structural And Thermodynamic Calculations, Travis H. Russell
Composition Dependence Of The Flory-Huggins Interaction Parameter In Polymer Blends: Structural And Thermodynamic Calculations, Travis H. Russell
Doctoral Dissertations
Flory-Huggins Theory has been the basis for understanding polymer solvent and blended polymer thermodynamics for much of the last 60 years. Within this theory, a parameter (χ) [chi] was included to quantify the enthalpic energy of dispersion between distinct components. Thin film self-assembly of polymer melts and block copolymers depends critically on this parameter, and in application, χ has generally been assumed to be independent of the concentrations of the individual components of the system. However, Small-Angle Neutron Scattering data on isotopic polymer blends, such as polyethylene and deuterated polyethylene, have shown a roughly parabolic concentration dependency for …
Ab Initio Studies Of Proton Transport In Proton Exchange Membranes, Jeffrey Keith Clark
Ab Initio Studies Of Proton Transport In Proton Exchange Membranes, Jeffrey Keith Clark
Doctoral Dissertations
A molecular-level understanding of the factors that contribute to transport properties of proton exchange membranes (PEMs) for fuel cell applications is needed to aid in the development of superior membrane materials. Ab initio electronic structure calculations were undertaken on various PEM ionomer fragments to explore the effects of local hydration, side chain connectivity, protogenic group separation, and specific side chain chemistry on proton dissociation and transfer at low hydration. Cooperative interactions between both intra- and inter-molecular acidic groups and hydrogen bond connectivity were found to enhance proton dissociation at very low degrees of hydration. The energetics associated with proton transfer …
Nanolayer Polymeric Coatings To Enhance The Performance And Service Life Of Inorganic Membranes For High Temperature-High Pressure Biomass Pretreatment And Other Applications, Vincent C. Kandagor
Nanolayer Polymeric Coatings To Enhance The Performance And Service Life Of Inorganic Membranes For High Temperature-High Pressure Biomass Pretreatment And Other Applications, Vincent C. Kandagor
Doctoral Dissertations
Membrane technology has become increasingly attractive in several applications including water filtration, food industry, oil and gas, and biomedical applications. Most recently the quest for renewable, bioenergy has called for use of membranes in biomass pretreatment and other stages of producing biofuel. The success and advancement of the membrane technology for these various applications has, however, been impeded by the fouling of membranes, which causes the pores in the microporous structure to block, resulting in reduced efficiency, and in some cases, total failure of the membranes system. This challenge leads to a tremendous increase in the cost of using membranes …