Rheological Properties of Epoxidized Linseed Oil Composites with Micro-Silver Flake Fillers

Renewable, "green" materials are being used with increasing popularity in industry, especially in the areas of energy and electronics. Vegetable oil is one such material. It is a renewable, biodegradable, low cost material capable of a plethora of uses. Epoxidized linseed oil (ELO) prepared by epoxidation of natural linseed oils can be used as a green monomer for preparing epoxy thermosets. Due to its weak mechanical properties, however, ELO on its own is not always useful. Therefore, we have pursued the study of ELO to be part of an organic/inorganic composite. Silver is a suitable candidate to be used as an inorganic filler in the composite. It offers desirable properties, such as good electric conductivity, relatively low cost, and facile surface modification. It is predicted that the ELO/silver composites could find a purpose in the electronics industry, for uses such as conductive ink for circuit boards and electromagnetic shielding, or as electrically conductive solder.;This thesis represents a comprehensive structure-property investigation of the rheological properties of silver/ELO composite material for different size and shapes of silver particulates. It is important to understand the rheology of conductive inks so that one can predict how the ink will behave in varying composite concentrations, with different sizes of metal particles, and at varying temperatures. Several series of measurements were taken via rheometer and viscometer. First, the effect of silver flake particle size was determined by analyzing five different sizes of silver flake all at the same concentration. Next, the effect of concentration of silver flake in ELO was examined by varying the loading of one size of silver particle. Also, cross-linking behavior was determined on three concentrations of the same silver as the previous experiment. Each cross-linked sample was viewed using scanning electron microscopy to help further understand the variations in cross-linking behavior. Finally, surface modification was performed on silver particulates using thiol-based self-assembled monolayers and the effect of this modification on the rheology of ELO was determined. These measurements together offer a comprehensive understanding of the rheological properties of an ELO/silver flake composite.