College of Engineering
Materials Engineering Department
BS in Materials Engineering
Meissner Filtration uses amine-hardened epoxy as a high-performance adhesive to encapsulate hollow fiber membranes at the ends of rigid filter housings. Dimensional change of the epoxy while curing can result in residual stress formation that is detrimental to the manufacturing of the filter and causes structural integrity issues when the filter is used in industrial processes where heating and cooling cycles are implemented. The residual stresses can cause cracks, microscopic fractures, and delamination from the housing, resulting in failure of the filter. The goal of this project was to evaluate how changes in processing conditions could minimize dimensional variability due to chemical and thermal mechanisms to reduce system failures. Two epoxy materials were provided for testing by Meissner, classified as Epoxy 1 and Epoxy 2. To determine the relationship between dimensional changes and chemical curing, six resin to hardener ratios were tested for Epoxy 1 and four ratios were tested for Epoxy 2. To study the effect of increasing initial crosslink density in the form of prepolymer material in the amine hardener, 5% prepolymer samples were performed in two mix ratios of Epoxy 1 and a 10 % prepolymer mixture was tested in one ratio of Epoxy 1. Both epoxy materials were cured at 55 °C and then heated to 125 °C. The linear contraction due to chemical bonding in both epoxies was measured after the material had been cured. It was found that there is lower linear contraction when the mix ratio had higher resin content as there were fewer reactive sites available, leading to more free space in the polymer. Increasing prepolymer content was found to further reduce the amount of chemical contraction. The thermal effect on linear expansion was examined after curing the epoxy and was correlated to the glass transition temperature. It was also found that moderate hardener levels provided the highest glass transition temperature in both epoxies and the lowest thermal expansion in the post cure processing in Epoxy 1. Overall, Epoxy 2 provided less dimensional change throughout the curing process than Epoxy 1. The prepolymer content increases the glass transition temperature of the epoxy, however results are unclear of its effect on thermal expansion. Results indicate that there is an ideal mix ratio that would minimize dimensional change during the cure cycle of both epoxies therefore provide a reduction of filter failures.
Available for download on Wednesday, June 12, 2024