THE KINETICS OF THE REACTIONS OF KOsub2sub 2 AND KOH WITH WATER

This report gives the results of a kinetic study of the reactions of potassium hydroxide and potassium superoxide with water vapor and carbon dioxide, describes the equipment used, and furnishes the mathematics required for calculating time dependent concentrations. (author

Molecular modeling of the influence of crosslink distribution on epoxy polymers

Experimental studies on epoxies report that the microstructure consists of highlycrosslinked localized regions connected with a dispersed phase of low-crosslink density epoxy. Because epoxies play a major role in many structural applications, the influence of the crosslink distribution on the thermo-mechanical properties must be determined. But as experiments cannot reliably report the exact number or distribution of crosslinked covalent bonds present in the molecular network, molecular modeling is a valuable tool that can predict the influence of crosslink distribution on thermo-mechanical properties. In this study, molecular dynamics are used to establish well-equilibrated molecular models of an EPON 862-DETDA epoxy system with a range of crosslink densities and distributions. Crosslink distributions are varied by forming highly crosslinked clusters within the epoxy network and then forming additional crosslinks that connect between clusters. Results of simulations on these molecular models indicate that the thermal expansion coefficient decreases with overall crosslink density, both above and below the glass transition temperature. It is also found that within the range of crosslink distributions investigated, there is no discernible influence of crosslink distribution on the linear thermal expansion coefficient of the epoxy. © 2012 by Gregory M. Odegard