Effects of water on epoxy cure kinetics and glass transition temperature utilizing molecular dynamics simulations

Abstract

Effects of water on epoxy cure kinetics are investigated. Experimental tests show that absorbed water in an uncured bisphenol‐F/diethyl‐toluene‐diamine epoxy system causes an increase in cure rate at low degrees of cure and a decrease in cure rate at high degrees of cure. Molecular simulations of the same epoxy system indicate that the initial increase in cure rate is due to an increase in molecular self‐diffusion of the epoxy molecules in the presence of water. Effects of water on the glass transition temperature (Tg) of the crosslinked thermoset are also studied. Both experiments and simulations show that water decreases Tg. Both types of results indicate that Tg effects are small below 1% water by weight, but that Tg depression occurs much quickly with increasing water content above 1%. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1150–1159

Molecular Dynamics Simulations of Photo-Induced Free Radical Polymerization

“…Sharp et al 20 used MDS to investigate the effects of water on epoxy curing kinetics. A distance-based criterion was also used in the simulations.…”

Hygrothermal Damage Monitoring of Composite Adhesive Joint Using the Full Spectral Response of Fiber Bragg Grating Sensors

“…This transformation is a chemical reaction that involves temperature change and volumetric contraction. The rate of cure, or chemical reaction, depends on a number of factors such as temperature, humidity and the availability of the correct stoichiometric ratio [ 78 , 79 ]. Local variation of these factors invariably exists, causing differential curing.…”

“…Firstly, the curing process is a chemical reaction that often involves temperature changes and the progressive solidification involves volume contraction. The rate of cure depends on a number of factors such as temperature, humidity and stoichiometric ratio [ 78 , 79 ]. Local variations of these factors invariably exist and differential curing rate at different vicinities of the FBG and at different locations along the FBG will lead to a varying residual stress distribution acting on the grating, modifying the reflected spectrum.…”

Halloysite Nanotubes as an Additive to Ensure Enhanced Characteristics of Cold-Curing Epoxy Resins under Fire Conditions

“…Therefore, the very first thermal stress was that experienced in the DSC furnace during the first heating of the resin. The effect of moisture (described in [ 51 , 52 ]) or other volatile residues was thus minimized, and among other outcomes, an increased level of polymer chain cross-linking was also expected. The T g values were evaluated as the inflection point of the steep decrease in the DSC curve during the glass transition.…”