The transport mechanism for the evaporation of dispersing liquid during the solidification of an epoxy dispersion that had been stabilized to prevent crack formation with a latex dispersion was studied.Aqueous dispersions consisting of an experimentally determined ratio of epoxy resin and nitrile latex were evaporated at 3Sdeg C.When the dispersion was evaporated under controlled conditions without forced air flow,a flexible and adherent polymer material formed.The mechanism for coalescence was related to the loss in weight of dispersing liquid during an initial zero order kinetics stage.This was followed by a rate-controlled Pick's law diffusion through the developing coating with subsequent evaporation to the atmosphere.Experimental measurements are compared with theoretical predictions.The rate constant for the zero order time frame is 0.086(+-)0.02 hr~(-1).In the second time frame,Ficks's law evaporation rate constant is 0.046(+-)0.017 cm-hr~9-1)with a diffusion coefficient of 0.00092 + 0.00051 cm~2-hr~2 at35(+-)l deg C and RH 35 + 7.Applications for evaporation kinetics are discussed.
展开▼
