Mechanisms of electrolyte (coagulant) dipping for thin nitrile gloves

Two mechanisms for film deposition during the electrolyte dipping process are examined. The conventional, widely accepted, mechanism proposes that electrolyte on a former, immersed in latex compound for a controlled dwell time, diffuses into the compound and a wet gel coagulates on the former where the electrolyte concentration is above the critical coagulation value. An alternative mechanism proposes that deposition occurs via particle movement towards the former, driven by diffusiophoresis. The two mechanisms are examined using dipping nitrile latex compound and various mono and divalent cation electrolytes. The similarity of the total solids content (TSC) of the deposit on the former to that of the compound, the coagulated nature of the deposit and the success, at short dwell times, of a diffusion-coagulation model show that diffusion and coagulation operates exclusively for the divalent cations. For the monovalent cation electrolytes, this mechanism is also dominant, but the TSC of the deposits suggests that diffusiophoresis also plays a small part in the deposition process. A model for the two mechanisms acting together was devised and applied to deposition given by three monovalent electrolytes. This gave deposit TSCs that agreed with the diffusiophoretic prediction and was independent of dwell time. Quantitatively, the calculated amounts of deposit agreed reasonably well with experiment. The model therefore provides some support for diffusiophoresis affecting deposition for monovalent electrolytes. The reason(s) for the different diffusiophoresis behaviour of the monovalent and divalent electrolytes is suggested to be due to the much lower critical coagulation concentration for the divalent cations.