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Making rubber gloves

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Thin rubber gloves are used extensively in medicine and lab settings. Over 300 billion are manufactured each year from either natural latex or synthetic nitrile rubber. The manufacturing process involves using a hand shaped mould – called a former. This is dipped into a concentrated calcium nitrate solution, dried and then dipped into an aqueous colloidal dispersion of the polymer. Diffusion of electrolyte into the latex bath causes aggregation onto the former and generation of a wet gel. After a set time in the latex bath the former is dried, washed and then the glove is removed. We model the formation of the wet gel to predict the thickness of the glove as a function of dipping time. A simple diffusional model works well at short dwell times, but at longer times the wet gel growth is reduced, which we ascribe to a limited quantity of electrolyte and a reaction between calcium ions and surfactant.

Contrary to experimental observation, typical flow velocities are predicted to dominate diffusional transport. The wet gel restricts flow so that diffusion is dominant close to the former and further away flow dominates. We include a flow term in the model for wet gel growth, match the two solutions and predict the wet gel size. We have built a flow tank to investigate wet gel growth and compare our predictions with the experiments.

This talk is part of the BPI Seminar Series series.

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