We all use latex and nitrile thin gloves. Over 180 billion of them are manufactured each year. The method of manufacture involves taking a ceramic former and dipping it into a solution of electrolyte, typically calcium nitrate. The coated former is dried and then dipped into a bath of dilute, aqueous polymer latex. The calcium nitrate (called coagulant) causes the latex particles to aggregate onto the former forming a weak, water containing film described in the industry as wet gel. Upon removal and subsequent drying the film transforms into the glove, which is then removed from the former and packaged. We sketch the process in the figure.
We have recently proposed a model where the transport of coagulant into the latex bath is driven by diffusion. The wet gel thickness is experimentally found to be thinner than that predicted and, after considering many mechanisms for the discrepancy, we concluded that a reaction between calcium ions and anionic surfactant ions from the latex reduces the calcium concentration and hence the wet gel thickness.
Despite its industrial importance, many aspects of thin glove manufacture are not yet understood. The application of a better understanding could reduce the environmental impact of the process. For example, to obtain a thin final film, a large amount of water is used in the initial stage to dilute the latex. At the final stage of production, this water is evaporated with a high energy cost.
Once we have a refined model, we will be able to predict the glove thickness and rate of formation as a function of all process parameters. We will then apply our knowledge to a production plant and see how to optimise the process. In particular we seek to minimise the energy input to the plant. This is likely to involve using a latex dispersion with as high a polymer content as possible consistent with producing a thin (< 0.1mm) film, to reduce the cost of adding then evaporating water. Consequently we think the industrial questions to answer are