Use of Diffusion Modeler to Help Identify Safer Solvents to Replace Dichloromethane for Conformal Coating Removal

Dichloromethane, also known as Methylene chloride or DCM, is a commonly used chemical in industry for the dissolution of polymer coatings. However, DCM is a highly toxic substance with known affects to human health that pose a serious risk for workers who utilize the chemical in the workplace. Finding alternative solvents as replacements for DCM would greatly improve worker safety while on the job. This research focused on the usage of a diffusion modeling software to help identify solvent candidates for the replacement of DCM. Diffusion models are used widely to simulate the barrier properties of polymer films, simulating the rates of diffusion into a polymer over time. It is expected that diffusion plays a critical role in the ability of a solvent to dissolve a given polymer. Thus, the possible use of a diffusion model as a tool for helping identify candidate solvents was of particular interest. A diffusion model based off polymer-solvent interactions was used to simulate the diffusion of various solvents into an acrylic coating. A linear assumption for change in diffusion coefficients over time based off Fickian Diffusion was tested. A non-linear concentration dependent assumption for the change in diffusion coefficients over time was also tested. The dissolution data from laboratory experiments shows that a non-linear diffusion model can better describe the behavior of coating dissolution as compared to a linear diffusion model, with results from linear model indicating unrealistically long diffusion times. The findings from the research suggest the use of a non-linear diffusion model as a tool to help identify safer alternatives to DCM. Development of an advanced diffusion-based modeler that takes into account other possible reactions (e.g., dissolution) would enable more accurate simulation results and more affective recommendations for the replacement of DCM.