WEB Anomalous Bulk Diffusion Mechanism of Methylen Diphenylmethane-4,4′-diisocyanate in Cross-linked Poly(dimethylsiloxane)
In industrial applications of the vacuum casting process, silicone casting molds are used to replicate prototypes and small series made of poly(urethane) . The undesired diffusion of the isocyanate component into the silicone leads to degradation of the casting tools . In this contribution, we present a detailed description of the chemical and physical mechanisms of diffusion at the molecular level and the modelling of the anomalous bulk diffusion process. The polymerization of the methylen diphenylmethane-4,4′-diisocyanate with residual moisture to poly(urea) within the cross-linked poly(dimethylsiloxane) matrix leads to a time dependence of the diffusion coefficient and thus require more complex solutions to Fick’s 2nd law to describe the concentration distribution over time and cross-section.
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