The functionalization of polyolefin fibers is a complex multiphase reaction-diffusion process. Depending on the application, the extent of functionalization ranges from fiber surface treatment to complete fiber stabilization. The objective of this effort is to design a process to achieve a fully stabilized polyolefin fiber in which each filament is sulfonated uniformly from the surface to the core. During this process, the reactant diffuses from the bulk liquid phase through a bundle of hundreds to thousands of filaments to the polymer surface. Subsequently, the reactant diffuses into and reacts with the polymer. This paper presents the development and application of a reaction-diffusion model for the liquid phase sulfonation of a single polyethylene filament. The model computes the radial distribution of sulfonated polyethylene, unreacted polyethylene, and diffusing SO3. Experimental data from elemental analysis (CHSN/O) and scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS) enable quantification of the extent of sulfonation as a function of radial position in partially sulfonated filaments produced in a continuous, multistage sulfonation reactor. These data provide the basis for estimates of diffusion coefficients and reaction rate parameters. Experiments conducted under conditions of partial conversion combined with this reaction-diffusion model of the polyolefin sulfonation process identified the key rate controlling steps, providing insights into key factors for developing a robust process that can achieve the objective of uniform functionalization.

Rate limiting steps in polyolefin fiber sulfonation

251st National Meeting (2016)

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