Dynamic Sorption Measurements Research Articles

An Experimental and Theoretical Investigation into the Diffusion of Olefins in Semi‐Crystalline Polymers: The Influence of Swelling in Polymer‐Penetrant Systems

AbstractA comprehensive dynamic diffusion model is developed to calculate the diffusion coefficients of low molecular weight penetrants (i.e., α‐olefins) in semi‐crystalline polyolefins from dynamic sorption measurements. The model also takes into account the extent of polymer swelling on the penetrant diffusion flux, resulting in a moving boundary value problem. The free volume theory is employed to calculate the dependence of the diffusion coefficient on the penetrant concentration. The solubilities and diffusivities of ethylene and propylene in semi‐crystalline high density polyethylene films were measured at different temperatures and pressures, using a Rubotherm® magnetic suspension microbalance operated in series with an optical view cell for the measurement of the degree of polymer swelling. It is shown that model predictions are in excellent agreement with the experimental dynamic measurements on the mass uptake of the sorbed species. Moreover, it is shown that the proposed model can predict correctly the diffusion coefficient of α‐olefins in semi‐crystalline polyolefins.magnified image

Dynamic wetting of plasma-treated polypropylene nonwovens

Various techniques have been employed to improve the wettability of polypropylene materials for a wide range of applications. In this study, polypropylene nonwovens were treated in oxygen plasma for improving water adsorption properties. The effects of plasma treatment on wetting and water adsorption behavior were characterized using dynamic contact angle measurements and dynamic sorption measurements. The introduction of hydrophilic groups was detected by attenuated total reflection–Fourier transform infrared spectroscopy. The plasma treatment roughened the fiber surface revealed by atomic force microscopy. The roughened and hydrophilic surface resulted in the change in advancing and receding contact angles. The dynamic sorption measurements also examined the water adsorption behavior of the materials. The investigation revealed that plasma treatment could significantly improve the water adsorption properties of polypropylene nonwovens. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2157–2160, 2007