Effects of carbon nanofiber on the dissolution and diffusion of CO2 in polypropylene nanocomposites

• The solubility and diffusion coefficient of CO2 in PP/CNF composites was determined.
• A modified Henry model correlated well the solubility data in PP/CNF composites.
• A modified Maeda model correlated well the diffusion data of CO2 in PP composites.

The effects of nanofiller with elongated structure on the dissolution and diffusion behaviors of CO2 in polypropylene (PP)/carbon nanofiber (CNF) composites were investigated in this work. The solubility of CO2 in PP and PP composites containing 5 wt% and 10 wt% CNF was measured by using magnetic suspension balance (MSB) combined with the experimental swelling correction by using a self-designed high-temperature and -pressure view cell at the temperatures of 200 and 220 °C and pressures up to 20 MPa. The diffusion coefficient of CO2 in PP and PP composites was also determined from the sorption line at CO2 pressures ranging from 5 to 10 MPa. It was found that the solubility and diffusivity of CO2 in PP/CNF composites increased with increasing the filler content, which should be mainly attributed to the change of the distribution of free volume in the polymer matrix besides the small amount of adsorption capacity of CO2 in CNF. A modified Henry model incorporated with Langmuir adsorption factor was proposed to correlate the solubility of CO2 in the PP/CNF composites with an average relative deviation less than 3%. A new model based on free volume theory incorporated with the diffusion driving force factor was established to correlate the experimental diffusion coefficient of CO2 in the PP/CNF composites within an average relative deviation of 2%.

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