Mass transfer kinetics and diffusion coefficient estimation of bioinsecticide terpene ketones in LDPE films obtained by supercritical CO2-assisted impregnation

Release kinetics of thymoquinone and R-(+)-pulegone impregnated in low-density polyethylene (LDPE) films into air and the effect of supercritical CO2-assisted impregnation process on the diffusional properties of these films were investigated. The incorporation of both ketones into LDPE films was performed under different conditions (pressure, depressurization rate, time, and initial ketone mole fraction). Release experiments were performed under controlled laboratory conditions (24 degrees C, 60% relative humidity), and the total release profile was determined gravimetrically, while the individual release of each ketone was quantified by Fourier transformed infrared. The experimental data were used to fit a mass transfer model based on the second Fick's law for unsteady-state diffusion, and the diffusion coefficients of both ketones in LDPE were estimated, ranging from 2.35 x 10(-13) to 5.53 x 10(-13) m(2)s(-1) (thymoquinone) and from 1.24 x 10(-13) to 4.52 x 10(-13) m(2)s(-1) (pulegone). Finally, analysis of variance testing indicated that impregnation pressure and depressurization rate (and their combination) have significant effects on the diffusion coefficient values. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45558.