Supercritical CO2-assisted impregnation of LDPE/sepiolite nanocomposite films with insecticidal terpene ketones: Impregnation yield, crystallinity and mechanical properties assessment

•Terpene ketones were loaded into LDPE/sepiolite films by scCO2 impregnation.•The presence of sepiolite increased the impregnation yield of LDPE films.•Pressure, ketone concentration and time significantly affect impregnation yield.•Sepiolite modified LDPE crystallinity degree and morphology.•The impregnation process had a very low impact on the film mechanical properties.

In this contribution, supercritical CO2-assisted impregnation of LDPE/sepiolite nanocomposite films with two insecticidal terpene ketones (thymoquinone and R-(+)-pulegone) is investigated, as a strategy to enhance the loading capacity compared to pure LDPE. A factorial experimental design was applied in order to evaluate the effect of five process variables at two levels (sepiolite content: 1-10% w/w; initial ketone mole fraction: 0.0017-0.0025; pressure: 9-13 MPa; depressurization rate: 0.5-2.0 MPa/min; time: 2-4 h) on impregnation yield, at 45 °C. ANOVA test of the results indicated that pressure, time and ketone mole fraction significantly affect impregnation yield (ranging between 2.36 ± 0.18 and 8.60 ± 1.66% w/w). Thermal analysis (DSC) and X-ray diffraction (XRD) allowed to investigate the nanocomposite morphology and the modifications induced by the impregnation. The mechanical properties of the films were assessed by stress-strain tests, showing that the impregnation process had a very low impact on the material ductility and strength.

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