A comparative analysis on the impregnation efficiency of a natural insecticide into polypropylene films by means of batch against semi-continuous techniques using CO₂ as solvent

In the present paper the application of the supercritical impregnation technology to the production of a polypropylene (PP) film with insecticides properties has been studied for its potential application in greenhouse facilities. A statistical experimental design was conducted to determine the effect of impregnation time, amount of sample, pressure and temperature on the impregnation loading of pyrethrins in PP. Two experimental procedures have also been evaluated and compared: batch mode and semi-continuous mode. Optimal impregnation time was established at 5 h, but, variation in pyrethrin amounts (1-2 mL) did not show any significant effects on the loading of the sample. On batch mode, the maximum impregnated extract loadings were obtained at 55 degrees C and 10 MPa. Nevertheless, the batch mode presents some difficulties with regard to scaling up. On the other hand, the semi-continuous mode presented adequate results at 35 degrees C.