Abstract Plasticized PVC is very often used for packaging for liquid foods or blood and blood components. Two simultaneous matter transfers may take place, one concerned with the liquid entering the PVC, and the other with the plasticizer leaving the PVC. Both transfers are controlled by diffusion in transient conditions with concentration-dependent diffusivities. By using information obtained on the profiles of concentration of both these liquids developed through a PVC sheet during the process and with the help of a model based on an explicit numerical analysis with finite differences, we have developed a method of preparation of plasticized PVC sample with very low matter transfers. The principle of this method is as follows: after soaking the sample in a liquid for a definite short time, the sample is extracted and the liquid is evaporated. The concentration of the plasticizer is high within the PVC, but very low on the surface; the sample is therefore not permeable to liquids.