Recyclage de PVC plastifié par incorporation dans des plastisols : modélisation du comportement rhéologique et étude de la compatibilité

Current environmental issues regarding disposal of polymer wastes encourage PVC industry stakeholders to replace the linear economic system in force by a circular process. Mechanical and chemical techniques employed to recycle PVC materials are well-known but only little attention has been given to the reuse of plasticized PVC wastes by incorporation into plastisols, despite their industrial importance. Processing of the latter is indeed strongly dependent on rheology, widely affected by the addition of plasticized recycled PVC which tends to increase the extent of viscosity aging and to speed up the gelation process. These mechanisms being governed by diffusion of plasticizer which penetrates and swells PVC particles, a kinetic study conducted in the frame of model systems has been performed to determine diffusion coefficients. The glass transition temperature of PVC was proven to be of utmost importance. A model based on the rheology of concentrated suspensions was subsequently developed to predict the aging and gelation behavior of plastisols containing a recycled fraction. The effects of several key parameters, such as the quantity of recycled PVC as well as its particle size and plasticization level, have been examined. Further investigations have been conducted regarding the compatibility of recycled PVC with the matrix composed of plasticized virgin resin, with particular emphasis on the mechanical performance of the coated material. Results actually demonstrate that such a recycling procedure requires compromise between a bearable increase of plastisol viscosity during storage, to meet industrial constraints, and the preservation of mechanical performance after processing. A final series of experiments has been performed on semi-industrial systems to assess the feasibility at a larger scale and some recommendations are suggested.