Résumé
Polyethylene terephthalate (PET) is one of the world's most widely used polymers, mainly in food packaging and textiles. This material lightness, transparency and mechanical properties make it indispensable [1]. However, PET waste is very common, with a very long natural degradation time. Non-recycled PET therefore contributes significantly to the pollution of both marine and terrestrial ecosystems [2]. However, current recycling methods, which are mainly mechanical, have limitations, including the degradation of material properties after several cycles and high energy consumption [3]. An original and promising alternative is to transform recycled PET into matrixes for performant composites, such as fiber-reinforced thermoplastic tapes.Polymer recycling has become a major issue in the current context of ecological transition and the development of the circular economy [4], [5]. Composite materials with thermoplastic matrices, in particular thermoplastic tapes (reinforced with fibers), offer a promising solution for reducing environmental pollution while meeting the requirements of the most demanding industrial sectors in terms of flexibility and performance. However, the manufacturing of this type of material from recycled polymers such as PET faces technological challenges, particularly in terms of homogeneous impregnation of fibrous reinforcements and control of residual porosity.The aim of this work is to develop an optimized method to manufacture thermoplastic tapes from recycled PET, based on an in-depth understanding of the physico-chemical mechanisms involved. The main objective is to minimize structural defects, such as porosity, while guaranteeing high mechanical properties compatible with demanding industrial applications. This research is part of the exploration of a methodical and innovative approach to producing high-quality recycled and recyclable thermoplastic tapes. First of all, an optimum solvent and non-solvent pair was identified [6] to effectively dissolve recycled PET and enable it to be recovered [7], [8]. This pairing was rigorously selected to ensure good interaction between the solvents and the fibrous reinforcements in order to minimize structural defects in the final composite.Optimizing the performance of tapes required in-depth study of the phenomena of dynamic wetting and spontaneous impregnation of recycled polymer into fibers. Dynamic wetting behavior is highly dependent on fiber and polymer surface properties, polymer solution viscosity and displacement speed [9], [10]. These analyses enabled us to optimize the operating parameters to maximize adhesion and uniform distribution of the polymer in the fibers. Spontaneous impregnation tests were also carried out, providing the necessary information for solution composition.Particular attention was paid to the rheological characterization of the polymer solution, in order to determine the optimum viscosity range. A solution that is too fluid may not adhere sufficiently to the fibers, while a viscosity that is too high limits penetration into the porous structure of the reinforcements [11]. In addition, the physico-chemical interactions between solvents and fibres, and particularly the roving used in the manufacture of tapes, also play an essential role in the process.These analyses allowed to define operating parameters for optimizing the manufacture of thermoplastic tapes from recycled PET. By controlling solution properties and impregnation conditions, porosities can be reduced and impregnation maximized.