Co-authors​ :

 Monica CAMPO GOMEZ (SPAIN), Tamara RUIZ-CALLEJA , Isaac LORERO , Alberto JIMÉNEZ-SUÁREZ (SPAIN), Silvia G.PROLONCO  

One of the challenges for society and industry is the development of recyclable and environmentally sustainable materials. For this reason, one of the main industrial challenges within the field of composite materials is to solve their recyclability and reprocessing problem. This technological challenge entails significant research efforts to solve the current problems to separate and reuse the components of composite materials. In this sense, resins with Diels-Alder bonds allow the generation of polymeric networks that can be broken down by applying temperatures between 100-150 ºC. Thus, the covalent network existing at room temperature decomposes, giving rise to a structure like that of an oligomer, causing the material to have a significantly lower rigidity, even a certain fluidity. This characteristic can be used so that the material, once its useful life has ended, can be reprocessed with a new geometry, and can even be subjected to thermomechanical recycling processes. In thermomechanical recycling, the material can be completely crushed, subjecting the resulting powder to a hot compaction process with which a new geometry with mechanical properties like the original ones can be generated. Another way to recycle these resins is thermochemistry. This variant is especially interesting in the case of composite materials that incorporate these resins as a matrix. Thermomechanical processes cause the fragmentation of the long fiber, which would give rise to a recycled composite material with exceptionally inferior characteristics to the original. However, with the thermochemical route solvents at Diels-Alder bond inversion temperatures can be used to separate the matrix and recover the long fiber separately. In this sense, it should be noted that the operating conditions are not very aggressive compared to the usual temperatures necessary for the conventional thermosetting matrices. Subsequently, the solution can be treated to recover a new polymer network that can be used in other applications, thus allowing the composite material to be recycled in its entirety.
For these reasons, in the present work the manufacture of an epoxy matrix composite material with thermo-reversible Diels-Alder joints reinforced with carbon fiber is developed, which shows mechanical properties like those of a conventional epoxy resin laminate. Subsequently, a thermomechanical reprocessing will be studied and, on the other hand the viability of the chemical dissolution of the matrix. Finally, the recovery of the fiber thermochemically has been studied for its reuse to manufacture new composite materials and textile coatings.