DEVELOPMENT OF A RECYCLABLE NATURAL BASED THERMAL INSULATOR NANOCOMPOSITE

This work was focused on the development of a fully recyclable thermal and acoustical insulation nanocomposite with improved fire resistance behavior in which Graphene Oxide (GO) was used as flame retardant. The nanocomposite was based on a previously developed alginate-based insulator foam, in which fibre-glass waste is down-cycled by incorporation into the polyanionic gel matrix before lyophilization. The complete functional recycling was carried out by designing a new process capable of disassembling and then rebuilding the ionic matrix – which is initially formed by the interaction between a cation (e.g. calcium) and the negatively charged alginate backbone – with the use of a chelator (Ethylenediaminetetraacetic acid disodium salt, EDTA) easily controlled via pH shift. The effectiveness of the recycling process was primarily assessed through characterization of the functional properties on an optimized version of the alginate composite, at first, and on the GO nanocomposite afterward. Data showed that thermal, acoustical and mechanical properties were maintained or even improved in the recycled samples. A multi parametric life cycle assessment (LCA) study showed that, at the lab scale, the recycling option is preferable to simple material disposal and substitution due to the reduction of the environmental footprint of the recycling process. A second comparative analysis, operated also by defining an industrial scaled version of the recycling process, allowed to identify, in the electric energy consumption and in the EDTA syntheses, the most environmentally critical contributors associated with the recycling process, paving the way to futures developments. Cone calorimetry was used to evaluate the fire resistance effect of the introduction of GO in the nanocomposite: data show major improvements at a concentration of only 2\%${_{wt}}$ with the GO acting with a physical barrier mechanism. In addition both the recycled foam and nanocomposite showed an improved fire resistance behavior respect to their original counterparts primarily ascribed to modifications introduced by the recycling process. Eventually, to improve flame resistance activity of GO and compatibilization with the alginate matrix, different GO functionalization, with polyamines and nano-aluminium hydroxides, were synthesized and fully characterized.