Abstract
This doctoral research investigates the design, synthesis, and evaluation of rare earth compound (REC)–based flame retardant and thermal barrier formulations for use in both thermoplastics, thermosets, and technical textiles. The work was conducted in collaboration with Neo Performance Materials and systematically explores the synergistic effects of selected rare earth oxides, hydroxides, phosphates, and their complexes, primarily based on La and Ce with conventional FR systems.
A comprehensive screening of over 50 formulations was undertaken across multiple polymer matrices, including polypropylene, epoxy resin, polymethyl methacrylate, and polystyrene, as well as textiles like cotton and polyester/cotton, and technical fabrics such as aramid, and polyimide. RECs were evaluated both individually and in combination with the intumescent flame retardant, ammonium polyphosphate and pentaerythritol; the mineral fillers magnesium hydroxide and aluminium trihydroxide; and the bio-based additive, phytic acid.
Thermal and fire behaviours were analysed using thermogravimetric analysis, limiting oxygen index, UL-94 vertical burn testing and cone calorimetry. Results demonstrated that specific RECs–particularly La₂O₃, CePO4, LaPO4, and lanthanum-phytic acid (LaMP) complexes significantly improved flame retardancy metrics by promoting char formation, reducing peak heat release rates (PHRR), and increasing ignition resistance. Notably, the LaMP–IFR system in epoxy showed a synergistic flame retardant effect, achieving UL-94 V-0 rating and enhanced LOI (26.7%), attributed to catalytic crosslinking and the formation of a robust intumescent char barrier.