Hybrid Strategies for the Improvement of the Flame Retardancy of in-situ Silica-Epoxy Nanocomposites cured with Aliphatic Hardener

The aerospace industry requires materials showing good mechanical performance, durability, and thermal stability to satisfy very stringent requirements in several applications. Epoxy-based composites can be a suitable solution, due to the peculiar characteristics of the polymer matrix. Epoxy resins can be cured by aliphatic or aromatic hardeners. The use of aliphatic amines is preferable because of their lower toxicity, though these curing agents are easily flammable. Recently, hybrid systems conjugating in-situ modified epoxy matrix with organic and inorganic additives have been developed to flame retard aliphatic epoxy composites. This short review summarizes some applications of such strategies, which are based on the use of the sol-gel technique, DOPO-based flame retardants, bio-waste compounds and other synergists. The review describes the main concept of this approach and the preparation of no-dripping selfextinguishing silica-epoxy hybrid composites showing low phosphorus loadings, tailored interphases and good mechanical properties.