Polymers and polymer based composites have noticeable properties such as their higher flexibility and much lower density compared to other engineering materials (e.g. metals). Also by addition of nanoscale particles into polymeric matrices, “polymer nanocomposites” are produced. Polymer nanocomposites have improved mechanical properties, thermal stability and flame retardancy. Higher strength and modulus is attained by a nanoscale material since nanofillers possess very high aspect ratios and matrix-reinforcement surface area providing effective stress transmittance. Flame retardancy of polymer nanocomposites is improved remarkably by the synergism of conventional flame retardants and nanoscaled particles. Boron compounds could be candidates for the replacement of especially halogenated conventional flame retardants in order to eliminate their hazardous toxic effects.