Highly transparent and flame-retardant epoxy composites based on a hybrid multi-element containing POSS derivative

Abstract

The development of a multi-element synergistic flame-retardant depends largely on the design and synthesis of flame-retardants comprising a mixture of elements such as P, N and Si. Herein, we prepare a novel POSS derivative named octa-(N,N-(bis-(9,10-dihydro-9-oxa-10-phosphaphenanthene-10-yl)methyl)aminopropyl) silsesquioxane (ODMAS) that features a high content of P. The chemical structure of ODMAS was confirmed by FT-IR, 1H NMR, 29Si NMR, 31P NMR and elemental analysis. Because of the excellent compatibility between ODMAS and epoxy resin, the as-prepared ODMAS/EP composites are highly transparent as well as possessing improved flame-retardancy and mechanical properties. The results show that the LOI value reaches 37.1% with a low phosphorus content (1.6 wt%), samples only 5 wt% loading are classified with the V0 rating in the UL-94 test, and the char yield significantly increased and the maximum weight loss rate decreased with increased ODMAS loading. Results of a three-point bending test show that the flexural modulus of ODMAS/EP is higher than that of the pure epoxy resin. All results indicate that this novel flame retardant not only has good solubility in the polymer matrix, but can also simultaneously improve the flame resistance and mechanical properties of the polymeric material.