Effect of phosphorus-modified nickel phyllosilicates on the thermal stability, flame retardancy and mechanical property of epoxy composites

In this study, the phosphorus-modified nickel phyllosilicate (P-NiPS) particles were synthesized, and the effect on the thermal stability, flame retardancy and mechanical properties of epoxy (EP) composite was investigated. A phosphorus-containing silane agent was first chemically obtained and then adopted as a silicon source to synthesize the P-NiPS particles via a facile sol-gel method, which were then physically mixed with EP to yield EP composites. Results showed that the introduced P-NiPS could enhance the thermal stabilities, showing the suppressed mass loss rate and increased residual chars. Also, the flame retardancy of EP/P-NiPS composites was enhanced significantly. With the addition of 5 wt%, the limiting oxygen index increased from 23.8% up to 29.2% while the burning time dropped from 214 s down to 7 s remarkably, achieving the UL-94 V-0 rating. The peak heat release rate and total heat release were also declined considerably by 62.5% and 23.7%, respectively, when compared with pure EP. Simultaneously, the smoke and carbon monoxide productions were also suppressed significantly. According to the analysis of residual chars and pyrolysis products, the major retardant mechanism was discussed. The elastic modulus of EP composites was boosted to some extent while the tensile strength and elongation at break were decreased reasonably. This work provided a promising method for preparing EP composites with excellent flame retardancy.