Abstract:

A flame retardant， piperazine-1，4-dialkyl bis（diphenylphosphine oxide） （PPDO）， was successfully synthesized with diphenylphosphinyl chloride and piperazine as raw materials and then was incorporated into epoxy resin （EP） to prepare flame-retardant EP compounds. The flame retardant performance， thermal decomposition behaviors， combustion behaviors and mechanical properties of the resultant EP compounds were investigated extensively by vertical burning test， oxygen index test， thermogravimetric analysis， cone calorimeter and mechanical performance tests. The results indicated that the EP compounds achieved the UL 94 V-0 classification as well as a limiting oxygen index of 28.9 vol% with the addition of 17 wt% PPDO. After the water resistance tests， the EP compounds still kept high flame-retardant efficiency due to the good hydrophobic properties of PPDO. Meanwhile， the EP matrix exhibited excellent compatibility with PPDO， leading to the good transparency and mechanical properties of the EP compounds. In addition， the introduction of PPDO significantly promoted the premature degradation and char formation of the EP matrix， resulting in the formation of a dense and stiff expansion protective char layer during the combustion process. This effectively reduced the total heat release of the EP compounds and endowed them with satisfactory flame retardant properties.

Key words: epoxy resin, piperazine-1, 4-dialkyl bis（diphenylphosphine oxide）, flame retardancy, transparency, water resistance