The Synthesis And Flame-retardant Application Of Polysilsesquioxane With The Caged/ladder-like Structure

Halogen-free flame retardant polymer is a new development direction of the flame retardant polymer field in recent years. Moreover, synthesis of halogen-free flame retardant and preparation of polymer have become key scientific and technological projects. In this paper, halogen-free flame retardants are the focus. Main reseaches are as following:Three designed phosphorus containing POSSs with T8 caged structures were synthesized via the addition reaction between octa vinyl POSS and diphenylphosphine(DPP),diphenylphosphine oxide(DPOP), or DOPO(9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), which were a series of new halogen-free flame retardants. These POSSs all contain phosphorus and silicon, possessing of good thermal stabilities.DPP-POSS, DPOP-POSS, and DOPO-POSS were used to flame-retard epoxy resin(DGEBA/DDS). And then, the impacts of DPP-POSS, DPOP-POSS, and DOPO-POSS on the pyrolysis and fire behavior of an epoxy resin were investigated under temperature programmed heating(TGA-FTIR), forced flaming conditions(cone calorimeter) and small flame conditions(LOI and UL-94). The flame-retardant performance and mechanisms of DPP-POSS, DPOP-POSS, and DOPO-POSS were assessed and discussed in detail by TGA-FTIR, XPS, and FTIR. The main flame retardant activity of DPP-POSS, DPOP-POSS,and DOPO-POSS are the especially strong condensed phase activity through charring and intumescence due to the synergistic between phosphorus and silicon in these three POSSs.DPP-POSS, DPOP-POSS, and DOPO-POSS have combined gaseous phase and condensed phase flame retardant activity. The gaseous phase activity occurred are caused by the released phosphorus volatiles. Whereas the main flame retardant activity of DPP-POSS, DPOP-POSS, and DOPO-POSS are the especially strong condensed phase activity through charring and intumescence due to the synergistic between phosphorus and silicon in these three POSSs. Phosphorus containing POSS with perfect T8 caged structures showed a highly flame-retardant efficiency for epoxy resin in very low phosphorus elementcontent, and may work for a greater variety of polymeric systems as a new class of flame retardant.The synthesis of cyclic ladder-like polyphenylsilsesquioxane(CL-PPSQ) was optimized,the 50 L pilot-plant amplification was realized. The product of the system still has the ladder-like structure of high stereoregularity, possessing of highly thermal stability. At the same time, oligomeric polyphenylsilsesquioxane(pre-PSQ) was extracted from the reaction system that the hydrolysis and condensation of phenyl trichlorosilane(PhSi Cl3) leaded to the ladder-like polyphenylsilsesquioxane(L-PPSQ). Then, pre-PSQ was used to flame-retard PC. The reasult shows pre-PSQ has good flame-retardancy to PC. Besides, by the adjustment of adding quantity, pre-PSQ can have the same flame-retardant effect as the CL-PPSQ, saying that 8wt% pre-PSQ and 6wt% L-PPSQ can have similar flame retardant effects on PC.