Design,Construction And Synergistic Flame Retardant Mechanism Of Functionalized Alkylphosphinates

Aluminum dicyclohexenyl hypophosphite(ADCP),magnesium dicyclohexenyl hypophosphite(MDCP)andzinc dicyclohexenyl hypophosphite(ZDCP)are synthesized.Sodium dicyclohexylphosphinate was synthesized by using sodium hypophosphite and cyclohexene under normal pressure.The solution of the sodium dicyclohexylphosphinate obtained by the reaction was adjusted to a pH to obtain an aqueous solution of sodium dicyclohexene alkylphosphinate under basic conditions.Then,a certain mass concentration of the aqueous metal salt solution was added dropwise thereto under basic conditions,and finally a solid precipitate was obtained by neutralizing with acid.Molecular structures were characterized by FT-IR and 1H NMR.Product thermostability was analyzed via thermogravimetric analyzer.Then the effects of reaction temperature,reaction time and metal salt concentration on the metathesis reaction were explored.The optimum reaction conditions for ADCP are: reaction temperature70°C,reaction time 4 h,water consumption 30 mL,the yield was stabilized at 83%,and its average particle size is 71 ?m.The optimum reaction conditions for MDCP were as follows:reaction temperature was 70°C,reaction time was 4h,and water consumption was 40 mL,the yield was stabilized at 57%,and its average particle size is 78 ?m.The optimum reaction conditions for ZDCP are: reaction temperature 70°C,reaction time 4 h,water consumption 40 mL,the yield is stable at 66%,and its average particle size is 75 ?m.Through thermogravimetric analysis,it was found that ADCP and ZDCP have good thermal stability.MDCP is generally stable in thermal stability.The synthesized ADCP,MDCP and ZDCP were added to PA66 to study the flame retardancy of the meterials and the dicyclohexylphosphinate The effect of mechanical properties of PA66.Experimental data show that the flame retardant effect of ADCP is the best.When the amount of ADCP added was 15%,UL-94 reached V-0 and the mechanical properties were good.The nano-silica and ADCP were compounded to study the synergistic flame retardant effect between ADCP and nano-silica,through limiting oxygen index(LOI)and horizontal vertical burning experiments(UL-94)to confirm the burning grade of the composite.After adding 15%ADCP,the LOI of PA66 increased to 32%,and the combustion level reached V-0 of UL-94.The addition amount was 12%,the amount of nano silica added was 5% by weight,the LOI of PA66 composite was 35.2%,and UL-94 was V-0.Cone calorimeter experiments show that ADCP flame retardant PA66 with nano-silica is compared with ADCP flame retardant system without nano-silica.The heat release rate and total heat release of the PA66 composites decreased significantly,and the time to reach the peak heat release rate(PKHRR)was also significantly prolonged.By observing the SEM image of the residue after the cone calorimetry experiment by scanning electron microscopy.The ADCP flame retardant system with nano-silica added has a more compact and dense carbon layer structure than the PA66/ADCP composite without the addition of nano-silica,effectively preventing heat transfer and flammable gas from entering the flame zone.Thereby achieving a flame retardant effect.