Preparation Of Novel Encapsulated Red Phosphorus And Its Flame Retardant Performance In Polymer Materials

Red phosphorus(RP)is an important halogen-free flame retardant.It has many advantages such as low smoke,low toxicity,low price and high flame retardant efficiency which make it one of the research hotspots in flame retardant area.Nevertheless,RP also has some disadvantages including high moisture absorption and reddish brown color which limit its application in polymer materials.As a result,some surface treatments were taken to overcome these disadvantages of RP when used as a flame retardant.The most common surface treatment method for RP is encapsulation.But the existing encapsulated red phosphorus also has many problems such as complex preparation process,low phosphorus content,no positive synergistic effect between RP and coating materials and so on.All the above problems lead to the low flame retardant efficiency and high cost of encapsulated red phosphorus flame retardant.In this thesis,aluminum phosphate(AHP)with high phosphorus content was chosen as the coating materials to prepare a novel encapsulated red phosphorus(ERP).Applying these ERPs to glass fiber reinforced nylon 66(GFPA66),glass fiber reinforced poly(butylene terephthalate)(GFPBT),polypropylene(PP),and the flame retardancy and flame retardant mechanism of these three polymer materials were studied by comparing with the simple mixture of RP and AHP(MIXRP).The main contents are as follows:1)By depositing AHP on the surface of red phosphorus particle by chemical precipitation,we obtained novel encapsulated red phosphorus ERPs with different AHP content.The feasibility of this coating method was confirmed by FTIR and SEM characterization.The AHP content in ERPs was measured by ICP-OES characterization.The coating rate of ERPs was determined by XPS characterization.Comparing with MIXRPs,we studied moisture absorption,color and thermal stability of ERPs by moisture absorption test,color comparison and TGA characterization.The results showed that AHP was successfully coated on the surface of red phosphorus.And with the increase of AHP content,the moisture absorption rate of ERP presents a continuous decline,the coating rate of ERP presents a continuous increase.Besides,there is obvious interaction between RP and AHP.These interaction is stronger inERPs due to the larger contact area between RP and AHP compared to MIXRPs.The specific performances of these interaction are that: 1.AHP coating treatment can promote the depolymerization and volatilization of RP under nitrogen atmosphere.2.AHP coating treatment makes more RP oxidized and retained in the condensed phase under air atmosphere.2)After applying ERPs and MIXRPs to GFPA66,we studied the flame retardancy and flame retardant mechanism of ERPs in GFPA66 by comparing with MIXRPs through LOI,UL-94,TGA,ICP,infrared thermal imaging and SEM characterization.The results showed that there is a synergistic effect of P-P between RP and AHP.The flame retardant effect of ERPs in GFPA66 is better than that of MIXRPs.7.5 wt% ERP4 can make GAP66 pass V-0 rating compared to the V-1 rating of MIXRP4 flame retardant one,and the difference between their LOI value is as high as 1.1.In addition,it was found that ERP4 exerts more gaseous phase action and promotes GFPA66 to form a continuous,smooth and compact char protective layer compared to MIXRP4.3)After applying ERPs and MIXRPs to GFPBT,we studied the flame retardancy and flame retardant mechanism of ERPs in GFPBT by comparing with MIXRPs through LOI,UL-94,TGA,ICP,infrared thermal imaging and SEM characterization.The results are similar to GFPA66,and it also showed that there is a synergistic effect of P-P between RP and AHP.The flame retardant effect of ERPs in GFPBT is better than that of MIXRPs.15wt% ERP3 can make GAPBT pass V-0 rating compared to the V-1 rating of MIXRP3 flame retardant one.In addition,it was found that ERP3 exerts more gaseous phase action and promotes GFPBT to form a continuous,smooth and compact char protective layer compared to MIXRP3.4)After applying ERPs and MIXRPs to PP,we studied the flame retardancy and flame retardant mechanism of ERPs in PP by comparing with MIXRPs through LOI,UL-94,TGA,ICP,infrared thermal imaging and SEM characterization.The results are different from GFPA66 and GFPBT.It showed that the flame retardant effect of ERPs in GFPBT is worse than that of MIXRPs.When the amount of flame retardant is 5%,PP-ERP2 can’t achieve any UL-94 rating,but PP-MIXRP2 can pass the V-2rating.Besides,it was found that in PP matrix MIXRP3 exerts more gaseous phaseaction compared to ERP3 which makes it present a better flame retardancy in PP.