Preparation of Polyurea Elastomer with Flame Retardant,Insulation and Thermal Conductivity Properties

By using 6,6-((sulfonylbis (4,1-phenylene)) bis (azanediyl)) bis (thiophen-2-ylm-ethylene)) bis (6H-di-benzo[c,e][1,2]oxaphosphinine 6-oxide (DOPO-N) as phosphorus-nitrogen flame retardant,the polyurea (PUA) with flame retardant properties (PUA/DOPO-N) was prepared.In addition,organically modified montmorillonite (OMMT) and magnesium hydroxide (MH) were used as co-effectors respectively,and the flame retardant PUA (PUA/DOPO-N/OMMT and PUA/ DOPO-N/MH) were also prepared.Thermal properties,flame retardant properties,flame retardant mechanism and mechanical properties of PUA/DOPO-N,PUA/ DOPO-N/OMMT and PUA/DOPO-N/MH were investigated by thermogravimetric (TG) analysis,limiting oxygen index (LOI),UL 94,cone calorimeter test,scanning electron microscopy (SEM),and tensile test.The results show that the LOI value of PUA/20%DOPO-N,PUA/18%DOPO-N/2%OMMT and PUA/15%DOPO-N/5%MH are 27.1%,27.7%,and 28.3%,respectively,and UL 94 V-0 rating is attained.Compared with PUA,the peak heat release rate (pk-HRR),total heat release (THR) and average effective heat combustion (av-EHC) of PUA/20%DOPO-N,PUA/18% DOPO-N/2%OMMT and PUA/15%DOPO-N/5%MH decrease significantly.SEM results indicate that the residual chars of PUA/20%DOPO-N,PUA/ 18%DOPO-N /2%OMMT and PUA/15% DOPO-N/5%MH are completer and more compact.The complex of DOPO-N/OMMT and DOPO-N/MH have synergistic flame retardancy.The mechanical properties of PUA can be improved by the addition of DOPO-N,DOPO-N/OMMT and DOPO-N/MH,respectively.The insulation performance test shows that the volume resistivity of PUA/20%DOPO-N is 6.25×1016Ω.cm.Furthermore,by using modified boron nitride (MBN) as heat dissipating material,the complex of PUA/MBN was prepared,and the thermal conductivity of PUA/MBN was investigated.The thermal conductivity of PUA/8%MBN complex coating at room temperature is 0.166 W/(M·K),which is a 163% improvement over pure PUA.