Controllable Preparation And Flame Retardant/Smoke Suppression Properties Of Cerium And Zinc-Based Inorganic Nano Flame Retardants

PVC（polyvinyl chloride）is one of the five general-purpose plastics and is widely used in many fields due to its excellent performance.However,PVC will burn violently and release a large amount of heat and smoke when heated.Since a large amount of plasticizer needs to be added during processing,the flammability and smoke release of flexible PVC are greatly increased.Therefore,flame-retardant and smoke-suppressing modification of flexible PVC composite materials can improve their safety during use,greatly expand the application fields of PVC,and meet the practical application of PVC.Inorganic flame retardant smoke suppressants often need to be added in large quantities of polymers by physical mixing method to exert better flame retardant smoke suppression properties,but due to the poor compatibility between inorganic materials and polymer matrix,they are unevenly dispersed in the polymer,and the improvement of flame retardant smoke suppression performance is limited,and the deterioration of the mechanical properties of the polymer also leads to the deterioration of the mechanical properties of the polymer,which seriously restricts the use scenarios of inorganic flame retardant smoke suppressants.This paper modifies flexible PVC around two flame retardant smoke suppressants,improves the flame retardant and smoke suppression performance of flexible PVC,and also avoids the problem of deterioration of physical properties of materials due to the addition of inorganic additives,and expands the application scope of flexible PVC.The research content of this paper mainly includes the following four aspects:（1）In view of the huge amount of smoke produced by PVC during static combustion,PVC/Zn₃B₆O₁₂composite material was prepared by in-situ composite method with the help of the high-efficiency smoke suppression performance of zinc compounds.In static combustion test,the maximum smoke density of the material decreased by 229,which was reduced by68.29%.In dynamic combustion test,THR,SPR,and TSP of PVC/Zn₃B₆O₁₂composite material decreased by 33.45%,17.85%,and 48.62%,respectively,showing good smoke suppression performance.The UL-94（3mm）vertical combustion test grade of the material did not change,LOI decreased to 20.2%,PHRR increased by 35.32%,but THR decreased,indicating that Zn₃B₆O₁₂can accelerate the rapid decomposition of flexible PVC in a short time,shorten the combustion time,and both work together to reduce the total heat release of composite materials.（2）Based on the reaction between the oxides and rare earth ions produced during the thermal decomposition of rare earth compounds and free radicals,free radical precursors,and cracking products in the combustion products,the combustion process can be blocked.PVC/Ce₂O（CO₃）₂composite material was prepared by quasi in-situ composite method.The material has good flame retardancy and smoke suppression performance:compared with pure PVC,the LOI value of PVC/Ce composite material increased from24.6%to 36.9%,and UL-94（3mm）vertical combustion grade increased from V-2 grade to V-0 grade.In dynamic combustion test,PHRR,THR,SPR,and TSP were reduced from 390.21 k W/m²,47.63 MJ/m²,0.27 m²/s,and 23.65 m²to 211.79 k W/m²,27.01 MJ/m²,0.19 m²/s,and 17.64 m²respectively.In static combustion test,the maximum smoke density of PVC/Ce₂O（CO₃）₂composite material decreased from 725 to 528.It shows that Ce₂O（CO₃）₂has good flame retardancy for flexible PVC.（3）The mechanical properties of flexible PVC composite materials prepared by quasi in-situ composite method are better than those prepared by physical mixing method.The tensile strength and elongation at break of PVC/Ce prepared by in-situ composite method increased from 11.82 Mpa、96.32%to 21.00 Mpa、165.85%,respectively,and those of PVC/Zn₃B₆O₁₂composite material increased to 22.36 Mpa and 177.75%.With the increase of flame retardant and smoke suppressant addition amount,the mechanical properties of composite materials prepared by mechanical mixing method decreased to a certain extent,which also reflects another advantage of quasi in-situ composite method for preparing PVC composite materials.（4）Ce₂O（CO₃）₂and Zn₃B₆O₁₂were compounded with other general plastics（PE,PS）by in-situ composite method to obtain composite materials with good flame retardant smoke suppression properties,which proved that the use of this method and flame retardant smoke suppressant had universal applicability to improve the flame retardant smoke suppression performance of general plastics.