Study On Synergistic Flame Retardant Epoxy Resin With Ammonium Polyphosphate/Layered Double Metal Hydroxide

Epoxy resin(EP)is a common thermosetting plastic in daily life.With its good electrical conductivity,mechanical properties and bonding properties,it is widely used in machinery manufacturing,aerospace,wind power generation,coatings,potting materials and composite materials and other fields.However,EP is very easy to burn in the air,accompanied by the release of a large amount of black smoke and toxic gases,which seriously endangers human health.The flammability of EP largely limits its application in many fields.In order to solve this problem,people have conducted research on the flame retardant technology of epoxy resin.Among them,phosphorus flame retardant is a hot spot in flame retardant EP research due to its environmental protection and no secondary hazards.Ammonium polyphosphate(APP),as an efficient inorganic phosphorus flame retardant,has the advantages of high phosphorus and nitrogen content,high thermal decomposition temperature,and low cost.However,the application of APP has the following problems:(1)When APP is applied to flame-retardant EP,it can only be used as an acid source and part of the gas source due to its flame-retardant efficiency is low;(2)The compatibility with polymers is poor due to hydrophilicity,which is serious,which is damage to the mechanical properties and processing properties of the polymer matrix.Therefore,it is necessary to add other flame retardant synergists to improve the flame-retardant efficiency and processing performance of APP in polymer materials.This article synthesizes zinc-iron layered double metal hydroxide(Zn-Fe-LDH),and the boron-modified Zn-Fe-B-LDH to compound with ammonium polyphosphate to synthesize composite flame-retardant epoxy resin.Firstly,the composite material was successfully prepared,and the flame retardant performance,combustion behavior and mechanical properties of the composite material were studied at the same time.The main results of this thesis are as follows:(1)Zn-Fe-LDH was prepared with ferric nitrate and zinc nitrate as raw materials,and its structure was characterized by a series of materials such as XRD,SEM and EDX.Then,Zn-Fe-LDH and APP were compounded and applied to epoxy resin,and the composite material(Zn-Fe-LDH+APP)/EP was successfully prepared.The flame retardant properties of composite materials are characterized by LOI and UL-94 tests.The test results show that when the addition amount of Zn-Fe-LDH and APP is 5 wt%,the LOI is 28.6%,which can pass the UL-94 V-1 level.The combustion behavior of the composite material was studied through the cone volume test,combined with the relevant data of HRR,THR,SPR,TSP and so on in the cone calorimetry,which shows that the flame retardant of(Zn-Fe-LDH+APP)has good flame retardancy and inhibition.Compared with 5APP/EP,the PHRR value of 5(Zn-Fe-LDH+APP)/EP is reduced by 11.0%,and FGR value is reduced from 9.78 to 8.61 k W/(m².s),The peak value of SPR decreased from 0.29 m².s^-1to0.20 m2.s^-1.The mechanical performance test and characterization show that the tensile strength and flexural strength of 5(Zn-Fe-LDH+APP)/EP have been significantly enhanced compared to 5APP/EP.(2)Zn-Fe-LDH was modified by boric acid,and Zn-Fe-B-LDH was successfully prepared,which was compounded with ammonium polyphosphate and applied to epoxy resin(Zn-Fe-B-LDH+APP)/EP.When the addition amount of Zn-Fe-B-LDH and APP is 5wt%,the LOI is 29.6%and UL-94 can pass the V-1 level.The cone calorimetry results show that when the addition amount of Zn-Fe-B-LDH and APP is 5 wt%,the PHRR and THR of 5(Zn-Fe-B-LDH+APP)/EP are reduced to 464.5 k W/m²and 47.2 MJ/m²,respectively.Compared with(Zn-Fe-LDH+APP)/EP,(Zn-Fe-B-LDH+APP)/EP has better heat reduction and smoke suppression efficiency.The results of mechanical properties show that,compared with(Zn-Fe-LDH+APP)/EP,the mechanical properties of(Zn-Fe-B-LDH+APP)/EP have no obvious change.