Preparation And Combustion Performance Of Bio-based Flame Retardant Epoxy Resin

Epoxy resin(EP)is widely used in daily life because of its excellent mechanical properties,electrical insulation properties and adhesion properties.The limiting oxygen index(LOI)of Pure EP is only 20%,and after the EP is ignited,it will release a large amount of heat,carbon monoxide,smoke and carbon dioxide,etc.,which will cause great fire safety hazards to the use of EP in daily production and life.But,adding flame retardants to EP can effectively reduce the heat,smoke,carbon monoxide and carbon dioxide produced after EP combustion.The use of bio-based flame retardants can not only increase the fire resistance of EP,but also increase the efficiency of the use of biological materials in nature,which meets the needs of sustainable development.In this paper,four kinds of EP composites were prepared:(1)EP/IFR(OP)composites were prepared by adding orange peel powder(OP)as a carbon source in intumescent flame retardant(IFR)to EP;(2)EP/SA@(MA/OPC)composites were prepared by adding a flame retardant(SA@(MA/OPC))microcapsules prepared by orange peel charcoal and melamine encapsulated with sodium alginate to EP;(3)EP/TUDP composites were prepared by adding TUDP synthesized from tartaric acid,urea and 9,10-dihy-dro-9-oxa-10-phosphaphenanthrene 10-oxide(DOPO)to EP;(4)EP/IFR/TUDP composites were prepared by adding the bio-based flame retardant TUDP and IFR to EP.In addition,the combustion performances and mechanical properties of these four kinds of EP composites were studied by LOI,thermogravimetric(TG),UL-94 vertical burning test,cone calorimeter test,mechanical test.The structure of residual char after combustion was characterized by scanning electron microscopy(SEM),the residual char surface of the burned EP composite was elementally mapped by scanning electron microscopy-energy dispersive x-ray spectroscopy(SEM-EDX),and the distribution of C,O,N,P elements on the residual char surface was characterized.The main research results are as follows:(1)EP/IFR(OP)fireproof coatings were prepared by adding orange peel powder,ammonium polyphosphate and melamine to EP.The results showed that compared with Pure EP,the LOI of EP/IFR(OP)was improved,and the UL-94 test reached V-0 rating.The peak heat release rate(PHRR)of EP/IFR(OP4)decreased by 84.4% compared to Pure EP.Total smoke production(TSP)of EP/IFR(OP1)decreased by 55.8% compared to Pure EP without any additives.SEM results showed that EP composites with OP as carbon source could be better charring during combustion.This type of char layer produced in the combustion process of EP composites through the char layer by layer isolation of heat more difficult to spread into the matrix,effectively isolated the heat source.(2)EP/SA@(MA/OPC)fireproof coatings were prepared by adding a flame retardant(SA@(MA/OPC))microcapsules prepared by orange peel charcoal and melamine encapsulated with sodium alginate to EP.The test results indicated that the initial thermal decomposition rate of EP/SA@(MA/OPC)3 was much smaller than that of EP/(SA/MA/OPC),and the LOI of EP/SA@(MA/OPC)3 and EP/SA@(MA/OPC)4increased by 6.5% and 5.5% respectively compared with Pure EP,both reaching UL-94V-0 rating without melt dripping phenomenon.In the cone calorimeter test,the PHRR of EP/SA@(MA/OPC)3,EP/SA@(MA/OPC)5 decreased by 74.2%,73.2%,respectively compared with Pure EP,and the TSP of EP/SA@(MA/OPC)3 decreased by24.7%,showing good fire safety performance.(3)EP/TUDP fireproof coatings were prepared by adding TUDP synthesized from tartaric acid,urea,and 10-dihydro-9-oxa-10-phenanthrene-10-oxide(DOPO)to EP.The test results showed that the LOI of EP/TUDP13 and EP/TUDP21 increased by 1.5% and4.5% respectively compared to Pure EP,and the LOI of EP/TUDP21 increased by 1.5%,but passing the V-2 rating of the UL-94 test.In the cone calorimeter test,the PHRR of EP/TUDP13 decreased by 57.9%,and THR of EP/TUDP1 decreased by 43.5%.It indicated that TUDP can effectively improve the flame retardant performance of EP.(4)EP/IFR/TUDP fireproof coatings were prepared by adding TUDP and IFR to EP.The test results of LOI and UL-94 showed that the LOI of Pure EP was as low as20.0%,and the LOI value of EP/IFR/TUDP1.3 in EP composites with TUDP was as high as 25.5%.Pure EP’s UL-94 test failed,and EP/IFR/TUDP achieved V-0 rating without dripping.The combustion test results of cone calorimeter showed that the PHRR and THR value of EP/IFR/TUDP0.7,EP/IFR/TUDP1.3,EP/IFR/TUDP2.6 and EP/IFR/TUDP4.0 were significantly lower than that of Pure EP.It indicated that the synergistic impact between TUDP and IFR could significantly improve the flame retardant performance of EP.