The Flame Retardant Based Of LDHs And Its Application In Polypropylene

In this dissertation,MgAl-LDHs were prepared by coprecipitation method.The effects of some flame retardants,such as,MgAl-LDHs,MgAl-LDHs/PPAP(piperazine pyrophosphate)and MgAl-LDHs/PPAP/AHP(aluminum hypophosphite)and MgAl-LDHs/IFR(APP:PER=3:1)with different addition on the mechanical properties and flame retardancy of PP composites were investigated by experiments.The mechanism of action of different flame retardants on the combustion behavior of PP composites were preliminarily discussed.The main research work and conclusions are as follows:(1)MgAl-CO₃^2--LDHs with good crystal form and regular inter-layer were prepared by coprecipitation method.(2)With the increase of MgAl-LDHs content,the LOI of MgAl-LDHs/PP composite increased while the mechanical properties decreased;when the MgAl-LDHs content was50%,the LOI of composite was 23.4%,and the tensile strength,flexural strength,impact strength and tensile strain at break of composite decreased by 40.7%,17.1%,56.9%and59.4%,respectively.At the same time,the ignition time(TTI)of the composites increased,the heat release rate(HRR)decreased significantly,and the total heat release(THR),smoke release rate(RSR)and CO release(COP)decreased significantly.(3)When the ratio of MgAl-LDHs to PPAP in flame retardant MgAl-LDHs/PPAP was3:2,the PP composite can meet the requirement of V-1 in UL-94 combustion test which has the LOI value of 25.8%,and the ratio of carbon residue was 30.31%,Pk-HRR reduced by 86.5%,THR reduced by 15.7%;when the ratio of MgAl-LDHs to PPAP to AHP in flame retardant MgAl-LDHs/PPAP/AHP was 3:1:1,the PP composite can meet the requirement of V-0 in UL-94 combustion test which has the LOI value of 28.6%,the ratio of carbon residue was 32.00%,Pk-HRR and THR reduced by 87%and 18.7%,respectively.The smoke emission rate and CO emission decreased as well.(4)According to the carbon residue photos,FE-SEM images and TG analysis,the flame retardancy of MgAl-LDHs/PPAP and MgAl-LDHs/PPAP/AHP composite flame retardants can be summarized as"synergistic char forming flame retardancy mechanism",and the synergistic effect among MgAl-LDHs,PPAP and AHP can obviously promote the forming of char when combusting,thus delaying or stopping the decomposition of the PP composite.(5)As to the composite flame retardant MgAl-LDHs/IFR,when the addition ratio of MgAl-LDHs was 2%,the LOI of the composite sample can reach 32.6%,and can meet the requirement of V-0 in UL-94 combustion test,the ratio of carbon residue was 19.61%,the Pk-HRR decreases by 87.2%,the THR decreases by 15.2%,and the smoke release rate and CO release decrease obviously as well;meanwhile,different mass ratio of MgAl-LDHs to IFR had no significant effect on the mechanical properties of the PP composite.(6)According to the carbon residue photos,FE-SEM images and TG analysis,the formation of dense and continuous expanded carbon residue layer significantly improved the flame retardancy of MgAl-LDHs/IFR/PP composite.