Study On The Combustion Property Of Ni-contained Intumescent Flame Retardant Polypropylene Composites And Its Mechanics Of Flame Retardant

Polypropylene(PP)has advantages of easy processing and high corrosion resistance and so on,which makes it one of the most widely used polymer materials.However,PP is flammable,which limits its application.In this paper,we firstly reviewed and summarize a large number of literatures about the flame retardant technique of PP,especially,the intumescent flame retardant(IFR)and synergistic flame retardant.Then,with the combination of IFR and synergistic techniques,this study have carried on multiple researches and made a series of original achievements in the field of Ni contained synergist.Firstly,we prepared two nickel phosphates,VSB-5 and NiPO-NT,with special structure.By the study of the synergistic effects of VSB-5 and NiPO-NT,it turns out that these two nickel phosphates are both efficient synergist in this system.After that,this study prepared nickel phosphates VSB-1,with different particle morphology,and stuied their synergistic effect in IFR,discussing the optimization design of Ni-contained synergist.Three efficient synergists were added into a novel IFR,which contains tris(2-hydroxyethyl)isocyanurate(THEIC)as char-forming agent,to study their applicability in novel IFR system.In the last part,we creatively used the organic synthesis method to introduce the synergistic element of Ni into the structure of THEIC,preparing an integrative Ni-contained char-forming agent and studied its abilities of flame retardant and char-forming.Main research works are as follows:(1)The nickel phosphate of VSB-5,which contain the pore structure of 24 NiO6 octahedron,was prepared by hydrothermal synthesis.Then,its synergistic effect in intumescent flame retardant PP composite was studied.From the results,it can be found that VSB-5 could enhance the flame retardant of composites efficiently:when the content of VSB-5 is 1.5wt%,the LOI value of composite is the highest of 32.5,reaching the V-0 rate in UL-94 test.Meanwhile,compared with the composite containing no synergist,the pHRR of composite reduced from 374.7 kW m-2 to 340.5 kW m-2,the THR value also reduced.The thermogravimetic analysis showed that the addition of VSB-5 increases the thermal stability of composites.SEM is used to characterize the morphology of the char layer after burning,its results shows that VSB-5 could enhance the consistency of char.(2)The nickel phosphate of NiPO-NT,which contains the nanotube structure of Ni,was prepared by hydrothermal synthesis.Then,its synergistic effect in intumescent flame retardant PP composite was studied.The results showed that NiPO-NT could enhance the flame retardant of composites.When the content of NiPO-NT is 0.3wt%,the LOI of composite is the highest of 33.9.And,the pHRR of composite reduced from 374.7 kW m-2 to 340.5 kW m-2,showing efficient synergistic effect.Meanwhile,the addition of NiPO-NT was proved that could improve the thermal stabilith of the composite and enhance the compactness of the char layer.(3)Through regulating the reaction conditions,such as reactant ratio,pH value,reaction time and surfactant,nickel phosphates VSB-1,which contain the pore structure of 24 polyhedra and 12 P-OH group in each window of the channels,with different morphology were synthesized.Between them,the tipical morphology of mushroom and needle-like were chosen to added into intumescent flame retardant PP composite,as synergists.It turns out that VSB-1 with two morphologies could both effectively enhance the flame retardant of composites.The needle-like morphology of VSB-1,rather than mushroom morphology,shows better synergistic effect.The results of thermal expansion shows that needle-like VSB-1 could better promote the char-forming process of IFR.The factor of morphology plays an important role in the synergistic effect:when the synergist has the lower dimension of particial and higher specific surface area,it shows better consistency in IFR systm,which may lead to more efficient synergistic effect.(4)VSB-5,NiPO-NT and VSB-1 were added into novel intumescent flame retardant composite as synergist,respectively,and their synergistic effect and mechanism were studied.From the results of LOI,to some degree,all three synergist show synergistic effects in this IFR system.Between them,NiPO-NT shows better flame retardance with relatively lower content.The SEM results shows that composite with higher flame retardancy could generate char layer with higher compactness.XPS results shows that the Ni-contained synergists could reinforce the cross-linked effect of IFR.(5)A novel Ni contained char-foming agent,TTPN,was synthesized using organic synthesis method.Conbining TTPN with OS-MCAPP(as acid source),we made novel PP/IFR composite.From the results of multiple testing methods,TTPN couldsignificantly improve the LOI value,decrease the heat and smoke release.Besides,TTPN could efficiently suppress the release of CO2 and CO.The TG-IR and XPS results prove that it is the Ni inTTPN that improve the thermal stability and cross-linked effect of composite.