Preparation Of Metal Ion Modified Bio-based Flame Retardants And Research On Flame Retardancy And Smoke Suppression In Polyurethane

In recent years,there are numerous types of flame retardants.Among these, metal compounds have attracted extensive attention from researchers due to their good smoke suppression performance.However,a single component as a flame retardant needs to be added in large quantities to be able to show significant effects,severe damage to mechanical properties.Thus,it is usually used as a synergistic agent.Additionally,with the consumption of non-renewable resources,the development of bio-based flame retardants has received widespread attention.Inspired by the smoke suppression properties of metal compounds,herein this paper has reported the preparation of bio-based flame retardants modified by copper,nickel and manganese ions,which were applied to the polyurethane（PU）with the disadvantages of being extremely flammable and smoky.The main research contents are as follows:（1）We have prepared a series of bio-based flame retardants with starch（ST）, soluble starch（SS）and meglumine（MN）as carbon sources,phytic acid（PA）as acid source,and melamine（MA）as nitrogen source.Firstly,phytic acid melamine salt（MP）was synthesized by the neutralization reaction of PA and MA.Then,the residual phosphoric acid group of MP was reacted with the hydroxyl group in SS and the amine group in MN respectively for the preparation of two types of"triple-in-one"bio-based intumescent flame retardant melamine phytate-soluble starch lipids（MPS）and melamine phytate meglumine salt（MPN）.In order to compare the differences in the flame retardancy of the different combinations of the three sources and the differences in the flame retardancy of the different carbon source,a mixed flame retardant PST+MA,which is a compound of phytate starch ester（PST）and MA,was designed and synthesized.The structures were characterized by FT-IR and XRD,the thermal properties were tested by TGA/DTG,and the thermal degradation process of the flame retardant was analyzed.（2）In the second chapter,on the basis of the three bio-based flame retardants PST+MA,MPS and MPN that have been prepared,nine metal-modified bio-based flame retardants PST-M+MA,MPS-M and MPN-M（M=Cu,Mn,Ni）were obtained through the strong complexing ability of PA to make these flame retardants reacted with copper acetate monohydrate,manganese acetate tetrahydrate and nickel acetate tetrahydrate respectively.Then,we also explored the effects of metals on flame retardancy,smoke suppression and thermal degradation.The structure and composition of the target flame retardants were characterized by XRD and XPS,and the thermal degradation behavior of the flame retardants was characterized by TGA/DTG.（3）In order to explore the structure-activity relationship of flame retardants,polyether polyol（4110）and isocyanate（PM-200）were used as the main raw materials,and a variety of additives such as catalyst,crosslinking agent and foaming agent were added to prepare flame retardants PU foam by all-water foaming method.The results of LOI and UL-94 experiments showed that the flame retardancy of metal modified system is slightly inferior to that of unmodified system at the same dosage,and the performance of small molecule carbon source is better than that of large molecule carbon source.The smoke density test showed that the smoke density grade and the highest smoke density value of each series decreased first and then rose after the addition of flame retardant.The smoke suppression effect of metal ion modified flame retardant showed an increasing trend with the increase of metal content.PST-Ni+MA/PU,MPS-Ni/PU and MPN-Ni/PU were selected for TGA/DTG,Cone calorimetry（Cone）and mechanical properties.TGA/DTG results showed that the T_50%of the flame retardant system was delayed,and the residue was increased at 800℃.The effect of metal ions can be summarized as follows:the low temperature region before about 300℃ promotes the degradation of PU,and the high temperature region after about 400℃ slows down the degradation rate of PU,resulting in the increase of carbon residue.Cone tests showed that:When the dosage was 20%,PHRR of PST-Ni+MA/PU,MPS-Ni/PU and MPN-Ni/PU decreased by 29.3%,42.1%and 35.2%,and total heat release（THR）decreased by 15.1%,28.0%and 18.3%,respectively,compared with blank PU.Total smoke production（TSP）,smoke production rate（SPR）,total smoke release（TSR）all decreased to different degrees,and 20wt%MPS-Ni/PU showed outstanding smoke suppression performance,while TSP and TSR decreased by 52.9%and 54.0%,respectively.The mechanical properties test results showed that the tensile and bending properties of PU were reduced by flame retardants,and the mechanical properties of PU modified by metal ions decreased more seriously than those of the non-modified system.In the research scope of this paper,considering the flame retardancy,smoke suppression and mechanical properties,the author considers that MPS-Ni is the most suitable flame retardancy for PU.