Preparation And Properties Investigation Of Rigid Polyurethane Foam Insulation Material Based On Iron Tailings

Iron tailings（ITS）is the waste after ore dressing.With the continuous development of mining and iron and steel industry,ITS output is also rising.In 2018,the output of ITS in China was about 476 million tons,accounting for 39.31%of the total output of tailings.In 2019,the output was 520 million tons,accounting for40.9%of the total output.Although it has been successfully used in building materials,road construction,soil improvement and other fields,there are still a large number of ITS can not be effectively used and accumulated due to technical limitations,which not only occupy a large number of land resources,but also cause great damage to the surrounding ecological environment.Therefore,how to improve the comprehensive utilization rate of ITS has become a hot issue.The continuous rise of building energy consumption has promoted the development of building insulation materials.Rigid polyurethane foam（RPUF）is widely used because of its excellent insulation effect and light weight,but it is easy to be ignited and releases a large number of toxic smoke in the combustion process,laying a huge potential safety hazard for its use.In recent years,many fires related to RPUF have caused huge economic losses,which has also attracted people’s attention to the flame retardant modification of RPUF.Based on this,this paper organically combined the resource utilization of ITS with the flame retardant modification of RPUF to improve the fire safety of RPUF while improving the utilization rate of ITS.In this paper,ITS,ITS and traditional flame retardants,and ITS derivatives were introduced into RPUF,and a series of flame retardants RPUF（FR-RPUF）were prepared by one-step full-water foaming.The flame retardancy,thermal stability,combustion performance,gas phase products and the morphology of char residue were investigated by limiting oxygen index（LOI）,thermogravimetric（TG）,cone calorimetric（CCT）,thermogravimetric-infrared spectrometry（TG-FTIR）,Raman and scanning electron microscopy（SEM）.The research results of this paper are as follows:（1）A series of RPUF/ITS composites were prepared by adding ITS as flame retardant filler into RPUF,and the effects of addition amount on the properties of RPUF/ITS composites were investigated.Flame retardant test showed that ITS inhibited the melt dripping of RPUF,and had a certain flame retardant effect.TG confirmed that ITS improved the thermal stability of the composites.The T_-5%(except T_-5%of RPUF-2),T_-50%,T_max1,T_max2and char residue rates at 700^oC rates at700 ^oC of the composites were higher than those of the pure samples,and the char residue rate of RPUF-5 was as high as 41.03 wt%.CCT indicated that the peak heat release rate（PHRR）of RPUF/ITS composite was negatively correlated with content,and the PHRR of RPUF-6 was 22.75%lower than that of the pure sample.The smoke factor（SF）,fire growth index（FGI）and fire performance index（FPI）indicated that the addition of ITS improved the fire safety of the composites.TG-FTIR showed that ITS reduced the total amount of gaseous products of the composites,reduced the release intensity of CO₂,isocyanates,CO,aromatic compounds and esters,and delayed their release time.SEM and Raman tests showed that ITS was not conducive to carbonization of RPUF,and most of ITS were still distributed on the surface of carbon residue in granular form.（2）ITS was combined with traditional flame retardant ammonium polyphosphate（APP）to flame retardant RPUF.SEM showed that the addition of ITS/APP could destroy the cell structure of RPUF.TG indicated that ITS/APP improved the thermal stability of the composites.The composites showed a degradation stage.char residue rates at 700^oC,T_-5wt%and T_max1were higher than those of the pure samples,and the char residue rates of RPUF-3 and RPUF-4 were143.98%and 168.07%higher than those of the pure samples.CCT showed that ITS/APP reduced the thermal hazard and non-thermal hazard of composites,and the PHRR,total heat release（THR）,total smoke production（TSP）and total smoke release（TSR）of RPUF-4 presented a decrease of 29.08%,19.21%,14.62%and10.73%compared with pure RPUF,respectively.TG-FTIR confirmed that ITS/APP reduced the release intensity of hydrocarbons,isocyanate compounds,aromatic compounds,esters and NH₃.SEM and Raman tests showed that the expanded carbon layer appeared in RPUF-4,and the thickness and graphitization degree of the carbon layer were improved compared with the pure sample.（3）A flame retardant synergistic system composed of ITS and traditional flame retardant aluminum hypophosphite（AHP）was used for flame retardant RPUF.SEM showed that ITS/AHP reduced the porosity and uniformity of the composites,and the composites were damaged to varying degrees.TG indicated that ITS/AHP made the T_-5wt%,T_max1and char residue rates at 700^oC of the composites higher than that of the pure sample and the composites with ITS and AHP alone,and the degradation process became a stage.CCT showed that the addition of ITS/AHP made the THR,TSP,TSR and SF of RPUF-4 lower than that of RPUF-6 with AHP alone.TG-FTIR indicated that the release curves of hydrocarbons,aromatic compounds and esters of RPUF-4 were lower than those of pure sample,and the release peaks of CO,CO₂and isocyanate compounds were lower than those of RPUF-6.SEM and Raman tests showed that ITS/AHP promoted the formation of dense graphitized carbon layer.（4）Modified iron tailings（MITS）were prepared by KH550 surface modification of ITS and used as synergistic agent with expandable graphite（EG）to flame retardant RPUF.SEM showed that MITS/EG destroyed the cell structure of the composites.LOI showed that MITS and EG had obvious synergistic effect,the LOI of the composites was 23.3 vol%～26.6 vol%and all passed UL-94 V-0.TG confirmed that the T_-50wt%,T_max1,T_max2and char residue rates at 700^oC of RPUF-4was higher than that of the pure RPUF,and the char residue rates at 700°C was82.82%higher than RPUF.CCT indicated that MITS/EG reduced the fire hazard of the composites.Compared with those of RPUF,the PHRR,SPR and TSR of RPUF-4 were decreased by 61.55%,66.02%and 77.99%respectively.TG-FTIR showed that MITS/EG reduced the total gas product release intensity of the composites.SEM and Raman tests showed that carbon layer of RPUF-4 showed wormlike structure and the degree of graphitization was higher than that of pure sample.（5）Zinc-containing mesoporous silicate（MAO-Zn）was prepared from ITS and compounded with APP to flame retardant RPUF.TG showed that MAO-Zn and MAO-Zn/APP improved the high temperature stability of the composites,and the T_{-5 wt%},T_maxand char residue rates at 700^oC of RPUF-2 and RPUF-4 were higher than those of the pure samples.CCT indicated that MAO-Zn and MAO-Zn/APP provided the safety fire of the composites.The THR and TSR of RPUF-2 presented a decrease of 21.31%and 39.61%compared with pure RPUF,and The PHRR and THR of RPUF-4 presented a decrease of 29.29%and 38.45%compared with pure RPUF,respectively.TG-FTIR showed that the G-S curve,isocyanates,CO,aromatic compounds and ester release curves of RPUF-4 were lower than those of RPUF/APP30.