Construction Of Functionalized Hollow Microspheres And Its Flame Retardant Mechanism For TPU

In this paper,a series of hollow spheres including phenolic resin hollow spheres(PHM),carbonized phenolic resin hollow spheres(CPHM),carbonized acidified phenolic resin hollow spheres(CAPHM),ammonium molybdate coated acidified phenolic resin hollow spheres(AMPHM),molybdenum oxide modified phenolic resin hollow spheres(MOPHM)and sodium silicate coated phenolic resin hollow spheres(SSMPHM)were synthesized respectively.And flame retardant TPU composites were prepared based on hollow spheres.The flame retardant and thermal decomposition properties of TPU composites were studied by means of cone calorimeter(CCT),micro calorimeter(MCC),thermogravimetry(TG),thermogravimetry infrared(TG-IR),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS)and X-ray photoelectron spectroscopy(XPS).1.Flame retardant TPU using PHM.The results showed that PHM could effectively reduce the heat and smoke hazards of TPU.In CCT,the peak value of heat release rate(pHRR),smoke release rate(pSPR)and CO release rate of TPU/P-4(4 wt%PHM)were reduced by 61.6%,57.9%and 86.2%compared with those of pure TPU.After CCT,the surface of char residues of TPU/P-4 was smooth and continuous,with uniform spherical protrusions.This was because PHM migrated to the surface of char residues to form a hollow accumulation layer during the melting process,which effectively prevented the transfering of heat and volatile pyrolysis combustible products,thus reducing the heat and smoke release from TPU composites,and significantly reducing the toxicity of fire smoke.2.Flame retardant TPU using CPHM.The results showed that CPHM had better flame retardant effect on TPU composites than PHM and CAPHM.In CCT,compared with pure TPU,TPU/P-4 and TPU/CAP-4(4.0wt%CAPHM),the pHRR of TPU/CP-4(4.0wt%CPHM)reduced by 64.4%,7.4%and 24.4%,respectively.And the pSPR reduced by 74.8%,40.0%and 54.2%,respectively.CPHM could improve the compactness and graphitization degree of char residues of TPU/CP-4,effectively reduced the pyrolysis rate of the underlying material,and further reduced the heat and smoke hazards of the material.3.Flame retardant TPU using MOPHM.The results showed that MOPHM had better flame retardant and smoke suppression effect on TPU composites than CAPHM and AMPHM.In CCT,compared with TPU,TPU/CAP-4 and TPU/AMP-4(4.0wt%AMPHM),the pHRR of TPU/MOP-4(4.0wt%MOPHM)reduced by 63.4%,22.3%and38.2%,respectively.And the pSPR reduced by 53.3%,13.6%and 22.7%,respectively.MOPHM could form a char residue containing layered molybdenum compounds in the combustion process,improve the compactness of the char residues,effectively reduce the heat release and smoke release of the material.4.Flame retardant TPU using SSMPHM.The results showed that SSMPHM had better flame retardant effect on TPU composites than PHM.In CCT,compared with pure TPU and TPU/P-4,the pHRR of TPU/SSM-4(4wt%SSMPHM)reduced by 66.0%and11.6%,respectively.SSMPHM could promote the formation of char residues containing Si O₂ on the surface of TPU composite and effectively prevent the heat transfer..5.Compared with pure TPU,the pHRR of TPU/P-4,TPU/CP-4,TPU/MOP-4 and TPU/SSM-4 reduced by 61.6%,64.6%,63.4%and 66.0%,the pSPR reduced by 57.9%,74.8%,53.3%and 57.0%,and the peak of CO release rate reduced by 86.2%,86.2%,72.4%and 67.0%,respectively.TPU/SSM-4 had significant effect in reducing heat release,TPU/CP-4 had significant effect in reducing smoke release,and TPU/P-4 and TPU/CP-4 had significant effect in reducing CO release.