Study On Flame Retardant Thermoplastic Polyurethane Based On Modified Hollow Materials With Ionic Liquid

In this paper,two kinds of ionic liquids containing ester-bases,1-??ethoxycarbonyl?m-ethyl?-3-methylimidazoliumhexafluorophosphate?[EOOEMIm][PF₆]?and 1-??ethoxyca-rbonyl?methyl?-3-methylimidazolium tetrafluoroborate?[EOOEMIm][BF₄]?,were used to modify hollow materials?hollow glass microspheres,fly ash beads?,respectively.And four new flame retardants,HGM@[EOOEMIm][PF₆],HGM@[EOOEMIm][BF₄],FB@[EOOEMIm][PF₆],and FB@[EOOEMIm][BF₄]have been prepared,and then applied to thermoplastic polyurethane?TPU?by melt blending.Their effects on the flame retardancy and thermal stability of TPU were studied by means of cone calorimeter test?CCT?,smoke density test?SDT?,limit oxygen index?LOI?,thermogravimetric analysis?TGA?and thermogravimetric analysis/infrared spectrametry?TG-IR?,respectively.Specific studies are as follows:?1?Study on the flame retardant properties of TPU/HGM composite materials.The test results showed that HGM could significantly improve the flame retardant properties of TPU,such as 2.0 wt%HGM can make the luminous flux of TPU increased from 5%to24%,the peak heat release rate decreased by 73%,and the total smoke production reduced by 26%.During the combustion process,HGM could catalyze the decomposition of TPU and migrate to the surface of the material,improving the structure of the carbon layer and reducing the formation of combustible gases and smoke particles.?2?Study on the flame retardant properties of TPU/HGM@[EOOEMIm][PF₆].The test results showed that HGM@[EOOEMIm][PF₆]could further improve the flame retardancy of TPU on the basis of HGM.For example,0.125 wt%HGM@[EOOEMIm][PF₆]made the heat release rate reduced by 23.7%and the total smoke production decreased by 10.6%.HGM@[EOOEMIm][PF₆]could also migrate to the surface of the samples.[EOOEMIm][PF₆]had catalytic effect on Friedel-Crafts reaction,which could promote char cross-linking formation of materials when the polymer composite was heated and further improve the structure of the carbon layer and the strength and thermal stability of the carbon layer.In addition,[EOOEMIm][PF₆]contains a small amount of flame-retardant elements such as P,F.They also could improve the flame retardancy of the material.?3?Study on the flame retardant properties of TPU/HGM@[EOOEMIm][BF₄].HGM@[EOOEMIm][BF₄]could also further improve the flame retardancy of TPU on the basis of HGM.0.125 wt%HGM@[EOOEMIm][BF₄]could reduce the heat release rate by14.1%and the total smoke production by 23.0%.The carbon layer was also improved obviously.?4?Study on the flame retardant properties of TPU/FB,TPU/FB@[EOOEMIm][PF₆],TPU/FB@[EOOEMIm][BF₄].FB is hollow materials as same as HGM,but the cost is reduced exponentially.2.0 wt%FB made the heat release rate reduced by 61.4%,the total smoke volume decreased by 24.5%,and the smoke generation rate decreased by 54.0%.The flame retardant properties of TPU were significantly improved.For example,when the addition of FB@[EOOEMIm][BF₄]was 1.0 wt%,the peak value of HRR?356.3kW/m²?was lower than those of pure TPU?1172.9 kW/m²?and the sample with the same content of FB?588.8 kW/m²?,reduced by 69.6%and 39.5%,respectively.In addition,both of them could significantly increase the luminous flux of TPU,reduce the yield of smoke,improve the thermal stability of TPU,and reduce the formation of smoke particles,toxic and harmful gases.In conclusion,the hollow material modified by ionic liquid has a good application prospect in improving the flame retardancy and thermal degradation of TPU.