Fumctionalized Hollow Glass Microspheres And Its Flame Retardant Mechanism In Thermoplastic Polyurethane

In this paper,the hollow glass microspheres?HGM?coated with Fe₂O₃?HGM@Fe₂O₃?,TiO₂?HGM@TiO₂?,Ammonium molybdate?HGM@AMP?,Graphite oxide?HGM@GO?was synthesized and characterized by scanning electron microscopy?SEM?and X-ray photoemission spectroscopy?XPS?,respectively.Then,the flame retardant and smoke suppression mechanism of HGM@Fe₂O₃,HGM@TiO₂,HGM@AMP and HGM@GO in thermoplastic polyurethane?TPU?composites have been investigated intensively using several methods,including cone calorimeter test?CCT?,smoke density test?SDT?,scanning electron microscopy?SEM?and thermogravimetric analysis/infrared spectrometry?TG-IR?.The specific research works are as follows:? Synthesis of HGM@Fe₂O₃ and its flame retardant mechanism in TPU: HGM@Fe₂O₃ has good flame retardant effect.Compared with TPU1-1,the PHRR value of the sample with 0.5 wt% HGM@Fe₂O₃ decreases from 1591 k W/m2 to 885 k W/m2,the TSR value of the sample decreases from 786 m2/m2 to 592 m2/m2,Thermoplastic polyurethane can be softened by heat,and then HGM@Fe₂O₃ can migrate progressively onto the surface of the sample,which can improve the stability of the char residue layer,protecting the inner matrix and reducing the amount of combustible gas and smoke-forming materials in the gas phase during combustion;Fe₂O₃ has effect on catalytic carbonation,forming a dense char residue layer,which could be act as barrier for heat from outside and smoke particulates from underlying materials.? Synthesis of HGM@TiO₂ and its flame retardant mechanism in TPU: HGM@TiO₂ has good flame retardant effect on TPU composite.Compared with TPU2-1,the PHRR value of the sample with 1.0 wt% HGM@TiO₂ decreases from 1117 k W/m2 to 405 k W/m2;the SF value of the sample decreases from 733 MW/m2 to 304 MW/m2.It can be explained that TiO₂ has excellent charactics of infrared radiation reflection,making the decomposition of material relaxed.The migration of TiO₂ onto the surface of simple can be accelerated by HGM,then change the structure of char layer in advance and increase carbon layer strength and thermal stability.? Synthesis of HGM@AMP and its flame retardant mechanism in TPU: Compared with TPU3-1,the PHRR value of the sample with 1.0 wt% HGM@AMP decreases from 1140 k W/m2 to 514 k W/m2;the TSR value of the sample decreases from 712 m2/m2 to 640 m2/m2.It can be explained that the AMP on the surface of HGM@AMP can be decomposed to form phosphoric and molybdate and so on.The phosphoric and molybdate can promote the crosslinking of macromolecular chain and catalysis isocyanate into carbon by dehydration reaction,increasing carbon layer strength and thermal stability.? Study on a series of functional HGM synergy with APP and its flame retardant mechanism in TPU: HGM@Fe₂O₃ HGM@TiO₂ HGM@AMP and HGM@GO with APP have good synergistic flame retardant effect.The mechanism of action:?1?Fe₂O₃ and APP can decrease the initial decomposition temperatures of TPU,promoting formation of a dense carbon layer,restraining the heat release and smoke generation.?2?TiO₂ and APP generate titanium phosphate at high temperature,then the carbon layer becomes harder,further enhancing the level of thermal and dense carbon layer.?3?AMP is migrated by HGM onto surface of the carbon layer.The molybdenum form AMP can further improve the formation of carbon layer,and reduce the generation of flammable gas,playing an important role in flame retardant and smoke suppression.?4?The lamellar structure of GO promote the crosslinking of TPU chain,forming a skeleton structure in the surface of TPU matrix,enhancing the strength of the carbon layer.