Preparation Of Hollow Glass Microsphere Based Porous Composites And Their Thermal Insulation And Flame Retardancy

Aerogel is a kind of porous polymer with low density,low thermal conductivity,high porosity and strong adsorption,which is widely used in the field of construction as thermal insulation materials.However,aerogel materials have certain defects:inorganic aerogel is fragile and has low mechanical strength,while organic aerogel has the risk of flammability,which makes aerogel materials have certain limitations in practical applications.Therefore,it is an important research direction of building aerogel materials to enhance the flame retardancy and mechanical properties of aerogel while having excellent thermal insulation properties.Hollow glass microsphere(HGM)is a kind of spherical glass based particulate matter with cavity structure.It has many advantages,such as low thermal conductivity,low price,high mechanical strength and environmental friendliness.It has become an ideal choice for building a new type of heat insulation and flame retardant aerogel material.Based on this,this paper starts with improving the mechanical properties,heat insulation properties and flame retardant properties of aerogel composites,and prepares a series of new HGM-based aerogel composites through reasonable experimental design,providing basic experimental data and research ideas for the design,preparation and application of new aerogel materials in the field of heat insulation and flame retardant.The research of this paper mainly includes the following three aspects:(1)Magnesium hydroxide was deposited on the surface of hollow glass microspheres(HGM)by co-deposition method,and then it was mixed into chitosan(CSA)matrix.Aerogel composite(CSA-HGM-Mg(OH)2)was prepared by freeze-drying method.CS A-HGM-Mg(OH)2 aerogel has abundant macroporous structure,good mechanical strength and low thermal conductivity(0.035 W m-1 K-1).Secondly,CSA-HGM-Mg(OH)2 aerogel has excellent flame retardancy,its peak heat release rate(pHRR)value is only 24.12 kW m-2,the limiting oxygen index(LOI)is 50.8%,and it can reach(UL-94)V-0 level through vertical combustion test.(2)Ammonium polyphosphate(HGM-APP)was grafted on the surface of hollow glass microsphere with silane coupling agent(KH550)by chemical grafting method,and then filled into sodium alginate matrix.Aerogel composite(SA-HGM-APP)was prepared by freeze-drying method.The porosity of SAHGM-APP aerogel is as high as 80.5%,and it has excellent mechanical properties,thermal insulation properties(thermal conductivity is 0.035 W m-1 K-1)and flame retardancy.The pHRR of SA-HGM-APP aerogel composite is significantly reduced to 14.14 kW m-2.LOI value is up to 100%,which can reach UL-94 V-0 level.(3)The flame-retardant polyurethane foam(PU-HGM)was prepared by immersing hollow glass microspheres(HGM)into polyurethane foam through polydimethylsiloxane(PDMS).PU-HGM sponge is still elastic and has a rich macroporous structure,with excellent thermal insulation performance.In addition,PU-HGM sponge has good thermal stability and flame retardancy.The pHRR value of PU-HGM sponge is 209.35 kW m-2.HGM significantly improved the flame retardance of PU sponge.