Study On Preparation And Properties Of Hollow Microspheres Porous Materials For Exterior Wall Thermal Insulation

In recent years,fire accidents happened frequently due to the using of organic insulation materials as the external wall insulation materials.In order to ensure the safety of construction insulation materials,in the light of problems,such as easy to aging and burning existed in organic thermal insulation materials,safe and high-performance inorganic thermal insulation material are needed to prepare.We develop a new type of inorganic building insulation with its unique characteristics,such as lightweight and high strength,low thermal conductivity et al,which is not only beneficial for the recovery and utilization of solid waste resources,but also provide a new way for the building exterior insulation materials.In this paper,waste glass powders and fly ash were used as raw materials to fabricate hollow microsphere by particle stabilized foamed slurry and spray drying technology.Hollow microsphere porous materials were prepared with hollow microsphere.The influence of raw materials and process parameters on the preparation and properties of hollow microsphere porous materials were investigated.The effect of moisture content on the thermal conductivity of hollow microsphere porous materials was studied.Besides,the alkali corrosion resistance of hollow microsphere porous materials was also investigated.The main innovative conclusions are as follows:Hollow microsphere porous materials were successfully fabricated by waste glass powders,which show small cell size and uniform structure,high compressive strength and low thermal conductivity.The influence of temperature on the properties of hollow microsphere porous materials was investigated.With the increase of sintering temperature,the bulk density decreased first and then increased,volumetric water content increased and the strength decreased.Hollow microsphere porous material was prepared with bulk density of 0.15 g/cm3,volumetric water content of 0.9%,compressive strength of 2.07 MPa,thermal conductivity of 0.051 W/m·K when sintered at 680 oC。The Ministry of Public Security Fire Research Institute of Tianjin detected,the porous material fire rating to A1 level.The influence of moisture content on the thermal conductivity of hollow microsphere porous materials,Expanded Polystyrene(EPS)boards and Glass Wool(GW)boards was investigated.The results show that thermal conductivity of samples increases with the increase of moisture content.When moisture content was 5%,the growth rate of thermal conductivity of EPS,hollow microsphere porous materials and GW boards were 60.4%,66.7% and 84.6%,respectively.EPS and hollow microsphere porous materials boards were the solid-phase continuous insulation materials,while GW was the gas-phase continuous insulation materials.So the influence of moisture content on the thermal conductivity of gas-phase continuity insulation materials is more significant.For the hollow microsphere porous materials,when moisture content is less than 5%,the thermal conductivity increases rapidly;while moisture content is more than 5%,the thermal conductivity increases slowly.Growth rate of thermal conductivity increases with the increase of relative saturation,thermal conductivity increases the more significantly especially for the higher water absorption samples.The alkali corrosion resistance of hollow microsphere porous materials was studied.With the prolong time of the sample in the alkali solution,the mass of the sample increased first and then decreased,compressive strength decreased continuously.Mass and compressive strength decreased more obviously for the sample with higher water absorption.The internal structures of the non-corrosive sample are mainly close cells,while much more “window" can be found in the cell wall after corrosion.It can be understood that the alkali solution reacts with the hollow microsphere porous materials.Hollow microsphere porous materials were successfully prepared by a green spheres technique,which used waste glass powder and fly ash as the main material.Besides,borax and Si C were introduced as fluxing agent and foaming agent,respectively.The optimum composition is 30 wt% fly ash,70 wt% waste glass,15 wt% borax and 0.5 wt% Si C.Ultra-light ceramic foams sintered at 680~780 °C possess bulk density of 0.14~0.41 g/cm3,porosity of 82.86~94.08%,compressive strength of 0.91~6.37 MPa and thermal conductivity of 0.070~0.121 W/m·K,respectively.This method is convenient,low-cost and environment friendly,which makes it a promising way for recycling solid wastes.