The Research On The Key Fabrication Process And Properties Of Na₂O-CaO-B₂O₃-SiO₂ Ultra-fine Glass Wool

Glass wool feature extremely light weight,low thermal conductivity,high sound-absorbing performance,chemical durability,and non-combustible property,so they have been widely used as high-quality heat-insulating and sound-absorbing materials in transport system,nuclear power industry,refrigeration and buildings.However,the applications of glass wool are limited to the construction and industrial sound insulation in China due to their low quality,such as large diameter?6-8 ?m?,high density?30-100 kg/m3?and low thermal insulation property?0.037-0.05 W/?m·K??,or even cause itching.They can not satisfy the cutting-edge thermal-insulating fields such as aircrafts and ships.In this dissertation,the ultra-fine glass wools of Na₂O-CaO-MgO-B₂O₃-Al₂O₃-SiO₂ were prepared by centrifugal-spinneret-blow?CSB?process.The main goal of this dissertation was to investigate the effect of diameters on thermal conductivity and thermodynamic property,analyze the formation processing of the ultra-fine glass wool,and pinpoint the mechanisms of heat-insulation and hygroscopic aging.It was to investigate the bio-solubility of ultra-fine glass wool of Na₂O-CaO-MgO-B₂O₃-Al₂O₃-SiO₂,and the effect of diameters on vitro cytotoxicity of human bronchial epithelial cells?BEAS-2B?.The viscosities at different temperature of different glass were tested by rotating cylinder viscometer?RCV?.The crystalline degrees of different glass were tested by forced crystallizing method.The microstructure and morphology of the glass fibers were observed and characterized using scanning electron microscopy and 3D X-ray microscopy.The chemical composition of the glass fibers were examined by X-ray diffraction?XRD?and inductively coupled plasma-optical emission spectroscopy?ICP-OES?.The thermal conductivity was determined by heat flow meter thermal conductivity instrumentation.The strengths of single fiber and glass wool were identified by multi-function single fibre tensile strength tester and universal testing machine.The internal frictions of glass and glass fibers were estimated by dynamic mechanical analyzer?DMA?.The water absorbency of glass wool was performed with differential scanning calorimetry?DSC?,thermogravimetry?TG?and X-ray photoelectron spectroscopy?XPS?.The bio-soluble evaluation of glass wool was estimated by intratracheal instillation.The cellular activity,apoptosis and death were determined by MTS assay,fluorescent microscope and flow cytometry.The levels of reactive oxygen species?ROS?of different stimuli were identified by fluorescein probe.The main conclusions and innovative results of this dissertation are drawn as follows:1.The research work of ultra-fine glass wool of Na₂O-CaO-MgO-B₂O₃-Al₂O₃-SiO₂ by centrifugal-spinneret-blow technology is systematicly carried out.The bio-soluble composition is SiO₂: 65.5%,Al₂O₃: 1.5%,CaO: 7%,MgO: 3%,Na₂O+K2O: 18%,B₂O₃: 5%.2.We analyze the formation mechanism of ultra-fine glass wool.The molten glass undergoes mainly three stages.Firstly,the primary fibers with the diameter of 0.3mm to 1mm are caused by the action of centrifugal force?Fc?and gravity?G?.And then the secondary fibers are formed by the drawing force of annular airflow with high temperature and high speed.The secondary fibers with some viscosity are finally stretched and broken by the annular cool air.3.We reseach the mechanism of heat-insulation for ultra-fine glass wool.The numbers of interior pores in the glass wool with small fibers are extremely higher than the coarse fibers.Meanwhile,the internal thermal conduction paths are increased with the numbers of glass fibers rise per unit volume in small fibers.The smaller the diameter of glass fiber is,the lower the thermal conductivity of glass wool is.With the increment of the density,the thermal conductivity of glass wool decreases first before it increases again.4.We propose hygroscopic aging mechanism of glass wool,and research the effect of diameters on the thermodynamic property of single fiber and glass wool,and the effect of moisture content on the thermal conductivity of glass wool.The elutriation and migration of alkali-metal ion?Na+?cause the hygroscopic aging of glass wool.5.We propose the bio-dissolution model of glass wool of Na₂O-CaO-MgO-B₂O₃-Al₂O₃-SiO₂,and pinpoint the mechanism of ultra-fine glass fiber on apoptosis of BEAS-2B.There are significant dose-response relationship and diameter-response relationship for the cellular activity on BEAS-2B.Ultra-fine glass wool induced apoptosis of BEAS-2B through mitochondria-dependent pathway.