| With the development of urbanization,more and more people have moved into cities,and various kinds of buildings with comprehensive functions,such as complex buildings,underground buildings,and high-rise and super high-rise buildings,have emerged in a large number.At the same time,fire safety wins much concern of the people.Especially the fire safety of high-rise buildings becomes a big challenge for the modern society.Fire-resistant glass is a special type of glass that maintains its integrity/thermal insulation during prescribed fire tests.There are different types of fire-resistant glass in terms of composition and manufacturing processes.Silicate-based fire-resistant glass is currently the safest fire-resistant glass in terms of sysem integration and thermal insulation,not only has a reliable fire-resistant integrity but also forms a thermal barrier with excellent thermal insulation properties.Silicate-based fire-resistant glass mainly includes two alkali silicates:K2O·nSiO2 and Na2O·n SiO2 as basic chemicals of the interlayer.Which one of the two types of silicate-based fire-resistant glass is advantageous,the related research has not been carried out.The main purpose of this work was to find a formulation of the interlayer with optimized properties for the fire-resistant glass,and to study the difference between potassium silicate-based and sodium silicate-based interlayer,and to explore the fire resistant mechanism and the factors that affect the transparency of fire-resistant glass,and to solve the problem of bubbles in silicate-based fire-resistant glass.By adding antifreezing agents and flame retardants to improve the cold-resistant and fire-resistant properties of fire-resistant glass,it aims to provide theoretical support and basic data for producing fire-resistant glass with improved properties both in fire safety and stability.The main work includes the following aspects:1.Silica sol and alkali reagents are used as the main raw materials for the preparation of fire-reistant slurries.The concentration of silica sol is 40%,45%,and 50%,and the particle size is measured.The alkali reagents are KOH,NaOH and LiOH.Based on comprehensive considerations of orthogonal experiments and results of particle size measurement,it has been found that the best formulation contains silica sol in a concentration of 50%,sodium hydroxide and potassium hydroxide,and the best molar ratio:Si O2/MOH=2.6:1?M=Na,K;KOH/NaOH=3:1?,the optimal reaction temperature is 80°C with the optimum curing temperature at 70°C.2.In order to compare the properties of potassium silicate-based and sodium silicate-based interlayer of fire-resistant glass,and investigate fire protection mechanism and the factors that affect the transparency of fire-resistant glass.The single-factor experiments were carried out to study the effects of molar ratio of SiO2/MOH?M=K or Na?,alkali reagents and curing temperatures on the light transmittance,fire-resistant performance of fire-resistant glass,foaming performance and water content of gel,respectively.The chemical structure of the gels and foamed layers was characterized by Fourier transform infrared?FTIR?spectroscopy.The water content of the gel and the high temperature resistance of the foamed layer were analyzed by Thermal Gravimetry with Differential Scanning Calorimetry?TG-DSC?and X-ray diffraction?XRD?.The morphology of surface and interior of the foamed layer was characterized by Scanning electron microscope?SEM?.The test results show that the fire resistance of the fire-resistant glass rises with the increase of molar ratio SiO2/MOH?M=Na,K?in a certain range,and the light transmittance of the fire-resistant glass of potassium silicate-based interlayer is higher than that of the sodium silicate-based interlayer,but the fire resistance of sodium-based interlayer prevails over that of potassium silicate-based interlayer at the same molar ratio;sodium silicate gel contains more water than potassium silicate gel at the same molar ratio;the foam layer becomes denser and contains more and smaller closed pores with increase of molar ratio.The foaming layer shows good high-temperature stability.The difference between potassium silicate and sodium silicate gel is mainly caused by the content of-Si-O-Si-bonds in the gel and the difference in Na+and K+ion diameter.The fire protection mechanism of the glass with new silicate-based interlayer can be described as follows:the glass directly exposed to fire is broken firstly under the heat impact of high temperature,water in the gel absorbs heat to evaporate,and at the same time,foam structure with a huge number of closed-pores is formed as a result of the evaporation.The expanded foam layer acts as a barrier to flame,smoke and heat radiation.It can be concluded that the light transmittance of fire-resistant glass is related to the uniformity of the interlayer gel.A better uniformity results in higher light transmittance.3.In order to improve the low temperature stability and fire resistance of fire-resistant glass,antifreeze and flame retardant were used to further improve the performance of fire-resistant glass.By adding 5%ethylene glycol,the fire-resistant glass possesses excellent cold resistance even at-50°C.By adding4%boric acid,the duration of fire resistance of 15mm thick fire-resistant glass with 5 mm thick silicate gel layer was increased by 6 minutes on the basis of 62minutes under the used experimental conditions.4.The sources of bubbles in interlayer were discussed.The main sources are the preparation process and the curing process of fire-resistant slurry.The bubbles in the gel were eliminated by low-pressure preparation and low-temperature curing or high-pressure curing.High-temperature and high-pressure conditions were chosen to achieve silicate gel with high molar ratio and high light transmittance.Irradiation resistance test shows that the light transmittance of composite silicate-based interlayer decreases by only 1.89%after treatment for 100 hours,which is far less than 10%as prescrtibed in the national standard GB15763.3-2009,which indicates that the new interlayer has excellent weatherability. |
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