Preparation of foam glass with waste glass fiber hard wires

Preparation of foamed glass with waste glass fiber hardwires Chen Jianhua, Li Yuhua, Li Yushou (Department of Materials Engineering, Yancheng Institute of Technology, Yancheng 224003, Jiangsu, China), and its foaming mechanism was discussed. It is considered that the foaming mechanism is that part of the gas evolved by the foaming agent is encapsulated in the green body to form tiny bubbles. When the temperature rises to the foaming temperature, the volume of the bubble-expanding green body increases to become a foam glass when the glass is softened. . The introduction of properly blended foam stabilizers, the addition of binders, and pressure molding can promote sintering, which has a positive effect on the formation and stabilization of bubbles.

Foamed glass is widely used as a heat insulating material due to its characteristics such as small bulk density, low thermal conductivity, low water absorption, good chemical stability, good frost resistance, non-combustibility, sound absorption, easy processing and forming, and easy paste construction. And sound-absorbing materials. Foam glass is generally made of waste glass as its main raw material, and is produced by sintering. Natural minerals such as perlite, volcanic ash and fly ash, or industrial waste can also be added. 3. Hard wire is solid waste produced during the production of glass fiber. . Since no good treatment has been found, landfills have long been used for treatment. The purpose of this study is to develop foamed glass using waste glass fiber hard wire as the main raw material, comprehensively utilize industrial waste, protect the environment, and explore its foaming mechanism.

1. Foaming Agents Anthracite, coke, limestone and soda ash are all industrial products. Stabilizing agents A and B are chemically pure reagents. The binders are industrial water glass and polyvinyl alcohol.

Sample Preparation Table 1 Chemical Composition of Waste Glass Fiber Hard Wire The ground glass powder, foaming agent, and foam stabilizer were accurately weighed, mixed thoroughly, and then an appropriate amount of binder was added. After compression molding, drying, and firing into a furnace. The firing process includes preheating, sintering, foaming, and annealing.

1.3 Performance Measurement and Foaming Mechanism Study The foam glass samples prepared under different compositions and different preparation conditions were mainly measured for their bulk density, pore size, observation aperture morphology and distribution, and the relationship between composition, preparation conditions and foam glass quality. The main physical properties such as bulk density, compressive strength, thermal conductivity, and water absorption were determined for samples with good test results. WCT-2 microcomputer differential thermal fund project was used for various foam glass batch materials: the Yancheng Institute of Technology Youth Research Funding Project determined the TG and DTA curves, studied the effect of various additives and the foaming mechanism, and the heating rate was 10 2 . From the table, it can be seen that the use of waste glass fiber hard wire as the main raw material, the addition of appropriate foaming agents, foam stabilizers and binders, and the use of a reasonable process system can produce foam glass with a quality that meets the requirements. The prepared foam glass has a moderate bubble diameter, a uniform distribution, a small bulk density and thermal conductivity, and a high compressive strength.

After a lot of experiments and researches, suitable batch materials were obtained as follows: coke and soda ash were suitable as foaming agents, and their optimal dosages were 1.5% and 2.5% respectively. Stabilizing foams A and B were required to be used in combination. The appropriate dosage was 2% each. The suitable sintering process parameters are: foaming temperature 850*C, foaming time 40 min sintering temperature range 710~730*G4. Table 2 Main physical properties of foamed glass 2.2 Foaming mechanism for coke and pulverized coal The TG, DTA curve of the foaming agent (the amount of both are 2%) of the batch material. From the TG and DTA curves (medium curves 1 and 1') of coke as foaming agent shown in the figure, it can be seen that in the temperature range from 500 to 650*C, the DTA curve has a distinct exothermic peak, which is coke As a result of fixed carbon oxidation, the peak temperature was 591 * Q. With the exothermic effect, the TG curve had a significant weight loss process with a weight loss rate of 1.94%. The weight loss before 120 * C was mainly due to The removal of residual moisture, the subsequent weight loss is due to the decomposition and oxidation of the binder and foam stabilizer in the batch. The TG and DTA curves of the anthracite powder as the foaming agent batch material (The middle curve 2 and 2' shapes are similar to the coke batch materials except that the temperature range of the oxidation exotherm and the weight loss is wider than the coke, and is not very concentrated. Its DTA curve is placed on The peak-to-peak temperature of 581C is 1.67% in the temperature range of 500 ~ 650C. The TG and DTA curves of the blending materials using limestone 2% and soda ash 2% respectively are shown in the figure. Below 100C, due to the elimination of residual moisture, there is a significant weight loss process on the TG curve.The temperature at which soda begins to decompose is low and the decomposition temperature range is wide.The soda ash from 290C began to show obvious weightlessness, until about 700C. At the end of this time, the weight loss rate in this temperature range was 0.86% (curve 2), while the limestone batch had a significant weight loss in the temperature range of 690 to 770C, with a weight loss rate of 0.75% (curve 1). As a result of the other components, the limestone's pyrolysis temperature decreases, and essentially all of the gas is liberated within this temperature range.In addition, from the DTA curve shown, the heat corresponding to the limestone TG curve can be seen. In the decomposition temperature range, there is an obvious endothermic process on the DTA curve, but the temperature of the endothermic valley after the temperature rises to the upper limit of the temperature range, so the figure of the endothermic valley is not complete (curve 1) The decomposition temperature of the soda ash is low and the decomposition temperature is low. The wide range plus the use of less, so the thermal effect is not obvious (curve 2'), and due to the complex physical and chemical changes in the other ingredients in the heating process, in this temperature range, the DTA curve appears more complex changes.

From the characteristics of the above-mentioned changes of carbon and carbonate blowing agents in the heating process, it can be seen that under the action of other components of the batch material, the foaming agent actually starts to decompose or oxidize before the batch material is sintered. . Since the green body has started to sinter at this time, most of the gases generated by the decomposition or oxidation of the foaming agent escape out of the green body, and part of the gas is trapped inside the green body due to sintering of the green body, forming numerous closed microscopic bubbles. As the temperature rises and the sintering process continues, the gas pressure within the microbubbles increases as the blowing agent continues to evolve gas, the temperature increases, and the confinement of the sintered body. When the temperature rises to the foaming temperature, the glass gradually softens, the resistance to the bubble wall movement decreases, the bubble volume expands, and the gas pressure in the bubble gradually decreases until the gas pressure in the bubble is balanced with the external pressure. At this point, the foam glass has the largest volume and the smallest bulk density. After the end of foaming, due to the decrease of temperature during the annealing process, the volume of the gas in the bubbles will gradually decrease, and the volume of the foam glass will decrease accordingly, and the bulk density will increase accordingly. When the temperature drops to the strain point of the glass, the particles in the glass can theoretically be prevented from migrating and adjusting, and the volume of the glass bubbles will be fixed. In fact, when the temperature drops to a glass transition point or slightly higher temperature, the volume and shape of the blister glass is already substantially fixed.

The function of the foam stabilizer is mainly to prevent the small bubbles from combining with each other to form large bubbles or to form connected pores. Stabilizers are generally thought to stabilize bubbles by increasing the viscosity of the glass and lowering the surface tension of the glass. In addition, foam stabilizers are often fluxes that can form at low temperatures with other ingredients in the batch. The eutectic is used to promote sintering, so that the gas released from the foaming agent stays more in the green body, and it is advantageous to obtain a foamed glass having a small bulk density and a uniform pore size.

Under the same foaming conditions, the foam glass without the foam stabilizer used had a completely softened interior and the surface melted to the required viscosity for foaming, but with only a small number of small pores, its bulk density was as high as 850 kg/m3. This was because there was no The sintering temperature of the stabilizer of the foam stabilizer is high, most of the gas emitted by the foaming agent escapes to the blank before the blank is sintered, and only a small amount of gas liberated after sintering is left in the blank. Form bubbles.

Using two foam stabilizers A and B, the relationship between the volume density of the foam glass prepared by fixing the amount of one of the two and varying the amount of the other and the amount of foaming agent used is shown in the following. As can be seen from the figure, when a foam stabilizer is used alone, the bulk density of the foam glass is high and the effect is not good. When two foam stabilizers are used in combination, the volume density of the foam glass is the lowest when the amount of the foam stabilizer B is 2%. When the amount of foam stabilizer A is less than 1.5%, the bulk density of the foam glass decreases significantly, and thereafter the amount thereof continues to increase. Although the bulk density of the foam glass continues to decrease somewhat, the decrease amplitude tends to slow. Considering the quality and cost of foamed glass, the suitable dosages of foam stabilizers A and B are 2% each. Because the two foam stabilizers used can increase the viscosity of the glass and reduce the surface tension of the glass in addition to the fluxing effect. At the foaming temperature, the higher viscosity and lower surface tension can prevent the small bubbles from being combined with each other to form large bubbles and stabilize the bubbles, resulting in a foam glass having a small bulk density and a small and uniform bubble diameter. The use of these two foam stabilizers together with the use of a foam stabilizer has better effects of increasing the viscosity and lowering the surface tension than using only one type of foam stabilizer, and this effect is best when the amount of the two foam stabilizers is a certain proportion.

2. Influence of binders From the above-mentioned foaming mechanism, it can be seen that the factors affecting the sintering of the green body have a great influence on the quality of the foam glass. For example, reducing the glass powder particle size and increasing the specific surface area of ​​the glass powder can significantly reduce the sintering temperature. And bulk density of foam glass Fig.RdationbetweenstabiKzercontmtand glass. In addition, the addition of a suitable amount of binder densityoffoamglass made of a relatively compact body can also significantly promote the sintering, reducing the bulk density of glass bubbles. After the dry batch material without any binder was placed in the mold with a little pressure and compaction, the foam glass obtained had only a small amount of small bubbles, and the bulk density was 760 kg/m3. In this study, the water glass and the polyvinyl alcohol aqueous solution were respectively used as binders. Pressure forming. The test results show that the binding effect of the two binders is similar, the bulk density of the green body is significantly higher than that without the binder, the green billet strength and the dry billet strength of the green body can meet the technological requirements, and the bulk density of the prepared foam glass is About 300kg/m3. This shows that after the binder is added and pressure-molded, the contact between the powder particles is tight, the reaction cross-sectional area is increased, sintering can be promoted, and the resistance of the blowing agent to evolve gas out of the body is greatly increased. A lot of gas stays in the body, which reduces the bulk density of the foam glass and improves the quality.

3 Conclusions Using waste glass fiber hard wire as the main raw material, adding appropriate foaming agents, foam stabilizers and binders, and adopting a reasonable technological system can produce a smaller bulk density, higher compressive strength and lower thermal conductivity. Bubble glass.

The foaming mechanism of the foamed glass is as follows: at the foaming temperature, the glass softens to expand the volume of the bubbles entrapped in the sintered body and further decompose the foaming agent to increase the volume of the green body to generate the foamed glass.

Stabilizers help to melt and improve the properties of the glass melt. Properly combined, can significantly improve the quality of the glass foam. The addition of a binder and compression molding promotes sintering and therefore has a positive effect on the quality of the foam glass.