Principle Of Non Alkali Glass Fiber Resistance To High Baking

Basically, it can be divided into two categories: natural fiber and man-made fiber.

Natural fibers can be divided into organic fibers (such as plant fibers) and inorganic fibers, such as asbestos.

Synthetic fibers can also be classified into organic fibers (such as polymeric organic fibers) and inorganic fibers, such as glass fibers.

Natural organic fiber and man-made polymer organic fiber have poor temperature resistance, while natural inorganic fibers such as asbestos have high temperature resistance. Unfortunately, it has high carcinogenicity. Many countries prohibit and restrict their production and use by legislation.

SiO2 content determines high temperature resistance of fibers

Quartz fiber, high silica glass fiber and alkali free glass fiber have such a high temperature difference because the SiO2 content in their fibers is different.

Although these 3 fibers all take SiO2 as their main component, the content is quite different: quartz fiber is a high purity man-made inorganic fiber, SiO2 content >99.9% (can be used as one component), it can withstand 1200 degrees high temperature, its softening point is as high as 1730 degrees Celsius. The SiO2 content of high silica glass fiber can withstand 900 degrees ~1000 ~1000 high temperature, while the SiO2 content of alkali free glass fiber is only about 54%, and its long-term working temperature is <300 <300.

In the case of high silica glass fiber, the SiO2 content of its original glass fiber is 60%~70%, and its temperature resistance is not high. However, after acid leaching, its SiO2 content is equal to 96%, so that it achieves high temperature resistance and becomes a high silica glass fiber.

Of course, further acid leaching will further improve the temperature resistance of SiO2 by increasing the content of SiO2 (above 98%).

However, due to acid leaching, the strength of the non SiO2 component in the fiber is reduced, the non SiO2 component is removed more cleanly, the higher the SiO2 content is, the lower the intensity is, which may affect the application. Of course, it is not cost-effective to consider from the production cost. Therefore, the SiO2 content of high silica glass fiber is less than 96%, and its temperature resistance performance can only reach 900 C ~1000 C.

The selection of acid leach parameters is crucial.

High silicon oxygen

The composition of raw glass can be divided into two categories, namely, two yuan and three yuan.

The two yuan system is SiO2-Na2O, three yuan is Na2O-CaO-SiO2 and Na2O-B2O3-SiO2 (our country is three yuan), regardless of two yuan system or three yuan system's original glass composition, the original glass fiber of melting and drawing has phase separation, that is, SiO2 enrichment phase and Na2O: B2O3 enrichment phase, and the latter is easily soluble in acid.

Based on this principle, high silica glass fiber is used to remove the non SiO2 components from the original glass fiber by using hot acid solution, so that the fiber can form a porous silicon oxygen tube rack structure with a SiO2 content of more than 96%.

After sintering, the micropores are closed, the skeleton structure tends to be compact, and the strength is improved to become high silica glass fiber.

Of course, some of them must be treated by surface chemistry to meet the requirements of subsequent production, processing and application.

Alkali free glass fiber is a glass fiber with alkali metal oxide content of <1% in silicate glass. Its typical components are: SiO2-53.56%, B2O3-10.75%, Al2O3-15.2%, CaO-14.5%, MgO-4.16%, Na2O-1.75%.

The alkali free glass fiber also has phase separation. Therefore, high silica glass fiber acid leaching method can be used to remove some non SiO2 components in the fiber, thereby improving the SiO2 content in the fiber and improving its high temperature resistance.

Domestic high silica glass fiber acid leach mainly adopts two methods: continuous and intermittent.

Intermittent acid leaching is used.

For alkali free fiberglass, yarn or fabric is recommended to adopt intermittence. This can reduce investment and increase productivity and reduce acid gas leakage.

Of course, the acid leaching parameters should be different from that of high silica glass fiber.

According to the characteristics of alkali free glass fiber, the author puts forward some immature suggestions.

First, choose suitable wetting agent to produce alkali free glass fiber.

As the fiber is to be acid leached, the wetting agent on the surface of the fiber should be removed first, so as to facilitate ion exchange and accelerate the acid leaching process.

Therefore, as long as the wetting agent has good wire drawing process and textile technology, the product is easy to remove in acid solution, and the products produced will not affect the acid leaching process.

That is to say, this kind of wetting agent should be different from the wetting agent commonly used in the production of alkali free glass fiber. Therefore, it is necessary to conduct special research.

At present, it is recommended to use paraffin type wetting agent, because the wetting agent has good wire drawing technology and textile technology, and the technology is mature and the price is cheap.

Of course, some adjustments should be made to this wetting agent formula to make it easier to remove during acid treatment.

It is also necessary to make some tests on the oil content of fiber so as to achieve the best oil content.

Two is the first dewaxing and then acid treatment.

Acid leaching of alkali free glass fiber produced by paraffin type wetting agent to prepare high temperature resistant glass fiber is a suitable choice at home.

Because of the high content of oil lubricating components in paraffin type soaking agent, the continuous film formed on the surface of the glass fiber is not conducive to ion exchange. Moreover, the reaction of these oil substances with the acid solution may produce some reactants that affect the acid leaching rate. Therefore, after heat treatment (dewaxing), the membrane of the wetting agent on the surface of the fiber is removed to make it a bare fiber, which is conducive to ion exchange between the fiber and the acid solution.

Of course, this may increase the cost of production.

Domestic dewaxing of glass fiber is usually divided into three grades: high, medium and low according to its heat treatment temperature.

Since the product is to be leached by acid, it does not need to be as high as the waxing material required as an augmented material. Secondly, because the fiber has a significant decrease in acid leaching strength, the higher the retention rate of the dewaxing fiber is, the better the low temperature dewaxing should be.

The three is to select suitable acid leaching parameters.

Acid concentration.

It has a certain effect on the acid leaching rate. The higher the concentration, the faster the acid leaching rate is, but the concentration is more corrosive to the fiber, so the lower concentration is favorable.

Acid temperature.

The temperature is high, the ion kinetic energy is large, the ion exchange speed is fast, but the temperature is high, and the fiber is corroded severely. Therefore, it is also advisable to adopt the medium low temperature (such as 80 ~90 C).

Acid leaching time.

After a certain period of time, the reaction is stable. According to the requirements of this product (SiO2 content <85%), the time should not be too long, and different acid leaching time should be selected according to different high temperature resistant grades.

In conclusion, the choice of these 3 acid leach process parameters not only guarantees the SiO2 content of alkali free glass fiber after acid treatment to achieve its temperature resistance requirements, but also ensures that some key components do not disappear too much and affect the performance.

For example, Ai2O3, if it loses too much, the fiber strength will drop very badly.

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The high temperature resistance of alkali free glass fiber must be improved.

Alkali free glass fiber has better temperature resistance than polymer organic fiber and natural organic fiber, so it has been widely applied in some high temperature fields of national economy.

For example, China's cement, steel and so on are the world's largest producers. The automobile industry is also the largest producer in the world. At the same time, it is also a large automobile spare parts manufacturer in the world. Therefore, the development of China's carbon black industry is also very fast.

And cement, carbon black and metallurgical production are inseparable from high-temperature filter material.

This is to meet the needs of the rapid development of China's industry, and also to meet the requirements of environmental protection. Moreover, the filtration of cement and carbon black flue gas can not only remove dust, but also can be recycled high-grade products, so it not only has social effects, but also has good economic benefits.

With the acceleration of urbanization in China, the disposal of municipal solid waste has been put on the agenda of every municipal government. Garbage disposal is usually incineration in the world, but the resulting dust must be treated by dust removal. Because of its potential dioxin, it is impossible to carry out electrostatic precipitation and only bag dust removal.

However, because of the complex and diverse components of domestic waste, incineration flue gas has high temperature, high water content, high oil content and high corrosiveness. Therefore, glass fiber filter material is required to have high performance.

These high temperature flue gas dedusting can only be carried out with high temperature fiber filter material. Glass fiber, especially alkali free glass fiber, is the most widely used and most widely used filter material in the world.

Of course, in terms of high temperature resistance, alkali free glass fiber is not high, it can only work at 260 degree temperature for a long time, and in a short time, it can only withstand 300 degrees Celsius.

Therefore, for some flue gases with temperatures exceeding 300 degrees, they can only be cooled by cooling first and then filtered by glass fiber.

For example, if the flue gas temperature of the dry cement kiln tail is 350 ~400 C, the temperature must be treated so that the flue gas temperature can reach 260 degrees Celsius.

For example, the blast furnace gas of the ironworks is dedusting and its flue gas temperature is 300 ~350 C.

However, cooling by pumping cold air will increase the amount of flue gas and increase the load of filter bags. The use of water cooling will waste a lot of water resources, and will also reduce the thermal efficiency and produce two pollution.

All these are due to the high temperature resistance of alkali free glass fiber filter materials.

For example, friction materials and high temperature sealing materials industry, because the high temperature resistant asbestos has serious harm to human health, most of the world uses fiberglass instead of asbestos as friction material and high temperature sealing material fiber reinforced material.

But because of the limited resistance to high temperature of glass fiber, it will affect its application in some high-end fields (friction materials and sealing materials), such as aviation friction materials can only use high price carbon fiber as reinforcement material.

From the three application areas mentioned above, it is necessary to improve the high temperature resistance of alkali free glass fiber.

Good prospects for medium and high temperature alkali free glass fiber.

Quartz fiber can withstand high temperatures of 1200 degrees Celsius. It is mainly used in high temperature and high end fields. Because of its high price, the general industrial sector can not afford it.

High silica glass fiber can withstand high temperatures of 900 ~1000 C, and is also mainly used in high temperature and high end fields, and the price is also very high.

These two high temperature resistant fibers are mainly used in aerospace, national defense industry and some high temperature fields in the national economy.

The long-term working temperature of alkali free glass fiber is 260 degrees Celsius, so it is mainly used in the <300 temperature field.

Although basalt is resistant to high temperature around 600 degrees Celsius, it is difficult to occupy the application area of medium and high temperature at 300 ~600 C due to its poor performance and glass fiber.

After acid leaching, the SiO2 content of the alkali free glass fiber is increased, and its temperature resistance is also improved. When the SiO2 content reaches 85%, its high temperature resistance may reach above 800 C.

It can be envisaged that if its SiO2 content reaches about 60%, its high temperature resistance may reach above 300 C.

That is to say, the SiO2 content of alkali free glass fiber can be changed by acid leaching, so that it can reach 300 C ~800 C and different high temperature resistance.

It is technically feasible to fill the current high temperature section of high temperature resistant non-metal fiber.

Can we further improve the high temperature resistance of alkali free glass fiber by acid leaching, such as reaching a high temperature of 900 degrees Celsius.

Theoretically speaking, the SiO2 content in fiber can be further increased by acid leaching, for example, greater than 90% or even 96%.

Of course, its high temperature resistance can be increased to >800 degrees, even to 900 degrees Celsius.

The content of SiO2 in the raw glass fiber of three component high silica glass fiber was 65%. After acid leaching, the content of SiO2 was 96%, fiber weight loss was 32.29%, fiber strength decreased by 40%~50%, and its high temperature resistance range was 900 degrees C ~1000 C.

The high temperature resistance can reach 800 degrees Celsius. When the acid content leached SiO2 content to 80%, the weight loss of the fiber is 32.5%, assuming that its strength decreases by 40%~45%, and its heat resistance reaches 600 degrees centigrade. When the SiO2 content is 75%, the weight loss of the fiber is about 28%, assuming that the strength decreases by 35%~40%, and its high temperature can reach 500 degrees centigrade. When the SiO2 content is 70%, the fiber weightlessness is 70%. Assuming that the strength decreases, the high temperature can reach the temperature of 0. Based on this calculation, the author makes a bold assumption of alkali free glass fiber: E glass fiber SiO2 content is 54%, acid leaching leached SiO2 content to 85%, fiber weight loss 36.48%, assuming strength drop 45%~50%

If this assumption is established, we can divide the acid resistant leached alkali resistant glass fiber into 5 temperature resistant grades, 300 C ~400 C as the first grade, 400 C ~500 C two, 500 C ~600 C three, 600 C ~700 C four, 700 c c c five.

Of course, all of these are a kind of assumption, and need to carry out specific tests and tests to obtain SiO2 content, strength and temperature resistance of all temperature and alkali free fibers.