How to Maintain Chemical Stability of Glass Balls During High-Temperature Melting and Drawing?
Release Time : 2026-02-19
Specialty glass balls, as the core raw material for glass microfibers used in air filter paper, directly determine the filtration performance and lifespan of the final product due to their chemical stability. During high-temperature melting and drawing, glass components are prone to volatilization, crystallization, or phase separation, leading to decreased microfiber strength and weakened chemical resistance.
1. Precise Design of Raw Material Composition
The chemical stability of glass balls primarily depends on their basic formulation. By adjusting the proportions of main components such as silica, alumina, and boron oxide, a highly stable network structure can be constructed. For example, increasing the silica content improves high-temperature resistance, while an appropriate amount of boron oxide can lower the melting temperature and inhibit crystallization. Furthermore, strictly controlling the content of alkali metal oxides prevents their volatilization at high temperatures, which could lead to component shift. The purity of the raw materials must reach 99.9% or higher to reduce the interference of coloring impurities such as iron and titanium on stability.
2. Temperature Control of the Melting Process
Melting temperature is a core parameter affecting chemical stability. Too low a temperature will result in excessively high viscosity of the molten glass and uneven mixing of components; too high a temperature will exacerbate component volatilization, especially of alkali metals and boron. A segmented heating strategy is adopted: first, pre-melting at 1200℃ to eliminate bubbles, then raising the temperature to 1450-1550℃ to complete homogenization. This is combined with a platinum channel heating system to ensure temperature fluctuations are controlled within ±5℃, avoiding component segregation caused by localized overheating.
3. Atmosphere Protection and Volatilization Inhibition
Oxygen and water vapor must be isolated during the melting process to prevent oxidation or hydrolysis of glass components. High-purity nitrogen or argon is introduced into the furnace to create a protective atmosphere, while trace amounts of fluoride are added as a clarifying agent to promote bubble removal without introducing new impurities. For volatile boron oxide, a closed feeding system is used to reduce exposure time, and refractory fragments are placed on the liquid surface to form a physical barrier, reducing the volatilization rate.
4. Rapid Cooling During Wire Drawing
The molten glass must solidify within milliseconds after flowing from the stencil to prevent phase separation or crystallization at high temperatures. By optimizing the matching between the stencil aperture and the drawing speed, the fiber diameter is controlled within the range of 1-5 micrometers. The cooling air system employs a laminar flow design, with the temperature gradient abruptly reduced from 800℃ to 200℃, inhibiting crystal nucleation. Simultaneously, a coupling agent is coated on the fiber surface, protecting the chemical structure and enhancing subsequent adhesion to the filter paper matrix.
Maintaining the chemical stability of glass balls during high-temperature melt drawing requires coordinated efforts across the entire chain, from raw material design and process control to monitoring and feedback. Through precise component control, stable thermal regimes, effective atmosphere protection, and rapid curing technology, chemical changes at high temperatures can be minimized, ensuring that the glass microfibers possess excellent filtration efficiency, temperature resistance, and mechanical strength, meeting the stringent requirements of high-end air filtration applications.
1. Precise Design of Raw Material Composition
The chemical stability of glass balls primarily depends on their basic formulation. By adjusting the proportions of main components such as silica, alumina, and boron oxide, a highly stable network structure can be constructed. For example, increasing the silica content improves high-temperature resistance, while an appropriate amount of boron oxide can lower the melting temperature and inhibit crystallization. Furthermore, strictly controlling the content of alkali metal oxides prevents their volatilization at high temperatures, which could lead to component shift. The purity of the raw materials must reach 99.9% or higher to reduce the interference of coloring impurities such as iron and titanium on stability.
2. Temperature Control of the Melting Process
Melting temperature is a core parameter affecting chemical stability. Too low a temperature will result in excessively high viscosity of the molten glass and uneven mixing of components; too high a temperature will exacerbate component volatilization, especially of alkali metals and boron. A segmented heating strategy is adopted: first, pre-melting at 1200℃ to eliminate bubbles, then raising the temperature to 1450-1550℃ to complete homogenization. This is combined with a platinum channel heating system to ensure temperature fluctuations are controlled within ±5℃, avoiding component segregation caused by localized overheating.
3. Atmosphere Protection and Volatilization Inhibition
Oxygen and water vapor must be isolated during the melting process to prevent oxidation or hydrolysis of glass components. High-purity nitrogen or argon is introduced into the furnace to create a protective atmosphere, while trace amounts of fluoride are added as a clarifying agent to promote bubble removal without introducing new impurities. For volatile boron oxide, a closed feeding system is used to reduce exposure time, and refractory fragments are placed on the liquid surface to form a physical barrier, reducing the volatilization rate.
4. Rapid Cooling During Wire Drawing
The molten glass must solidify within milliseconds after flowing from the stencil to prevent phase separation or crystallization at high temperatures. By optimizing the matching between the stencil aperture and the drawing speed, the fiber diameter is controlled within the range of 1-5 micrometers. The cooling air system employs a laminar flow design, with the temperature gradient abruptly reduced from 800℃ to 200℃, inhibiting crystal nucleation. Simultaneously, a coupling agent is coated on the fiber surface, protecting the chemical structure and enhancing subsequent adhesion to the filter paper matrix.
Maintaining the chemical stability of glass balls during high-temperature melt drawing requires coordinated efforts across the entire chain, from raw material design and process control to monitoring and feedback. Through precise component control, stable thermal regimes, effective atmosphere protection, and rapid curing technology, chemical changes at high temperatures can be minimized, ensuring that the glass microfibers possess excellent filtration efficiency, temperature resistance, and mechanical strength, meeting the stringent requirements of high-end air filtration applications.