Are you familiar with the applications and preparation techniques of fiberglass?
With the continuous advancement of technology, people have increasingly higher requirements for material performance. Glass fiber, as an important composite material reinforcement, has been widely used in high-end equipment manufacturing fields such as aerospace, automotive, construction, and electronics due to its excellent properties such as high modulus, lightweight, and radiation resistance. Understanding the preparation technology and applications of glass fiber is of great significance for promoting the development of related industries.
1. Glass Fiber Raw Materials
Glass fiber is a high-performance inorganic non-metallic material, mainly composed of SiO2, Al2O3, CaO, and MgO, accounting for approximately 90% of the fiber composition. It is primarily composed of natural mineral raw materials such as pyrophyllite, kaolin, quartz sand, limestone, dolomite, borocalcite, and boromagnesite. These mineral raw materials are ground into ore powder according to a specific formula, mixed with chemical raw materials such as boric acid and soda ash, and then manufactured through processes such as high-temperature melting in a tank furnace and fiber drawing.
From the perspective of fiberglass production cost composition, pyrophyllite, quartz sand, limestone, and other mineral raw materials account for approximately 21.7% of the cost, with pyrophyllite accounting for about one-third, and quartz sand and limestone together also accounting for a certain share.
1.1 Pyrophyllite
Pyrophyllite is a layered aluminosilicate clay mineral with a 2:1 crystalline structure and the chemical formula Al2[Si4O10](OH)2. The main purpose of using pyrophyllite in fiberglass is to introduce Al2O3 to replace aluminum powder, reducing costs and improving the mechanical strength of the fiberglass. A medium-aluminum pyrophyllite with an Al2O3 mass fraction of 16%-22% is preferred; excessively high or low Al2O3 mass fractions significantly affect the production process.
1.2 Kaolin
Kaolin mainly provides SiO2 and Al2O3 in fiberglass production. Fiberglass companies in Europe and America mostly use selected or high-quality kaolin instead of pyrophyllite as fiberglass raw materials. In my country, kaolin is mainly divided into coal-series kaolin and non-coal-series kaolin. Hard kaolin, with its SiO2 and Al2O3 content meeting the requirements for glass fiber raw materials, can be used as a stable and high-quality raw material for glass fiber production by reducing the Fe2O3 and TiO2 content through beneficiation technologies such as magnetic separation and flotation, and by lowering the COD value through calcination.
1.3 Quartz Sand
Quartz sand, also known as silica sand, is mainly composed of silicon dioxide and is an important raw material for nearly a hundred industrial products, including glass, electronics, and electrical appliances. my country has abundant quartz resources, including natural crystal, quartz sandstone, quartzite, powdered quartz, vein quartz, natural quartz sand, and granite pegmatite quartz.
Quartz sand is distributed in most provinces and regions, but its resources are scattered and mainly produced in small and medium-sized areas. Major domestic quartz sand producing areas include: Donghai and Xinyi in Jiangsu Province; Qichun in Hubei Province; Fengyang and Bengbu in Anhui Province; Heyuan in Guangdong Province; Zhundong in Xinjiang Province; Yinan in Shandong Province; and Lingshou in Hebei Province.
1.4 Chemical Raw Materials
The main chemical raw materials used in glass fiber production include boric acid and soda ash, which are used to prepare sizing agents. In glass fiber production, sizing agents effectively bond the fiber monofilaments into filaments and prevent inter-filament adhesion during unwinding. They also protect the fibers from wear during various manufacturing stages. Depending on the different process requirements of the formed products, sizing agents impart certain special properties to the fibers, such as bundleability, choppability, and dispersibility, and can improve the compatibility and adhesion between the fibers and the resin matrix.
2. Glass Fiber Preparation Technology
2.1 Tank Furnace Drawing Method
The tank furnace drawing method is currently the main method for glass fiber production. This method melts glass raw materials into molten glass in a high-temperature furnace, and then draws the molten glass into thin filaments through a porous perforated plate. The tank furnace drawing method has advantages such as high production efficiency, stable product quality, and low cost, and is the main glass fiber preparation technology in my country.
2.1.1 Raw Material Preparation
The main raw materials for glass fiber include pyrophyllite, rare earth elements, quartz sand, limestone, dolomite, borocalcite, and boromagnesia. These raw materials require strict screening and processing to ensure their purity and quality.
2.1.2 Melting Process
The raw materials are mixed in a certain proportion and then added to a furnace for melting. The furnace temperature is generally between 1500℃ and 1600℃. Continuous stirring is required during the melting process to ensure the uniformity of the molten glass.
2.1.3 Fiber Drawing Process
The fiber drawing process is a crucial step in glass fiber production, directly affecting the physical properties, mechanical properties, and production efficiency of the final fiber. After the molten glass flows out of the furnace, it is drawn into fine filaments through a perforated stencil. The aperture and number of holes in the stencil are selected according to the required diameter and output of the glass fiber. Temperature, speed, and other parameters need to be carefully controlled during the fiber drawing process to ensure the quality of the glass fiber. The rotation speed during processing has the greatest impact on glass fiber length, followed by the slurry mass fraction and processing time, with their influence being relatively close.
2.1.4 Twisting Process
The twisting process in glass fiber production directly affects the mechanical properties and process stability of the final fiber product. The raw filament, after being processed by the initial twister, needs to achieve a low-twist characteristic in a single strand to facilitate subsequent weaving processes. Therefore, precise control of the initial twister parameters, including twist, tension, and winding speed, is required to ensure that the obtained finished yarn has the required low-twist characteristics.
2.2 Crucible Drawing Method
The crucible drawing method is a traditional method for preparing glass fibers. This method involves placing the glass raw material in a crucible, melting it into molten glass at high temperature, and then drawing the molten glass into fine filaments manually or mechanically. The crucible drawing method has advantages such as simple equipment and low investment, but its low production efficiency and unstable product quality have led to its largely phased out by large-scale glass fiber manufacturers.
2.2.1 Raw Material Preparation
Similar to the tank furnace drawing method, the raw materials for the crucible drawing method also require strict screening and processing. Pyrophyllite, quartz sand, limestone, borosilicate, soda ash, and other mineral raw materials need to be mixed in a certain proportion to prepare a batch.
2.2.2 Melting Process
The above raw materials are placed in a crucible and melted in a high-temperature furnace. Continuous stirring is required during melting to prevent the molten glass from separating.
2.2.3 Drawing Process
The drawing process can be done manually or mechanically. Mechanically drawn molten glass is drawn from a lower perforator, forming droplets. These droplets are guided down, allowed to solidify, and then bundled together and wound onto a uniformly rotating winding drum to obtain bundled fibers. The rotation speed of the winding drum determines the diameter of the glass fiber; if a single-hole perforator is used, monofilament fibers can be obtained. Temperature, speed, and other parameters need to be carefully controlled during the drawing process to ensure the quality of the glass fibers.
3. Characteristics of Glass Fiber
3.1 High Strength
Glass fiber has a strength far exceeding that of ordinary glass, with tensile strength reaching over 1000 MPa. It is an excellent structural material, surpassing many metals. This allows glass fiber to withstand greater stress in reinforced composite materials, improving both strength and stiffness. For example, in automobile manufacturing, glass fiber reinforced plastics can replace some metal parts, reducing vehicle weight while maintaining structural strength.
3.2 Corrosion Resistance
Glass fiber possesses excellent corrosion resistance, enabling long-term use in harsh environments such as acids, alkalis, and salts. This allows it to maintain stable performance even in harsh conditions, extending product lifespan. In chemical and environmental fields, glass fiber products, such as pipes and storage tanks, can withstand various corrosive media, ensuring the safety and stability of production processes.
3.3 Good Insulation
Glass fiber is an excellent insulating material with high resistivity and dielectric strength. This makes it widely used in the electrical and electronic fields, such as in the manufacture of insulation layers for wires and cables, and as encapsulation materials for electronic components. 3.4 Heat Resistance: Glass fiber possesses high heat resistance, maintaining stable performance within a certain temperature range. Generally, its long-term operating temperature can reach 200-300℃, and its short-term operating temperature can even be higher.
In high-temperature environments, such as aero-engines and industrial furnaces, glass fiber reinforced composites can replace some metal materials, meeting the requirements of high-temperature working conditions.
3.5 Lightweight
Glass fiber has a low density, approximately 2.5-2.7 g/cm³, much lighter than steel. This makes glass fiber lighter in weight for the same volume, which helps reduce product weight and improves portability and transportation efficiency.
For example, in the aerospace field, the use of glass fiber reinforced composites can significantly reduce the weight of aircraft, improve fuel efficiency, and enhance flight performance.
