Development and Application Prospect of Continuous Basalt Fiber
Continuous Basalt Fiber (CBF) is produced using natural volcanic rocks as raw materials. The rocks are crushed and melted in a furnace at temperatures ranging from 1450°C to 1500°C, then drawn into continuous fibers using platinum-rhodium alloy spinnerets. CBF can be used as a reinforcing material to produce various high-performance composite materials, widely applied in fields such as firefighting, environmental protection, aerospace, military industry, automotive and shipbuilding, engineering plastics, and construction. Therefore, CBF is hailed as a new material for the 21st century. With continuous improvement in foreign technological processes and the exploration of new markets, basalt fibers are expected to become the fourth largest high-strength and high-modulus fiber.
1.Development and Research Status at Home and Abroad
1.1Development and Research Status at Home and Abroad
Development and Research Status Abroad rock wool production using basalt as the primary raw material has a history of more than 160 years, since its first successful trial in Wales, UK, in 1840. In 1922, a Frenchman named Paul proposed a technology for manufacturing basalt fibers in the United States (Patent No. OS1438428), but more substantive production was needed.
In the early 1950s, Eastern European countries such as Germany, the Czech Republic, and Poland produced basalt wool with an average fiber diameter of 25μm to 30μm using centrifugal methods. Subsequently, in the early 1960s, the United States, the former Soviet Union, Germany, and other countries vigorously developed the vertical blowing method, leading to a rapid increase in the output of basalt wool. The former Soviet Union introduced the patented technology for manufacturing mineral wool using the vertical blowing method from Germany. After digestion and absorption, this technology was successfully applied to the production of basalt wool, with a designed production capacity of 38 to 40 tons per day. Research on basalt fibers was mainly concentrated in the former Soviet Union. Basalt fibers were developed by the Moscow Institute of Glass and Plastic in the Soviet Union in 1953-1954. The former Soviet Union devoted itself to research on continuous basalt fibers in the 1960s and 1970s. Ukraine's Ministry of Building Materials Industry established a joint research and production organization to develop CBF and its products. The organization's research laboratory began to develop CBF in 1972 and successfully developed production processes for more than 20 kinds of CBF products. In 1973, the former Soviet news agency reported extensively on the widespread application of basalt fiber materials domestically. In 1985, industrial production was first achieved in the former Soviet Union, and the products were used in the defense, aerospace, and aviation fields.
After the dissolution of the former Soviet Union in 1991, this project began to be publicized and used for civil projects. Currently, the primary research and production bases for continuous basalt fibers are in Russia and Ukraine. The dissolution of the Soviet Union objectively affected the promotion and application of CBF. However, due to the excellent properties of basalt fibers, which are different from those of carbon fibers, aramid fibers, and ultra-high molecular weight polyethylene fibers, and their cost-effectiveness, they have attracted significant attention in the defense industry in the United States, the European Union, and other countries.
1.2 Development and Research Status in China
Since the 1970s, China has intermittently researched CBF but has yet to do so. In 2001, the Harbin Institute of Technology established a dedicated research team to focus on developing basalt fiber preparation technology. In 2007, Jiangsu Tianlong Basalt Continuous Fiber High-Tech Co., Ltd. further researched and improved the manufacturing equipment for continuous basalt fibers and developed terminal products.
2002, China officially included continuous basalt fibers in the national 863 Program. Jiangsu Tianlong Basalt Continuous Fiber High-Tech Co., Ltd. invested 50 million RMB in the project and established Jiangsu Tianlong Basalt Continuous Fiber High-Tech Co., Ltd. in May 2007. After nearly two years of technological development, Jiangsu Tianlong Basalt Continuous Fiber has achieved research results in the production of continuous basalt fibers using innovative production technology and the "one-step" process with pure natural basalt (without adding any additives) as raw materials and has successfully achieved industrial production. The developing Jiangsu Tianlong Basalt Continuous Fiber is the sixth-largest production factory in the world after Russia and the United States. Experts predict that by 2010, the national production of continuous basalt fibers will reach 10,000 tons; by 2020, it will be 70,000 to 100,000 tons.
2.Basalt Fiber (CBF) Properties
2.1 New Environmental Material
CBF possesses a natural origin without artificial synthesis. Moreover, its production process is harmless, and the product has a long lifespan, making it an ideal low-cost, high-performance, and environmentally friendly material. During the melting process of basalt, no boron or other alkali metal oxides are emitted, resulting in no harmful substances being released into the atmosphere from the furnace during CBF production. This absence of harmful emissions prevents environmental pollution from industrial waste or toxic substances. Basalt fiber can replace glass fiber and has extensive applications in aerospace, petroleum, and chemical industries, the automotive sector, construction, and other fields. Therefore, CBF is hailed as the "stone-to-gold" new environmentally friendly fiber of the 21st century.
2.2 Excellent Functional Material
CBF is the fourth central high-tech fiber pillar after carbon, aramid, and ultra-high molecular weight polyethylene fiber. In many cases, it can replace carbon and aramid fiber; in some instances, it even outperforms the two fibers mentioned above. The outstanding properties of basalt fiber and its products are manifested in several aspects:
(1) Remarkable high-temperature resistance and thermal shock stability: The operating temperature range of CBF is -260°C to 880°C, which is significantly higher than that of aramid fiber, alkali-free E-glass fiber, asbestos, rock wool, and stainless steel, and is comparable to silicon fiber, alumina-silica fiber, and ceramic fiber. It exhibits excellent thermal shock stability, remaining unchanged at 500°C and losing only 3% of its original weight at 900°C.
(2) Low thermal conductivity: The thermal conductivity of CBF ranges from 0.031 W/m·K to 0.038 W/m·K, lower than that of aramid fiber, alumina-silica fiber, alkali-free glass fiber, rock wool, silicon fiber, carbon fiber, and stainless steel.
(3) High modulus of elasticity and tensile strength: The elastic modulus of CBF ranges from 9100 kg/mm² to 11000 kg/mm², higher than that of alkali-free glass fiber, asbestos, aramid fiber, polypropylene fiber, and silicon fiber. The tensile strength of CBF ranges from 3800 MPa to 4800 MPa, higher than that of large filament carbon fiber, aramid fiber, PBI fiber, steel fiber, boron fiber, and alumina fiber, and comparable to S-glass fiber.
(4) Good chemical stability: CBF exhibits better acid and alkali resistance than aluminum borosilicate fibers. Its durability, weather resistance, resistance to UV radiation, water resistance, and oxidation resistance can be compared to natural basalt stone.
(5) High sound absorption coefficient: CBF's sound absorption coefficient ranges from 0.9 to 0.99, higher than alkali-free glass fiber and silicon fiber. With excellent transparency and specific wave absorption properties, CBF exhibits outstanding sound absorption and insulation performance, making it suitable for stealth materials.
(6) Good electrical insulation and dielectric properties: The specific volume resistance of CBF is significantly higher, at 1×1012 Ω·m, compared to alkali-free glass fiber and silicon fiber. Its volume resistivity is higher than insulating E-glass fibers, with a 50% higher dielectric loss tangent.
(7) Lower moisture absorption: CBF's moisture absorption is less than 0.1%, lower than aramid fiber, rock wool, and asbestos.
(8) Natural silicate compatibility: CBF exhibits good dispersibility and strong binding with cement and concrete, consistent thermal expansion and contraction coefficients, and excellent weather resistance.
3.Applications of Basalt Fiber (CBF)
3.1 Application in Fireproofing and Thermal Insulation
The use of CBF in fireproof suits is still in its early stages. Still, it holds significant advantages in this field due to its unique properties. As an inorganic fiber, CBF possesses non-flammability, temperature resistance (-269°C to 650°C), no toxic gas emission, excellent insulation, non-melting or dripping, high strength, and no thermal shrinkage. However, it is heavier than aramid fiber, resulting in less comfort when worn in fireproof suits. Blending CBF with other fibers can produce flame-retardant fabrics, offering clear advantages for military equipment.
Fireproof fabrics woven from CBF exhibit high-temperature resistance, excellent thermal insulation, absence of melting or dripping, no emission of toxic gases, and no thermal shrinkage. They serve as exceptional materials for fireproof suits, blankets, and curtains, withstanding temperatures up to 650°C and having a limiting oxygen index greater than 68, far superior to aramid and other organic fibers. Although CBF's high-temperature performance is lower than that of alumina and silicon carbide fibers, it surpasses all organic fibers in this regard, exhibiting superior performance at ultra-low temperatures. Furthermore, regarding cost-effectiveness, CBF is the most affordable among high-performance fibers. While DuPont's Kevlar, Nomex, and Teflon have been preferred choices for fireproof fabrics due to their high-temperature and chemical resistance properties, they undergo carbonization and decomposition at temperatures above 370°C. Therefore, the use of CBF in fireproof suits holds significant advantages, given its unique properties. Basalt fiber is an inorganic fiber with non-flammability, temperature resistance (-269°C to 700°C), no toxic gas emission, excellent insulation, non-melting or dripping, high strength, and no thermal shrinkage. However, it is heavier than aramid fiber, resulting in less comfort when worn.
3.2Applications in the field of filtration and environmental protection
Application in Filtration and Environmental Protection CBF is a new green environmental material for filtering, adsorbing, and purifying harmful substances and gases in the environmental protection field, particularly in high-temperature filtration. With a long-term operating temperature of 650°C, CBF outperforms traditional filtering materials, making it the preferred material for filter fabrics, filter materials, and high-temperature-resistant felts.
Currently, filtration materials mainly comprise natural, synthetic, inorganic, and metal fibers. While materials like Nomex, Procon, Torcon, Basfil, and P84 have been introduced to meet the demand for high-temperature resistance, none can address the filtration of high-temperature media. Conversely, CBF can operate within -269°C to 650°C range, making its high-temperature resistance unparalleled. Albarrie, a Canadian company specializing in industrial dust collection filter materials for over 30 years, has been using CBF as the supporting base fabric for filter felts for over a decade.
3.3 Application of CBF reinforced resin matrix composites
Application in CBF-Reinforced Resin-Based Composite Materials CBF exhibits excellent technical characteristics such as low density, low thermal conductivity, low moisture absorption, and chemical stability against corrosive media. This makes it suitable for reducing structural weight and forming new structural materials, with extensive applications in military and civilian fields. Basalt fiber-reinforced resin-based composite materials are used in manufacturing tank armor vehicles to reduce their weight and make gun materials. Remarkably, they significantly enhance the accuracy and precision of artillery when used as materials for gun barrel thermal sleeves. They find extensive applications in various areas, such as ammunition, igniters, ammunition clips, heavy machine gun mounts, thin armor plating for tank armor vehicles, automobile engine covers, and vibration-damping devices. In the shipbuilding industry, they are used in large quantities for hulls, machinery compartment insulation, and superstructure. CBF honeycomb panels can be used to manufacture railway carriage panels, reducing carriage weight while serving as excellent flame-retardant materials.
CBF demonstrates excellent reinforcement effects. Single-fiber tensile tests show CBF exhibits higher bonding strength with epoxy polymers than E-glass fibers. Furthermore, its bonding strength is further enhanced with the use of silane coupling agents. Therefore, as reinforcement materials for high-temperature structural composites, rubber products, etc., basalt fiber can replace asbestos, which is prohibited, as reinforcement materials for brake pads, clutches, and other friction materials. Table 2 compares the mechanical properties of various fiber-reinforced epoxy resin composites.
Additionally, CBF is a low-cost alternative to carbon fiber, offering a range of excellent properties. It is the only environmentally friendly, non-carcinogenic green glass fiber product derived from natural minerals without additives. Hence, the application of basalt fiber in composite material reinforcement has attracted widespread attention and is expected to develop rapidly.
3.4Applications in the field of electronic technology
Application in the Electronics Technology Field CBF exhibits excellent dielectric properties. While it contains a considerable amount of conductive oxides, making it unsuitable for dielectric materials, treatment of the fiber surface with specific impregnating agents significantly reduces its dielectric loss tangent compared to conventional glass fibers. Its volume resistivity is one order of magnitude higher than that of E-glass fibers. Therefore, CBF is highly suitable as a heat-resistant dielectric material.
CBF serves as an excellent insulating material. Leveraging its dielectric properties, low moisture absorption, and temperature resistance, it can be used to produce high-quality printed circuit boards. Additionally, CBF can serve as reinforcement material for wind turbine blades.
4玄武岩纤维（CBF）生产工艺
Basalt Fiber (CBF) Production Process Although the CBF production technology appears simple, it is complex and requires various technical tricks to achieve high-quality industrial basalt production. Consideration must be given to the technical complexity and design of specialized equipment.
Figure 1 depicts the typical CBF production process: First, suitable basalt ore raw materials are selected, crushed, and washed. The crushed and washed basalt raw materials are stored in hopper 1 for later use. They are then conveyed to dosing unit 4 via feeder two and conveyor three and fed into the primary melting unit of the furnace. The basalt raw materials undergo primary melting at around 1500°C in the high-temperature zone 5. Currently, all basalt melting furnaces use combustion heating from natural gas nozzles six installed at the top. The molten basalt flows into the pre-drawing furnace 7 to ensure thorough melting, chemical uniformity, and the volatilization of internal bubbles within the melt. This typically requires raising the melting temperature in the pre-drawing furnace and guaranteeing a longer residence time for the melt. Finally, the molten basalt enters two temperature-controlled zones to adjust the temperature to approximately 1350°C for the drawing process. The initial temperature control zone is used for coarse adjustment of the melt temperature, while the forming zone temperature control band is used for fine adjustment of the melt temperature. The qualified molten basalt from the forming zone is drawn into fibers through a platinum-rhodium alloy bushing with 200 orifices. The drawn CBF is passed through an applicator for the appropriate impregnating agent, through a bundler, and a fiber tensioner before reaching the automatic winding machine.
1- Hopper; 2- Feeder; 3- Lift Conveyor; 4- Quantitative Feeder; 5- Primary Melting Zone; 6- Natural Gas Nozzle;
7- Secondary Melting Zone (Pre-furnace); 8- Platinum-Rhodium Alloy Bushing; 9- Application of Impregnating Agent; 10- Bundler; 11- Fiber Tensioner; 12- Automatic Winding Machine
Despite the outstanding characteristics exhibited by continuous basalt fiber (CBF) in various aspects, some technical challenges remain to be overcome in order to fully utilize these properties.
5. Current Challenges
5.1 High Volatility in Basalt Composition
The production of Continuous Basalt Fiber (CBF) faces several challenges. Different types of basalt ores possess varying characteristics and chemical structures. As basalt is formed from Earth's lava, its inherent deficiency lies in the fluctuation of its composition. Different ore deposits exhibit significant composition variations, and even within the same ore site, a specific range of composition fluctuations exists. This directly results in substantial volatility in the performance of basalt fibers, limiting their extensive application in high-end fields. Manufacturing CBF requires selective basalt raw materials, preferably devoid of heat-resistant crystal phases, as these phases can form secondary crystalline nuclei during incomplete melting processes, affecting the stability of the basalt fiber drawing process.
5.2 Consumption Costs During Production
The main costs of continuous basalt fiber production are primarily associated with natural gas fuel consumption, the consumption rate, and the lifespan of platinum-rhodium alloy bushings.
1.Higher Energy Prices: Natural gas prices in China are relatively high. To ensure the cost-effectiveness of continuous basalt fiber production, it is necessary to retrofit ore melting furnaces, gas-air systems, and gas burner structures and adopt new process technologies, energy supply systems, and refractory and insulation materials.
2.Consumption of Platinum-Rhodium Alloy Bushings:
During Continuous Basalt Fiber production, as the temperature of the bushing increases, high-temperature creep affects the stability of the fiber forming process and the lifespan of the bushing. The presence of iron oxide components in the melt significantly increases the erosion of the platinum-rhodium alloy. The bushing used for platinum-rhodium drawing is a piece of vital equipment in the basalt fiber production process, directly impacting production efficiency, fiber quality, maintenance cycles, and production costs. Further research is needed for over 2000 tons of pool-kiln production and the 1200-2000-hole porous extensive bushing drawing process.
6. Conclusion and Prospects
From a global perspective, the technology and scale of basalt fiber production are still in the primary stage worldwide, providing significant development space and market opportunities for us to catch up with and surpass advanced foreign technologies. We must fully realize: firstly, the considerable gap and urgent need for strengthening the development of continuous basalt fiber in China compared to developed countries; secondly, the importance of maintaining the engineering research of processes and equipment, further enhancing the informatization and standardization of high-tech fiber industry, as exemplified by the "Short Basalt Fiber for Cement Concrete and Mortar" (GB/T 23265-2009) national technical standard formulated under the leadership of Zhejiang Shijin Basalt Fiber Co., Ltd., which will be fully implemented on November 5th this year. We must continue to strengthen the formulation of relevant detection standards further, promoting the safety and sustainable development of the continuous basalt industry.
