Fiberglass ! who are you?
I. What is Glass Fiber? Glass fiber is a high-performance inorganic non-metallic material with many varieties. The diameter of a single filament ranges from a few micrometers to over twenty micrometers, equivalent to 1/20 to 1/5 the diameter of a human hair. Each bundle of fiber consists of hundreds or even thousands of single filaments. 1. Raw Material Source: Glass spheres or waste glass, etc. 2. Main Components: Silica, aluminum oxide, calcium oxide, boron oxide, magnesium oxide, sodium oxide, etc. 3. Forming Process: High-temperature melting, drawing, winding, weaving, etc. 4. Main Advantages: Good insulation, strong heat resistance, good corrosion resistance, high mechanical strength, low cost. 5. Reference Density: Glass fiber density 2.5 g/cm³.
II. Main Classifications of Glass Fiber Glass fibers are generally distinguished by different alkali metal contents. Alkali metal oxides are one of the main components of ordinary glass, primarily lowering the melting point of the glass. The higher the content, the lower the chemical stability, electrical insulation properties, and strength of the glass fiber. 1. Alkali-free glass fiber (E glass fiber): Alkali metal oxide content <0.05%, good chemical stability, electrical insulation, and strength. Mainly used as electrical insulation material and reinforcing material for fiberglass. Alkali-free glass fiber is a major filler type for plastic modification, accounting for over 95% of the industry's production scale.
2. Medium-alkali glass fiber (C glass fiber): Alkali metal oxide content 11.5-12.5%, high alkali content, cannot be used as electrical insulation material. Its chemical stability and strength are relatively good, generally used as latex cloth, woven fabric substrate, acid filter cloth, window screen substrate, etc., and can also be used as acid filter cloth and window screen substrate (lower cost, wider application).
3. High-alkali glass fiber (A glass fiber): Alkali metal oxide content >15%. Glass fibers drawn from crushed flat glass, crushed bottle glass, etc., belong to this category. Can be used as separators for storage batteries, pipe wrapping cloth, and felt, etc., for waterproofing and moisture resistance. 4. Specialty Glass Fiber (S-glass): High-strength glass fiber (S-glass) composed of pure magnesium, aluminum, and silicon ternary materials. It mainly includes magnesium-aluminum-silicon high-strength, high-elasticity glass fiber, silicon-aluminum-calcium-magnesium chemically resistant glass fiber, lead-containing fiber, high-silica fiber, and quartz fiber. If classified according to monofilament diameter, it can be divided into five categories: ultrafine fiber (<4µm), high-grade fiber (3-10µm), medium-grade fiber (10-20µm), primary fiber (>20µm), and coarse fiber (30µm). The plastics modification industry generally uses 10-14µm medium-grade fiber.
III. Roles of Different Components in Glass Fiber
1. Silicon Oxide (SiO2): Material basis, skeleton
2. Aluminum Oxide (Al2O3): Reduces crystallinity and expansion coefficient, improves stability and strength
3. Boron Oxide (Be2O3) and Iron Oxide (Fe2O3): Fluxing, improves fluidity
4. Calcium Oxide and Magnesium Oxide: Reduces viscosity at high temperatures, promotes melting, clarifies, and increases drawing speed
IV. Role of Glass Fiber in Plastic Modification: Adding glass fiber to plastic modification formulations can significantly improve the mechanical strength, heat resistance, dimensional stability, and flame retardancy of plastics. For example, PP-GF/LGF is used in automotive front bumpers, with a strength-to-weight ratio four times that of steel and twice that of aluminum, and excellent corrosion resistance. Glass fiber can be compounded with various resins (such as PP, ABS, PC), and its performance can be flexibly optimized by adjusting the fiber length (short or long fibers) and addition ratio (from 5% to 60%+).
V. How to Prevent "Glass Fiber Injuries"
1. Improved Filling Process: In modified plastics, glass fiber is tightly bound to the resin through dispersion and mixing, forming a dense coating, resulting in extremely low risk of fiber detachment. To prevent fiber detachment during the filling process, the compatibility between glass fiber and resin can be enhanced. For example, silane coupling agents can be used to improve the interfacial bonding between the fiber and the matrix, suppressing the "candle wick effect" while ensuring that mechanical properties do not degrade. 2. Risk Management: Exposed glass fiber products in building or home furnishing products (such as tent frames and inferior umbrella ribs) lack resin encapsulation and are prone to releasing fiber debris when aging or damaged. Risks need to be mitigated by regulating the service life (recommended ≤10 years), application scenarios (stress strength), and process optimization (such as edge passivation). Under scientific management, the risks associated with its use as a reinforcing filler in modified plastics will be significantly different from the "demonized" image perceived by the public.
VI. The Green Path for Glass Fiber: Under the trend of green environmental protection, the obsolescence and recycling of aged glass fiber materials will be a new challenge that industry practitioners need to address.