Introduction
In the modified plastics industry, glass fiber (GF) is one of the most mature and widely used reinforcing materials. It serves as the core solution to improve rigidity, strength and dimensional stability in engineering plastic systems such as PP, PA and PBT.
1. Material Nature of Glass Fiber
Glass fiber is produced by melting silicate raw materials at 1400-1600C and drawing into filaments, with a typical monofilament diameter of 5-20 micrometers.
For standard E-glass fiber, the typical mechanical properties are:
- Tensile strength: 2000-3500 MPa
- Elastic modulus: 70-76 GPa
- Density: 2.5 g/cm3
2. Fiber Diameter: Impact on Strength and Interface
Fiber diameter is an underrated yet critical parameter. Monofilament test data shows:
- 12-13 micrometer diameter: Tensile strength approximately 1000-1500 MPa
- 5-7 micrometer diameter: Tensile strength rises to 2000-2500 MPa or higher
This difference is tied to internal defect distribution. Thicker fibers are more likely to contain microcracks or inhomogeneities.
3. Alkali Content: Key to Long-Term Durability
E-glass (alkali-free glass fiber), the industry standard, has an alkali content less than 0.5% and significantly lower mass loss in water than medium-alkali glass fiber.
4. Fiber Length: Lab Data vs Engineering Reality
In production, chopped short fibers (initial length 3-6 mm) usually retain an effective length of 0.3-0.8 mm after injection molding. Long fibers (LFT systems, 10-25 mm initial length) maintain millimeter-scale or longer structures after processing.
Test data shows that at equal fiber loading, long fiber reinforced materials achieve 30%-100% higher impact strength than short fiber counterparts.
Key Takeaways
The performance of glass fiber in modified plastics results from synergistic interactions of multiple parameters. Diameter affects strength and interfacial bonding; length governs load transfer efficiency; alkali content determines long-term stability.