Key properties and selection of fiberglass
1. Types:
E-glass Fiber (Alkali-Free Glass Fiber): The most common (>90%). Features high mechanical strength, high modulus, good insulation, weather resistance, and low cost. Suitable for reinforcing most plastics.
S-glass Fiber/High-Strength Glass Fiber: Features significantly higher strength, modulus, and heat resistance than E-glass, but is more expensive. Used in high-performance applications such as aerospace, high-end sports equipment, and military applications.
C-glass Fiber (Acid-Resistant Glass Fiber): Offers excellent chemical resistance (especially acid resistance), but lower mechanical strength than E-glass. Used in specific corrosion-resistant applications.
AR-glass Fiber (Alkali-Resistant Glass Fiber): Primarily used to reinforce cementitious composites (GRC), rarely used in plastic modification.
2. Forms and Specifications:
Chopped Strand: The most common form. Lengths typically range from 3mm, 4.5mm, and 6mm. Chopped Strand is directly mixed with plastic pellets for injection molding or extrusion. Chopped Strand length selection requires a balance between dispersion, flowability, and reinforcement (longer strands offer better reinforcement but are more difficult to disperse). Long-fiber pellets/long-fiber reinforced pellets: Glass fibers are encapsulated in a plastic matrix in a continuous or long form (typically > 10mm). This allows for longer fiber lengths to be retained during injection molding, resulting in superior mechanical properties (especially impact toughness) and lower anisotropy. Cost is generally higher than short-fiber reinforced materials.
Glass fiber yarn/roving: Primarily used in continuous molding processes such as winding, pultrusion, and hand lay-up to manufacture composite materials (not the focus of this document, but can be used as a raw material for long-fiber pellets).
Milled fiber: Extremely short (<1mm), primarily used to improve dimensional stability, reduce warpage, and lower costs, but with limited reinforcement benefits.
3. Diameter:
Common diameter ranges: 9μm, 13μm, and 17μm. Smaller diameter:
✔ Larger specific surface area → Greater contact area with the resin → Stronger theoretical bonding strength.
✔ More fibers per unit weight → More even distribution → Potentially higher reinforcement efficiency.
✔ However, higher cost and increased susceptibility to breakage during processing. 13μm is generally a cost-effective, general-purpose option.
4. Surface Treatment - Sizing:
Critical! Directly determines the interfacial bonding strength between the glass fiber and the plastic matrix, impacting the properties of the final composite material.
Main Components:
Film-Forming Agent: Protects the fiber and provides processing properties (bundling and abrasion resistance). Commonly used are polyester, epoxy, and polyurethane.
Coupling Agent: The key component! One end is glass fiber-friendly (silane group), and the other end is plastic-friendly (organic functional group), forming a "molecular bridge."
Common Silane Coupling Agents:
Aminosilane: General-purpose, suitable for polar and non-polar plastics such as PA, PP, PBT, and PC. Excellent results at a reasonable cost.
Epoxysilane: Particularly suitable for epoxy resin matrices, but also for PA, PC, and PBT.
Methacryloxysilane: Primarily used in UP (unsaturated polyester), but also for PMMA.
Cationic Silane: Suitable for non-polar polyolefins such as PP and PE. Lubricants, antistatic agents, etc.: Improve processing performance.
Selection principle: Must match the target plastic substrate! Incorrect selection can lead to poor interfacial bonding and significantly reduced performance.