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38 clicksGlass fiber (GF) content is the key variable determining the overall properties of reinforced PA66. Within the common range of 15%–50%, strength, rigidity and heat resistance increase with GF content, while toughness, elongation and processing fluidity decrease accordingly. Around 30% is usually the optimal balance for overall cost performance.
1. Effects of Different GF Contents on Core Properties of PA66 (15%–50%)
1.1 Mechanical Properties (Most Significant Changes)
| Properties | 15% GF | 30% GF | 40%–50% GF | Trend |
| Tensile Strength | 120–150 MPa | 160–200 MPa | 220–260 MPa | Increases linearly, slows after 30% |
| Flexural Modulus | 5–7 GPa | 8–11 GPa | 12–15 GPa | Greatly improved, significantly enhanced rigidity |
| Notched Impact Strength | 8–12 kJ/m² | 5–8 kJ/m² | 3–6 kJ/m² | Continuously decreases, material becomes brittle |
| Elongation at Break | 3%–5% | 1%–2% | <1% | Rapidly reduced, poor ductility |
1.2 Thermal and Dimensional Stability
- Heat Deflection Temperature (HDT, 1.8MPa): neat PA66 ~85℃; 15% GF≈240℃; 30% GF≈260℃; 50% GF≈285℃.
- Coefficient of Linear Thermal Expansion: significantly reduced with increasing GF content, greatly improved dimensional stability, suitable for precision injection molded parts.
- Heat Aging Resistance: high GF (≥30%) significantly improves long-term heat resistance, suitable for high-temperature environments such as engine compartments.
1.3 Processing and Appearance
- Fluidity: higher GF content leads to higher melt viscosity, more difficult injection molding, and defects such as fiberglass exposure, weld lines and fiber breakage.
- Density: increases from 1.25 (15% GF) to 1.60 (50% GF), weight increases.
- Cost: higher GF ratio leads to higher material cost.
2. Performance Characteristics and Typical Applications of Key Content Ranges
2.1 Low GF (15%–20%)
- Characteristics: good toughness retention, good processability, low cost; limited improvement in strength/rigidity.
- Application: low-stress structural parts, housings, shields, common gears, connectors.
2.2 Medium GF (25%–35%, Mainstream)
- 30% GF (Golden Ratio): optimal combination of strength, rigidity, heat resistance, toughness and processability, highest cost performance.
- Tensile≈170–190 MPa, Flexural Modulus≈10 GPa, HDT≈260℃, Notched Impact≈6–8 kJ/m².
- Application: automotive structural parts, engine peripherals, industrial gears, bearing seats, high-strength connectors, power tool housings.
2.3 High GF (40%–50%)
- Characteristics: strength/rigidity/heat resistance close to metal level, but extremely brittle, difficult processing, serious fiberglass exposure, high cost.
- Application: ultra-high temperature/ultra-high load structural parts, aerospace components, heavy-duty machinery, high-rigid molds, special industrial equipment.
3. Additional Effects of Glass Fiber Types (Besides Content)
- Chopped GF (Mainstream): length 0.1–0.3 mm, good injection dispersion, good isotropy, suitable for mass production.
- Long GF (LFT): length≥10 mm, superior strength/creep resistance/impact resistance to chopped GF, but higher equipment requirements and cost.
- GF Surface Treatment: coupling agents (e.g. silane) improve GF-PA66 interfacial bonding, significantly enhancing strength, toughness and water resistance.
4. Material Selection Recommendations
- Prioritize 30% GF: covers most engineering applications with balanced performance, processing and cost.
- For high rigidity/high precision: choose 35%–40% GF, control fiberglass exposure and brittleness.
- For high toughness/easy processing: choose 15%–20% GF, suitable for thin-wall and appearance parts.
- Extreme conditions: choose 45%–50% GF or long glass fiber reinforced PA66.
