The differences in strength and wear resistance between polyester (PET) and nylon (PA) hot melt yarns stem from their molecular structures and material properties. Below is a systematic comparison with supporting data:
1. Strength Comparison
1.1 Tensile Strength
| Material | Dry Tensile Strength (MPa) | Wet Strength Retention | Elongation at Break (%) |
|---|---|---|---|
| PET | 50–70 | 85–90% | 15–30 |
| PA6 | 70–85 | 80–85% | 60–100 |
| PA66 | 80–100 | 75–80% | 50–80 |
PET: High modulus (2.5–3.5 GPa), rigid, but lower elongation at break and higher brittleness.
Nylon: Hydrogen bonding from amide groups enhances toughness. Significant wet strength loss (PA6 moisture absorption: ~3.5%; PA66: ~2.5%).
1.2 Impact of Hot Melt Processing
PET Yarn: Melting point ~250–260°C, high melt viscosity requiring higher spinning pressure (>100 bar).
Nylon Yarn: PA6 melts at 220°C, PA66 at 260°C. Better melt flow (20–30% lower viscosity), enabling uniform bonding.
2. Wear Resistance Comparison
2.1 Wear Test Data
| Test Method | PET (Cycles) | PA6 (Cycles) | PA66 (Cycles) |
|---|---|---|---|
| ASTM D3884 (Martindale) | 15,000–20,000 | 25,000–35,000 | 30,000–40,000 |
| ASTM D5963 (Sole Abrasion) | Weight loss <5% | Weight loss <3% | Weight loss <2% |
PET: High surface hardness (Rockwell R118) but prone to static-induced pilling.
Nylon: Lower friction coefficient (0.1–0.2 vs. PET's 0.3–0.4), superior elasticity, and fatigue resistance.
2.2 Wear Mechanisms
PET Wear: Brittle fracture dominates, with flake-like peeling (observed via SEM).
Nylon Wear: Plastic deformation creates smooth surfaces and protective transfer films.
3. Application Recommendations
| Performance Requirement | Recommended Material | Typical Applications |
|---|---|---|
| High rigidity + low cost | PET | Luggage frames, industrial filters |
| High toughness + flex resistance | PA6 | Sports shoe uppers, seatbelts |
| Extreme wear + high temperature | PA66 | Climbing ropes, tire cords |
| Anti-static needs | PET + conductive additives | ESD protective clothing |
4. Modification Strategies
Enhancing PET Wear Resistance:
Add 1–3% nano-SiO₂ → 40–50% wear resistance improvement.
Plasma surface treatment → 30% lower friction coefficient.
Boosting Nylon Strength:
30% glass fiber (GF) reinforcement → tensile strength reaches 150–180 MPa.
Copolymer modification (e.g., PA6/PA66 blend) → balances melting point and toughness.
5. Environmental Adaptability
| Condition | PET Performance | Nylon Performance |
|---|---|---|
| 60% RH humidity | Strength retention >95% | PA6 strength drops 15–20% |
| 100°C long-term exposure | Thermal shrinkage <2% | PA6 shrinkage 3–5% |
| UV aging (500 hours) | Strength loss 20–30% | Strength loss 40–50% (requires UV stabilizers) |
