In making synthetic leather and coated fabrics, polyester cloth is very important. The cloth is the base that holds the coating and gives strength. In factories, high heat, high humidity, and long use can cause problems:
- Coating peeling
- Cloth breaking
- Leather becoming hard or cracking
Low carboxyl PET chips (Low COOH PET) are now used to make products last longer and stay strong.
1. Why high carboxyl PET can cause problems
Normal polyester has high carboxyl at the ends. This can cause:
- Water damage: Water breaks the polyester chains in heat or humidity
- Heat and oxygen damage: Heat and air break chains faster
- Broken chains: Cloth and coating get weaker
Effects:
| Problem | What happens |
|---|---|
| Strength drops | Cloth can lose 20–30% strength after heating or coating |
| Coating peels | PU or PVC coating can lift or bubble |
| Becomes hard or brittle | Leather can crack over time |
| Yellowing | Especially in car seats or outdoor leather |
2. How low carboxyl PET helps
Low COOH PET has less carboxyl at the ends. This keeps the chains strong and stable.
a) Stops water damage
Test: PU leather cloth baked at 170°C, 80% humidity for 72 hours
- Normal PET: strength drops 25–30%
- Low COOH PET: strength drops only 5–8%
✅ Factory benefits:
- Less coating peeling
- Waste rate drops 10–15%
- Fewer customer complaints
b) Keeps cloth strong
Low COOH PET keeps chains strong in hot ovens and coating.
Test: PU leather cloth baked 180°C for 1 hour
- Normal PET: strength drops 20%
- Low COOH PET: strength drops 6%
⚡ Factory benefits:
- Rolls are easier to process
- Later steps like stretching, pressing, and glueing are smoother
c) Improves coating stickiness
High carboxyl can react with PU coating, causing peeling or bubbles. Low COOH PET keeps the surface stable.
Test: After 1000 bending cycles
- Normal PET: >10% peeling
- Low COOH PET: ≤2% peeling
💡 Factory benefits:
- Less rework and scrap
- Better look and feel
d) Makes leather last longer
Low COOH PET performs better in outdoor and car leather.
| Test | Normal PET | Low COOH PET |
|---|---|---|
| UV light 500h | Strength drops 25% | Drops 10% |
| Heat + humidity 70°C / 90% RH 72h | Peels or cracks | Mostly stable |
| Water soak 24h | Absorbs water, shape changes | Low water, keeps shape |
✅ Factory benefits:
- Products can be exported
- Fewer complaints
e) Makes production smoother
Low COOH PET helps in glueing, foaming, and pressing:
- Shrinkage drops 30–50%
- Rolls are flat
- Coating spreads evenly 15–20% better
💡 Factory benefits:
- Higher production speed
- Lower waste
- More consistent quality
3. Summar
Low COOH PET solves the problems of normal PET in heat, humidity, and long use. Factory benefits include:
- Stronger cloth and coating
- Lower waste and higher efficiency
- Longer product life (30–100%)
- Better for export and high-end products
💡 Conclusion:
Low COOH PET is not just a “costly choice.” It is a key material for factories to improve quality, reduce scrap, and satisfy high-end customers.
