Synthetic leather is a material that simulates the structure and properties of natural leather through artificial synthesis. It is often used to replace genuine leather and has the advantages of controllable costs, adjustable performance, and environmental diversity. Its core process involves three steps: substrate preparation, coating lamination, and surface finishing. The following is a systematic analysis from the classification system to the process details:
1. Core Classification of Synthetic Leather
Types: Nubuck leather
Nubcuk leather/Yangba leather
Suede leather
Sanded leather/Frosted leather
Space leather
Brushed PU leather
Varnish leather
Patent leather
Washed PU leather
Crazy-horse leather
Blushed leather
Oil leather
Pull-up effect leather
PVC artificial leather: knitted/non-woven fabric + PVC paste, waterproof and wear-resistant, low cost, but poor breathability. Suitable for furniture coverings and low-end luggage.
Ordinary PU leather: non-woven fabric + polyurethane (PU) coating, soft and breathable, but prone to aging and cracking. Shoe uppers, clothing linings
Fiber leather: Island-in-the-sea microfiber + impregnated PU, simulates leather pore structure, abrasion and tear resistance, suitable for high-end sports shoes and car seats
Eco-synthetic leather: Recycled PET base fabric + water-based PU, biodegradable, low-VOC emissions, suitable for eco-friendly handbags and maternity products
II. Core Production Process Detailed Explanation
1. Substrate Preparation Process
Non-woven carding:
Polyester/nylon staple fibers are carded into a web and needle-punched for reinforcement (weight 80-200g/m²).
Application: Ordinary PU leather substrate
-Island-in-the-sea fiber spinning:
PET (island)/PA (sea) composite spinning is performed, and the "sea" component is dissolved by solvent to form 0.01-0.001 dtex microfibers. Application: Core substrate for microfiber leather (simulated leather collagen fibers)
2. Wet Process (Key Breathable Technology):
Base fabric is impregnated with PU slurry → immersed in a DMF/H₂O coagulation bath → DMF precipitates to form a microporous structure (pore size 5-50μm).
Features: Breathable and moisture-permeable (>5000g/m²/24h), suitable for high-end shoe leather and automotive interiors.
- Dry Process:
-After coating, the PU slurry is hot-air dried (120-180°C) to evaporate the solvent and form a film.
-Features: Highly smooth surface, suitable for luggage and electronic product casings. 3. Surface Finishing
Embossing: High-temperature pressing (150°C) with a steel mold creates a simulated cowhide/crocodile leather texture, suitable for sofa fabrics and shoe uppers.
Printing: Gravure/digital inkjet printing creates gradient colors and custom patterns, suitable for fashion handbags and apparel.
Polishing: Sanding with an emery roller (800-3000 grit) creates a waxy, distressed effect, suitable for vintage furniture leather.
Functional Coating: Adding nano-SiO₂/fluorocarbon resin creates a hydrophobic (contact angle > 110°) and anti-fouling effect, suitable for outdoor equipment and medical supplies.
III. Innovative Process Breakthroughs
1. 3D Printing Additive Manufacturing
- Using TPU/PU composite filament, direct printing of hollow "bionic leather" reduces weight by 30% and improves resilience (e.g., the Adidas Futurecraft 4D shoe upper). 2. Bio-based Synthetic Leather Process
- Base Fabric: Corn Fiber Non-Woven Fabric (PLA)
- Coating: Water-Based Polyurethane (PU) Derivative from Castor Oil
Features: Biochar Content >30%, Compostable (e.g., Bolt Threads Mylo™)
3. Smart Responsive Coating
- Thermodynamic Material: Microcapsules Encapsulating Thermosensitive Pigments (Color Change Threshold ±5°C)
- Photoelectric Coating: Embedded Conductive Fibers, Touch-Controlled Illumination (Interactive Panels in Automotive Interiors)
IV. Impact of Process on Performance
1. Insufficient Wet Coagulation: Poor Micropore Connectivity → Reduced Air Permeability. Solution: DMF Concentration Gradient Control (5%-30%).
2. Reuse of Release Paper: Reduced Texture Clarity. Solution: Use Each Roll ≤3 Times (2μm Accuracy).
3. Solvent Residue: Excessive VOCs (>50ppm). Solution: Water washing + vacuum devolatilization (-0.08 MPa)
V. Environmental Upgrade Directions
1. Raw Material Substitution:
- Solvent-based DMF → Water-based Polyurethane (90% VOC reduction)
- PVC Plasticizer DOP → Citrate Esters (Non-toxic and Biodegradable)
2. Leather Waste Recycling:
- Crushing scraps → Hot-pressing into recycled substrates (e.g., EcoCircle™ technology, 85% recovery rate)
VI. Application Scenarios and Selection Recommendations
High-end Car Seats: Microfiber Leather + Wet-Process PU, Abrasion Resistance > 1 Million Times (Martindale)
Outdoor Waterproof Footwear: Transfer Coating + Fluorocarbon Surface Treatment, Hydrostatic Pressure Resistance > 5000 Pa
Medical Antimicrobial Protective Gear: Nanosilver Ion-Impregnated Microfiber Leather, Antibacterial Rate > 99.9% (ISO 20743)
Fast Fashion Eco-Friendly Bags | Recycled PET Base Fabric + Water-Based Dry Coating | Carbon Footprint < 3 kg CO₂e/㎡ Summary: The essence of synthetic leather manufacturing lies in the combination of "structural biomimetic" and "performance optimization."
- Basic process: Wet-process pore creation simulates the breathable structure of leather, while dry-process coating controls surface precision.
- Upgrade path: Microfiber substrates approach the feel of genuine leather, while bio-based/intelligent coatings expand functional boundaries.
- Selection Keys:
- High wear resistance requirements → Microfiber leather (tear strength > 80N/mm);
- Environmental priority → Water-based PU + recycled base fabric (Blue Label certified);
- Special features → Add nano-coatings (hydrophobic/antibacterial/thermosensitive).
Future processes will accelerate toward digital customization (such as AI-powered texture generation) and zero-pollution manufacturing (closed-loop solvent recovery).
Post time: Jul-30-2025
