Cupro (Cuprammonium Regenerated Cellulose / 铜氨纤维)
Cupro (cuprammonium rayon, Bemberg™) is a regenerated cellulose fiber produced by dissolving cotton linters in cuprammonium hydroxide solution (copper oxide dissolved in aqueous ammonia) and wet-spinning into a coagulation bath. Its defining characteristics are an ultra-fine, perfectly round filament cross-section and the finest individual filament fineness achievable among all man-made fibers — as fine as 0.4 dtex per filament. This gives cupro an unmatched silk-like luster, fluid drape, and smooth surface that make it the fiber of choice for premium garment linings. Global production is small (~0.2 Mt/year), dominated by Asahi Kasei (Japan) under the Bemberg™ brand.
Quick Facts
| Type | Regenerated cellulose (cuprammonium process) |
| Raw material | Cotton linters (short fibers on cotton seeds, otherwise waste); dissolved in cuprammonium hydroxide (CuO + NH₃) |
| Spinning method | Wet spinning; stretched in hot water → ultra-fine filaments possible |
| Commercialized | 1890s (Despeissis); Bemberg™ (J.P. Bemberg AG, Germany); now produced by Asahi Kasei (Japan) |
| Global production | ~0.2 million tons/year (~2% of MMCFs); Asahi Kasei is the dominant producer |
| Cross-section | Perfectly round; smooth surface; no skin-core; uniform structure |
| Filament fineness | As fine as 0.4–1.44 dtex — finest of all man-made fibers; silk-like |
| Moisture regain | 11–13% (comparable to viscose and lyocell) |
| Density | 1.50–1.53 g/cm³ |
| Key trade name | Bemberg™ (Asahi Kasei) |
Properties
| Property | Value | Engineering implication |
|---|---|---|
| Dry strength | 1.5–2.0 cN/dtex · ★★☆☆☆ | Similar to viscose; moderate strength; suitable for linings and lightweight fabrics |
| Wet strength | Better than viscose · ★★★☆☆ | Higher wet strength than standard viscose due to uniform structure; still below cotton |
| Filament fineness | 0.4–1.44 dtex · ★★★★★ | Finest of any man-made fiber; enables ultra-lightweight, silk-like fabrics; unique market position |
| Luster and drape | ★★★★★ Silk-like | Round cross-section + smooth surface = natural prism effect; fluid, elegant drape — the defining cupro aesthetic |
| Anti-static | ★★★★★ Excellent | Natural moisture absorption dissipates static charge; critical advantage for linings (no clinging to outer garments) |
| Breathability | ★★★★★ Excellent | High moisture absorption + fine denier → very breathable; comfortable in warm conditions |
| Elastic recovery | ★★☆☆☆ Poor | Similar to other MMCFs; wrinkles without finishing |
| Biodegradability | ★★★★★ Yes | 100% biodegradable cellulose; cotton linter feedstock uses waste material |
Advantages vs. Limitations
Advantages
- Finest filament among all man-made fibers (as fine as 0.4 dtex)
- Silk-like luster, drape, and hand — best silk alternative
- Excellent anti-static properties (natural moisture absorption)
- Superior breathability and comfort
- Uses cotton linter waste as raw material
- Biodegradable
- Perfectly round, smooth cross-section — no skin-core defects
- Ultra-lightweight fabrics possible
Limitations
- Very limited production scale (~0.2 Mt; supply constraints)
- Complex, expensive manufacturing process (copper + ammonia chemistry)
- Environmental concern: copper and ammonia in waste stream require treatment
- Moderate strength — not for high-stress applications
- Higher cost than viscose — premium niche fiber
- Poor elastic recovery (shared MMCF limitation)
- Residual acid/alkali from processing can damage fiber if not properly washed
Yarn Engineering Guide
| Application | Form | Key criteria |
|---|---|---|
| Premium suit / coat linings | Cupro filament, 33–84 dtex | Anti-static; breathable; smooth surface; silk-like drape — prevents clinging and improves garment comfort |
| Luxury dress / blouse fabrics | Cupro filament or spun; fine denier | Fluid drape; luster; lightweight; often used as silk substitute |
| Cupro/cotton blends | Cupro staple blended with cotton | Adds sheen and smoothness to cotton fabrics; improves drape |
| Scarves and lightweight accessories | Cupro filament; ultra-fine | Silk-like aesthetic at lower cost than silk; anti-static for comfort |
Summary
Cupro is the ultimate silk-mimic among regenerated fibers — ultra-fine, round, lustrous, and anti-static. Its niche is small but irreplaceable: premium linings and lightweight luxury fabrics where silk-like aesthetics are required but at lower cost than silk, with the added benefit of anti-static performance. For the yarn engineer, cupro's key value is filament fineness and surface smoothness — properties that no other MMCF matches. See the Textile Material framework.