Chlorofiber (PVC / 氯纶 / Polyvinyl Chloride Fiber)
Chlorofiber is polyvinyl chloride (PVC) fiber — a synthetic in which ~57% of the mass is chlorine atoms (from the vinyl chloride monomer), giving it the highest inherent flame resistance of any conventional textile fiber. Its limiting oxygen index (LOI) can reach 45% — far above wool (25%), polyester (22%), and cotton (18%) — making it self-extinguishing in air. This property, combined with excellent chemical resistance and good thermal insulation, defines its niche in protective clothing, military textiles, and industrial applications. However, very poor heat resistance (softens at 70–80°C), difficult dyeability, and PVC's environmental controversy limit its apparel use.
Quick Facts
| Type | Synthetic (addition polymer); polyvinyl chloride; ~57% chlorine by mass |
| Commercialized | 1931 (research); 1946 (Germany: industrial production) |
| Flame resistance | LOI 35–45% — highest of any conventional textile fiber; inherently flame-retardant; self-extinguishing |
| Density | 1.38–1.42 g/cm³ (similar to polyester) |
| Moisture regain | 0% (completely hydrophobic — like PP) |
| Heat sensitivity | Softens at 70–80°C; shrinks at 100°C; melts ~180–200°C — extreme heat sensitivity limits processing |
| Chemical resistance | Excellent: resists strong acids, alkalis, oxidizers, and most chemicals; attacked by some organic solvents |
| Strength | 1.5–2.5 cN/dtex — comparable to cotton; adequate for protective clothing |
Properties
| Property | Rating | Engineering implication |
|---|---|---|
| Flame resistance | ★★★★★ LOI 35–45% | Highest among all conventional fibers; the defining chlorofiber advantage; no FR finish needed — inherent |
| Chemical resistance | ★★★★★ Excellent | Resists strong acids, alkalis, oxidizers; suitable for chemical protection and filtration |
| Thermal insulation | ★★★★★ Excellent (dry) | Zero moisture + chlorine content → excellent dry warmth; used in thermal underwear (historical) |
| Sound insulation | ★★★★☆ Good | PVC's density and structure provide good acoustic damping; used in soundproofing textiles |
| UV / light resistance | ★★★★☆ Good | Better than cotton and wool; chlorine atoms provide some UV stability |
| Heat resistance | ★☆☆☆☆ Extremely poor | Softens at 70–80°C — cannot be ironed, hot-washed, or heat-processed; the critical limitation |
| Dyeability | ★☆☆☆☆ Very poor | Difficult to dye; limited color range; dull appearance; solution-dyeing preferred |
| Abrasion resistance | ★★★☆☆ Moderate | Better than cotton and wool; adequate for protective clothing service life |
Advantages vs. Limitations
Advantages
- Highest inherent flame resistance (LOI 35–45%) — self-extinguishing in air
- Excellent chemical resistance (acids, alkalis, oxidizers)
- Excellent thermal insulation when dry
- Good UV and light resistance
- Good abrasion resistance (better than cotton and wool)
- Sound-insulating properties
- Low cost
Limitations
- Extreme heat sensitivity — softens at 70–80°C (cannot be ironed, hot-washed, or tumble-dried)
- Very difficult to dye; limited colors
- Zero moisture regain — uncomfortable against skin
- Emits HCl gas when burned (toxic, corrosive) despite being self-extinguishing
- PVC production and disposal are environmentally controversial (chlorine chemistry, dioxin risk)
- Limited production scale — specialty fiber, not commodity
- Melts at relatively low temperature (~180–200°C) with toxic fumes
Applications
| Application | PVC form | Key criteria |
|---|---|---|
| Military / flame-resistant clothing | PVC staple or filament; woven or knitted | Inherent FR (no finish to wash out); chemical protection; limited comfort acceptable for protective use |
| Chemical protection suits | PVC-coated fabrics; PVC filament | Acid/alkali resistance; impermeability; FR; disposable or limited-reuse |
| Industrial filtration | PVC staple; needle-punched nonwoven | Chemical stability; FR; low cost for disposable filters |
| Decorative / contract textiles | PVC fiber or PVC-coated fabrics | FR compliance (building codes); color from solution-dyeing; sound insulation |
| Thermal underwear (historical) | PVC staple; knitted | Excellent dry warmth; health concerns (chlorine against skin) have largely eliminated this use |
Summary
Chlorofiber is the ultimate flame-resistant conventional fiber — LOI up to 45%, self-extinguishing in air without any chemical finish. This single property sustains its niche in military, protective, and industrial textiles where fire safety is non-negotiable. Its extreme heat sensitivity (softens at 70°C) and environmental controversy confine it to applications where the FR benefit outweighs all other limitations. For the yarn engineer, chlorofiber is a specialty protective fiber — not a general-purpose textile material. See the Textile Material framework.