Phase-Change Fibers
Functional / Latent Heat Storage (Outlast® / PCM)
Quick Facts
| Type | Functional fiber; incorporates phase-change materials (PCMs) that absorb or release latent heat during solid↔liquid phase transition at a specific temperature |
| PCM types | Paraffin waxes (C₁₆–C₂₈; 18–40°C range; 200–300 J/g; most common); Salt hydrates (CaCl₂·6H₂O, Na₂SO₄·10H₂O; <35°C; 120–300 J/g; water-based); Polyethylene glycol (PEG, solid-solid transition; 18–40°C; 150–200 J/g; no leakage) |
| Incorporation | Microencapsulated PCM (1–10 μm capsules) embedded in fiber (Outlast® acrylic/viscose) or coated onto fabric surface; hollow fiber filled with PCM (less common) |
| Key brand | Outlast® — the dominant commercial PCM fiber brand; originally developed for NASA spacesuit thermal regulation |
Properties
| Property | Rating | Engineering implication |
|---|---|---|
| Thermal buffering | ★★★★★ | Absorbs excess body heat when warm → releases stored heat when cool; reduces microclimate temperature fluctuations by 2–5°C; the 'air-conditioning' effect |
| Comfort perception | ★★★★★ | Reduces peak heat and chill sensations; wearers report feeling 'just right' longer; subjective comfort improvement is significant |
| Durability | ★★★☆☆ | Microencapsulated PCMs survive 50–100 washes; gradual loss over garment life; better than topical finishes, worse than permanent fiber properties |
Applications
| Application | Form | Key criteria |
|---|---|---|
| Bedding (pillows, mattresses, duvets) | Outlast® viscose or polyester filling fiber | Thermal regulation during sleep; reduces night sweating; premium bedding market |
| Performance base layers | Outlast® acrylic or polyester knit; next-to-skin | Temperature buffering during activity; reduces overheating → reduces sweating → reduces post-exercise chill |
| Footwear linings | Outlast® nonwoven or knit lining | Foot temperature regulation; reduces sweating and discomfort; premium outdoor and work boots |
Summary
Phase-change fibers buffer temperature — absorbing heat when you're hot, releasing it when you're cold. They don't cool or heat; they smooth the peaks. The effect is real but subtle (2–5°C range) and marketed as comfort, not performance. See the Textile Material framework.