Functional fills add a claim on top of loft: antimicrobial, far-infrared, phase-change, “self-heating.” Some of those are measurable fibre physics. Some are a powder in a binder and a brochure. TrimGem will sample the article. The claim needs a method, a number and a wash remaining. “Graphene warmth” without a clo or an emissivity is art.
Do not treat these as a substitute for fill power and gsm. They are extras on a polyester (or other) wadding that still has to loft.
Four heating stories (fibre level)
- Heat of wetting. Hydrophilic groups bind water; kinetic energy becomes heat. High-regain fibres (wool, some modified cellulosics) do this. Ordinary polyester and acrylic do it poorly unless modified. The heat is real and finite — it is not a stove.
- Solar / IR storage. Particles absorb short-wave energy and re-radiate longer-wave IR.
- Phase change (PCM). A paraffin or similar melts and freezes in a comfort band, storing latent heat. Encapsulation must not leak in carding, washing or sitting in a car.
- Joule heat. Conductive yarns plus a battery. That is electronics in a garment, not a wadding gsm.
Far infrared
Ceramic or other powders with high emissivity at skin temperature (about 35–37 °C). Skin absorbs strongly around 8–12 μm. Marketing claims a few degrees of “inside warmer than a control cloth” (3–5 °C is a figure that appears in mill sheets). A working definition used in Chinese technical talk: a textile that absorbs and emits FIR at ambient with emissivity >65% may be called far-infrared. Mill examples quote 0.83–0.87. Write the method and the remaining value after wash.
PCM, graphene, aerogel as catalogue language
Suppliers combine graphene, aerogel and PCM in honeycomb webs, claiming dynamic buffering, high loft, and antimicrobial rates (e.g. 99% with a named organism, remaining after 50 washes). Hollow microfibre plus IR (emissivity >0.83, 2.6–3.0 °C radiation temperature rise) appears with clo tables at a stated gsm — e.g. clo ~4–5.5 and warmth retention ~83–87% at 200 g/m², mapped to rough climate bands. Those numbers are vendor-measured until your lab repeats them.
Negative-ion counts, “5A antimicrobial,” IGCC graphene marks, OEKO-TEX Class I — each is a separate certificate. Stacking logos is not a thermal test.
Antimicrobial
Silver, zinc, quaternary finishes, “graphene” bacteriostasis: name the organism, the standard, the % or log, and washes. Skin-contact fills need the same RSL as other next-to-skin textiles (formaldehyde, APEO, amines — GB 18401 / OEKO-TEX). Antimicrobial is not a licence to skip that pack.
How to write a claim that survives
- Thermal: clo or warmth retention at a stated gsm, method, and a control fibre.
- FIR: emissivity (and temperature rise if used), method, wash remaining.
- PCM: melt range, enthalpy, leakage after wash/heat.
- Heat-of-wetting: a regain-linked test, not a winter-parka substitute.
- Antimicrobial: standard + organism + wash.
- Safety: OEKO-TEX or equivalent on the fill, not only on the shell.
If the brief is a 200 g polyester puffer, a honest siliconised hollow fibre with a gsm and a down-proof lining may beat a “nano heating” 80 g that clo-tests like a shirt. Functional fills are part of the catalogue. Unmeasured adjectives are not. Put the report next to the swatch.