Polypropylene (PP) Fibre

Polypropylene fibre is produced by melt spinning of isotactic polypropylene (iPP, MFI 8–35 g/10 min depending on application, Mw 150,000–400,000 g/mol, Ziegler-Natta or metallocene catalyst) at 230–265°C through spinnerets — the lightest commercial textile fibre (density 0.91 g/cm³, vs PET 1.38, PA6 1.14, cotton 1.54) with zero moisture regain (0.0%) and excellent chemical resistance, produced at the lowest cost of all synthetic fibres ($0.80–1.00/kg). Global production 4.0 million tonnes (2023): dominant in nonwovens (2.6 million tonnes — spunbond PP for diapers, hygiene, geotextiles, medical; meltblown PP for filtration, N95 respirators), industrial applications (1.0 million tonnes — BCF carpet fibre, geotextile tape, ropes, sacks), limited apparel (0.4 million tonnes — base layer sportswear, thermal underwear — Smartwool PP/wool blend, Helly Hansen Lifa). PP fibre properties: tenacity 2.5–5.0 cN/tex (BCF carpet) to 6.0–9.0 cN/tex (high-tenacity industrial), moisture regain 0.0% (completely hydrophobic — wicks moisture by capillary action in microfibre woven fabric, no moisture absorption), chemical resistance exceptional (acid, alkali, bleach — maintained up to pH 1–14), thermal stability limited (Tm 163–170°C, maximum use temperature 100–110°C, low Tg −10°C → cold flex excellent, warm creep tendency), dyeability near-zero with conventional dyes (solution dyeing, pigment masterbatch required — PP has no polar groups, no acid/disperse dye affinity). PP limitations versus PET/PA: undyeability with conventional dyes (restricts fashion apparel application), poor UV resistance unless UV stabilised (HALS hindered amine light stabiliser, 0.2–0.5% masterbatch), low melting point limiting ironing temperature (steam iron 110°C maximum, versus 200°C PET), tendency to float (density <1.0) in water — advantage for marine ropes, disadvantage for sink-float separation recycling.