Acrylic and Polypropylene Fibre Testing
topic
Acrylic fibre (polyacrylonitrile PAN ≥85% AN content, ISO 2076 definition) testing focuses on bulk development potential (high-bulk acrylic, HBA: two-component relaxation shrinkage measured at 100°C steam treatment — high-shrinkage component 20–40% boiling water shrinkage versus regular component 0–3% BWS; bulk development ratio = HS%/LS% optimum 5–10 for full bulk knitwear), hot-air shrinkage (DIN 53840, 130°C 15 min, 4.9 mN pretension: high-shrinkage component 25–40%), tenacity (ISO 5079, 25–35 cN/tex), elongation (30–50%), and birefringence (polarised light microscopy, birefringence 0.005–0.030 indicates draw ratio — higher birefringence = higher tenacity and lower shrinkage). Polypropylene (PP) staple fibre testing emphasises thermal shrinkage (dry heat 130°C, 30 min: optimum <5% for geotextile grade, <2% for carpet fibre), fibre density verification (ρ = 0.91 g/cm³ versus PET 1.38 g/cm³ — burn test and density gradient column ISO 1183 differentiate PP from PET), tenacity (40–60 cN/tex, high-tenacity grades for geotextile and rope applications 60–80 cN/tex), and UV stability (xenon arc 500 hours, ISO 105-B02: unstabilised PP retains <20% tenacity; UV-stabilised (HALS additive, 0.3–0.5%) retains >80%). Moisture regain: PP 0.0% versus PET 0.4% — PP zero moisture absorption gives inherent wicking advantage in activewear when texturised but creates static problems in dry conditions (surface resistivity >10¹⁴ Ω/sq without antistatic finish).
Role
Acrylic and polypropylene fibre testing characterises the unique thermal and mechanical properties that define these fibres' performance in their primary application sectors — acrylic bulk development in knitwear requiring precise HS/LS ratio verification, and PP thermal shrinkage and UV stability in geotextile applications where 10-year outdoor service life depends on polymer stabiliser package adequacy verified at incoming quality control.