Linear Density Measurement: Denier and Dtex
topic
Linear density of polyester: dtex = mass (g) per 10,000 m; denier = mass (g) per 9,000 m; dtex = denier × 10/9. Measurement: vibroscope (resonance frequency of vibrating fibre segment: dtex = T/(4L²f²) where T=tension, L=length, f=resonance frequency); gravimetric (weigh known length); USTER® capacitance tester (mass variation along yarn). BISFA standard: 50 cm sample, 10 replicates, 0.1 mg balance. Tolerance: ±5% for commercial specifications.
Role
Linear density is the primary specification parameter for all polyester fibre and yarn products. Understanding measurement methods — especially vibroscope and capacitance testing — and their limitations is fundamental to fibre characterisation and quality control.