Thermogravimetric Analysis of Fibre Degradation
topic
Thermogravimetric analysis (TGA, ISO 11358-1, Mettler-Toledo TGA2, TA Instruments TGA550, 10–15 mg fibre, 10°C/min scan, 25–700°C, nitrogen or air atmosphere) measures continuous mass loss as temperature increases, characterising fibre thermal stability, decomposition mechanism, residue (char) content, and blend composition by sequential decomposition of each component at its characteristic temperature. Key parameters: onset degradation temperature Td₅% (temperature at 5% mass loss, conservative stability indicator), maximum degradation rate temperature Tmax (derivative DTG peak, °C, precise degradation characterisation), residual mass at 700°C (char%, g = residue/initial × 100 — char-forming fibres: cotton 8–12% char in N₂, viscose 15–25%, wool 25–35%, PAN/carbon precursor 50–55%; non-char-forming: PET <1%, PP <1%, nylon <2%). Thermal stability ranking: PTFE Td₅% 500°C > Nomex meta-aramid 430°C > PBO 420°C > Kevlar para-aramid 400°C > PET 395°C > PA6 350°C > PP 340°C > cotton 300°C — ranking directly informs maximum process temperature limits for each fibre. Blend composition by TGA: PES/WO (polyester/wool) blend — wool decomposes 250–400°C (protein degradation, NH₃ release, N₂ step), polyester decomposes 400–500°C (C−O−C scission) — mass loss at each stage gives blend ratio ±2%. Fire retardant efficacy assessment: TGA in nitrogen versus air reveals FR mechanism — condensed-phase char promoters increase residue from 3% to 35% at 700°C for phosphorus-FR cotton; vapour-phase inhibitors (bromine, phosphorus radical quenchers) show no char increase but raise Tmax by 50–80°C.
Role
TGA fibre degradation testing defines the thermal processing window for each fibre type by identifying decomposition onset temperatures, enables blend composition verification by sequential mass-loss analysis, and provides mechanistic evidence for flame retardant efficacy — data used in protective clothing thermal design, fibre producer quality control, and FR treatment development where thermal decomposition temperatures directly determine processing safety margins.