Colour Fastness to Hot Pressing and Sublimation
topic
Hot pressing fastness (ISO 105-P01) and sublimation fastness (ISO 105-P04) characterise the thermal stability of dyes under contact heat — sublimation being the primary failure mechanism for disperse dyes on polyester that volatilise from fibre matrix at temperatures above their sublimation onset (typically 160–220°C depending on molecular size). ISO 105-P01 procedure: specimen (40 mm × 100 mm) placed face-down on clean wool woven adjacent fabric on heated plate, pressed by cold flat plate (unheated) at 4 kPa pressure for 15 seconds, repeated at 110°C (wool iron setting), 150°C (cotton iron setting), and 200°C (linen iron setting) — separate specimen for each temperature. Colour change of specimen and staining of adjacent wool fabric assessed by grey scale after each temperature. ISO 105-P04 (sublimation fastness test, no adjacent fabric contact, dry heat oven, no pressure): specimen in 160°C, 180°C, and 210°C oven for 30 seconds without adjacent fabric contact — measures vapour-phase dye loss from fibre without mechanical transfer, isolating sublimation mechanism from contact thermal staining. Disperse dye sublimation classification (SDC): Low energy (E) disperse dyes — small molecular weight, high vapour pressure, sublimation onset 150–170°C: grade 2–3 at 150°C (poor, avoid for high-temperature processing); Medium energy (SE) — onset 170–190°C: grade 3–4 at 150°C; High energy (S) disperse dyes — large molecular weight, onset >190°C: grade 4–5 at 200°C (suitable for heat-transfer printing and high-temperature polyester dyeing at 195°C). Polyester heat-transfer print sublimation fastness: transfer-printed polyester jersey (sublimation ink, 200°C press, 40 sec) sublimation fastness grade 4–5 at 180°C if correct high-energy dye selection; grade 2–3 if low-energy dyes selected — wrong dye selection detected immediately by sublimation fastness test before commercial production.
Role
Hot pressing and sublimation fastness testing is the primary quality qualification test for disperse-dyed and sublimation-printed polyester textiles — with sublimation onset temperature of the dye class determining the maximum safe ironing temperature, process temperature during heat-setting (195°C for polyester requires high-energy disperse dyes to avoid grade loss during production), and the colour permanence of sublimation-printed sportswear and promotional apparel over multiple pressing cycles.