Influence of raw material quality and the spinning process on the physicochemical properties and dyeability of polyester filaments

Abstract Polyester oligomers seriously impair the dyeing uniformity of polyethylene terephthalate (PET) fibres and hinder high‐quality coloration. This study adopts an upstream regulation strategy to explore oligomer generation and inhibition during melt‐spinning by comparing commercial PET chips. Four filament variants (oil‐free, partially oriented filaments [POY], fully drawn filaments [FDY], draw textured filaments [DTY]) were systematically characterised. Results show that Sinopec chips feature severe thermal degradation, abundant byproduct residues and low intrinsic polymerisation degree, while Hengli chips exhibit contrasting structural traits with mild degradation, few retained byproducts and high polymerisation degree. Filament oligomer content decreases in the order: oil‐free filament > POY > DTY > FDY. The initial oligomer leaching amount is mainly determined by the intrinsic physicochemical properties of polyester chips, whereas final residual oligomer content depends on subsequent melt‐spinning operations. Owing to high‐temperature stretching under high draw ratios, FDY obtains improved crystallinity, molecular orientation and tensile strength. For FDY samples, the D5 non‐aqueous medium enhanced the colour depth by over 1.2‐fold for fibres characterised by relatively high crystallinity, low oligomer content and well‐ordered amorphous regions. Conversely, a reduction in colour depth was observed for fibres with relatively low crystallinity, high oligomer content and disordered amorphous structures. This work clarifies the relationships among chip performance, spinning behaviours, oligomer evolution and fibre dyeability, offering theoretical support for industrial spinning‐parameter optimisation and dyeing for high‐performance polyester fibres.