Structural Mechanics, Tribological Dynamics, and Microplastic Generation in High-Speed Spinning of Recycled Fibre Blends: A Multi-Physics Quantitative Investigation

The large-scale adoption of mechanically recycled cotton (MRC) and chemically recycled polyester (rPET) into high-speed ring spinning lines represents one of the most physically demanding transitions in contemporary textile manufacturing. This investigation presents a rigorous multi-physics analysis of the structural degradation, tribological dynamics, and environmental consequences arising from high-volume recycled fibre processing, explicitly scoped to the experimental configurations reported in the primary literature. Within the four-level recycling cycle dataset examined, MRC and rPET exhibit short fibre content (SFC) exceeding 11% after a single recycling cycle — approximately double the virgin baseline of 5.2% — fundamentally destabilising roller drafting mechanics through creation of an uncontrolled floating-fibre population. A three-component total drafting force decomposition model (F_D = F_E + F_F + F_T) is developed, validated against published draftometer data, and shown to isolate the transitional slip phase (Stage B, draft ratio 1.1–1.7) as the primary generator of sliver irregularity in high-SFC blends. Within the two gauge settings and four break draft levels studied, the coefficient of variation of the drafting force (CV_D) is minimised at break draft ratios of 1.55–1.75 with the narrower back-gauge setting. A dimensionless lapping risk index R_L = exp[γ(R_a − R_opt)²] is introduced and parametrised for three blend configurations, confirming that surface roughness values outside the 0.6–0.9 μm window generate exponentially increasing adhesion risk via mechanistically distinct failure modes. Microplastic fibre (MPF) shedding across the four recycling levels studied follows a power-law model with exponent δ = 1.322, framing mechanical textile recycling as an environmental paradox. Integration of man-made cellulosic fibres (MMCF) as a carrier matrix is identified as the highest-impact single intervention within the blend ratios tested, enabling recycled cotton content to be doubled from 20% to 40% while maintaining commercial yarn quality thresholds. All models, conclusions, and recommendations are explicitly bounded by the scope of the data from which they are derived.