Global fibre and clothing production has doubled since the early 2000s, largely driven by the rise of fast fashion. Fibre production imposes significant environmental costs, including the water-intensive cultivation of cotton and the reliance on non-renewable resources for synthetic fibres. Life Cycle Assessments (LCAs) indicate that mechanical textile recycling (MTR) can help reduce these impacts. Although MTR has been practiced for centuries, it has recently gained renewed attention due to rising sustainability concerns. Despite this, technical understanding of the process remains limited within the academic community. Furthermore, from January 2025, all EU countries must implement separate textile waste collection, underscoring the need for scalable recycling solutions. MTR offers a promising pathway to repurpose textile waste into raw material for future textile production.

A key limitation of MTR is the fibre shortening caused by the harsh recycling process. Fibre length and yield are essential quality metrics for mechanically recycled textiles, reflecting process efficiency. This thesis investigates the factors influencing MTR efficiency, with a particular focus on fibre length loss.

Key findings highlight parameters affecting fibre shortening during MTR. Minimising mechanical stress during the recycling process helps preserve fibre length. Lubricant pre-treatment was shown to decrease inter-fibre friction, mitigating fibre shortening in both cotton and polyester (PES), while also reducing the melting of thermoplastic PES. Textiles with less dense structures and longer floats experienced reduced fibre length loss. Wear simulations revealed that fibre damage accelerates shortening, whereas wear that merely opens the structure has no adverse effect. Moreover, aligning the feed along one thread system in woven textiles significantly improved material opening and reduced fibre length loss.

Two novel test methods were developed to enhance process evaluation. The first is an inter-fibre cohesion test, designed to optimise lubricant loading for pre-treatment. The second is a non-destructive air permeability method for measuring the opening degree, avoiding altering the material content often caused by carding in traditional methods.