Several qualities influence the processability of textile staple fibers: inter-fiber cohesion being one of the most important properties. Although various methods to measure this property have been explored, there is no consensus on the optimal technique, and existing methods often require specialized machinery. This article introduces and evaluates a straightforward method that utilizes only a carding machine and a tensile tester, both standard equipment in yarn laboratories. The proposed cohesion test method involves preparing carded webs, cutting them into nine rectangles, and then subjecting these samples to tensile testing. The method was initially assessed for repeatability and the normalization of results. Further experiments varied the fiber material (cotton and polyester), fiber organization, direction of fiber hooks, and finishing treatments. Force curves and their gradients were analyzed, alongside video footage, to study inter-fiber interactions during testing. The results demonstrated that the new test method could differentiate between fiber materials, fiber organizations, and quantify the effects from finishing treatments. The cohesion force (CF) of CO fibers was 30 % of that of PES fibers; carding had a greater impact on CO fibers compared to PES fibers, and treatment with lubricant reduced the CF by up to 35 %. However, the weight and dimensions of the samples must be controlled to ensure repeatability. In conclusion, the developed inter-fiber cohesion test method offers a promising and accessible approach to analyzing inter-fiber interactions in staple fibers.

The mechanical textile recycling process significantly reduces fibre length. Previously, we explored how lubricant pre-treatment before mechanical recycling reduced the fibre length loss. In this study, we added simulated wear to assess its influence on the fibre length output. We also evaluated the influence of sample shape and feed direction on recycling efficiency. We treated plain woven cotton textiles were subjected to either sandpaper grinding or steel needle raising. Finishing treatments with polyethylene glycol 4000 and Afilan CFA 100 were also used in combination. Samples were prepared in two shapes and fed into the recycling machine with warp threads oriented longitudinally, perpendicularly, or diagonally. Recycling efficiency was evaluated based on fibre length and the degree of fibre opening using a novel air flow permeability test. The results showed that sandpaper treatment degraded fibres, while the raising treatment improved recycling efficiency. A previously unreported finding was that the size, shape and feeding direction of woven fabrics showed significant effects on the fibre length output. Material fed with a thread system aligned longitudinally to the recycling machine direction resulted in a higher proportion of opened fibres and fewer unopened fabric pieces. It was further observed that the yarns aligned longitudinally with the feed direction exhibited significant opening, while those oriented perpendicularly remained largely unopened. The new method for measuring the degree of opened fibres proved effective and holds promise for future application. These findings provide tangible guidance on the mechanical recycling protocol and means to improve output assessment procedures.

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.

The environmental burden of the textile industry can be decreased with an increased use of mechanically recycled fibers. However, it is well known that the recycling process is harsh and shortens the fibers substantially. Still, little has been investigated about the influencing factors of the fiber length loss. 

Previous research has shown that the parts of a garment that is more worn, lose less fiber length in the mechanical recycling process.1 One explanation could be that a loss of fibers during wearing create a more open structure of the textile. By removing fibers from the yarns in a textile, the yarn structure is partly broken down, and the yarn linear density is decreased. The strength of spun staple fiber yarns is dependent on the friction and contact surfaces between fibers. In addition, fiber migration, the variation of radial position of a fiber in the yarn, causes the fibers to lock between different helical layers and thus creates a self-locking mechanism giving strength to the yarn.2 Removal of any fiber in such a yarn affect all fibers in contact with that fiber. This in turn makes both the textile and yarns weaker and consequently more easily disentangles in a mechanical recycling process – keeping more of the fiber length. 

The work at hand investigated this theory by subjecting woven cotton textiles with abrasion treatment prior to mechanical recycling. We compared two different methods of abrasion with unabraded textile. The two pre-treatment abrasion methods used were rubbing with sandpaper and raising with steel pins. By measuring the fiber length post mechanical recycling, we could estimate the efficiency of the recycling process in respect to preservation of the fiber. 

Results showed that only the raising process had a positive impact in mitigating fiber length loss through the recycling process. During the rubbing with sandpaper, the fabric was pressed and thus became denser. On the contrary, the raising process pulled out the fibers and created a fuzzy surface. As the removal of any fiber affect all fibers in direct contact, even fibers in the center of the yarn are affected when surface fibers are pulled out or weakened. The raising process extracted fibers which opened up the fabric and affected the yarn structure. Hence, the yarns were more easily disentangled in the recycling process. The result gives great insight into the mechanisms of mechanical recycling and can be used for future development of the same. 

Although there has been some research on how to use short fibers from mechanically recycled textiles, little is known about how to preserve the length of recycled fibers, and thus maintain their properties. The aim of this study is to investigate whether a pre-treatment with lubricant could mitigate fiber length reduction from tearing. This could facilitate the spinning of a 100% recycled yarn. Additionally, this study set out to develop a new test method to assess the effect of lubricant loading. Inter-fiber cohesion was measured in a tensile tester on carded fiber webs. We used polyethylene glycol (PEG) 4000 aqueous solution as a lubricant to treat fibers and woven fabrics of cotton, polyester (PES), and cotton/polyester. Measurements of fiber length and percentage of unopened material showed the harshness and efficiency of the tearing process. Treatment with PEG 4000 decreased inter-fiber cohesion, reduced fiber length loss, and facilitated a more efficient tearing process, especially for PES. The study showed that treating fabric with PEG enabled rotor spinning of 100% recycled fibers. The inter-fiber cohesion test method suggested appropriate lubricant loadings, which were shown to mitigate tearing harshness and facilitate fabric disintegration in recycling.

To decrease the environmental burden of the textile industry and at the same time reduce textile waste, the fibers of discarded textiles can be re-used into new yarns and fabrics. The shortening of fibers during mechanical shredding direct the use of the recovered fibers to low value products. With the use of a lubricant pre-treatment on cotton and polyester fabrics, we decreased the friction during shredding. The reduction in friction was shown with a developed inter-fiber friction test. Further, the pre-treatment was shown to give longer recovered fibers and eliminate melted areas in polyester material.

Friction and cohesion forces have great influence on the processability of a fibre as well as causing fibre breakage during mechanical recycling of textiles. Through pre-treatment of the fibres or textiles with a lubricant, the friction and cohesion forces can be decreased. However, the measurement of friction coefficient on staple fibres is challenging and needs special machinery. With the development of a new test method of the fibre cohesion force we can measure the effect of a treatment on fibre cohesion, predict the spinnability of a fibre as well as see the effect of a lubricant on the tearing efficiency in textile mechanical recycling.