As the textile industry increases its focus on circularity, mechanical recycling is being used to reduce textile waste and its associated environmental impact. However, recycled cotton fibers can vary significantly in their physical characteristics, making consistent classification and processing a challenge.
Uster’s Recycled Fiber Matrix provides a structured approach for assessing mechanically recycled cotton and linking fiber quality with suitable spinning methods and product applications. The system is intended to support recyclers, spinners and brands in evaluating what different recycled fiber lots can be used for and how they can be processed.
Evaluating the Key Fiber Parameters
Physical data on recycled fibers is important for determining their behaviour during spinning and their suitability for different end uses.
The Recycled Fiber Matrix focuses on parameters including fiber length (L(n)), length of the longest 5% of fibers (5% L(n)) and short fiber content (SFC(n)).
Its development included testing a significant number of 100% mechanically recycled cotton fiber samples from key recycling regions, including China, India and Europe. The samples covered greige, colored and bleached recycled fibers, with sources including post-industrial, pre-consumer and post-consumer waste distributed as evenly as possible.
Measurements were conducted using the Uster AFIS 6, with the resulting data forming the basis for identifying trends incorporated into the Recycled Fiber Matrix.
Uster subsequently developed an application report examining the current state and potential challenges associated with using different types of mechanically recycled cotton fibers in spinning.
The matrix is described as an ongoing process, with additional samples being collected and analysed from recycling hubs worldwide as source materials and processing conditions change.
Two-Dimensional Assessment of Recycled Cotton
Measured Uster AFIS 6 values are presented through quality levels ranging from A to D, with colour coding intended to make the information easier to apply in practice.
The different areas of the matrix connect fiber parameters with typical raw material sources and provide guidance for yarn production.
Uster notes that mechanically recycled cotton cannot be adequately classified using a single fiber parameter. The Recycled Fiber Matrix therefore applies a two-dimensional evaluation, allowing two interacting properties to be considered simultaneously.
For example, one axis may represent a length parameter such as mean fiber length, while the other may represent a quality-limiting factor such as short fiber content or nep count. This allows differences between fiber lots with similar mean lengths but different short fiber contents to be identified and compared.
Applications in Industrial Processing
The Recycled Fiber Matrix allows AFIS measurements to be translated into defined quality categories, providing information on the quality level and limitations of individual fiber lots.
The resulting classification can be used for bale management and machine settings. It can also help estimate expected short-fiber load and determine suitable blending ratios to support yarn performance.
Uster experts advise enhancing fiber sorting by separating bales according to length, source and colour to reduce variability. Bale management can help maintain consistency in important fiber parameters throughout production.
Adjustments to the spinning process may also be required according to recycled fiber quality, including changes to draft settings, twist and spinning speed. Increased maintenance and cleaning frequency are also recommended.
Blending recycled cotton with virgin cotton or synthetic fibers remains a strategy for compensating for quality deficiencies. Uster is currently working on this area to establish benchmarks for blend levels and assess their subsequent influence on yarn quality.
Free Application Report Available
The Uster Recycled Fiber Matrix provides a data-based framework for classifying recycled fiber lots. Uster has made its application report on the matrix available as a free download.
The report includes graphs and illustrations covering the assessment approach and provides information intended to help spinning mills, recyclers and brands evaluate fiber suitability and make processing decisions.
The report is available at www.uster.com/recycledfibermatrix.
Uster plans to continue collecting and analysing data as recycling technologies and fiber preparation methods develop. The ongoing updates to the matrix are intended to refine classification accuracy and support the use of mechanically recycled cotton in textile production.