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9 September 2026

Preliminary Cross-Platform Comparison of Nep Counts in Five Industrial Batches of Mechanically Recycled Cotton: Ranking, Technical Variability, and Measurement Disagreement

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1
Doctoral School, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Valencia, Spain
2
Recover™ Textile Systems, S.L., Carrer de les Molines 77, 03450 Banyeres de Mariola, Alicante, Spain
3
Department of Graphic Engineering, Universitat Politècnica de València, Plaza Ferrándiz y Carbonell s/n, 03801 Alcoy, Alicante, Spain
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Department of Applied Mathematics, Universitat Politècnica de València, Plaza Ferrándiz y Carbonell s/n, 03801 Alcoy, Alicante, Spain
Textiles2026, 6(3), 109;https://doi.org/10.3390/textiles6030109
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Abstract

Mechanically recycled cotton is heterogeneous, and nep counts obtained from different analytical platforms may not be numerically interchangeable. This study provides a preliminary cross-platform comparison of five industrial batches selected in the original industrial work to span the available production range of total nep count (TotNep). The batches differed in product category, color, supplier/feedstock designation, and production line; Batch was therefore treated as a composite material identity rather than an isolated structural-severity factor. USTER® Neptester 720 measurements comprised three bales per batch and two technical determinations per bale; USTER® LVI 920 used the same three bales and three determinations per bale; USTER® AFIS Pro 2 used one of those bales per batch and ten determinations. Descriptive variability was reported as mean, standard deviation, and coefficient of variation. The primary inferential analysis compared Neptester 720 and LVI 920 on the 15 matched bales. Although the overall mean paired difference was +45.5 neps/g (95% CI: 14.0–76.9; p = 0.0078), batch-specific mean differences ranged from −13.6 to +101.4 neps/g and differed significantly among batches (p = 0.025), showing that +45.5 neps/g is not a transferable correction factor. A secondary exploratory analysis was restricted to the five bales measured by all platforms (one bale per batch). These deliberately range-spanning bales retained the Neptester-defined order (Spearman ρ = 1.00), but the coefficient is descriptive and does not constitute independent validation of cross-platform ranking. Exploratory Bland−Altman mean differences were +32.0, +99.3, and +67.2 neps/g for LVI 920-AFIS Pro 2, Neptester 720-AFIS Pro 2, and Neptester 720-LVI 920, respectively, with wide limits of agreement. Because no reference method was available and each platform was confounded with laboratory, operator, measurement date, and procedural conditions, these values describe cross-platform disagreement rather than instrument-specific measurement bias. The results support ordinal recognition of the selected batches but do not establish validated severity classes, numerical interchangeability, or formal interlaboratory reproducibility. Larger balanced studies using matched bales, documented conditioning, harmonized procedures, and fuller fiber characterization are required.

1. Introduction

The transition of the textile industry toward circular production models has increased both industrial and scientific interest in mechanical cotton recycling as a strategy to reduce dependence on virgin raw materials and reduce textile waste generation. However, the incorporation of mechanically recycled fibers into higher-value textile applications remains constrained by the structural degradation introduced during mechanical opening processes, particularly through fiber shortening, increased short-fiber content (SFC), and the generation of nep-like structures [1,2].
From a circular-economy perspective, the large-scale substitution of virgin cotton by mechanically recycled cotton requires secondary raw materials to be sorted, specified and allocated to appropriate processing routes using reliable quality descriptors [2,3,4]. Recent studies show that the processing performance and end-use suitability of recycled cotton depend not only on the availability of textile waste, but also on measurable attributes such as fiber-length distribution, short-fiber content, opening degree, residual unopened yarn or fabric fragments, nep content, and mechanical properties, which determine its suitability for spinning, blending, or nonwoven applications [1,2,5,6,7].
Among these phenomena, nep-like structures represent one of the most relevant parameters affecting downstream processability and final product quality. Previous studies have shown that although the influence of fiber length and short-fiber content has been extensively investigated, the behavior and quantification of neps in mechanically recycled fibers remain comparatively less understood despite their direct impact on yarn appearance, process stability, and spinning performance. Furthermore, increasing opening intensity generally improves material separation but may simultaneously increase structural damage and defect formation, creating a trade-off between fiber opening efficiency and fiber preservation [2,4,6].
One of the main challenges in recycled fiber characterization is the absence of standardized testing approaches and dedicated reference materials capable of supporting reliable comparison across analytical platforms. Existing fiber testing technologies were originally developed for conventional cotton applications and rely on different detection principles, sample preparation procedures, calibration concepts, and data interpretation strategies. As a result, direct comparison of nep values generated by different systems remains difficult, and absolute values frequently show limited equivalence despite exhibiting similar overall trends [2,8,9].
Industrial recycled-cotton batches can also differ in waste category, color, product history, feedstock designation, opening conditions, fiber-length distribution, short-fiber content, and sample preparation [3,5,6,10,11,12,13,14,15]. These attributes may influence the measured fiber population and can be confounded with nep count. In addition, a formal method-comparison or interlaboratory study requires matched materials and a predefined protocol that separates method, laboratory, operator, and material effects [16,17]. Agreement should be assessed from paired differences and limits of agreement rather than rank correlation alone [18,19].
In the original industrial study, the five batches were ordered using USTER® Neptester 720 values to cover the available TotNep range. USTER® LVI 920 and USTER® AFIS Pro 2 measurements were available for overlapping bale sets. Because the ordering was constructed with Neptester 720, its preservation by the other platforms cannot be interpreted as independent validation of transferable severity classes. Accordingly, the objective of this revised study is to provide a preliminary cross-platform comparison of the selected batches by describing the actual bale and technical-determination structure, reporting technical variability, comparing Neptester 720 and LVI 920 on 15 matched bales, and exploring ranking and agreement on the five bales measured by all three platforms. Conclusions are restricted to this dataset. The 15-bale Neptester 720-LVI 920 comparison is therefore treated as the primary inferential analysis, whereas all analyses involving AFIS Pro 2 are retained only as secondary exploratory evidence.

2. Materials and Methods

2.1. Industrial Batches and Operational Ordering

Five mechanically recycled cotton fiber batches originating from industrial-scale production were selected from the available records to span a broad TotNep range within this dataset. The selected materials corresponded to three commercially produced cotton fiber categories, including indigo, ecru, and white recycled cotton fibers. Together, the evaluated batches represented more than 43 t of industrial production. Their industrial provenance is a strength because the materials were not laboratory-prepared; however, five heterogeneous batches are insufficient to represent the wider population of mechanically recycled cotton. All batches were produced in 2024. The study codes S1RCW-S5RDI denote the ascending operational order assigned from batch-level USTER® Neptester 720 TotNep (Uster Technologies AG, Uster, Switzerland) values. They are labels for this dataset and not validated severity classes. Because the batches differ in product designation, color, supplier/feedstock designation, and production line, Batch was treated as a composite material identity rather than a pure structural-severity factor (Table 1).
Table 1. Industrial batches included in the study.
The available records did not provide a factorial description of feedstock origin or recycling conditions. Fiber-length distribution, short-fiber content, trash, maturity, nep morphology, number of recycling passes, and detailed opening conditions were not included in the dataset. Consequently, the observed batch differences cannot be attributed causally to color, product category, supplier/feedstock designation, production line, or any single unmeasured fiber property.

2.2. Analytical Platforms and Retained Laboratory Metadata

Three analytical platforms commonly used for cotton fiber characterization were included in the study. The selected systems differ in their measurement principles and analytical approaches, but all provide information related to nep occurrence in cotton fibers (Table 2). USTER® Neptester 720 was used as the operational classification platform for the original ordering. USTER® LVI 920 (Uster Technologies AG, Uster, Switzerland) and USTER® AFIS Pro 2 (Uster Technologies AG, Uster, Switzerland) were included as comparative platforms. Because each platform was associated with a specific site, operator set, and measurement date, the present design cannot separate instrument effects from laboratory and procedural effects. Accordingly, the observed differences are described as cross-platform disagreement under platform-specific measurement conditions and not as instrument-specific bias or trueness relative to a reference method.
Table 2. Instrumental systems included in the study.
The retained records documented TotNep count for all platforms and nep-size output for LVI 920 and AFIS Pro 2. For the AFIS Pro 2 measurements, the fibre samples were conditioned for 24 h at 22 ± 2 °C and 65 ± 4% relative humidity in accordance with DIN EN ISO 139. Fresh 0.500 g test portions were taken from different locations within each available 10–15 g sample, manually opened, and formed into an approximately 30 cm sliver of uniform thickness; no additional mixing was performed. Measurements were conducted in nep-testing mode using the standard USTER settings and manufacturer-defined detection parameters (Nep module version 4.22), following the official USTER operating instructions. These values are therefore reported as unavailable rather than replaced by manufacturer-recommended settings. This missing metadata limit reproducibility and prevent the study from being interpreted as a formal interlaboratory comparison. A future prospective protocol should document standard conditioning, such as ISO 139, and harmonized instrument settings [8,16].

2.3. Bale Sampling and Independence of Measurements

The experimental unit and technical-determination structure differed among platforms. For USTER® Neptester 720, three bales per industrial batch were examined, with two technical determinations per bale. The same three bales were examined with USTER® LVI 920, using three technical determinations per bale. For USTER® AFIS Pro 2, one of those three bales was measured for each batch, with ten technical determinations. The number of technical determinations used for each platform followed the corresponding manufacturer’s operating recommendations. Individual determinations were therefore nested within bales and were not treated as independent material replicates in the revised inferential analyses (Table 3).
Table 3. Bale allocation across the three analytical platforms.
The available dataset did not record the criterion used to select the single AFIS bale from each batch. Accordingly, the five-bale three-platform analysis is descriptive and exploratory. The Neptester 720-LVI 920 comparison uses all 15 matched bales and is the strongest paired component of the dataset. For evidential weighting, the 15-bale Neptester 720-LVI 920 comparison was designated as the primary analysis, while all AFIS-containing comparisons were designated as secondary and exploratory and were not used to support the principal inferential conclusions.

2.4. Statistical Analysis

TotNep count, expressed as neps/g, was the primary response. First, all available technical determinations were summarized within each batch−platform combination as mean, sample standard deviation (SD), and coefficient of variation (CV = 100 × SD/mean). For Neptester 720 and LVI 920, these descriptive SD and CV values combine between-bale and within-bale technical variation; for AFIS Pro 2, they represent technical variation within a single selected bale. They are therefore not directly equivalent estimates of between-bale repeatability.
Second, Neptester 720 and LVI 920 were compared using the mean of the technical determinations within each of the same 15 bales. The paired difference was defined as Neptester 720 minus LVI 920. The overall mean difference was tested with a paired t-test and reported with its 95% confidence interval. A one-way analysis of variance of the paired differences, with Batch as the factor and bale as the independent unit, assessed whether the platform difference varied among batches. Tukey’s HSD was used for post-hoc comparisons. Normality of the paired-difference residuals and homogeneity of variance were checked before interpretation. This 15-bale paired analysis was the primary inferential comparison in the study.
Third, the five bales measured by all three platforms were used to compare batch ordering and agreement. Spearman rank correlations were calculated on the five bale means. Exploratory Bland−Altman analyses used the paired mean on the horizontal axis and the difference between platforms on the vertical axis; the mean paired difference and 95% limits of agreement were calculated as the mean difference ± 1.96 SD of the paired differences [18,19]. Because the three-platform comparison comprised only five common bale-level observations (n = 5), and because the batch order was originally constructed using Neptester 720, these results were not used to validate severity classes or conversion equations. This three-platform step was treated as secondary and exploratory because AFIS Pro 2 contributed only one bale per batch. The rank coefficient was reported only as a descriptive check of order preservation in a deliberately range-spanning, Neptester-defined panel; it was not interpreted as independent validation or as a generalizable estimate of cross-platform ranking performance. In the absence of a reference method, the paired differences were not interpreted as estimates of trueness or instrument-specific bias.
The revised analyses were performed in Python 3.13 using SciPy 1.17.0 and statsmodels 0.14.6. The significance level was alpha = 0.05. Raw observations, bale-level means, paired differences, agreement summaries, and nep-size summaries are supplied in the revised Supplementary Data File S1. All statistical analyses were performed using STATGRAPHICS Centurion 19, version 19.7.01 (Statgraphics Technologies, Inc., The Plains, VA, USA).

3. Results

3.1. Descriptive TotNep Counts and Technical Variability

Table 4 summarizes TotNep count across all available technical determinations. Mean values increased from S1RCW to S5RDI on each platform. This preservation of order is descriptive: S1RCW-S5RDI were assigned from the original Neptester 720 ordering, and the batches were not independent reference materials.
Table 4. TotNep count as mean ± SD (CV, %) for each batch−platform combination.
For Neptester 720 and LVI 920, the SD and CV include both between-bale and within-bale technical variation from three bales. For AFIS Pro 2, they reflect ten determinations from one selected bale. Consequently, the lower or higher CV of one platform should not be interpreted as evidence of superior repeatability. Mean nep-size values recorded by LVI 920 and AFIS Pro 2 are provided in Supplementary Data File S1 and are reported descriptively because platform-specific definitions and detection procedures were not harmonized. Accordingly, Table 4 is used only to describe dispersion within each platform-specific sampling design and not to compare platform repeatability.

3.2. Batch-Dependent Paired-Bale Comparison of Neptester 720 and LVI 920

The Neptester 720 and LVI 920 measurements were available for the same 15 bales. Table 5 summarizes the platform means and paired differences. Across all bales, Neptester 720 exceeded LVI 920 by 45.5 neps/g on average (SD = 56.8; 95% CI: 14.0–76.9). The paired t-test was significant (t(14) = 3.10, p = 0.0078), showing that the average paired difference was positive across the selected dataset but this does not imply that a constant offset was applied to every batch.
Table 5. Paired Neptester 720-LVI 920 comparison based on three matched bales per batch.
The paired difference varied among batches (F(4,10) = 4.46, p = 0.025). Tukey’s HSD identified only the S2RCW-S5RDI contrast as significant at alpha = 0.05; the remaining pairwise contrasts were not significant. Assumption checks did not indicate marked departures from normality or homogeneity of variance (Shapiro−Wilk p = 0.744; Brown−Forsythe/Levene p = 0.694). The result supports batch-dependent numerical differences between these two platforms but does not identify the physical cause of those differences. More importantly, the batch-specific mean differences ranged from −13.6 neps/g in S2RCW to +101.4 neps/g in S5RDI. The overall +45.5 neps/g value is therefore an aggregate summary, whereas batch-dependent disagreement is the primary interpretation and precludes the use of a single correction factor.

3.3. Secondary Exploratory Common-Bale Ranking Across Three Platforms

One bale per batch was measured by all three platforms (Table 6). The five common-bale means retained the order S1RCW < S2RCW < S3RCW < S4RCW < S5RDI on each platform, giving Spearman rho = 1.00 for each pairwise platform ranking. Figure 1 shows that ordinal agreement coexisted with increasing divergence in absolute values at the upper end of the selected range. Because the batches were deliberately selected to cover a broad TotNep range and the order was defined using Neptester 720, the value ρ = 1.00 is reported only descriptively and is not an independent validation result.
Table 6. Mean TotNep counts for the five bales measured by all three platforms.
Figure 1. Mean TotNep count for the five common bales. The x-axis follows the original batch order established from Neptester 720 values; preservation of this order is descriptive and is not an independent validation of transferable severity classes.

3.4. Secondary Exploratory Agreement Analysis on the Five Common Bales

Exploratory Bland−Altman results are summarized in Table 7 and Figure 2. LVI 920 showed a mean positive difference of 32.0 neps/g relative to AFIS Pro 2. Comparisons involving Neptester 720 showed larger mean differences and substantially wider limits of agreement. With only five paired bales, the limits are imprecise and should not be generalized beyond the measured materials. Because no platform was designated as a reference and platform was confounded with site, operator, measurement date, and procedure, these estimates quantify disagreement under the observed platform-specific conditions rather than instrument bias. These AFIS-containing estimates are secondary to the 15-bale Neptester 720-LVI 920 comparison and are presented only as hypothesis-generating evidence for a future balanced study. Visual inspection of Figure 2 also suggests that paired differences may increase as the pair mean increases, with the pattern appearing more marked in comparisons involving Neptester 720. Given the five-bale sample and the deliberately range-spanning panel, this possible magnitude-dependent effect is treated only as an exploratory observation and was not formally tested.
Table 7. Exploratory Bland−Altman summaries for the five common bales.
Figure 2. Exploratory Bland−Altman plots for the five bales measured by all three platforms: (a) LVI 920-AFIS Pro 2; (b) Neptester 720-AFIS Pro 2; and (c) Neptester 720-LVI 920. Solid lines represent mean paired differences and dashed lines represent the mean difference ± 1.96 SD. The estimates are descriptive because n = 5. No platform was designated as a reference method, so the plots characterize cross-platform disagreement rather than instrument-specific bias. All five-bale comparisons shown here are secondary to the 15-bale paired Neptester 720-LVI 920 analysis. Visual inspection suggests possible magnitude-dependent disagreement at higher pair means; this pattern was not formally tested and should be regarded as hypothesis-generating rather than conclusive.

4. Discussion

The revised analysis supports a narrower conclusion than the original manuscript. The five industrial batches form an operationally ordered panel within the available records, and their order was reproduced by the three platform means. However, the panel is not a validated quality-assurance severity gradient: the ordering was constructed with Neptester 720, the materials were not independently certified, and only one common bale per batch was available across all three platforms. Accordingly, the 15-bale Neptester 720-LVI 920 comparison carries the principal inferential weight, whereas the AFIS-containing three-platform results are secondary, exploratory, and hypothesis-generating.
Batch identity was strongly confounded with material and production attributes. S1RCW was the only ecru/pristine-labelled batch and S5RDI was the only indigo/denim-labelled batch; suppliers/feedstock designations and production lines also differed. Mechanical recycling studies show that waste category, opening conditions, pre-treatment, and fiber configuration can modify fiber length, short-fiber content, neps, and processability [3,5,6,10,11,12,13,14]. The observed TotNep differences therefore cannot be assigned to color, feedstock origin, recycling intensity, or any single structural mechanism using the present design. Because fiber-length distribution, short-fiber content, nep morphology, recycling history, and harmonized testing conditions were unavailable, no mechanistic explanation is advanced for the observed cross-platform differences. The cited literature identifies possible contextual factors only and does not demonstrate causation in these batches.
The replicate audit was also consequential. The individual observations were technical determinations nested within bales, not independent material replicates. Treating all 125 determinations as independent would underestimate uncertainty and overstate evidence for platform-by-batch effects. The revised analysis therefore uses bale means for inference and restricts the full three-platform comparison to the five actually matched bales. The CV values in Table 4 remain useful as descriptive indicators of the recorded measurement dispersion, but their different sampling bases prevent a direct ranking of platform repeatability. Specifically, AFIS Pro 2 CVs quantify within-bale technical dispersion from one selected bale per batch, whereas Neptester 720 and LVI 920 CVs combine within-bale technical dispersion with between-bale material variation from three bales per batch. The CVs are therefore not directly comparable as indicators of platform repeatability, and no repeatability ranking is inferred.
For the 15 bales shared by Neptester 720 and LVI 920, a significant overall mean difference and a batch-dependent pattern of paired differences were observed. The batch-dependent disagreement is the more informative result: batch-specific mean differences ranged from −13.6 neps/g in S2RCW to +101.4 neps/g in S5RDI, so the overall +45.5 neps/g value is only a dataset-level summary and not a common correction factor. This finding shows that a single numerical correction cannot be justified from the present data. On the five common bales, Bland−Altman analysis likewise showed positive mean differences and wide limits of agreement, especially for comparisons involving Neptester 720. Correlation or identical rank order does not demonstrate agreement, and agreement limits estimated from five heterogeneous materials are too uncertain to support conversion equations [18,19]. The two evidence tiers should not be weighted equally: the 15-bale Neptester 720-LVI 920 analysis is the principal quantitative result, whereas each AFIS-based estimate relies on one bale per batch. Moreover, the observed ρ = 1.00 may be partly facilitated by the deliberate selection of a broad TotNep range and by the use of Neptester 720 to define the order; it therefore cannot be interpreted as a representative estimate of general cross-platform ranking performance. Figure 2 additionally suggests a possible increase in paired differences at higher mean TotNep values. However, because this visual pattern is based on only five deliberately range-spanning bales, it cannot establish a proportional effect and should be tested in a larger, independently selected dataset.
The apparent greater spread of Neptester 720 values at higher batch codes must be interpreted cautiously. This platform was used to create the original ordering, so selection favors an ordered and potentially more separated Neptester response. The present results therefore do not establish superior discrimination by Neptester 720. A valid comparison of discrimination would require a panel selected independently of all candidate platforms or characterized by an external reference procedure.
The study is a cross-platform comparison under platform-specific laboratory conditions, not a formal interlaboratory comparison. Instrument, laboratory, operator, measurement date, conditioning, sample preparation, and undocumented routine settings are confounded. Standardized cotton and textile testing frameworks emphasize controlled atmosphere, calibration, specimen preparation, and replicated laboratory designs [8,16,17]. A future interlaboratory study should apply a common written protocol, use matched and randomized bale subsamples, include multiple laboratories per platform where possible, and separate reproducibility from repeatability effects. Consequently, the observed paired differences reflect the combined platform-specific measurement conditions and cannot be partitioned into instrument, laboratory, operator, measurement-date, or procedural components; they should not be attributed uniquely to an instrument.
Despite these limitations, the dataset has practical exploratory value. Within this deliberately range-spanning, Neptester-defined panel, the three platform means preserved the same order while absolute TotNep values remained platform-specific; this is a descriptive, hypothesis-generating observation rather than independent validation. For routine quality control, thresholds should therefore be developed and maintained within a specified platform and protocol rather than transferred numerically between systems. The five batches may be used as a pilot material panel for protocol development, but not as certified or transferable severity classes.
The principal limitations are the small number of batches, retrospective selection based on Neptester 720, one AFIS bale per batch, non-equivalent numbers of technical determinations, unrecorded AFIS bale-selection criterion, absent conditioning and detailed sample-preparation metadata, and lack of complementary fiber properties and nep-morphology data. The batches also differ in color, product category, supplier/feedstock designation, and production line. These limitations preclude causal attribution and broad generalization. Their industrial origin increases the practical relevance of the dataset, but it does not establish that this small, heterogeneous panel is representative of mechanically recycled cotton more broadly.
A confirmatory study should include a larger balanced set of independently selected batches; the same randomized and homogenized bale subsamples on every platform; documented temperature, relative humidity, conditioning time, test mass, calibration, and thresholds; and characterization of fiber length, short-fiber content, trash, maturity, blend composition, recycling history, and nep morphology. Pre-specified repeatability, reproducibility, and agreement analyses would then allow the development and validation of transferable classes or platform-specific conversion models. Such a study should also pre-specify an assessment of whether paired differences change with measurement magnitude.

5. Conclusions

This study provides a preliminary cross-platform comparison of TotNep measurements in five selected industrial batches of mechanically recycled cotton. The batch order was preserved descriptively across USTER® Neptester 720, USTER® LVI 920, and USTER® AFIS Pro 2, but the order was originally defined with Neptester 720 and therefore does not independently validate a severity scale. This ordinal result arose from a deliberately range-spanning, Neptester-defined panel and should not be interpreted as independent evidence of ranking validity.
On 15 matched bales, Neptester 720 produced values 45.5 neps/g higher than LVI 920 on average, and the paired difference varied among batches. Batch-specific mean differences ranged from −13.6 to +101.4 neps/g, making batch-dependent disagreement, rather than the overall +45.5 neps/g average, the central quantitative conclusion. This 15-bale paired comparison constitutes the principal inferential evidence of the study. By contrast, the AFIS-containing three-platform analyses are based on one bale per batch and are secondary and exploratory. On the five bales measured by all three platforms, exploratory agreement analyses showed cross-platform mean differences and wide limits of agreement. Absolute TotNep values should therefore not be treated as numerically interchangeable, and no conversion equation is proposed.
Although all batches contained more than 95% cotton, their detailed feedstock composition and production history were not fully characterized. The study therefore does not support causal attribution, assessment of formal interlaboratory reproducibility, or validation of transferable severity classes. The results are best used to guide a future balanced validation study and to reinforce the need for platform- and protocol-specific quality-control thresholds. Accordingly, the observed disagreements are attributed only to the combined platform-specific measurement conditions, not to any single instrument. The conclusions therefore apply only to the five selected industrial batches and should not be extrapolated to the wider population of mechanically recycled cotton. The observed patterns are therefore reported without mechanistic interpretation.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/textiles6030109/s1, Supplementary Data File S1 contains the raw TotNep observations, bale-level means, the five common-bale dataset, exploratory agreement calculations, the 15-bale paired Neptester 720-LVI 920 analysis, and descriptive nep-size summaries.

Author Contributions

Conceptualization, M.F.-R. and B.M.-V.; methodology, M.F.-R., S.O.-C., J.J.-N., D.L.-R. and B.M.-V.; validation, D.L.-R., J.J.-N. and B.M.-V.; formal analysis, J.J.-N., D.L.-R. and B.M.-V.; investigation, M.F.-R. and S.O.-C.; resources, M.F.-R., S.O.-C. and B.M.-V.; data curation, M.F.-R.; writing—original draft preparation, M.F.-R.; writing—review and editing, S.O.-C., J.J.-N., D.L.-R. and B.M.-V.; visualization, M.F.-R. and D.L.-R.; supervision, J.J.-N. and B.M.-V.; project administration, B.M.-V. All authors have read and agreed to the published version of the manuscript.

Funding

The APC was funded by Universitat Politècnica de València.

Data Availability Statement

The raw TotNep dataset, bale-level summaries, paired-bale analyses, agreement calculations, and nep-size summaries supporting the findings of this study are provided in Supplementary Data File S1. Further inquiries can be directed to the corresponding authors.

Acknowledgments

Funding for open access charge: Universitat Politècnica de València. The authors acknowledge Recover™ for providing the industrial recycled-cotton batches evaluated in this study and the associated production and laboratory records. The authors also thank the technical laboratory teams involved in sample preparation, measurement execution, and data traceability. During the preparation of this work, the authors used generative AI tools to assist with English-language editing, manuscript structuring and formatting, and consistency checking against author-provided data and statistical outputs. No generative AI tool generated experimental data or made scientific decisions independently. The authors reviewed, verified and edited all outputs and take full responsibility for the content of the manuscript.

Conflicts of Interest

Authors Marta Fabra-Regalado and Sabela Otero-Camaño were employed by Recover™ Textile Systems, S.L. Recover™ supplied the industrial recycled-cotton batches evaluated in this study and provided access to internal laboratory nep measurements. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

References

  1. Kanan, M.; Wannassi, B.; Azouz, B.; Ben Hassen, M.; Assaf, R.; Barham, A.S. Cotton recycling: An experimental study of the mechanical preparation process. Case Stud. Chem. Environ. Eng. 2024, 10, 100849. [Google Scholar] [CrossRef] [Scilit]
  2. Will, M.; Aslan, Ç. Enhancing Recycled Ring Yarn Quality: Unlocking the Potential of Recycled Cotton Blends with the Combed Process; Rieter Machines & Systems: Winterthur, Switzerland, 2023. [Google Scholar]
  3. Kärkkäinen, E.; Kamppuri, T.; Heikinheimo, L.; Silva, C.J.; Gomes, J.M. Characterization of mechanically recycled cotton denim fibers and the effects of their properties on yarns and knits. Recycling 2025, 10, 177. [Google Scholar] [CrossRef] [Scilit]
  4. Uster Technologies AG. Guidelines for Testing Mechanically Recycled Cotton Fibers Using USTER® AFIS Pro 2; Uster Technologies AG: Uster, Switzerland, 2025. [Google Scholar]
  5. Badara, O.; Rämö, V.; Rissanen, M.; Tehrani-Bagha, A.R. Mechanically recycled textile fibers in carded and needle-punched non-wovens: Implications on processability, structure, and performance. Text. Res. J. 2025, 95, 1617–1636. [Google Scholar] [CrossRef] [Scilit]
  6. Lindström, K.; van der Holst, F.; Berglin, L.; Persson, A.; Kadi, N. Mechanical textile recycling efficiency: Sample configuration, treatment effects and fiber opening assessment. Results Eng. 2024, 24, 103252. [Google Scholar] [CrossRef] [Scilit]
  7. Utebay, B.; Celik, P.; Cay, A. Valorization of fabric wastes through production of recycled cotton yarns by compact ring and open-end rotor spinning. J. Clean. Prod. 2023, 409, 137135. [Google Scholar] [CrossRef] [Scilit]
  8. Drieling, A.; Gourlot, J.-P.; Knowlton, J. (Eds.) Guideline for Standardized Instrument Testing of Cotton, Version 4.0; International Cotton Advisory Committee and International Textile Manufacturers Federation: Washington, DC, USA, 2025. [Google Scholar]
  9. Ten Berge, A.B.G.M.; Temmink, R.; Kuppen, M.; van Slagmaat, M.B.; Kamphuis, S.; Groeneveld, R.A.J.; Luiken, A.; Oelerich, J.; Mahy, J.W.G. An analytical toolbox to verify the presence, quantity and origin of recycled cotton fibers in textile garments. Sci. Rep. 2026, 16, 8999. [Google Scholar] [CrossRef] [Scilit]
  10. Islam, M.M.; Yin, R.; West, A. A brief review of mechanical recycling of textile waste. Textiles 2025, 5, 41. [Google Scholar] [CrossRef] [Scilit]
  11. Kanan, M.; Wannassi, B.; Barham, A.S.; Ben Hassen, M.; Assaf, R. The quality of blended cotton and denim waste fibres: The effect of blend ratio and waste category. Fibers 2022, 10, 76. [Google Scholar] [CrossRef] [Scilit]
  12. Lindström, K.; Sjöblom, T.; Persson, A.; Kadi, N. Improving mechanical textile recycling by lubricant pre-treatment to mitigate length loss of fibers. Sustainability 2020, 12, 8706. [Google Scholar] [CrossRef] [Scilit]
  13. Liu, Y.; Delhom, C.D. Investigation of laboratory saw ginning and blending on cotton fiber quality measurement. J. Cotton Res. 2025, 8, 41. [Google Scholar] [CrossRef] [Scilit]
  14. Delhom, C.D.; Kelly, B.; Martin, V. Physical properties of cotton fiber and their measurement. In Cotton Fiber: Physics, Chemistry and Biology; Fang, D.D., Ed.; Springer: Cham, Switzerland, 2018; pp. 41–73. [Google Scholar] [CrossRef] [Scilit]
  15. Kelly, C.M.; Hequet, E.F.; Dever, J.K. Interpretation of AFIS and HVI fiber property measurements in breeding for cotton fiber quality improvement. J. Cotton Sci. 2012, 16, 1–16. [Google Scholar]
  16. ISO 139:2005; Textiles—Standard Atmospheres for Conditioning and Testing. International Organization for Standardization: Geneva, Switzerland, 2005.
  17. ISO 5725-1:2023; Accuracy (Trueness and Precision) of Measurement Methods and Results—Part 1: General Principles and Definitions. International Organization for Standardization: Geneva, Switzerland, 2023.
  18. Bland, J.M.; Altman, D.G. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986, 1, 307–310. [Google Scholar] [CrossRef] [Scilit]
  19. Bland, J.M.; Altman, D.G. Measuring agreement in method comparison studies. Stat. Methods Med. Res. 1999, 8, 135–160. [Google Scholar] [CrossRef] [Scilit] [PubMed]
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