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Article

Upcycling Coffee Silverskin Waste into Functional Textile Coatings: Evaluation on Cotton, Lyocell, Wool, and Silk

by
Agata Nolasco
1,
Francesco Esposito
2,
Teresa Cirillo
2,
Augusta Silva
1 and
Carla Joana Silva
1,*
1
CITEVE—Centro Tecnológico das Indústrias Têxtil e do Vestuário de Portugal, R. Fernando Mesquita 2785, 4760-034 Vila Nova de Famalicão, Portugal
2
Department of Agricultural Sciences, University of Naples “Federico II”, via Università 100, 80055 Portici, Naples, Italy
*
Author to whom correspondence should be addressed.
Coatings 2025, 15(9), 1033; https://doi.org/10.3390/coatings15091033
Submission received: 24 July 2025 / Revised: 19 August 2025 / Accepted: 27 August 2025 / Published: 3 September 2025
(This article belongs to the Special Issue Advances in Coated Fabrics and Textiles)
Browse Figures
Versions Notes

Abstract

Agricultural and food by-products offer valuable opportunities for circular and bio-based innovation across sectors. In the textile industry, replacing fossil-based coatings with sustainable alternatives is increasingly urgent. This study evaluates the performance of a textile coating based on coffee silverskin (CS)—an abundant by-product of coffee roasting—applied to four natural fibre substrates: cotton, lyocell, wool, and silk. A formulation combining 60% CS sludge (8% solids), treated by wet ball milling, with an aliphatic polyester-polyurethane dispersion was applied via knife coating. Standardised tests assessed mechanical resistance, air permeability, colour fastness, moisture management, and water repellency, including contact angle and drop absorption analyses. Results revealed that all substrates were compatible with the CS-based coating, which reduced air permeability and increased hydrophobicity. Notably, silk showed the most significant functional enhancement, transitioning from hydrophilic to waterproof with increased durability—indicating strong potential for technical applications such as outerwear and performance textiles. Given the renewable origin of both the substrate and coating, this study highlights the feasibility of valorising agri-food waste in high-performance, bio-based textile systems. These findings demonstrate the potential of CS as a bio-based coating for technical textiles, supporting the development of high-performance and sustainable materials within the textile industry.

1. Introduction

The exploitation of agricultural and food by-products represents a strategic intersection of the circular economy and the bioeconomy. It aligns with the principles of resource efficiency and waste reduction [1], while supporting the bioeconomy’s goal of using renewable biological resources for sustainable production [2]. By transforming what would otherwise be waste into valuable resources, such as essential nutrients and functional compounds, these by-products offer potential applications in bioplastics, biofuels, animal feed, and functional food ingredients [3,4]. Importantly, diverting agri-food residues from landfilling or incineration reduces the environmental impact of the food industry [3].
Despite their sectoral differences, the food and textile industries show promising synergies. Through valorisation, agri-food by-products can be transformed into active ingredients with antimicrobial, absorbent, and mechanical properties [2,5]. These compounds can serve as natural dyes [6] or be used to produce bio-based materials for textile applications [7]. As demand grows for functional textiles with sustainability credentials, the challenge is to develop solutions that maintain the aesthetics, comfort, and tactile properties of traditional fabrics [8].
One promising area is the use of food waste–derived materials as textile coatings. Conventional coatings are typically fossil-based polymers derived from crude oil [9]. Although these materials are efficient and cost-effective, they raise significant environmental concerns. Recent efforts focus on replacing them with bio-based alternatives that offer comparable performance and reduced ecological impact [7,10]. The choice of textile substrate also plays a crucial role, as different fibres may interact uniquely with bio-based coatings, influencing durability, performance, and potential applications.
This study explores, for the first time, the influence of textile substrate type on the performance of a coating based on coffee silverskin (CS)—a residue generated during coffee bean roasting. CS is a lightweight membrane that detaches from beans during roasting and is readily available in large quantities. Although its use as a coating ingredient has been minimally studied, previous research demonstrated its compatibility with waterborne polyurethane binders after planetary ball milling treatment [11].
Building on this, we evaluated the performance of a CS-based coating on cotton, lyocell, silk, and wool fabrics selected for their renewable origin and common use in apparel. Each fabric’s interaction with the bio-based coating was tested for mechanical, colour fastness, and water resistance properties. The goal is to understand how substrate selection influences the coating’s functional properties and to assess the viability of CS as a sustainable alternative to conventional coating agents in textiles.

2. Materials and Methods

The following section presents a detailed description of the coffee silverskin coating production process, accompanied by a visual chart (Figure 1) to offer a clear and comprehensive overview of the topic.

2.1. Coffee Silverskin (CS) Sample

The coffee silverskin utilised in this study was procured from two distinct coffee enterprises located in the Campania region of Italy. The silverskin was obtained from a mixture of roasted green beans sourced from both Coffea arabica and Coffea robusta varieties, although the specific ratio was not disclosed. Coffee companies routinely blend different coffee varieties during roasting to achieve distinct aromas. The resulting coffee silverskin was collected using suction cyclones, a standard method in the industry [11].

2.2. Residue Pre-Treatments

Initially, a sample of coffee silverskin was ground to a particle size of 0.2 mm using the Retsch SM 300 cutting mill (Retsch GmbH, Haan, Germany). Subsequently, the ground coffee silverskin underwent further processing using a Retsch PM100 planetary ball mill (BM) system (Retsch GmbH, Haan, Germany) under wet conditions. The milling process was carried out using a 125 mL zirconia milling cup and 5 mm zirconia spheres, operating for 2 h at 400 rpm. A mixture comprising ground CS and distilled water in a ratio of 1:7 was utilised. Following the BM treatment, the outcome exhibited a sludge-like consistency.

2.3. Coating Paste Formulation

The coating paste was meticulously prepared by combining 60% of the sludge-CS (with an 8% CS solid content) obtained by BM treatment with Impranil ECO DLS (38%), serving as the polymer base, and Imprafix 2794 (2%), functioning as the crosslinker. Impranil ECO DLS, sourced from Covestro (Filago, Italy), is an anionic, aliphatic polyester-polyurethane dispersion in water, boasting a solids content of approximately 50%. Complementing this, Imprafix 2794, also generously supplied by Covestro, is an aliphatic blocked polyisocyanate with a water content of about 38%.
The coating was designed to optimise sustainability by incorporating coffee silverskin, an abundant agri-food by-product from the coffee roasting industry, as the main functional filler, thereby valorising a waste material and reducing the use of virgin raw materials. Additionally, Impranil® ECO DLS contains partially bio-based carbon content, contributing to a reduced reliance on fossil resources. High quality was maintained through formulation optimisation and confirmed by textile performance testing reported in our previous work [11].

2.4. Textile Substrates and Coating Process

The coating formulation was applied to different textile substrates to assess their influence on the performance differences. Specifically, substrates composed of pure cotton, lyocell, wool, and silk were chosen for this comprehensive analysis. The careful selection of various fabrics represented a strategic choice, aiming to encompass a wide spectrum of textiles, each celebrated for its distinct features and uses. This meticulous approach enabled a detailed evaluation of how the coffee silverskin coatings performed on diverse textile materials, of cellulosic and protein origin. The intentional selection of these substrates emphasised the research’s aim to deeply explore the interplay between coatings and specific base fabric compositions.
Before coating, all fabrics underwent a pre-treatment consisting of washing and drying under domestic conditions according to EN ISO 6330:2021, to simulate real-world textile use. Each textile substrate was then subjected to a knife coating process, involving the application of three coating layers to ensure uniform surface finishing and proper film adhesion. The initial layer, with a thickness of less than 0.01 mm, was succeeded by two layers each measuring 0.1 mm. Each layer underwent a drying process at 100 °C for 5 min. Subsequently, after the application of all layers, the substrate was thermofixed at 150 °C for another 5 min, ensuring the thorough bonding and stability of the coating. At the end, each coating was subjected to a calendaring process at 140 °C and 5 bar pressure for 30 s. The CS-based coating was applied to textile substrates using a Mathis Labcoater (Mathis, Oberhasli, Switzerland). Drying and thermo-fixation were also performed on the same equipment. Finally, the coated fabrics underwent calendaring using a Macpi Flat Bonding Press (Macpi, Treviso, Italy).

2.5. Determination of the Coatings’ Performance on Different Substrates

The coatings obtained underwent a meticulous evaluation process to assess their performance on different textile substrates. An extensive array of standardised tests was performed, including Martindale Abrasion Resistance test (ISO 5470-2:2003) conducted under dry conditions with a pressure of 12 kPa applied, the Resistance to damage by flexing (ISO 7854:1995) using the Crumple/Flex method, the Permeability to air (ISO 9237:1995) performed on a 20 cm2 sample under controlled atmospheric conditions of 20 °C and 65% relative humidity, the Colour fastness to rubbing (ISO 105-X12:2016) conducted under dry and wet conditions and the Colour fastness to water (ISO 105-E01:2013).
In addition to the aforementioned analyses, the study integrated supplementary evaluations to determine water resistance performance. A direct assessment of water resistance involved applying water droplets to both the fabric and the CS-coated fabric, measuring absorption times. The wettability of water droplets on the surfaces of cotton, lyocell, wool, and silk fabrics, as well as CS-coated fabrics, was also characterised by contact angle (Krüss DSA100, Hamburg, Germany), with 3 μL of deionised water droplets for static contact angle measurement. Furthermore, the fabric samples underwent a Liquid Moisture Management test (LMMT) (AATCC 195-2010) under two distinct conditions: with and without pre-treatment. The pre-treatment involved washing and drying under domestic conditions, following the guidelines outlined in EN ISO 6330:2021. This additional step aimed to simulate real-world scenarios and assess the impact of regular washing on the moisture management performance of the fabric. To conduct this test, as outlined by [12,13], the fabric specimens are securely held flat between the top and lower sensors under a specific pressure. A specific quantity of synthetic sweat solution is administered to the fabric’s upper surface. In this study, the fabric’s upper surface corresponds to the one with the CS-coating applied, with the aim of assessing how coatings on various substrates react to the management of liquid moisture. The instrument, connected to a specific software, documents alterations in resistance between each pair of neighbouring metal rings at both the upper and lower sensors. Following application, the salted solution disperses in three directions: outward spread on the upper surface, transfer from the upper to the lower surface, and outward spread on the lower surface. The resistance of each pair of adjacent metal rings changes due to the conductive nature of the solution. The results are classified into six grades, which are water-repellent fabric, slow absorbing fabric, fast absorbing and slow drying fabric, fast absorbing and quick drying fabric, water-penetration fabric and moisture management fabric [14].
All quantitative measurements, including contact angle and air permeability, were performed in triplicate (n = 3). Data are reported as means ± standard deviation. For qualitative evaluations (e.g., Martindale rating scale), three independent observers assessed the results to ensure consistency.

3. Results

The CS-coating underwent various analyses, briefly outlined below. Martindale Abrasion Resistance analysis simulated typical wear and tear, scrutinising fabric durability. Determination of Resistance to damage by flexing assessed flexibility, a critical attribute for garment resilience. Permeability to air measurement assessed breathability, enhancing comfort. Colour fastness tests, in both dry and wet conditions, ensured colour retention and aesthetic longevity. Colour fastness to water showed resistance to colour bleeding when exposed to moisture.
Another crucial evaluation method for textile products is the Liquid Moisture Management test. This specific test assesses a fabric’s ability to efficiently manage liquid moisture, making it particularly vital for performance wear, sports apparel, and activewear applications [12]. These detailed evaluations provided deep insights into the coatings’ performance, assessing their suitability for diverse practical applications in the textile industry. Additionally, understanding how the textile substrate influenced the coating is crucial for comprehending the material’s overall functionality and durability.
This section delves into a comprehensive discussion of the results categorised by the type of textile substrate, distinguishing between cellulose-based substrates, cotton and lyocell, and protein-based substrates, wool and silk. This allows for a thorough exploration of how these distinct fabric compositions interact with the applied coatings, shedding light on their unique characteristics and performance outcomes. Recognising these inherent differences is key to drawing accurate comparisons and deriving meaningful conclusions about the performance of the coatings across various textiles. The outcomes of these analyses are presented in Table 1, Table 2 and Table 3.
As shown in Table 3, the fabrics demonstrated different liquid transport behaviours depending on their fibre composition and pre-treatment. In the context of the Liquid Moisture Management Test (AATCC 195-2010), water repellency refers to the resistance to initial wetting, typically reflected by longer wetting times and higher contact angles. Water penetration describes the extent to which liquid passes from the face to the back surface of the fabric, indicated by absorption and spreading on the bottom side. Finally, water absorption denotes the amount of liquid taken up and retained within the fabric structure once wetting occurs, as shown by the absorption rate and maximum wetted radius on both surfaces. These distinctions are essential for interpreting the performance differences observed across the tested substrates.

3.1. Cellulose-Based Textile Substrates

Cellulose-based textile substrates, such as cotton and lyocell, are derived from natural sources and offer unique properties that make them valuable in the textile industry. Cotton, a traditional and widely used natural fibre, is sourced from the fluffy fibres of the cotton plant. Comprising predominantly cellulose, constituting approximately 90% of its structure [15], cotton’s framework is rooted in this complex carbohydrate. The cellulose molecules in cotton fibres are intricately arranged in a crystalline structure, providing the fabric with its robustness and longevity [15]. These elongated cellulose chains are held together by hydrogen bonds, ensuring the fabric’s stability and cohesiveness. Cotton’s hydrophilic hydroxyl groups, originating from cellulose, grant the fabric exceptional qualities such as flexibility, resilience, and impressive mechanical strength [16]. Furthermore, the fabric’s structural composition imparts cotton with its inherent softness, breathability, and versatility, rendering it a preferred choice in the textile industry for a wide array of applications [17]. These distinctive attributes make cotton an excellent substrate for textile coating applications, ensuring strong adhesion and durability of the applied materials.
In regard to lyocell, it represents a newer generation of cellulose fibres derived from wood pulp. Categorised as a regenerated-cellulosic fibre (RCF), lyocell undergoes a process where natural cellulose is chemically dissolved using organic solvent dry jet wet spinning treatments [18]. This method retains its inherent chemical structure, resulting in fibres that are lauded for their strength, resilience, and exceptional absorbency. The smooth surface of lyocell fabrics imparts a soft touch, and thanks to the high percentage of fibrillary structure, they excel in moisture-wicking, efficiently absorbing and releasing moisture for optimal comfort across various climates [19]. This makes them particularly well-suited for activewear and undergarments. Beyond comfort, lyocell fabrics boast high durability, wrinkle resistance, and easy care, making them a practical and versatile choice for everyday wear.
Considering these two textile substrates, the analyses detailed in Section 2.5, Materials and Methods, were conducted. Martindale Abrasion Resistance test (ISO 5470-2:2003) revealed different levels of resistance among cellulose-based textile substrates. CS-coated on cotton, in particular, exhibited moderate surface colour alterations (grade 3) after enduring 51,200 cycles under a constant pressure of 12 kPa. In contrast, the CS-coated on lyocell demonstrated exceptional resistance, achieving a grade 1 rating, indicating a slight change in the colour surface. Additionally, when evaluating the CS-coating on cellulose-based textile substrates for resistance to damage by flexing (ISO 7854:1995), the lyocell fabric displayed remarkable resilience, achieving a top-tier rating of grade 0. It showed no indications of mechanical stress, such as cracks or folds. Similarly, the CS-coated cotton substrate exhibited commendable flexibility and high resistance, securing a grade 1 rating. Surprisingly, the determination of permeability to air analysis (ISO 9237:1995) revealed unexpected outcomes. Despite the traditionally high air permeability of cotton, attributed to its breathable structure with loosely packed fibres, the CS-coated cotton fabric exhibited significant airflow resistance, measuring at 0.05 lm−2 s−1. Similarly, the CS-coated lyocell fabric demonstrated substantial airflow resistance (1.79 lm−2 s−1). This unanticipated shift in cotton’s air permeability, known for its breathability, suggests that the CS-coating’s uniform and well-adhered application may render it suitable for conditions demanding robust resistance to the passage of air. The specific values offer a quantitative comparison, emphasising the impact of the CS-coating on the air permeability of both cotton and lyocell substrates. Both cellulose-based textile substrates, cotton and lyocell, displayed consistent results in colour fastness to rubbing (ISO 105-X12:2016) under dry conditions, achieving a commendable grade of 4–5. This indicates their shared ability to withstand mechanical stress effectively in a dry environment. However, their colour fastness diminished when subjected to wet conditions during rubbing, resulting in colour fading for both substrates. On a positive note, in colour fastness to water tests (ISO 105-E01:2013), both coated fabrics, whether cotton or lyocell, exhibited good colour fastness with a grade of 4–5. This implies that the CS-coating effectively resisted colour bleeding or fading when exposed to water without undergoing mechanical stress like rubbing.
The outcomes derived from optical contact angle measurements and visual drop absorptions on the cotton fabric (Figure 2) clearly indicated that water droplets on the cotton fabric were rapidly absorbed. This was evident from a drop contact angle of 31.79° ± 1.04° and an absorption time of 2.95 s. These measurements provide valuable insights into the wetting behaviour of water on the cotton fabric. The low contact angle suggests high wettability, showcasing the fabric’s affinity for water. The short absorption time underscores the fabric’s efficiency in quickly absorbing and interacting with water, emphasising its excellent moisture absorption characteristics. In contrast, the optical contact angle of 111.48° ± 1.63° obtained for the CS-coating on the cotton textile substrate indicates the creation of a hydrophobic surface.
Regarding the lyocell fabric, optical contact angle measurements unveiled a notably high contact angle of 130.27° ± 7.88°. Nevertheless, water droplets applied to the fabric were completely absorbed in less than one minute (48.03 s ± 6.01 s), as illustrated in Figure 3. This aligns with the fabric’s well-known reputation for efficient moisture-wicking properties. Despite its initially hydrophobic appearance, the fabric demonstrated exceptional ability in absorbing moisture. Similar to the cotton fabric, the application of CS-coating on the lyocell fabric exhibited hydrophobic behaviour, featuring a contact angle of 116.15° ± 2.49° and a water-repellent surface.
For the CS-coated cotton and lyocell fabrics, the Liquid Moisture Management Test (AATCC 195-2010) results (Table 3) indicate “fast absorption and slow drying” for cotton, while lyocell retained effective moisture-wicking. At the same time, contact angle and drop absorption tests showed surface hydrophobicity for both fabrics. This reflects the different phenomena assessed: contact angle measurements capture resistance to initial wetting at the fabric surface, whereas the LMMT evaluates dynamic liquid transport under continuous exposure, more representative of perspiration. Consequently, the CS-coated cotton and lyocell fabrics can resist isolated surface droplets while still allowing internal moisture absorption and transport. This behaviour illustrates a balance between surface water repellency and internal liquid management, supporting wearer comfort.

3.2. Protein-Based Textile Substrates

Protein-based textile substrates, such as wool and silk, offer unique characteristics and applications distinct from cellulose-based fibres like cotton and lyocell. Wool is derived from the fleece of sheep and is primarily composed of the protein keratin. On the other hand, silk is produced by silkworms and is mainly composed of fibroin proteins. These protein-based fibres have inherent properties that set them apart in the textile industry.
Wool, a predominant source of keratin rich in amino acids like cysteine, glycine, and tyrosine [20], stands out as the most widely used animal fibre. Renowned for its numerous qualities, wool is prized for its warmth, antistatic nature, flame-retardant properties, heat insulation, elasticity, and its intrinsic ability to resist wrinkles and creases [21]. The distinctive structure of wool fibres, characterised by overlapping scales, significantly influences various properties such as moisture management, tactile characteristics, and felting/shrinkage behaviour [22,23].
Silk, originating from the silkworm Bombyx mori L., involves the spinning of a composite material consisting of two fibroin filaments enveloped by a sericin cementing layer [24]. The primary components of silk, constituting approximately 75% and 25% wt for fibroin and sericin, respectively, are proteins [24]. In the process of crafting garments from silk, the sericin is commonly removed before dyeing, a step known as degumming [25,26]. Fibroin, comprising various amino acids such as glycine, alanine, and serine [27], is a key component responsible for the unique texture of silk. Recognised for its lightweight and breathable qualities, silk stands as a preferred choice for crafting elegant and comfortable apparel. Moreover, according to existing literature, silk fibroin demonstrates exceptional properties as a biomaterial, being well-tolerated, seamlessly integrating into regenerating tissue, and undergoing gradual resorption over time [28,29,30].
Wool and silk are both protein-based natural fibres, but they differ in amino acid composition, which influences their structural and mechanical properties. The analyses conducted in this study unveiled comparable performance between wool and silk as coated textile substrates across a range of assessments. Following the Martindale Abrasion Resistance test, both samples exhibited a grade 2 out of 5, indicating slight alterations in colour on the coating’s surface after enduring 51,200 cycles under a constant pressure of 12 kPa. This implies a good resistance to abrasion for both wool and silk-coated textile substrates. In the determination of resistance to damage by flexing, the CS-coating on wool fabric demonstrated superior resistance with a grade of 1.5, signifying higher flexibility and resilience.
On the other hand, the CS-coating on the silk substrate received a grade of 2, indicating relatively less flexibility and presenting some folds during the flexing process. In the colour fastness to rubbing analysis, both protein-based textile substrates showed consistent values comparable to cellulose-based textile substrates. They exhibited high fastness to rubbing in dry conditions (grade 4–5), suggesting resistance to colour transfer during regular wear. However, under wet conditions during rubbing stress, colour fading was observed, highlighting a shared vulnerability to moisture. Moreover, in the colour fastness to water analysis, both wool and silk fabrics demonstrated good resistance (grade 3–4), indicating that the CS-coating effectively resisted colour bleeding or fading when exposed to water, although some degree of colour change was observed under wet conditions.
The evaluation of air permeability (ISO 9237:1995) yielded unexpected outcomes, particularly on CS-coating on silk textile substrate. While the notable resistance observed in CS-coated wool textile substrate (2.36 lm−2 s−1) aligns with the expected properties of wool, known for trapping air within its fibres and offering thermal insulation, the elevated resistance encountered in CS-coated silk was surprising (0.06 lm−2 s−1). This is noteworthy considering silk’s conventional attributes as a breathable and lightweight fabric, but it can be explained by the tight fabric construction of the fabric.
The outcomes obtained from optical contact angle measurements and visual drop absorption revealed intriguing results when comparing wool and silk fabrics with their respective CS-coated counterparts (Figure 4 and Figure 5). The distinctive composition of wool initially demonstrated hydrophobic characteristics, evidenced by a contact angle of 101.27° ± 3.18°, but after approximately 15.07 ± 5.43 min, the water droplets applied to the wool fabric were fully absorbed. In contrast, the CS-coating on wool exhibited a similarly high contact angle of 134.90° ± 1.70°. However, in this instance, water droplets were not absorbed by the fabric, owing to the hydro-repellent layer introduced by the coating (Figure 4).
The silk fabric exhibited the most pronounced improvement upon CS-coating, as demonstrated by both contact angle measurements and the Liquid Moisture Management Test (AATCC 195-2010). Uncoated silk showed a low contact angle of 26.71° ± 5.48° and an absorption time of ~2 s, confirming its highly hydrophilic character. After coating, the contact angle increased dramatically to 121.03° ± 1.26°, representing a shift of nearly +95°, and absorption was effectively prevented, indicating a complete transition to hydrophobic behaviour.
The Liquid Moisture Management Test (AATCC 195-2010) confirmed the effect of the CS-coating on protein-based fabrics. For wool, the coating produced a water-repellent behaviour, upgraded to waterproof after pre-treatment, showing enhanced resistance to liquid penetration. Uncoated silk was initially water-repellent, while CS-coated silk—especially after pre-treatment—reached a waterproof classification, indicating the coating delayed droplet absorption and effectively blocked liquid under dynamic conditions. These changes, combined with the largest increase in contact angle among all substrates, indicate that silk experienced the most pronounced improvement with CS application, highlighting its compatibility with the coating and suitability for technical applications requiring water resistance.

4. Discussion

This research builds upon the initial work of Nolasco et al. [11], which first explored coffee silverskin (CS) as a bio-based coating material for textiles. That prior research highlighted the significance of planetary ball mill (PBM) under wet conditions to reduce particle size, enhance dispersion, and improve adhesion of CS to textile substrates. The current work expands this approach by applying the optimised CS-based formulation to a variety of textile substrates—cotton, lyocell, wool, and silk—with the aim of understanding how fibre composition influences coating performance.
The structural effects of ball milling, driven by centrifugal and frictional forces, along with the generation of heat [31,32], were key to increasing the compatibility of CS with polymer matrices. This treatment likely promoted stronger interactions between CS’s functional groups and the anionic polyester-polyurethane (PU) binder used in the coating [33]. As supported by a previous study [11], such enhancement contributes to better film formation, allowing the CS to act as a partial plasticiser. Moreover, the inherent biochemical complexity of CS, which is rich in fibre and protein content, may contribute to its multifaceted performance as a bio-based coating material [34,35].
Among all substrates tested, silk demonstrated the most pronounced improvement following CS application, achieving high levels of water repellency and reduced air permeability, while maintaining mechanical integrity. This enhanced performance may result from the molecular affinity between the protein-based CS formulation and the fibroin structure of silk, improving surface bonding and coating durability. These findings are consistent with previous efforts to modify silk properties through acylation, nanoparticle integration, or fluoropolymer treatment [36,37,38], all aimed at boosting water resistance and robustness. The current approach provides a bio-based route to achieving comparable functionality.
The transformation of silk from a naturally hydrophilic material into a hydrophobic, water-repellent fabric after CS coating suggests its strong potential for use in technical textiles. This aligns with ongoing efforts to broaden silk’s applicability into sectors such as home textiles, activewear, and weather-resistant garments [39]. Notably, compared to synthetic fluoropolymer coatings [40], the CS-based formulation offers a more environmentally responsible solution, delivering performance benefits such as hydrophobicity, breathability control, and durability without reliance on petroleum-derived materials.
Beyond silk, all tested fabrics showed good compatibility with CS coatings, reinforcing the versatility of this bio-based system. The influence of polyurethane-based coatings without bio-fillers on textile wettability and moisture management has been documented in previous studies. For instance, Refs. [41,42] report that polyester–polyurethane dispersions, such as Impranil® ECO DLS, generally increase the contact angle of natural and regenerated cellulose fabrics by forming a continuous hydrophobic film, which also delays liquid absorption. These effects are consistent with the trends observed in the present study, suggesting that the incorporation of Coffee Silverskin primarily adds functional value through its bio-based origin and potential additional properties, while the hydrophobic behaviour is largely attributable to the polymer base itself.
Unlike conventional coatings that rely on synthetic PU systems or fluoropolymers, the CS-based coating developed here leverages lignocellulosic residues with minimal petrochemical-derived content. Supporting literature indicates that hybrid PU coatings that incorporate lignin exhibit a similar cradle-to-gate carbon footprint to fossil-based counterparts—but may become net-negative in CO2 emissions when accounting for biogenic carbon uptake [43]. Additionally, studies comparing individual coating additives have shown that bio-based components such as rice-husk biochar or nanocellulose can reduce carbon footprints by approximately 40–60% relative to conventional fillers or waxes [44].
Taken together, these findings demonstrate the broader relevance of coffee silverskin (CS) in textile innovation, supporting both the valorisation of agri-food waste and the reduction of fossil-based coating use. However, it is important to acknowledge the limitations of the present work. The study did not include a complete set of baseline measurements for uncoated fabrics, nor a direct comparison with polymer-only coated samples, which would have allowed a more precise quantification of the individual contributions of the Coffee Silverskin filler versus the polymer matrix. These aspects, together with the lack of detailed information on the structural characteristics of the textile substrates (e.g., weave, yarn type, and density), represent areas for improvement in future research. Nevertheless, the results presented here offer novel and valuable evidence of Coffee Silverskin’s potential as a sustainable coating material, highlighting both its functional effects on different fibres and its contribution to circular material innovation. By addressing the identified limitations in subsequent studies, this line of research can be further strengthened, ultimately supporting the development of bio-based alternatives to conventional textile coatings.

Author Contributions

Conceptualisation, A.N., A.S. and C.J.S.; methodology, A.N. and F.E.; investigation, A.N.; validation, T.C., F.E., A.S. and C.J.S.; data curation, A.N. and A.S.; writing—original draft preparation, A.N.; writing—review and editing, A.N., F.E., A.S. and C.J.S.; visualisation, A.N.; supervision, A.S. and C.J.S.; project administration, F.E., T.C. and C.J.S.; funding acquisition, C.J.S. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the integrated project Be@t—Textile Bioeconomy (TC-C12-i01, Sustainable Bioeconomy No. 02/C12-i01.01/2022), promoted by the Recovery and Resilience Plan (RRP), Next Generation EU, for the period 2021–2026. The APC was funded by the same project.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data are contained within the article.

Acknowledgments

The authors acknowledge the financial support from the integrated project be@t—Textile Bioeconomy, promoted by the Recovery and Resilience Plan (RRP), Next Generation EU.

Conflicts of Interest

The authors declare no conflicts of interest.

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Coatings 15 01033 g001
Figure 1. Visual flowchart of the steps carried out for the development of the Coffee Silverskin coatings on cotton, lyocell, wool and silk, as base textile substrates.
Figure 1. Visual flowchart of the steps carried out for the development of the Coffee Silverskin coatings on cotton, lyocell, wool and silk, as base textile substrates.
Coatings 15 01033 g001
Coatings 15 01033 g002
Figure 2. Representative visual images of contact angle and droplet absorption of cotton before and after CS-coating. The corresponding averaged quantitative values (based on three independent measurements) are reported in Table 3.
Figure 2. Representative visual images of contact angle and droplet absorption of cotton before and after CS-coating. The corresponding averaged quantitative values (based on three independent measurements) are reported in Table 3.
Coatings 15 01033 g002
Coatings 15 01033 g003
Figure 3. Representative visual images of contact angle and droplet absorption of lyocell before and after CS-coating. The corresponding averaged quantitative values (based on three independent measurements) are reported in Table 3.
Figure 3. Representative visual images of contact angle and droplet absorption of lyocell before and after CS-coating. The corresponding averaged quantitative values (based on three independent measurements) are reported in Table 3.
Coatings 15 01033 g003
Coatings 15 01033 g004
Figure 4. Representative visual images of contact angle and droplet absorption of wool before and after CS-coating. The corresponding averaged quantitative values (based on three independent measurements) are reported in Table 3.
Figure 4. Representative visual images of contact angle and droplet absorption of wool before and after CS-coating. The corresponding averaged quantitative values (based on three independent measurements) are reported in Table 3.
Coatings 15 01033 g004
Coatings 15 01033 g005
Figure 5. Representative visual images of contact angle and droplet absorption of silk before and after CS-coating. The corresponding averaged quantitative values (based on three independent measurements) are reported in Table 3.
Figure 5. Representative visual images of contact angle and droplet absorption of silk before and after CS-coating. The corresponding averaged quantitative values (based on three independent measurements) are reported in Table 3.
Coatings 15 01033 g005
Table 1. Characterisation results for Coffee Silverskin (CS)-coatings on cellulose-based textile substrates (cotton and lyocell), and protein-based textile substrates (wool and silk).
Table 1. Characterisation results for Coffee Silverskin (CS)-coatings on cellulose-based textile substrates (cotton and lyocell), and protein-based textile substrates (wool and silk).
Characterisation Results(Specific Conditions)Cellulose-BasedProtein-Based
CottonLyocellWoolSilk
Martindale Abrasion Resistance * (ISO 5470-2:2003) 3122
Determination of Resistance to Damage by Flexing * (ISO 7854:1995) 101.52
Determination of Permeability to Air (ISO 9237:1995)lm−2 s−10.05 ± 0.11.79 ± 1.02.36 ± 0.60.06 ± 0.1
Colour Fastness to Rubbing **
(ISO 105-X12:2016)		dry conditions4–54–54–54–5
wet conditions2–3222–3
Colour Fastness to Water **
(ISO 105-E01:2013)		 43–43–43–4
* Evaluation based on a scale from 0 (no alteration) to 5 (fabrics severe damaged). ** The ratings based on the Grey Scale for staining, vary from 1 (poor rating) to 5 (better rating).
Table 2. Average contact angle and water absorption time on raw fabrics and Coffee Silverskin (CS)-coated fabrics. Data are reported as means ± standard deviation. Representative visual images of droplet absorption are shown in Figure 2, Figure 3, Figure 4 and Figure 5.
Table 2. Average contact angle and water absorption time on raw fabrics and Coffee Silverskin (CS)-coated fabrics. Data are reported as means ± standard deviation. Representative visual images of droplet absorption are shown in Figure 2, Figure 3, Figure 4 and Figure 5.
Characterisation TestsRaw FabricsCS-Coated Fabrics
Contact AngleAbsorption TimeContact AngleAbsorption Time
Cellulose-basedCotton31.79° ± 1.04°2.55 ± 0.50 s111.48° ± 1.63°hydro-repellent
Lyocell130.27° ± 7.88°48.03 ± 6.01 s116.15° ± 2.49°hydro-repellent
Protein-basedWool101.27° ± 3.18°15.07 ± 5.43 m134.90° ± 1.70°hydro-repellent
Silk26.71° ± 5.48°1.50 ± 0.34 s121.03° ± 1.26°hydro-repellent
Table 3. Results of the Liquid Moisture Management Test (AATCC 195-2010) for cellulose- and protein-based fabrics coated with Coffee Silverskin, before and after pre-treatment. The data highlight differences in water repellency (resistance to initial wetting), water penetration (liquid transfer from face to back surface), and water absorption (amount retained within the fabric).
Table 3. Results of the Liquid Moisture Management Test (AATCC 195-2010) for cellulose- and protein-based fabrics coated with Coffee Silverskin, before and after pre-treatment. The data highlight differences in water repellency (resistance to initial wetting), water penetration (liquid transfer from face to back surface), and water absorption (amount retained within the fabric).
AATCC 195-2010Cellulose-BasedProtein-Based
CottonLyocellWoolSilk
Liquid Moisture Management testno
pre-treatment		fast absorption and slow drying fabricwater-penetration fabricwater repellent fabricwater repellent fabric
with
pre-treatment		fast absorption and slow drying fabricwater-penetration fabricwaterproof
fabric		waterproof
fabric
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MDPI and ACS Style

Nolasco, A.; Esposito, F.; Cirillo, T.; Silva, A.; Silva, C.J. Upcycling Coffee Silverskin Waste into Functional Textile Coatings: Evaluation on Cotton, Lyocell, Wool, and Silk. Coatings 2025, 15, 1033. https://doi.org/10.3390/coatings15091033

AMA Style

Nolasco A, Esposito F, Cirillo T, Silva A, Silva CJ. Upcycling Coffee Silverskin Waste into Functional Textile Coatings: Evaluation on Cotton, Lyocell, Wool, and Silk. Coatings. 2025; 15(9):1033. https://doi.org/10.3390/coatings15091033

Chicago/Turabian Style

Nolasco, Agata, Francesco Esposito, Teresa Cirillo, Augusta Silva, and Carla Joana Silva. 2025. "Upcycling Coffee Silverskin Waste into Functional Textile Coatings: Evaluation on Cotton, Lyocell, Wool, and Silk" Coatings 15, no. 9: 1033. https://doi.org/10.3390/coatings15091033

APA Style

Nolasco, A., Esposito, F., Cirillo, T., Silva, A., & Silva, C. J. (2025). Upcycling Coffee Silverskin Waste into Functional Textile Coatings: Evaluation on Cotton, Lyocell, Wool, and Silk. Coatings, 15(9), 1033. https://doi.org/10.3390/coatings15091033

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