Enhanced Moisture Management in Textiles via Spray-Coated Water-Based Polyhydroxyalkanoate Dispersions

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this paper, a sustainable coating based on chemically modified poly(3-hydroxybutyrate)-diol (PHB.E.0) was prepared. It was applied to the surfaces of polyester (PES) and cotton (CO) fabrics via a solvent-free spraying technique, and the properties of the resulting composite fabrics were systematically investigated. However, the paper needs major changes before it can be accepted for publication. My comments are listed as follows:

• Some key details were missing in the second section, for example, the specific power during ultrasonic treatment, the specific unit of spray flow rate, and the dropping height of 3 μL water droplets, among others.
• Figure 1. SEM micrographs of PES fabrics (A, B, and C) and CO fabrics (D, E, and F). Images A1–F1 correspond to the same substrates after undergoing the hot-pressing process (180 C). Images A, B, D and E were captured at 100× magnification, while images C and F were captured at 500× magnification.--However, what were the respective differences between A, B, and C, as well as between D, E, and F?
• This pronounced decline in air permeability is attributed to thermally induced densification and surface restructuring, characteristic of the thermoplastic behaviour of PES, as evidenced by morphological analyses and TGA observations.--How did thermally induced densification and surface restructuring affect its air permeability?
• Inconsistent use of some terms: “water vapor permeability” was alternately used with its abbreviation “WVP”, and “hot pressing” was partially expressed as “hot-pressing”.--The formats need to be standardized, for example, using “WVP (water vapor permeability)” throughout the paper (with the full name provided upon first appearance and only the abbreviation used thereafter) and uniformly adopting “hot pressing”.
• In the paper, the characteristic peaks of PHB.E.0 were observed via ATR-FTIR.--However, only a qualitative description of the presence of the coating was provided, and the residual amount of the coating on different fabrics under various hot-pressing conditions was not quantified through peak area integration.
• The TGA results showed that the initial degradation temperature of PHB.E.0 on CO fabric (252.2℃) was higher than that on PES (238.7℃). In the paper, it was hypothesized that “hydrogen bonds were formed between the hydroxyl groups of cellulose and the ester groups of PHB.E.0”.--However, the change in the chemical state of the O 1s peak was not analyzed via X-ray photoelectron spectroscopy, and no control group data of hydroxyl-free substrates (such as pure PES films) was compared either.
• The formats of the references were inconsistent, for instance, some references lacked a doi.

Author Response

In this paper, a sustainable coating based on chemically modified poly(3-hydroxybutyrate)-diol (PHB.E.0) was prepared. It was applied to the surfaces of polyester (PES) and cotton (CO) fabrics via a solvent-free spraying technique, and the properties of the resulting composite fabrics were systematically investigated. However, the paper needs major changes before it can be accepted for publication. My comments are listed as follows:

1. Some key details were missing in the second section, for example, the specific power during ultrasonic treatment, the specific unit of spray flow rate, and the dropping height of 3 μL water droplets, among others.

R. We appreciate the observations provided; indeed, this technical information should have been included. Therefore, it has already been presented in Sections 2.3 and 2.4.6, with all relevant details highlighted in red.

2. Figure 1. SEM micrographs of PES fabrics (A, B, and C) and CO fabrics (D, E, and F). Images A1–F1 correspond to the same substrates after undergoing the hot-pressing process (180 C). Images A, B, D and E were captured at 100× magnification, while images C and F were captured at 500× magnification. However, what were the respective differences between A, B, and C, as well as between D, E, and F?

R. The SEM micrographs A, B, and C correspond to PES substrates, while D, E, and F correspond to cotton substrates. The differences between A, B, and C are as follows: A and B were captured at 100× magnification. Image A shows the textile substrate without any coating, whereas B reveals the presence and distribution of polymeric particles beneath the textile surface. Image C was captured at higher magnification (500×) to analyze in greater detail the depth of polymer penetration into the textile substrate and the morphology of the polymeric particles on it. The same explanation applies to images D, E, and F for the cotton substrates.

3. This pronounced decline in air permeability is attributed to thermally induced densification and surface restructuring, characteristic of the thermoplastic behaviour of PES, as evidenced by morphological analyses and TGA observations. How did thermally induced densification and surface restructuring affect its air permeability?

R. We understand the reviewer’s question and have provided an explanation of the structural changes in the fabrics after hot pressing, taking into account the thermoplastic behaviour of PES. In lines 530–536 of the main manuscript, we previously included an explanation; however, we have slightly revised it to make it completely clear. The updated information is now as follows: The pronounced decline in air permeability is attributed to thermally induced densification and surface restructuring, characteristic of the thermoplastic behaviour of PES, as confirmed by SEM morphological analysis and TGA observations. During hot pressing, the PES fibres partially soften and rearrange, leading to compaction of the textile structure. This reduces pore size and inter-fibre spacing, significantly restricting convective airflow while largely preserving pathways for vapor diffusion. This explanation highlights that hot pressing reduces the spaces between fibers in the textile structure, consequently decreasing airflow (air permeability). We hope that this revision provides a clearer and more detailed understanding of the processes involved.

4. Inconsistent use of some terms: “water vapor permeability” was alternately used with its abbreviation “WVP”, and “hot pressing” was partially expressed as “hot-pressing”.--The formats need to be standardized, for example, using “WVP (water vapor permeability)” throughout the paper (with the full name provided upon first appearance and only the abbreviation used thereafter) and uniformly adopting “hot pressing”.

R. We are grateful for this observation. Taking your suggestions into consideration, we have revised the formatting and standardized it throughout the entire manuscript.

 5. In the paper, the characteristic peaks of PHB.E.0 were observed via ATR-FTIR. However, only a qualitative description of the presence of the coating was provided, and the residual amount of the coating on different fabrics under various hot-pressing conditions was not quantified through peak area integration.

R. We thank the reviewer for this comment. ATR-FTIR was used solely for the qualitative identification of PHB.E.0 on the textile substrates. Quantification via peak area integration is not reliable in this case because: (i) PHB is a polyester, and PES (the substrate) is also a polyester, so their characteristic peaks overlap, leading to potential errors; (ii) the polymer loading in the dispersion was low (~2%), resulting in weak signals. To quantify the coating, we evaluated alternative methods and concluded that TGA provides a more precise measurement, accurately reflecting the retained polymer in the range of 1.3-1.8%, as clearly explained in lines 427-430.

 

6. The TGA results showed that the initial degradation temperature of PHB.E.0 on CO fabric (252.2℃) was higher than that on PES (238.7℃). In the paper, it was hypothesized that “hydrogen bonds were formed between the hydroxyl groups of cellulose and the ester groups of PHB.E.0”. However, the change in the chemical state of the O 1s peak was not analysed via X-ray photoelectron spectroscopy, and no control group data of hydroxyl-free substrates (such as pure PES films) was compared either.

R. We thank the reviewer for this question. Initially, we hypothesized that hydrogen bonds could form between the hydroxyl groups of cellulose and the ester groups of PHB.E.0. However, we did not perform XPS analysis and are currently unable to do so due to practical limitations, including funding and lack of access to the equipment. Consequently, we have slightly revised our hypothesis, as the specific types of bonding between the substrates and the polymer cannot be confirmed. Between lines 408–416 (highlighted in red), we have altered the text to describe and explain the findings in a clearer and simpler way, based solely on experimental evidence. This ensures scientific accuracy, as we have removed speculative deductions and focused only on the observed results. We sincerely appreciate this technical observation, which has contributed to greater scientific rigor in our findings.

 7. The formats of the references were inconsistent, for instance, some references lacked a doi.

R. We appreciate this observation. To address it and ensure consistency across all references, we have added the two missing DOIs (highlighted in red). Regarding document number 21, entitled Coating with Polyhydroxyalkanoates: Biopolymers from Bacteria Protect Technical Textiles, no DOI is assigned, as it is not a regular scientific paper, but a communication report published by the well-known textile research centre DITF. Therefore, the reference has been formatted appropriately for this type of document.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The present work aims to develop a sustainable and eco-friendly textile coating in order to achive enhanced moisture management and avoid use of poorly degradable components. The introduction provides a sufficient background on the topic and highlights the reasons to conduct the research. The fabric testing was carried out in accordance with ISO. 

However, in some aspects the report is lacking and needs to be improved. Here are these notes in no particular order: 

1. Line 26 and further. It is better to avoid use of "/" if possible, to improve readability. E.g., l*m-2*s-1 instead of l/m2/s
2. Lines 126, 143 "weight average molecular weight" - probably a typo
3. The characterisation of the prepared PHB.E.0 must be reported in greater detail.  The rheological characteristics mentioned in line 284 as well as method of its determination must be reported in detail. The GPC results must be provided as well, possibly in the supplementary files. DLS data and other characterization methods must be included.
4. Line 284 "The systematic parameter optimization" must be described in greater detail, possibly in the Supplementary files. 
5. Fig.1. Please re-check the images. Fig.1D is supposed to be CO fabric with smooth surface, which it is not. Fig.1F1 is supposed to present clearly visible polymer particles on the fibre surface, which it does not. 
6. Fig.1. In this image it looks like the textile texture after hot pressing is considerably changed (A/A1 and B/B1). It is necessary to evaluate the tensile strenght of the textiles before and after coating anf hot pressing. 
7. Fig.2A. the bands at 2979 and 2935 cm-1 are highlighted and a noticeable shift is observed for these bands across the tested samples. Please discuss reasons for that in greater detail. 
8. Section 3.4. I suggest removing this section in its entirety. Both the initial textile and the coated textile contain oxygen and carbon. These are light elements which can not be detected using EDS with high precision. The observed change (59.8% to 61%, Line 370) lies within the error margin for this method. Presence of the coating is reliably established using several other methods which makes this section unneccecary. 
9. The loading of the polymer coating onto the textile surface must be quantified. The uniformity of the coating must be confirmed and more attention must be payed to that aspect.
10. The stability of the coating through several cycles of washing and drying must be evaluated. This is a key characteristic along with the tensile strength. 
11. Comparison of the water vapor permeability, air permeability, tensile strength values with the industry standard (e.g. Gore-Tex or some others) must be provided and discussed. 

Author Response

The present work aims to develop a sustainable and eco-friendly textile coating in order to achieve enhanced moisture management and avoid use of poorly degradable components. The introduction provides a sufficient background on the topic and highlights the reasons to conduct the research. The fabric testing was carried out in accordance with ISO. 

However, in some aspects the report is lacking and needs to be improved. Here are these notes in no particular order:  

1.    Line 26 and further. It is better to avoid use of "/" if possible, to improve readability. E.g., l*m-2*s-1 instead of l/m2/s

R. We appreciate this observation and have updated all relevant units consistently throughout the manuscript.

2. Lines 126, 143 "weight average molecular weight" - probably a typo

R. We thank the reviewer again for this observation. The manuscript has been updated to replace ‘weight average molecular weight’ with the correct term ‘weight-average molecular weight.’ We would like to clarify that this was not a typographical error but reflects standard terminology. Additionally, at its first occurrence, we have included the corresponding abbreviation, Mw.

 

3. The characterisation of the prepared PHB.E.0 must be reported in greater detail.  The rheological characteristics mentioned in line 284 as well as method of its determination must be reported in detail. The GPC results must be provided as well, possibly in the supplementary files. DLS data and other characterization methods must be included.

R.We appreciate these technical observations, which have indeed helped improve the quality of the manuscript. The rheological characteristics of the dispersion, along with the measurement conditions, have now been included. The GPC results, including the weight-average molecular weight and polydispersity index of the modified PHB polymer, are reported on lines 262–263 of the main manuscript, and the corresponding chromatogram is provided in Section S1 of the Supplementary Information. DLS results have also been incorporated (lines 278–282), with the corresponding graphs included in the Supplementary Information.

4. Line 284 "The systematic parameter optimization" must be described in greater detail, possibly in the Supplementary files. 

R. We appreciate this observation and have introduced the term “systematic” to emphasize that all steps were carefully planned to ensure the preparation of a stable aqueous PHA dispersion. In Section 3.1, we have added detailed information (highlighted in red) regarding all parameters considered, including polymer concentrations, limitations of the spray equipment, and procedures involving surfactants and dispersants, complementing the information previously provided. We believe this now offers a comprehensive explanation of all aspects involved in preparing the dispersion for spray application. Repeating these details in the Supplementary Information could be misleading, as many optimization steps rely on practical, visually assessed parameters. For example, during initial dispersion development, a wide range of surfactants and dispersants were tested individually and in combination. Stability assessments at this stage were primarily observational, such as monitoring sedimentation over time, and included variations in stirring and sonication conditions. Documenting every single iteration would be exhaustive and exceed the scope of this initial phase, which in itself forms the basis of a standalone publication.

This work represents the first stage of a broader project, where the primary objective was to overcome the technical limitations of the spray system and demonstrate the feasibility of applying aqueous polymeric solutions to textile substrates. We recognize that further optimization of biopolymeric dispersion stability is necessary, particularly regarding zeta potential and steric stabilization provided by surfactants. Adjustments to polymer concentration will also be explored in subsequent phases. The optimization process inherently encompasses all steps described in the manuscript, including polymer modification, dispersion development, and spray application, and will be refined progressively in future work.

Despite being an initial phase, this study is valuable to share as it provides proof of concept and establishes a foundation for demonstrating that aqueous-based biopolymer coatings can be successfully applied to textiles, opening avenues for further improvements and sustainable finishing strategies.

5. Please re-check the images. Fig.1D is supposed to be CO fabric with smooth surface, which it is not. Fig.1F1 is supposed to present clearly visible polymer particles on the fibre surface, which it does not. 

R. We thank the reviewer for this observation. Figure 1D shows the CO fabric without hot pressing, where the visible surface irregularities reflect the intrinsic texture of the cellulose-based material. In Figure 1F1, the polymer particles on the fibre surface undergo partial softening during hot pressing, leading to the formation of a coating that adheres more closely to the fibres. This explains the reduced visibility of discrete polymer particles, as they coalesce into a more continuous film on the fibre surfaces. A comparable effect can also be observed in Figure C1 for the PES substrate. These clarifications have been incorporated into Section 3.2 (lines 319–323) of the manuscript.

 

6. In this image it looks like the textile texture after hot pressing is considerably changed (A/A1 and B/B1). It is necessary to evaluate the tensile strenght of the textiles before and after coating anf hot pressing. 

R. We fully acknowledge the reviewer’s point and greatly appreciate this valuable observation. This study represents the initial phase of a broader project, focused on developing the modified polymer PHB.E.0, preparing its aqueous dispersion, and establishing a feasible spray application method. At this stage, the primary objective was to optimize polymer modification and dispersion while assessing its applicability to textile substrates. Fabric permeability was selected as the key property to evaluate, given its relevance for sports textiles. Accordingly, we examined the influence of the polymer and the effect of hot pressing on this property. Evaluation of additional textile characteristics, including tensile strength, is planned for subsequent phases. This stepwise approach ensures progressive development toward a comprehensive understanding. Sharing these initial results is valuable, as it advances research in the field and supports sustainable textile innovation.

7. Fig 2A. the bands at 2979 and 2935 cm-1 are highlighted and a noticeable shift is observed for these bands across the tested samples. Please discuss reasons for that in greater detail. 

R. We thank the reviewer for this useful observation, which enriches the manuscript. The shifts observed at 2979 and 2935 cm⁻¹, corresponding to C–H stretching vibrations in PHB.E.0, reflect substrate-dependent interactions. On cotton, stronger hydrogen bonding between the polymer’s ester groups and the fibre hydroxyl groups modifies the vibrational environment. In contrast, on polyester, interactions are dominated by weaker dipole–dipole and van der Waals forces, resulting in smaller shifts. These findings highlight that the nature of the substrate governs polymer–fibre interactions. This explanation has been integrated into the main manuscript.

 

8. Section 3.4. I suggest removing this section in its entirety. Both the initial textile and the coated textile contain oxygen and carbon. These are light elements which cannot be detected using EDS with high precision. The observed change (59.8% to 61%, Line 370) lies within the error margin for this method. Presence of the coating is reliably established using several other methods which makes this section unnecessary. 

R. We sincerely thank the reviewer for this insightful comment. We fully understand the concern regarding the limitations of EDS for detecting light elements such as carbon and oxygen with high precision. Indeed, the minor change observed (59.8% to 61%, Line 370) falls within the typical error margin of this technique and may not provide conclusive evidence for the presence of the polymer coating.

In light of this, and following the reviewer’s suggestion, we have removed Section 3.4 from the main manuscript. The presence of the PHB.E.0 coating is instead confirmed through of TGA, SEM, and FTIR, which collectively provide reliable and quantitative evidence. This revision ensures that the manuscript focuses on methods that deliver precise and meaningful insights while maintaining clarity and scientific rigor.

9. The loading of the polymer coating onto the textile surface must be quantified. The uniformity of the coating must be confirmed and more attention must be payed to that aspect.

R. We fully agree with the reviewer’s observation and acknowledge the importance of quantifying polymer loading and evaluating coating uniformity. To address this, the polymer content retained on the textile substrates was determined using thermogravimetric analysis (TGA), with measurements performed in triplicate. The results, reported in lines 404–411 of the manuscript, provide a precise assessment of the polymer coating. Consistent weight loss values across multiple points of the same sample further indicate uniform polymer distribution, and the low standard deviation demonstrates good dispersity of the polymer over the substrate.

10. The stability of the coating through several cycles of washing and drying must be evaluated. This is a key characteristic along with the tensile strength. 

R. We sincerely appreciate this valuable observation. The assessment of coating stability through repeated washing and drying cycles, along with its effect on tensile strength, is indeed a critical aspect. While these evaluations are beyond the scope of the present study, they are planned for the subsequent phases of the project, where the durability and mechanical performance of the coated textiles will be systematically investigated.

 

 11. Comparison of the water vapor permeability, air permeability, tensile strength values with the industry standard (e.g. Gore-Tex or some others) must be provided and discussed. 

R. We appreciate this insightful observation. Benchmarking against industry standards, such as GORE-TEX®, is indeed important for contextualizing the performance of our modified textiles. This comparison has already been incorporated and discussed in Section 3.7, “Permeabilities,” of the main manuscript.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

• This is an interesting manuscript. Authors prepared P3HB diol via alcoholysis of PH3B with ethylene glycol (EG) and applied it for surface modification of polyester (PES) and cotton fabrics (CO). During alcoholysis of P3HB with EG molecular weight and its polydispersity (M_w/M_n) of this biodegradable PES was significantly decreased 
• Comprehensive studies included following methods: SEM, EDS, ATR-FTIR, wettability, water absorption tests, contact angles measurements, and air and water vapor permeability tests.
• An aqueous dispersion and applied to PES and CO fabrics via a solvent-free spray-coating technique was used.
• What was stability of dispersions PH3b-diol with a nonionic surfactant (Tween 80) and a commercial solvent-free wetting and dispersing additive ?
• Modified coatings "offer a promising and environmentally responsible pathway for enhancing textile performance, contributing to the advancement of sustainable, high-performance materials for sportswear and technical apparel". However, in my opinion, a cost of P3HB synthesis is still relatively high.

Author Response

 

This is an interesting manuscript. Authors prepared P3HB diol via alcoholysis of PH3B with ethylene glycol (EG) and applied it for surface modification of polyester (PES) and cotton fabrics (CO). During alcoholysis of P3HB with EG molecular weight and its polydispersity (M_w/M_n) of this biodegradable PES was significantly decreased.

Comprehensive studies included following methods: SEM, EDS, ATR-FTIR, wettability, water absorption tests, contact angles measurements, and air and water vapor permeability tests.

An aqueous dispersion and applied to PES and CO fabrics via a solvent-free spray-coating technique was used.

What was stability of dispersions PH3b-diol with a non-ionic surfactant (Tween 80) and a commercial solvent-free wetting and dispersing additive?

R. We appreciate this insightful technical question. The stability of PHB-diol (PHB.E.0) dispersions containing the non-ionic surfactant Tween 80 and a commercial solvent-free wetting/dispersing additive was systematically evaluated using dynamic light scattering (DLS), zeta potential measurements, and rheological analyses. Detailed experimental procedures are provided in Section 2.4.1, with results and discussion in Section 3.1 (lines 268–272). The selected dispersion exhibited a consistent particle size distribution (≈572 nm) with low polydispersity (≈0.2), a zeta potential of −8.2 ± 18.9 mV, and a stable viscosity (≈2 cP), confirming its suitability for spray-coating applications. Despite the relatively low mean zeta potential, dispersion stability is ensured by the steric effects of Tween 80 and localized electrostatic repulsion from highly charged particles. Further studies are planned to deepen understanding of the contributions of polymer charge and additives to dispersion stability, following a stepwise approach to optimization.

 

Modified coatings "offer a promising and environmentally responsible pathway for enhancing textile performance, contributing to the advancement of sustainable, high-performance materials for sportswear and technical apparel". However, in my opinion, a cost of P3HB synthesis is still relatively high.

R. We sincerely thank the reviewer for this important comment. We fully recognize that the current cost of P3HB synthesis remains relatively high compared to conventional synthetic polymers, which is indeed a limiting factor for large-scale industrial adoption. However, several recent advances are steadily reducing this gap, such as the ones from the Waste2BioComp Horizon Europe project. These include the development of optimized bacterial strains, the use of low-cost and renewable feedstocks, and improvements in downstream processing that significantly reduce production costs.

Our work contributes to this broader effort by demonstrating that even at low polymer loadings, PHB-diol dispersions can be effectively applied as textile coatings while maintaining desirable functional properties. This highlights the potential for using these biopolymers to achieve performance benefits. Furthermore, the increasing global demand for sustainable and bio-based materials is driving investment and scaling strategies that are expected to reduce production costs in the near future.

Thus, while we acknowledge the current economic challenge, our study provides a valuable proof of concept for applying PHB-based materials in textiles, aligning with ongoing technological advances that will make these solutions increasingly cost-competitive.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have carefully revised the manuscript in accordance with the previous comments; however, some issues still remain. It is recommended that the manuscript be published after further revisions. The specific comments are as follows:

(1) The optimal dispersion composition (“2% w/v PHB.E.0, 6% w/v Tween 80, 3% w/v Disperbyk 190”) was mentioned in the manuscript, but the screening logic for the optimization process was not explained.

(2) The hydrogen bonding interaction between the CO substrate and PHB.E.0 was inferred by ATR-FTIR only through differences in characteristic peak intensities, while the interference from the functional groups of the substrate itself was not excluded.

(3) Only the water absorption percentage was reported in the water absorption test, and the sinking time of different samples (which reflects the kinetic differences in wettability) was not provided.

(4) When comparing with commercial products (e.g., Gore-Tex®), only “lower moisture vapor permeability” was mentioned, and the root cause of the performance gap from the perspective of structural differences was not analyzed.

Author Response

The authors have carefully revised the manuscript in accordance with the previous comments; however, some issues still remain. It is recommended that the manuscript be published after further revisions. The specific comments are as follows:

(1) The optimal dispersion composition (“2% w/v PHB.E.0, 6% w/v Tween 80, 3% w/v Disperbyk 190”) was mentioned in the manuscript, but the screening logic for the optimization process was not explained.

R. We appreciate the reviewer’ comment and thank him/her for their valuable feedback. The optimal composition (2% w/v PHB.E.0, 6% w/v Tween® 80, 3% w/v Disperbyk 190) was identified through a systematic optimization process aimed at achieving stable, homogeneous, and sprayable dispersions. PHB.E.0 concentrations between 1% and 5% w/v were first evaluated to determine the minimum polymer content capable of producing a uniform coating. Various surfactants (Span® 60, Span® 80, Tween® 20, Tween® 80, SDS) and dispersants (Disperbyk 190, 193, 195) were screened over a wide concentration range (0.05–6% w/v), while sonication times (1–45 min) and particle sizes (≤ 45 µm to ≤ 250 µm) were systematically varied to optimize dispersion stability and sprayability.

Through this iterative screening, all other tested conditions failed to achieve stable dispersions. The selected formulation, containing 2% w/v PHB.E.0 (particle size ≤ 40 µm), 6% w/v Tween® 80, and 3% w/v Disperbyk 190, provided the best balance of stability, homogeneity, and coating performance. These details are fully reported in the manuscript (lines 266–279) to clearly explain the rationale behind the optimization process for the readers.

 

(2) The hydrogen bonding interaction between the CO substrate and PHB.E.0 was inferred by ATR-FTIR only through differences in characteristic peak intensities, while the interference from the functional groups of the substrate itself was not excluded.

R. We thank the reviewer for this insightful comment. The hydrogen bonding interactions between the cellulose (CO) substrate and PHB.E.0 were inferred primarily from the shifts and intensity changes of characteristic ATR-FTIR bands, particularly the C–H stretching modes around 2932–2979 cm⁻¹ and the ester carbonyl band at ≈1723 cm⁻¹. We acknowledge that contributions from the substrate’s own functional groups to these spectral features cannot be completely excluded. Nevertheless, the observed differences between uncoated and PHB.E.0-coated CO fabrics, together with the comparison to PHB.E.0-coated PES fabrics, suggest substrate-dependent interactions, likely including hydrogen bonding. Importantly, we emphasize that this statement reflects only the observations directly supported by the ATR-FTIR data and does not imply additional unverified interactions. This interpretation has been clarified in the revised manuscript to avoid any ambiguous explanations.

 

(3) Only the water absorption percentage was reported in the water absorption test, and the sinking time of different samples (which reflects the kinetic differences in wettability) was not provided.

R. We thank the reviewer for this observation. While the water absorption percentage was the primary metric reported, we also observed differences in the sinking behaviour of the samples, which indeed reflect the kinetics of wettability. Specifically, all PES samples required more than 180 s to sink, consistent with their hydrophilic but relatively water-resistant nature, whereas CO samples sank immediately upon contact with the water surface, reflecting the intrinsic hydrophilicity and porous structure of cellulose fabrics. These qualitative observations have now been included in the revised manuscript to complement the water absorption percentages and provide additional insight into substrate-dependent wettability.

 

(4) When comparing with commercial products (e.g., Gore-Tex®), only “lower moisture vapor permeability” was mentioned, and the root cause of the performance gap from the perspective of structural differences was not analyzed.

R. We thank the reviewer for this comment. While our PHB.E.0-coated fabrics exhibit lower moisture vapor and air permeability than commercial products such as Gore-Tex®, this difference is primarily attributable to structural factors. Gore-Tex® is a multi-layer system, featuring a porous ePTFE membrane that allows water vapor and air to pass while blocking liquid water, combined with outer and inner fabrics for durability, protection, and enhanced performance. In contrast, our approach uses a single biopolymer coating applied via a simple, eco-friendly spray method, designed to impart functional properties to a variety of substrates. Although the performance does not yet match that of Gore-Tex®, these results clearly demonstrate the potential of greener methods for textile surface modification. We have updated the discussion to include air permeability alongside moisture vapor permeability, as detailed between lines 558–577, and we have clearly highlighted these differences in the manuscript to ensure that all readers fully understand the distinction between our initial approach and the well-established, extensively studied Gore-Tex® system.

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear authors! 

Thank you for the effort and dedication that you put towards the improvement of the Manuscript. I am fully satisfied with the answers you provided and the changes you implemented in the text. 

I understand that testing the coating stability as well as its mechanical properties is going to be a topic of an upcoming study and I hope that this part of research will stand strong as a separate publication. I'm looking forward to reading it. 

Best wishes! 

Author Response

Dear Reviewer,

We sincerely thank you for your kind words and positive feedback.
We truly appreciate the time and effort you have dedicated to reviewing our manuscript and for your valuable comments, which helped us improve the quality of our work.

Indeed, the study of the coating’s stability and mechanical properties will be addressed in our upcoming research, and we are grateful for your encouraging words regarding this future publication.

Thank you once again for your support and constructive input.

With kind regards,

Marta A. Teixeira