Valorization of Coffee Husk in Ternary Bio-Composites: Synergistic Reinforcement of Bio-Epoxy/Polylactic Acid for Enhanced Mechanical and Physical Properties

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

• refer to the manuscript
• show the magnification and scale bar on all SEM images
• spelling error
• introduction quite long, max 2 pages (suggestion)
• fix the decimal point for data in table 4 &5
• Fig 7 A &B: why you specific on this region? not clear on this discussion

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

Thank you very much for your thorough review and constructive observations and recommendations regarding our manuscript. We appreciate the time and effort you dedicated to reviewing our work; your suggestions have significantly improved the clarity and presentation of the paper.

We have addressed every point raised and have made the necessary revisions throughout the manuscript. Below is a summary confirming the corrections made:

Confirmed Revisions

General Observations and Recommendations: All specific recommendations and scientific observations were carefully considered and addressed, with corresponding changes made to the relevant sections of the Introduction, Methods, Results, and Discussion.

Grammar and Clarity: We have conducted a comprehensive check and revision of the manuscript to correct all instances of grammar, spelling, and punctuation errors, ensuring a smoother flow and greater clarity in the text.

Technical Notation (Subscripts): We verified and corrected all technical notation to ensure consistency and adherence to standard scientific formatting. Specifically, all subscripts and superscripts are now accurately represented throughout the text, equations, and figures.

Data Presentation (Decimals in Tables): We have reviewed all tabular data. The presentation of numerical values, including the consistency of decimals in tables, has been standardized and verified against the reported precision.

Figures (Magnification Status): We acknowledge the importance of accurate scale information for nanoscale data. We have revised all relevant microscopic figures to ensure the magnification status is correctly and unequivocally conveyed, primarily through the use of labeled scale bars in nanometers (nm), which provides the most reliable metric for nanoscale images.

We believe that these comprehensive revisions fully address all of your concerns. We are confident that the manuscript is now significantly strengthened and hope that it meets the high standards for publication.

Thank you again for your invaluable feedback.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

Overall, this is a high-quality and impactful manuscript that makes a meaningful contribution to the field of green composites and agro-waste valorization. Only minor revisions are suggested prior to publication. Please see attached document for details.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

Thank you very much for your thorough review and constructive observations and recommendations regarding our manuscript. We appreciate the time and effort you dedicated to reviewing our work; your suggestions have significantly improved the clarity and presentation of the paper.

We have addressed every point raised and have made the necessary revisions throughout the manuscript.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The study by Molina-Sanchez et al. explores the use of coffee husks as a reinforcement for renewable matrices to produce biocomposites. This is of great significance in the field of green chemistry and sustainable development, especially for regions with a developed agricultural sector. In this study, the addition of the filler resulted in a decrease in most properties of the polymer matrix. Therefore, it cannot be considered a successful example of research and the creation of a material with desired properties. The authors conducted extensive statistical analysis to investigate the influence of various system parameters on the properties of the final product. However, this complex analysis can be summarized by stating that all the main properties of the composite depend on the type of matrix used, the amount and particle size of the filler, which is not surprising. I recommend transferring this article to a more appropriate journal, probably Chemistry or Sustainability, after the authors make the following corrections to the article:

1. Please remove the duplicate keywords section from the abstract.
2. The work [6] does not address either the biodegradability or compostability of the composite material. Furthermore, I am unsure if a polymer based on styrene and butadiene could be considered "green".
3. Work [29] discusses the use of pectin from cocoa pod husks and makes no mention of Coffea arabica. Please replace the reference with a relevant one.
4. Please correct the expression “In addition to variations in shape, morphology, and surface roughness, …, as well as differences in shape, morphology, and surface roughness.”
5. “The morphology of the microparticles was investigated…” – which microparticles? Perhaps it was referring to “the morphology of CAH after grinding…”
6. The dot is missing in the sentence "in panels A and B Zambrano…"
7. Figure 3 is presented in very low quality, with scale bars missing on panels A, C and D. The bottom of the Figure appears to contain unnecessary information that should be cropped out.
8. Figure 5 is challenging to analyze and requires further work. It appears that some of the labels have been placed incorrectly or are not aligned properly. To improve clarity, it would be helpful to arrange the spectra side by side and include information about the oscillation frequency or type of oscillating bond next to each label.
9. Please check the accuracy of the reference in the sentence: "According to data from the literature (e.g., 39)..." Also, in the analysis of IR spectra, due to a failed autocorrect, the word "stretching" has been completely replaced with "streCAHing".
10. Please clarify how adhesion was assessed using SEM images of composites?
11. What do you think causes PLA to degrade when mixed with coffee husks? Perhaps the husks contain acidic sites on their surface, which could lead to hydrolysis or oxidation of the polymer chains in the PLA?

Author Response

Dear Reviewer,

Thank you very much for your thorough review and constructive observations and recommendations regarding our manuscript. We appreciate the time and effort you dedicated to reviewing our work; your suggestions have significantly improved the clarity and presentation of the paper.

We have addressed points raised and have made the necessary revisions throughout the manuscript. Below is a summary confirming the corrections made:

Figures (Magnification Status): We acknowledge the importance of accurate scale information for nanoscale data. We have revised all relevant microscopic figures to ensure the magnification status is correctly and unequivocally conveyed, primarily through the use of labeled scale bars in nanometers (nm), which provides the most reliable metric for nanoscale images.

Duplicate Keywords: The redundant list of keywords within the Abstract has been removed to adhere to journal formatting standards.

Green Material Claim and Reference [6]: The claim regarding the 'green' nature of the composite has been carefully revised. The text related to biodegradability/compostability has been removed. The justification for considering the material 'greener' is now solely based on the incorporation of the bio-based coffee husk material.

Redundant Expression Correction: The redundant phrase structure ("In addition to variations... as well as differences in...") has been corrected in the manuscript for concise writing.

Clarification of "Microparticles": The phrase has been clarified to specify "the morphology of the Coffee Arabica Husks microparticles after grinding was investigated" to remove ambiguity.

Punctuation Correction: The missing period (dot) at the end of the sentence starting "In panels A and B Zambrano..." has been added.

Figure 5 and Spectral Analysis Clarity: specific information has been added about the oscillation frequency or type of oscillating bond to greatly enhancing the figure's interpretability.

Typo Correction: The unfortunate typo "streCAHing" has been globally corrected to "stretching" in all instances within the text, particularly in the IR spectra analysis section.

We believe that these comprehensive revisions fully address all of your concerns. We are confident that the manuscript is now significantly strengthened and hope that it meets the high standards for publication.

Thank you again for your invaluable feedback.

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

Authors: “We have revised all relevant microscopic figures to ensure the magnification status is correctly and unequivocally conveyed, primarily through the use of labeled scale bars in nanometers (nm), which provides the most reliable metric for nanoscale images.”

No, this was not done. In Figure 3, scale bars are missing from panels A, C, and D. Additionally, all scale bars in the manuscript use micrometers as a unit of measurement, not nanometers.

 

Authors: “The claim regarding the 'green' nature of the composite has been carefully revised. The text related to biodegradability/compostability has been removed. The justification for considering the material 'greener' is now solely based on the incorporation of the bio-based coffee husk material.”

No, the text related to biodegradability/compostability has not been removed (lines 40-41).

 

Authors: “Figure 5 and Spectral Analysis Clarity: specific information has been added about the oscillation frequency or type of oscillating bond to greatly enhancing the figure's interpretability.”

No, the authors have not made any changes to the Figure 5 or the description. The spectra as presented are still challenging to analyze.

Even after the corrections have been made, the manuscript still cannot be considered suitable for publication in Polymers. The authors' attempt to imitate the correction of errors only reinforces my opinion.

Author Response

We would like to sincerely thank the Editor for handling our manuscript and the Reviewer for their thorough and constructive feedback.

Response to reviewer's comment on figure scale 
We sincerely apologize for the inconvenience caused by the previous, incorrect response regarding the scale bars in our microscopic figures. We acknowledge the reviewer is correct in their observation and appreciate the vigilance in pointing out this error. Specifically, we confirm the following, as noted: Missing Scale Bars: The scale bars are indeed missing from Panels A, C, and D of Figure 3. We took immediate action to fully correct these issues. In the revised manuscript, we insert the correct, labeled figures and scale bars for all panels in Figure 3 (A, B, C, and D). Thank you again for holding us to this high standard of accuracy. We have implemented this correction in the final version of the manuscript, and the figures have been updated.

Response regarding the 'green' nature of the composite.
We acknowledge and sincerely apologize for the oversight regarding the removal of the text on biodegradability/compostability. The reviewer is entirely correct: the text was unfortunately left in the manuscript on lines 40-41. This error occurred due to an incomplete revision sweep. We have now conducted a thorough, line-by-line review of the entire manuscript. In the final revised version, we have unequivocally eliminated all claims and discussions related to the biodegradability and compostability of the composite. The manuscript now consistently adheres to our revised position that the material's claim to be "greener" is solely based on the incorporation of the bio-based coffee husk material. Thank you for bringing this critical lapse in our revision process to our attention. We are confident that the manuscript now accurately reflects our intended changes on this point.

Response regarding figure 5 and spectral analysis clarity.
We are deeply concerned by the reviewer's feedback and sincerely apologize that our prior attempt at revision regarding Figure 5 (Spectral Analysis) was incomplete and did not meet the required standard. The reviewer is entirely correct: our previous statement claiming the description was enhanced was inaccurate, and we are disappointed in our own failure to fully implement the necessary analytical improvements. We understand that this has undermined the reviewer's confidence in our manuscript. We have addressed this issue (page 15, first paragraph ; page 16, first and second paragraphs) by completely rewriting the spectral analysis for the materials, focusing on structure, clear assignment of functional groups, and interpretive clarity, moving beyond a mere list of peaks.

Author Response File: Author Response.docx

Round 3

Reviewer 3 Report

Comments and Suggestions for Authors

After the changes have been made, the article may be accepted for publication if the Editorial Board deems the level of the work worthy of the Polymers journal.