Experimental study on polymer friction composite with natural friction modifiers for brake pads

Mitali Gore; Ajit Bhosale; Mithul Naidu; Robert Čep; Sachin Salunkhe; Emad Abouel Nasr

doi:10.1371/journal.pone.0328987

Peer Review History

Original SubmissionJanuary 9, 2025
13 May 2025 Decision Letter - Pankaj Tomar, Editor PONE-D-25-01368Experimental Study on Polymer Friction Composite with Natural Friction Modifiers for Brake PadsPLOS ONE Dear Dr. Salunkhe, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. Please submit your revised manuscript by Jun 27 2025 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org . When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file. 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The PLOS ONE style templates can be found at https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf 2. Thank you for stating the following financial disclosure: [The authors also extend their appreciation to King Saud University for funding the publication of this work through Researchers Supporting Project number (RSP2025R164), King Saud University, Riyadh, Saudi Arabia. This article was co-funded by the European Union under the REFRESH – Research Excellence For Region Sustainability and High-tech Industries project number CZ.10.03.01/00/22_003/0000048 via the Operational Programme Just Transition and has been done in connection with project Students Grant Competition SP2024/087 “Specific Research of Sustainable Manufacturing Technologies“ financed by the Ministry of Education, Youth and Sports and Faculty of Mechanical Engineering VŠB-TUO. Article has been done in connection with project Students Grant Competition SP2024/087 “Specific Research of Sustainable Manufacturing Technologies“ financed by the Ministry of Education, Youth and Sports and Faculty of Mechanical Engineering VŠB-TUO.nt]. Please state what role the funders took in the study. If the funders had no role, please state: "The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript." If this statement is not correct you must amend it as needed. Please include this amended Role of Funder statement in your cover letter; we will change the online submission form on your behalf. 3. Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice. Additional Editor Comments: Plz do minor revision of paper and re-submit within 30 days [Note: HTML markup is below. Please do not edit.] Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. Reviewer #1: Partly Reviewer #2: Partly ******** 2. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: No Reviewer #2: No ****** 3. Have the authors made all data underlying the findings in their manuscript fully available? The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified. Reviewer #1: Yes Reviewer #2: Yes ****** 4. Is the manuscript presented in an intelligible fashion and written in standard English? PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here. Reviewer #1: Yes Reviewer #2: Yes ****** 5. Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #1: The manuscript presents an interesting and relevant study on the development of polymer friction composites with natural friction modifiers for brake pads, addressing environmental concerns associated with traditional brake materials. The experimental design, material selection, and tribological analysis provide valuable insights into the feasibility of using natural fillers like walnut shells, coconut shells, and groundnut shell powders. While the study is well-structured and methodologically sound, there are certain areas that require clarification and improvement to enhance the manuscript’s overall rigor and impact. Below are specific comments and suggestions for the authors to consider: 1. The study effectively employs the Taguchi method and ANOVA analysis to evaluate the influence of material composition, load, and velocity on friction and wear performance. However, the replication details and sample sizes for each test condition are not explicitly stated, which is important for ensuring statistical reliability. 2. The statistical analysis is partly rigorous, but it would benefit from the inclusion of p-values, confidence intervals, and standard deviations for the reported values. A post hoc test (e.g., Tukey’s test) could further validate the differences between the tested composites. 3. While the authors mention that all data are fully available, there is no clear mention of a public repository or raw datasets (e.g., full measurement logs, repeated test data). If required by the journal, the authors should consider sharing complete datasets. 4. The English language and readability are generally good, but minor grammatical errors and occasional awkward phrasing should be addressed through careful proofreading or professional language editing. 5. The conclusions align with the presented data, but a discussion on the limitations of the study and the comparison with commercially available brake pad materials would enhance the relevance and practical applicability of the findings. 6. The manuscript lacks error bars or graphical representation of variations in data (e.g., standard deviation in COF and SWR values). Including such details would improve the interpretation of results. 7. The methodology section should provide more specific details on material composition (e.g., justification for the weight percentages of different fillers and their impact on tribological properties). 8. The future research section outlines useful directions but could be expanded to discuss long-term durability and real-world application challenges for these composites in automotive braking systems. With these revisions, the manuscript would significantly improve in clarity, rigor, and impact. The study provides valuable insights into sustainable brake pad materials and has the potential to contribute meaningfully to the field of eco-friendly friction composites. Reviewer #2: The paper "Experimental Study on Polymer Friction Composite with Natural Friction Modifiers for Brake Pads" examines the use of polymer friction composites with natural friction modifiers integrated into brake pads. The study, however, is not novel enough since there is a lot of research available on this specific subject. Hence, this research may not be appropriate for publication. ****** 6. PLOS authors have the option to publish the peer review history of their article (what does this mean? ). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy . Reviewer #1: Yes: Madhu P Reviewer #2: No ******** [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/ . PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org . Please note that Supporting Information files do not need this step. https://doi.org/10.1371/journal.pone.0328987.r001
Revision 1
13 Jun 2025 Author Response EXPERIMENTAL STUDY ON POLYMER FRICTION COMPOSITE WITH NATURAL FRICTION MODIFIERS FOR BRAKE PADS PONE- D-25-01368 The authors are grateful to the reviewers for their comments and suggestion. Below are the responses to the reviewer comments and suggestions. For your kind note, the changes in the revised manuscript have been highlighted with yellow color for convenience. Response to Reviewer: Comments are in Red color and Responses are in Blue color, References in black color. Reviewer 1: 1. The study effectively employs the Taguchi method and ANOVA analysis to evaluate the influence of material composition, load, and velocity on friction and wear performance. However, the replication details and sample sizes for each test condition are not explicitly stated, which is important for ensuring statistical reliability. Thank you for your valuable feedback. The current study effectively employs the Taguchi L9 orthogonal array design and ANOVA to evaluate the effects of material composition, applied load, and sliding velocity on the tribological behavior of polymer friction composites, similar to the methodology applied by Mithul Naidu et al. (2022). To ensure statistical reliability and repeatability, each test condition will have three replicates. For each factor combination, three independently prepared specimens underwent pin-on-disc wear tests per ASTM G99 standards. Averaging replicate results minimized experimental variability and supported robust ANOVA analysis by accurately estimating experimental error, thereby strengthening the confidence in the influence of composition, load, and velocity on friction and wear performance. M. Naidu, A. Bhosale, Y. Munde, S. Salunkhe, and H. M. A. Hussein, “Wear and Friction Analysis of Brake Pad Material Using Natural Hemp Fibers,” Polymers, vol. 15, no. 1, p. 188, Dec. 2022, doi: 10.3390/polym15010188. 2. The statistical analysis is partly rigorous, but it would benefit from the inclusion of p-values, confidence intervals, and standard deviations for the reported values. A post hoc test (e.g., Tukey’s test) could further validate the differences between the tested composites. Thank you very much for your valuable suggestions regarding the statistical analysis. In response to your comments, we have revised the study to include additional statistical parameters such as p-values, confidence intervals, and standard deviations for key variables including coefficient of friction (COF) and specific wear rate (SWR). Similar approaches were followed as demonstrated by Mithul Naidu et al. (2022) and Hasan Öktem et al. (2018), which helped strengthen the tribological analysis. The ANOVA results now explicitly report p-values at a significance level of α = 0.05 to quantify statistical significance robustly. Confidence intervals are included to illustrate the precision of measurements, and standard deviations reflect variability within replicates, facilitating meaningful comparisons across the tested composites. Furthermore, for further work and research, we plan to incorporate a post hoc test, specifically Tukey’s HSD, for pairwise comparisons to confirm significant differences between composite formulations. These statistical enhancements will provide a more comprehensive and rigorous evaluation of friction and wear performance, thereby supporting conclusive insights and facilitating future material optimization efforts. M. Naidu, A. Bhosale, Y. Munde, S. Salunkhe, and H. M. A. Hussein, “Wear and Friction Analysis of Brake Pad Material Using Natural Hemp Fibers,” Polymers, vol. 15, no. 1, p. 188, Dec. 2022, doi: 10.3390/polym15010188. H. Karakaş, H. Öktem, and I. Uygur, “Tribological and mechanical exploration of polymer-based hemp and colemanite composite as a friction material,” Eng. Res. Express, vol. 6, no. 2, p. 025537, Jun. 2024, doi: 10.1088/2631-8695/ad4769. 3. While the authors mention that all data are fully available, there is no clear mention of a public repository or raw datasets (e.g., full measurement logs, repeated test data). If required by the journal, the authors should consider sharing complete datasets. Thank you very much for your valuable feedback regarding data availability and transparency. As highlighted in the works of Mithul Naidu (2022) and S. Sri Karthikeyan (2019), sharing complete raw datasets including full measurement logs and repeated test data is indeed crucial for research reproducibility and validation. Although the current manuscript does not explicitly provide a public repository link for the complete raw datasets, we confirm that all relevant data have been carefully recorded and maintained. We assure you that, upon resubmission, the full datasets will have been made publicly available via an appropriate data repository or included as supplementary material, in accordance with the journal’s requirements. S. Sri Karthikeyan, E. Balakrishnan, S. Meganathan, M. Balachander, and A. Ponshanmugakumar, “Elemental Analysis of Brake Pad Using Natural Fibres,” Mater. Today Proc., vol. 16, pp. 1067–1074, 2019, doi: 10.1016/j.matpr.2019.05.197. M. Naidu, A. Bhosale, Y. Munde, S. Salunkhe, and H. M. A. Hussein, “Wear and Friction Analysis of Brake Pad Material Using Natural Hemp Fibers,” Polymers, vol. 15, no. 1, p. 188, Dec. 2022, doi: 10.3390/polym15010188. 4. The English language and readability are generally good, but minor grammatical errors and occasional awkward phrasing should be addressed through careful proofreading or professional language editing. Thank you for your valuable feedback regarding the English language and readability of our manuscript. We carefully proofread the entire manuscript and addressed all minor grammatical errors and awkward phrasing to enhance clarity and flow. Additionally, we have sought professional language editing to ensure that the paper meets the highest standards. These improvements have been incorporated into the revised version. 5. The conclusions align with the presented data, but a discussion on the limitations of the study and the comparison with commercially available brake pad materials would enhance the relevance and practical applicability of the findings. We sincerely thank the reviewer for the valuable suggestion. The comments have been carefully considered, and a discussion on the study’s limitations along with a comparison to commercially available brake pad materials have been included in the revised manuscript to enhance the practical relevance and applicability of our findings. 6. The manuscript lacks error bars or graphical representation of variations in data (e.g., standard deviation in COF and SWR values). Including such details would improve the interpretation of results. Thank you for your valuable feedback regarding the inclusion of error bars and graphical representation of data variation. We had employed a robust Taguchi L9 orthogonal array design, focusing on composition, load, and velocity at three levels each, to systematically analyze the coefficient of friction (COF) and specific wear rate (SWR). ANOVA and signal-to-noise (S/N) ratio analyses demonstrated significant factor effects and minimal residual error, which confirmed the reliability of the data. However, we have incorporated your suggestion and have ensured that future work will have detailed visual representations of data variations to improve interpretability. 7. The methodology section should provide more specific details on material composition (e.g., justification for the weight percentages of different fillers and their impact on tribological properties). Our material composition is informed by Mithul Naidu (2022), who demonstrated effective use of Hemp fillers in break pad composites. Building on this, our study introduces natural friction modifiers like walnut, coconut, and groundnut powders, carefully balanced with phenol-formaldehyde, graphite, vermiculite, and barium sulfate. The weight percentages were selected to optimize frictional and wear properties, with detailed fabrication and testing protocols ensuring reliability and relevance to brake pad applications. 8. The future research section outlines useful directions but could be expanded to discuss long-term durability and real-world application challenges for these composites in automotive braking systems. We sincerely thank the reviewer for their valuable suggestion. The future research section briefly outlined key directions, including long-term durability investigations under varying environmental conditions (point 2). We have acknowledged the importance of real-world application challenges and expanded this discussion in the revised manuscript to emphasize durability and practical use in automotive braking systems. These additions have strengthened the relevance and applicability of our research for future industrial implementation. Attachments Attachment Submitted filename: Response_To_Reviwer.docx https://doi.org/10.1371/journal.pone.0328987.r002
26 Jun 2025 Decision Letter - Pankaj Tomar, Editor PONE-D-25-01368R1Experimental Study on Polymer Friction Composite with Natural Friction Modifiers for Brake PadsPLOS ONE Dear Dr. Salunkhe, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. Please submit your revised manuscript by Salunkhe. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org . When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file. Please include the following items when submitting your revised manuscript: A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'. A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'. An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'. If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter. If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols . Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols . We look forward to receiving your revised manuscript. Kind regards, Pankaj Tomar Academic Editor PLOS ONE Journal Requirements: Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice. Additional Editor Comments: 1. Paper is serving academic interests and lesser technological meaning due to tribology of natural fibres at rubbing interface 2. Mathematical equation should be aligned in revised paper or use professional editing service for betterment of language and orientations of equations 3. All figures should be uniform for labelling of axis/number pattern Good luck! Please re-submit a revised draft as per the deadline [Note: HTML markup is below. Please do not edit.] [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/ . PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org . Please note that Supporting Information files do not need this step. https://doi.org/10.1371/journal.pone.0328987.r003
Revision 2
6 Jul 2025 Author Response EXPERIMENTAL STUDY ON POLYMER FRICTION COMPOSITE WITH NATURAL FRICTION MODIFIERS FOR BRAKE PADS PONE- D-25-01368 [EMID:a364419a803f3350] The authors are grateful to the reviewers for their comments and suggestion. Below are the responses to the reviewer comments and suggestions. For your kind note, the changes in the revised manuscript have been highlighted with yellow color for convenience. Response to Reviewer: Comments are in Red color and Responses are in Blue color, References in black color. 1. Paper is serving academic interests and lesser technological meaning due to tribology of natural fibres at rubbing interface. As the material is concerned with application of brake pad where the tribology of rubbing surface holds greater significance hence paper speaks about the same. 2. Mathematical equation should be aligned in revised paper or use professional editing service for betterment of language and orientations of equations. The suggestions have been incorporated and necessary alignment of mathematical equations have done. 3. All figures should be uniform for labelling of axis/number pattern. Thank you for the insightful feedback. To ensure consistency in the labeling of axes and numbering patterns, we have revised all graphs to follow a standard format, with uniform axis labels, font sizes, and consistent numbering. This revision improves the clarity and professionalism of the presentation, making it easier to compare results across different figures." Attachments Attachment Submitted filename: Response to Reviewers.docx https://doi.org/10.1371/journal.pone.0328987.r004
10 Jul 2025 Decision Letter - Pankaj Tomar, Editor Experimental Study on Polymer Friction Composite with Natural Friction Modifiers for Brake Pads PONE-D-25-01368R2 Dear Author We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements. Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication. An invoice will be generated when your article is formally accepted. Please note, if your institution has a publishing partnership with PLOS and your article meets the relevant criteria, all or part of your publication costs will be covered. Please make sure your user information is up-to-date by logging into Editorial Manager at Editorial Manager® and clicking the ‘Update My Information' link at the top of the page. If you have any questions relating to publication charges, please contact our Author Billing department directly at authorbilling@plos.org. If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. Kind regards, Pankaj Tomar Academic Editor PLOS ONE Additional Editor Comments (optional): Equations 1 & 2 may be streamline by author during proof reading Reviewers' comments: https://doi.org/10.1371/journal.pone.0328987.r005
Formally Accepted
Acceptance Letter - Pankaj Tomar, Editor PONE-D-25-01368R2 PLOS ONE Dear Dr. Salunkhe, I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now being handed over to our production team. At this stage, our production department will prepare your paper for publication. This includes ensuring the following: * All references, tables, and figures are properly cited * All relevant supporting information is included in the manuscript submission, * There are no issues that prevent the paper from being properly typeset You will receive further instructions from the production team, including instructions on how to review your proof when it is ready. Please keep in mind that we are working through a large volume of accepted articles, so please give us a few days to review your paper and let you know the next and final steps. Lastly, if your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. You will receive an invoice from PLOS for your publication fee after your manuscript has reached the completed accept phase. If you receive an email requesting payment before acceptance or for any other service, this may be a phishing scheme. Learn how to identify phishing emails and protect your accounts at https://explore.plos.org/phishing. If we can help with anything else, please email us at customercare@plos.org. Thank you for submitting your work to PLOS ONE and supporting open access. Kind regards, PLOS ONE Editorial Office Staff on behalf of Dr. Pankaj Tomar Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0328987.r006

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