Design and Preparation of PU/EP Blend Resin Grafted by Hydrophilic Molecular Segments

Round 1

Reviewer 1 Report

The manuscript is prepared extremely poorly especially in terms of results & discussion and for readers who is not familiar with the problem. The current version is not suitable for review process. I would suggest readers to be clear in terms of why they want to share results and to whom. Why should a reader read it and what can be beneficial for them? How can you help a reader who is not familiar with the problem get an information from your sharings which is meant to be scientific? So the manuscript is not suitable for any publication and especially not in "Coatings".

Author Response

Response 1: First of all, I'd like to thank the reviewer for reviewing the manuscript so carefully in their busy schedule. I'm really sorry to make you so negative about my article. Although the other three reviewers have given positive suggestions and even accepted the manuscript directly, I still think there are many problems in my manuscript and still need to be improved. Therefore, based on the opinions of all reviewers, I will rearrange the technical language of the article and supplement the marine hanging plate test of modified antifouling coating. I hope to get a positive reply again.

On the other hand, it’s necessary to re introduce my research ideas. This is an article on hydrophilic modification of antifouling coating film-forming resin, which has been described in the abstract and preface. For readers with basic professional knowledge, they can clearly obtain useful information about antifouling coatings. We all know that the hydrophilicity of antifouling coatings will affect the release of antifouling agents, and then affect the antifouling effect. The above results are largely related to the hydrophilicity of the film-forming resin. So, how to improve the hydrophilicity of film-forming resin while maintaining its mechanical properties becomes much more important. The relevant research of this paper is based on the above background.

Reviewer 2 Report

The subject of the paper is of interest to researchers and engineers working on marine applications, as there is the need to develop new antifouling coatings resistant to peeling. 

I have some recommendations which may improve the clarity and the quality of the paper:

1. In the Introduction section, the literature survey must be enriched. There are many papers on similar subjects and I have indicated some of them (see the Supplementary references section below this review). Various solutions of antifouling coatings should be presented and their benefits and shortcomings must be discussed.
2. The novelty and the originality of the paper are not completely assed in relationship with the published literature.  
3. The experimental Scheme 1 must be moved immediately after the title of Section 2 and before the title of section 2.1, as it is not a part of the Introduction.
4. The performances of the obtained antifouling coating must be compared against the existing similar solutions. Are the performances of the proposed coating better than of the existing antifouling coatings?

Supplementary references:

1. Yuchan Zhu, Bo Wang, Wei Gong, Lingmei Kong, and Qingming Jia, Investigation of the Hydrogen-Bonding Structure and Miscibility for PU/EP IPN Nanocomposites by PALS
   Macromolecules 2006 39 (26), 9441-9445
   DOI: 10.1021/ma0621066
2.  Mu, Z. G., Bai, X. L., Luo, Y. D., Mei, J. T., & Zhang, M. H. (2014). Study on Microwave Curing of Polyurethane (PU)/Epoxy (EP) Interpenetrating Networks (IPN). Applied Mechanics and Materials, 556–562, 649–652. https://doi.org/10.4028/www.scientific.net/amm.556-562.649
3. Wang, X. Q., Huang, Z. X., Zheng, J. L., & Mei, Q. L. (2011). Study on the Synthesis and Properties of EP/PU Composite. Advanced Materials Research, 221, 135–139. https://doi.org/10.4028/www.scientific.net/amr.221.135 

Author Response

Dear reviewer:

Special thanks to reviewer for the recognition of my work, and then give us constructive suggestions which would help us both in English and in depth to improve the quality of the paper. The following is a point-to-point response to the comments.

Sincerely yours

Gang Lu, ph.D.

Point 1: In the Introduction section, the literature survey must be enriched. There are many papers on similar subjects and I have indicated some of them (see the Supplementary references section below this review). Various solutions of antifouling coatings should be presented and their benefits and shortcomings must be discussed.

Response 1: More references on PU/EP materials have been added in the introduction section of the paper, including those provided by reviewers. In addition, the ways to improve the performance of antifouling coatings and their advantages and disadvantages have been listed.

The added content is shown below. “At present, most of the research on Antifouling Coatings starts from two aspects, such as improving the application environment matching of film-forming resin and the performance of antifouling agents and other additives. Although the latter will form an effective defense against marine fouling organisms, the contradiction between toxic pollution and marine ecological maintenance cannot be solved well in a short time. Therefore, in the future, most scholars will still start from the functional film-forming resin bearing the release of antifouling agent to improve its application environment matching as much as possible, so as to improve the effect of antifouling coatings, although the method is slightly conservative.”

“There are many cases of chemical modification of PU and EP. Effects of hydrogen bonding on the free volume and miscibility were first investigated for PU/EP interpenetrating polymer network (IPN) nanocomposites, It is found that the stronger the hydrogen-bonding interaction, the higher the average chain packing efficiency and the smaller the free volume hole size, the better the miscibility. Studies have shown that the PU/EP interpenetrating network structure prepared by microwave curing method not only has the same structure as thermal curing, but also the curing time will be greatly shortened. At the same time, the tensile properties of microwave cured IPN are better than thermal cured IPN, but the impact strength of thermal cured IPN is slightly higher. Some studies show that after blending Pu with EP, the damping performance of EP composites increases significantly with the increase of frequency, and the damping temperature range moves to high temperature. In recent years, the tribological properties of polyurethane/epoxy interpenetrating network (PU/EP-IPN) composites have been studied to guide the research and development of polymer friction materials under water lubrication. The results show that the friction and wear properties in water lubricated medium are greatly improved by adding different kinds of fillers (SiC submicron particles and short carbon fibers (SCF))”.

Point 2: The novelty and the originality of the paper are not completely assed in relationship with the published literature.

Response 2: Thank the reviewers for seeing that the innovation of this article is different from the existing literature. In this paper, hydrophilic groups are grafted onto EP molecular segments by chemical methods, which can greatly improve the hydrophilicity of grafted blends on the basis of retaining the properties of two parts of materials.

Point 3: The experimental Scheme 1 must be moved immediately after the title of Section 2 and before the title of section 2.1, as it is not a part of the Introduction.

Response 3: The position of Scheme 1 and related contents has been moved after the title of section 2 and before the title of Section 2.1.

Point 4: The performances of the obtained antifouling coating must be compared against the existing similar solutions. Are the performances of the proposed coating better than of the existing antifouling coatings?

Response 4: Special thanks to the reviewer for the suggestion. When the manuscript was submitted for the first time, the immersion time of antifouling coating had not been reached, so the content of coating performance verification was not included in the manuscript.

Now, the actual marine experiments of antifouling coatings prepared from hydrophilic modified film-forming resin and common antifouling coatings are supplemented in this paper. It can be seen from the information in the figure that after 120 days of marine hanging plate, the antifouling effect of the modified antifouling coating is better than that of the traditional antifouling coating under the experimental conditions.

Reviewer 3 Report

The placement of references inside the article is a deficiency. Redo.

References are old and very weak. Major additions with the current references are required.

The merit of the performed research to scientific community is unclear. The merit of the work and its impact on the overall field should be detailed.

Nobody knows what NCO is. Define/explain first. Also, write it out.

What are these highlighted in the Abstract (593 curing agents)?

The reader does not understand any of the terms used in Scheme 1. Why do not explain those first?

Table 1 has chine several times. Why do not use China?

Figure 1 has no y-axes. Why?

In, 2.2.1., molar ratio of 1:1. Why?

A high number of English and grammar errors like 100℃for 24 hours…. were set to be500mm/min…. 

Experiments, Characterization, and Analysis are extremely weak since they do not report any scientific details other than direct experimentation.

Figure 2 has no contribution to the current paper.

Add a legend to Figure 3. Colors do not mean anything to the readers.

Author Response

Dear reviewer:

We would like to thank the reviewer for giving us constructive suggestions which would help us both in English and in depth to improve the quality of the paper. The following is a point-to-point response to the comments.

Sincerely yours

Gang Lu, ph.D.

Point 1: The placement of references inside the article is a deficiency. Redo.

Response 1: Special thanks the reviewer for the suggestions. The citation format of references cited in this article has been corrected.

Point 2: References are old and very weak. Major additions with the current references are required.

Response 2: Special thanks the reviewer for the suggestions. References published in recent years have been supplemented,

Zhu Y.C.; Wang B.; Gong W.; et al. Investigation of the Hydrogen-Bonding Structure and Miscibility for PU/EP IPN Nanocomposites by PALS. Macromolecules2006, 39(26), 9441-9445.

Mu Z.G.; Bai X.L.; Luo Y.D.; et al. Study on Microwave Curing of Polyurethane (PU)/Epoxy(EP) Interpenetrating Networks (IPN). Applied Mechanics and Materials2014, 3207, 649-652.

Wang X.Q.; Huang Z.X.; Zheng J.L.; et al. Study on the Synthesis and Properties of EP/PU Composite. Advanced Materials Research2011, 221, 135-139.

Yu P.; Li G.T; Zhang L.G.; et al. Role of SiC submicron-particles on tribofilm growth at water-lubricated interface of polyurethane/epoxy interpenetrating network (PU/EP IPN) composites and steel. Tribology International2021, 153, 106611.

Point 3: The merit of the performed research to scientific community is unclear. The merit of the work and its impact on the overall field should be detailed.

Response 3: Special thanks the reviewer for the suggestions, which is of great significance to improve the readability and depth of this article. The work and its impact on the overall field have been supplemented in detail.

“However, the problem of poor hydrophilicity began to appear with the promotion of the above resin in the field of antifouling. As a result, it would be difficult for antifouling agents to release from the coating, leading to a remarkable decrease in the functional effect of antifouling coating. Besides, the hydrophilicity of coatings can also positively affect the adhesion of protein fouling organisms, and its anti-adhesion mechanism is one of the research hotspots around the world. Generally, how to properly improve the hydrophilicity of materials without reducing the comprehensive performance of film-forming resin has become increasingly essential in the field of Marine antifouling”.

“It can be seen from the above research that PU / EP materials are widely studied and the technology is relatively mature, the comprehensive properties have been optimized and improved. These studies also provide inspiration for the preparation of PU / EP hydrophilic graft blends. In this paper, the hydrophilic PU molecular chain was designed and then grafted onto the EP to effectively improve the hydrophilicity of PU/EP grafted blends without affecting the comprehensive properties of the material. It will provide a potential method to improve the antifouling effect of new antifouling coatings”.

Point 4: Nobody knows what NCO is. Define/explain first. Also, write it out.

Response 4: Special thanks to the reviewer for the suggestions, NCO means Isocyanate group, the revise part has been reflected in the abstract. “isocyanate group (NCO)”

Point 5: What are these highlighted in the Abstract (593 curing agents)?

Response 5: There is no need to highlight 593curing agent in the abstract. This part has been deleted.

Point 6: The reader does not understand any of the terms used in Scheme 1. Why do not explain those first?

Response 6: As other reviewers pointed out, this part has been transferred to the experimental part.

Point 7: Table 1 has chine several times. Why do not use China?

Response 7: Thanks to the reviewer’s reminder, “china” in Table 1 has been replaced by “China”

Point 8: Figure 1 has no y-axes. Why?

Response 8: In order to clearly compare the spectra of the materials before and after grafting, the spectra of the grafted PU / EP were translated downward along the longitudinal direction, so the Y coordinate was removed.

Point 9: In 2.2.1, molar ratio of 1:1. Why?

Response 9: According to the chemical reaction equation, the molar ratio of MPEG to TDI is 1:1.

Point 10: A high number of English and grammar errors like 100℃for 24 hours…. were set to be 500mm/min…. 

Response 10: I’m so sorry for the language mistakes, The English and grammar errors have been proofread by a professional English teacher.

Point 11: Experiments, Characterization, and Analysis are extremely weak since they do not report any scientific details other than direct experimentation.

Response 11: Thanks a lot for the reviewer’s reminder. A teacher who is engaged in material science writing has helped us to revise the technical language of this article again, especially in the experimental analysis part.

Point 12: Figure 2 has no contribution to the current paper.

Response 12: Special thanks to the reviewers, Figure 2 has been deleted.

Point 13: Add a legend to Figure 3. Colors do not mean anything to the readers.

Response 13: Special thanks to the reviewers, layer colors have been unified.

Reviewer 4 Report

I have carefully read the manuscript entitled “Design and Preparation of PU/EP Blend Resin Grafted by Hydrophilic Molecular Segments” and analyzed in context of publication in the MDPI journal Coatings.

In my opinion the problem of antifouling coatings for marine application is recent and important. However, in the manuscript subjected to my review I have found several flaws decreasing its value.

 I suggest accepting the article for publication after major revision.

Below I provide with detailed discussion of most important points.

1. In the Abstract few sentences regarding most important results should be added. .
2. The introduction provides with very brief background of the topic. I think that authors should extend the part including thorough analysis of literature concerning PU/EP system and draw on this canvas the explanation of importance and novelty of their research.
3. Experiments part is written to carelessly The description of procedures are not clear enough to follow the syntheses. Authors should revise the description part and adjust it to the level typical for scientific publication.
4. The citation indexes are neglectful and should be corrected according to the Journal requirements.
5. The term “hydrophilic test” in Scheme 1 is incorrect and has no corresponding entry in “characterization and analysis” part. replace with proper name of the test.
6. The term “formula” in schemes 3 and 4 are not adequate since they show chemical reactions equations.
7. The conclusions are quite confusing I still have doubts whether the whole work has positive or negative outcome and what the results add the general knowledge in the field.

Author Response

Dear reviewer:

We would like to thank the reviewer for giving us constructive suggestions which would help us both in English and in depth to improve the quality of the paper. The following is a point-to-point response to the comments.

Sincerely yours

Gang Lu, ph.D.

Point 1: In the Abstract few sentences regarding most important results should be added. .

Response 1: The most important results have been added in the abstract. “It can be concluded from the hydrophilic and mechanical properties of the materials that the comprehensive properties of PU/EP grafted blends are the best when the PU content is between 40% and 50%. The hanging plate test shows that the antifouling effect of the antifouling coating prepared by hydrophilic modified PU/EP film-forming resin was better than that of the traditional antifouling coating under the experimental conditions”.

Point 2: The introduction provides with very brief background of the topic. I think that authors should extend the part including thorough analysis of literature concerning PU/EP system and draw on this canvas the explanation of importance and novelty of their research.

Response 2: Special thanks the reviewer for the suggestions, which is of great significance to improve the readability and depth of this article. The research status of antifouling coatings has been discussed in the introduction. At the same time, the research status of PU/EP materials and the innovation of this article have also been refined.

Point 3: Experiments part is written to carelessly The description of procedures are not clear enough to follow the syntheses. Authors should revise the description part and adjust it to the level typical for scientific publication.

Response 3: The details of the experiment were accurately pointed out by the reviewer. A teacher who is engaged in material science writing has helped us to revise the technical language of this article again, especially in the experimental analysis part. We have improved the experimental procedure accordingly.

Point 4: The citation indexes are neglectful and should be corrected according to the Journal requirements.

Response 4: The citation has been revised according to the specific requirements of the journal.

Point 5: The term “hydrophilic test” in Scheme 1 is incorrect and has no corresponding entry in “characterization and analysis” part. replace with proper name of the test.

Response 5: “hydrophilic test” has been replaced with “Contact angle and water absorption test”

Point 6: The term “formula” in schemes 3 and 4 are not adequate since they show chemical reactions equations.

Response 6: “Formula” has been replaced with “Reaction equation”.

Point 7: The conclusions are quite confusing I still have doubts whether the whole work has positive or negative outcome and what the results add the general knowledge in the field.

Response 7: I’m deeply sorry for the confusion, which may be related to the imprecision of my technical language description. Now, I have rearranged the technical language and ideas of the full article, and added the content of antifouling effect test of antifouling coatings. We sincerely hope that the doubts of the reviewer can be eliminated , and we can get the accepted letter of the journal as soon as possible.

Round 2

Reviewer 1 Report

There is no improvement in the revised version of manuscript in terms of discussion and clarity. Since the revised version of manuscript has no line numbers and has messy changes, I can not understand what the changes are and why? It would be better to see all the changes and why in a response letter. Since there is no line, please understand where they come from. My comments are below:

-There are lots of typos in the paper, also unnecessary use of uppercase letters.

-The referencing and all structure of paper is poorly prepared. 

-There are lots of statements and conclusive notes in the introduction without any proper discussion. Why "cannot be solved well in a short time?" How can reader get more knowledge about this? Why "the method is conservative" Why "Urgent"? How can a scientific paper make a strong judgements without any showing adequate background.

-"Considering that it is easy for ship coatings to peel off under the shear stress of water flow at high speed, excellent mechanical properties of the film-forming resin are required because the mechanical properties of the coatings are mainly associated with film-forming resin" How can I understand it is easy? Is there reference for it? What are excellent mechanical properties? What does this sentence tell to us? 

-There are lots of vague sentences that adds only confusion and ambiguousness.

-The structure of sections are not clear. What is the different between experiments, characterisation, and analysis? Why Materials and Methods is not enough? "Section 2. Experiments", "Section 3. Characterisation and analysis "

-Results and discussion section does not include any investigation from literature and discussion. Please separate discussion part!

-"However, due to the influence of production cost and other factors, more detailed tests need to be further explored." Is this a discussion or any other vague comment? What are other factors? How did we end this conclusion? 

-There is no clear conclusion only the obtained values comparison. What will the conclusions guide for future studies or applications?

As a conclusion, this is not a scientific paper. It can only be a badly prepared report. Please read more literature, revisit your findings and focus on your clear conclusion rather than vague comments.

Author Response

Dear reviewer:

Special thanks to the reviewer for the detailed comments, which helped us both in English and in depth to improve the quality of the paper. Point-to-point responses to the comments are listed as followed. In the revised manuscript, all the revised parts since the first submission are in red font, and the most recently revised parts are highlighted in yellow.

Sincerely yours

Gang Lu, ph.D.

Point 1: There are lots of typos in the paper, also unnecessary use of uppercase letters.

Response 1: We are very sorry for my carelessness in these low-level mistakes. We have corrected typing errors and unnecessary uppercase letters in the manuscript. The changes have been highlighted in yellow.

Point 2: The referencing and all structure of paper is poorly prepared.

Response 2: References in related fields have been supplemented and the citation format of references has been revised, the changes have been highlighted in yellow. The structure of the manuscript is designed according to the requirements of journals. At the same time, the structure also refers to the structure of previously published papers.

Notably, the third part “3. Characterization and analysis” should be written as “3. characterization and testing”, which has been revised. The changes have been highlighted in yellow.

Point 3: There are lots of statements and conclusive notes in the introduction without any proper discussion. Why "cannot be solved well in a short time?" How can reader get more knowledge about this? Why "the method is conservative" Why "Urgent"? How can a scientific paper make a strong judgements without any showing adequate background.

Response 3: We are very sorry for the lack discussion or quotation in the introduction of the article. Some supplementary contents and citations have been highlighted in yellow in the revised manuscript. As shown below:

“At present, most of the research on antifouling coatings starts from two perspectives, such as improving the application environment matching of film-forming resin and the performance of antifouling agents and other additives. The latter can cause fatal damage to marine fouling organisms. However, the contradiction between toxic pollution and marine ecological maintenance cannot be well handled in a short time since the development of a non-toxic or low toxic antifouling agent that completely replaces toxic antifouling agents and complies with the law will under the process of screening, elimination and re-screening [5][6][7]. Moreover, the film-forming resin is the carrier of antifouling agents and other added materials. Therefore, the functional film-forming resin will be researched in the future to improve the matching of its application environment as much as possible and thus the effect of antifouling coatings, though this method is slightly conservative compared with the development of a kind of new antifouling agent [7].”

“Epoxies and polyurethanes provide the best overall combinations of film properties than any other organic coatings [12]”

“Urgent” has been replaced by “principle”.

Point 4: "Considering that it is easy for ship coatings to peel off under the shear stress of water flow at high speed, excellent mechanical properties of the film-forming resin are required because the mechanical properties of the coatings are mainly associated with film-forming resin" How can I understand it is easy? Is there reference for it? What are excellent mechanical properties? What does this sentence tell to us?

Response 4: The adhesion between antifouling coatings and marine facilities, such as ships, is mainly provided by film-forming resin. Considering that the dynamic shear force between the ship and the water flow at high speed is large, the antifouling modification will become meaningness if the coatings lose too many mechanical properties due to the modification.

The excellent mechanical properties can include tensile strength, shear strength, dynamic mechanical properties, and so on. The above sentence suggests that it is necessary to reduce the impact on its mechanical properties on the basis of improving the antifouling effect of the antifouling coating.

Point 5: There are lots of vague sentences that adds only confusion and ambiguousness.

Response 5: We are sorry for my technical language. The article has been revised again by professors in this field. Since some of the reviewer's comments are not specific enough, please understand what has not been revised this time. The changes have been highlighted in yellow.

Point 6:The structure of sections are not clear. What is the different between experiments, characterisation, and analysis? Why Materials and Methods is not enough? "Section 2. Experiments", "Section 3. Characterisation and analysis "

Response 6: It must be pointed out that the third part “3. Characterization and analysis” should be written as “3. characterization and testing”, which has been revised. Experiment means that the product is synthesized by using raw materials. Characterization indicates that the synthesized product is characterized by standard methods to determine whether the product is the target product. Analysis refers to the scientific analysis of the characterization and test results.

Among the main raw materials, KH550 (silane coupling agent) has been added in Table 1.

The changes have been highlighted in yellow.

Point 7: Results and discussion section does not include any investigation from literature and discussion. Please separate discussion part!

Response 7: As the reviewer's comments, related papers have been reviewed in the results and discussion part, and all specific contents are composed of objective facts and discussion analysis. The changes have been highlighted in yellow.

Point 8: "However, due to the influence of production cost and other factors, more detailed tests need to be further explored." Is this a discussion or any other vague comment? What are other factors? How did we end this conclusion?

Response 8: The comprehensive test of an antifouling coating, such as copper ion release rate, mechanical properties of the coating, antifouling timeliness and selection of biological species, should be considered. At the same time, it should be applied actual ships and other marine facilities so as to draw an accurate conclusion. However, the workload and cost brought by the above test are extremely large, making it difficult to conduct it comprehensively at one time. Therefore, we should explore step by step.

Point 9: There is no clear conclusion only the obtained values comparison. What will the conclusions guide for future studies or applications?

Response 9: The conclusions in this paper have been accurately described. The guiding significance of the next research is also explained in this section. The changes have been highlighted in yellow in the revised manuscript.

 As shown below:

Based on the hydrophilic modification of film-forming resin for antifouling coatings, PU / EP grafted blends were designed and synthesized by the two-step method in this paper. Besides, the target products were verified by infrared spectroscopy. Test results demonstrated that the hydrophilic modification of film-forming resin has no significant effect on the mechanical properties, meeting the expectation. The specific conclusions are drawn as follows.

(1) With the increase in the PU content, the hydrophilic properties of PU / EP grafted blends are significantly improved. It can be concluded from the hydrophilic and mechanical properties of the materials that the comprehensive properties of PU / EP grafted blends are the best when the PU content is close to 50%. Thus it is feasible to introduce hydrophilic segments into polymers to improve the hydrophilicity of materials.

(2) According to the dynamic mechanical properties of PU / EP grafted blends, the compatibility of PU / EP grafted blends becomes worse when the content of PU is less than 40%. When polymer blending modification is performed, the phase compatibility between them should be considered. Therefore, the content of PU shall be 40%-50% when PU is used for hydrophilic modification of EP material.

(3) The antifouling effect of the hydrophilic modified antifouling coating is better than that of the commercial antifouling coating under experimental conditions.

In the follow-up study of antifouling coatings, the hydrophilicity of film-forming resin could be appropriately improved to promote the antifouling effect of antifouling coatings. However, the experimental state of the hanging plate in this paper is static. The antifouling effect of antifouling coatings under dynamic conditions can be explored in the next step.

Point 10:As a conclusion, this is not a scientific paper. It can only be a badly prepared report. Please read more literature, revisit your findings and focus on your clear conclusion rather than vague comments.

Response 10: The conclusions in this paper have been accurately described. The guiding significance of the next research is also explained in this section. The changes have been highlighted in yellow in the revised manuscript.

 As shown below:

Based on the hydrophilic modification of film-forming resin for antifouling coatings, PU / EP grafted blends were designed and synthesized by the two-step method in this paper. Besides, the target products were verified by infrared spectroscopy. Test results demonstrated that the hydrophilic modification of film-forming resin has no significant effect on the mechanical properties, meeting the expectation. The specific conclusions are drawn as follows.

(1) With the increase in the PU content, the hydrophilic properties of PU / EP grafted blends are significantly improved. It can be concluded from the hydrophilic and mechanical properties of the materials that the comprehensive properties of PU / EP grafted blends are the best when the PU content is close to 50%. Thus it is feasible to introduce hydrophilic segments into polymers to improve the hydrophilicity of materials.

(2) According to the dynamic mechanical properties of PU / EP grafted blends, the compatibility of PU / EP grafted blends becomes worse when the content of PU is less than 40%. When polymer blending modification is performed, the phase compatibility between them should be considered. Therefore, the content of PU shall be 40%-50% when PU is used for hydrophilic modification of EP material.

(3) The antifouling effect of the hydrophilic modified antifouling coating is better than that of the commercial antifouling coating under experimental conditions.

In the follow-up study of antifouling coatings, the hydrophilicity of film-forming resin could be appropriately improved to promote the antifouling effect of antifouling coatings. However, the experimental state of the hanging plate in this paper is static. The antifouling effect of antifouling coatings under dynamic conditions can be explored in the next step.

Reviewer 2 Report

The authors responded to all my questions and amended the paper as requested. I recommend this paper for publication.

Author Response

Dear reviewer:

Special thanks to the reviewer for the detailed comments, which helped us both in English and in depth to improve the quality of the paper. In the revised manuscript, all the revised parts since the first submission are in red font, and the most recently revised parts are highlighted in yellow.

Sincerely yours

Gang Lu, ph.D.

Reviewer 3 Report

All the weaknesses were answered. Quality is better now.

Author Response

Dear reviewer:

Special thanks to the reviewer for the detailed comments, which helped us both in English and in depth to improve the quality of the paper. In the revised manuscript, all the revised parts since the first submission are in red font, and the most recently revised parts are highlighted in yellow.

Sincerely yours

Gang Lu, ph.D.

Reviewer 4 Report

The article was improved significantly. I recomend publishin it in current form 

Author Response

Dear reviewer:

Special thanks to the reviewer for the detailed comments, which helped us both in English and in depth to improve the quality of the paper. In the revised manuscript, all the revised parts since the first submission are in red font, and the most recently revised parts are highlighted in yellow.

Sincerely yours

Gang Lu, ph.D.