Improvement of the Tribological Properties and Corrosion Resistance of Epoxy–PTFE Composite Coating by Nanoparticle Modification

Round 1

Reviewer 1 Report

The research presented in the work "Improvement of the Tribological Properties and Corrosion Resistance of Epoxy-PTFE Composite Coating by Nanoparticle Modification" is part of the research area related to the improvement of epoxy composite coating properties. In particular, the aim of the research presented in this paper was to improve corrosion resistance, abrasion resistance and self-lubrication in the case of coatings intended for marine applications. The research concerned doping them with PTEE nanoparticles and TiO2 nanoparticles with modified organic functional groups. A large spectrum of surface engineering research methods was used to verify the obtained changes in the properties of coatings as a result of doping, i.e. infrared spectroscopy, EDS spectroscopy, scanning electron microscopy (SEM), tribological tests (wear, friction coefficient ..... The sequence of the conducted tests and their interpretation do not raise any objections.

However, it should be taken into account that so far numerous attempts have been made to improve these properties by doping the coatings with various nanoparticles, including oxidized graphene nanoplatelets or SiO2 particles. It would be advisable for the authors of the reviewed article to compare the properties of the coatings analyzed in their research with those of epoxy coatings doped with other particles.

Author Response

Dear reviewers:

Thanks for your comments. We have revised the manuscript based on the reviewers’ comments.

 

Open Review

(x) I would not like to sign my review report

( ) I would like to sign my review report

English language and style

( ) Extensive editing of English language and style required

( ) Moderate English changes required

(x) English language and style are fine/minor spell check required

( ) I don't feel qualified to judge about the English language and style

 

Yes Can be improved Must be improved Not applicable

Does the introduction provide sufficient background and include all relevant references?

(x) ( ) () ( )

Is the research design appropriate? (x) ( ) () ( )

Are the methods adequately described? (x) ( ) () ( )

Are the results clearly presented? (x) ( ) () ( )

Are the conclusions supported by the results? (x) ( ) () ( )

 

Comments and Suggestions for Authors

The research presented in the work "Improvement of the Tribological Properties and Corrosion Resistance of Epoxy-PTFE Composite Coating by Nanoparticle Modification" is part of the research area related to the improvement of epoxy composite coating properties. In particular, the aim of the research presented in this paper was to improve corrosion resistance, abrasion resistance and self-lubrication in the case of coatings intended for marine applications. The research concerned doping them with PTEE nanoparticles and TiO₂ nanoparticles with modified organic functional groups. A large spectrum of surface engineering research methods was used to verify the obtained changes in the properties of coatings as a result of doping, i.e. infrared spectroscopy, EDS spectroscopy, scanning electron microscopy (SEM), tribological tests (wear, friction coefficient ..... The sequence of the conducted tests and their interpretation do not raise any objections.

 

However, it should be taken into account that so far numerous attempts have been made to improve these properties by doping the coatings with various nanoparticles, including oxidized graphene nanoplatelets or SiO₂ particles. It would be advisable for the authors of the reviewed article to compare the properties of the coatings analyzed in their research with those of epoxy coatings doped with other particles.

Response: Thanks for your suggestions. We have added relevant discussions in the revision. (see line 74-86. highlighted in yellow) The literature information is detailed in the References section. (see line 430-433. highlighted in yellow)

 

Indeed, there has been a lot of research into improving the properties of coatings by doping different nanoparticles. Due to curing shrinkage and warpage deformation of epoxy, there are always a lot of micropores and cracks in the composite coating, this will cause corrosive medium to enter the micropores and cracks contact with the matrix, resulting in corrosion. Although the addition of PTFE can improve the anticorrosion performance, but the low hardness of PTFE will also lead to poor wear resistance of epoxy-PTFE composite coating. A viable solution is to add hard or inorganic particles, such as TiO₂, SiO₂, ZnO, Al₂O₃, etc. which will improve the properties of the coating.

 

SiO₂ nanoparticles are mainly used to improve the mechanical properties and heat resistance of epoxy composites, and their corrosion resistance is weak; It is difficult to prepare nano-zinc oxide modified epoxy resin, because nano-zinc oxide has high activity and large specific surface area, it is easy to agglomerate together, and it takes a long time to disperse before preparation; The surface of Al₂O₃ contains a large number of hydroxyl groups, which makes it difficult to evenly disperse in epoxy materials. On the contrary, TiO₂ not only has good chemical stability, but also has excellent heat resistance and UV protection, so it is widely used in the fields of UV resistant materials, packaging materials and coatings. At the same time as rigid nanoparticles and its strong adhesion, TiO₂ is often used as a modified filler to improve the bending strength, tensile strength and impact strength of epoxy resin. In the wear resistance test, TiO₂ nanoparticles can significantly improve the wear resistance of epoxy resin. This is because TiO₂ nanoparticles have a large specific surface area and a large contact surface with the substrate, which requires more external energy when sliding. In summary, for comprehensive performance considerations, this article selects TiO₂ nanoparticles for research.

 

We have also made editorial effort to improve the language of the manuscript. We would like to thank you again for reviewing the manuscript. Hope that the revised edition meets the publication requirements of the journal.

 

Regards,

Lixia Ying

Author Response File: Author Response.pdf

Reviewer 2 Report

Authors reports the TiO2 embedded epoxy PTFE coating and studies the tribological performance. This work is interesting. However authors needs to improve the quality of manuscript. Please address the following concerns:

1. Please specify the concentration of KH570 andbTiO2 “KH570 and TiO2 nanoparticles were added into”
2. Please describe the company details of all raw materials which are used in this study.
3. Please check the “15t% and 2%”
4. Why the Fe, C and Ni elements are not appeared in Fig.2
5. Please analysis thickness of coating materials in each case.
6. Introduction part, please cite these relevant articles: i. Synthesis and characterization of molybdenum disulfide nanoflowers and nanosheets: nanotribology; (ii) Tribological behaviour of MoS2/Au coatings; (iii) Synthesis and structural characterization of MoS2 nanospheres and nanosheets using solvothermal method
7. Please fit the equivalent circuit diagram for Fig. 10a .
8. Please specify the applied voltage for EIS studies.
9. there are several typo and format errors please rectify in revision.

Comments for author File: Comments.pdf

Author Response

Dear reviewers:

Thanks for your comments. We have revised the manuscript based on the reviewers’ comments.

 

Open Review

(x) I would not like to sign my review report

( ) I would like to sign my review report

English language and style

() Extensive editing of English language and style required

( ) Moderate English changes required

( ) English language and style are fine/minor spell check required

(x) I don't feel qualified to judge about the English language and style

 

Yes Can be improved Must be improved Not applicable

Does the introduction provide sufficient background and include all relevant references?

( ) () (x) ( )

Is the research design appropriate? ( ) (x) ( ) ( )

Are the methods adequately described? ( ) ( ) (x) ( )

Are the results clearly presented? ( ) ( ) (x) ( )

Are the conclusions supported by the results? ( ) ( ) (x) ( )

 

Comments and Suggestions for Authors

Authors reports the TiO₂ embedded epoxy PTFE coating and studies the tribological performance. This work is interesting. However authors need to improve the quality of manuscript. Please address the following concerns:

 

1.Please specify the concentration of KH570 and TiO₂ “KH570 and TiO₂ nanoparticles were added into”

Response: In the experiment, the mass ratio of KH570 and TiO₂ is 15: 100. We have added concentration in the revised manuscript. (see line 116-118. highlighted in yellow)

 

2. Please describe the company details of all raw materials which are used in this study

Response: Relevant experimental materials are added in the revised manuscript, including:

• The carbon steel SK85 was chosen as the substrate with dimensions of 30mm × 12mm × 1mm and with the nominal composition, as follows: 0.80%-0.90% C, ≤0.35% Si, ≤0.50% Mn, ≤0.03% P, ≤0.03% S, ≤0.20% Cr, ≤0.25% Ni, ≤0.30% Cu.
• The epoxy resin(E44) with viscosity range from 40000 to 45000 mPa.s at 25℃was purchased from Nanjing Star Synthetic Materials Co., LTD., China.
• The TiO₂nanoparticles (about 40nm) were supplied by Shanghai Macklin Biochemical Co., LTD., China.
• The silane coupling agent KH570( CH₂=C(CH₃) COOC₃H₆Si(OCH₃)₃, ≥99%, Nanjing, Silica Co., LTD., China) was used as modifier.
• The polytetrafluoroethylene (PTFE ) was provided by Minnesota Mining and Manufacturing Company (3M), America.
• The ethanol (CH₃CH₂OH, ≥99.7%, Tianjin, Fuyu Fine Chemical Co., LTD., China) was used as a dispersant.
• The acetic acid(CH₃COOH,≥99.8%, Sinopharm Group Chemical Reagent Co., LTD., China) was used to adjust the pH value of the solution.

All reagents were used without further purification. (see line 101-110. highlighted in yellow)

 

3. Please check the “15t% and 2%”

Response: Sorry, this is our carelessness, which we have corrected in the revised manuscript. (see line 129. highlighted in yellow) As described below:

 

The mass content of PTFE and TiO₂ was controlled at 15% and 2%.

 

4. Why the Fe, C and Ni elements are not appeared in Fig.2

Response: In the original manuscript, we mainly proved whether the organic functional group of KH570( CH₂=C(CH₃)COOC₃H₆Si(OCH₃)₃) was successfully grafted onto the surface of TiO₂ nanoparticles. Therefore, during the test, we only analyzed the relevant elements to prove that the organic functional groups were successfully grafted on the surface of TiO₂ nanoparticles. The other elements were not analysized. (see line 176-182, Figure 1. and Figure 2.)

 

5. Please analysis thickness of coating materials in each case.

Response: In the process of sample preparation, we used a small mold to ensure that the thickness of the samples are uniform at 52±3μm. We have made corresponding supplementary instructions in 2.3. Coating preparation. (see line 131-133. highlighted in yellow)

 

6. Introduction part, please cite these relevant articles: i. Synthesis and characterization of molybdenum disulfide nanoflowers and nanosheets: nanotribology; (ii) Tribological behaviour of MoS2/Au coatings; (iii) Synthesis and structural characterization of MoS2 nanospheres and nanosheets using solvothermal method

Response: In the revision, we have cited relevant articles. (see line 53-55. highlighted in yellow)  

The literature information is detailed in the References section. (see line 415-419. highlighted in yellow)  

 

7. Please fit the equivalent circuit diagram for Fig. 10a .

Response: In the original manuscript, we mainly analyzed the test data of the electrochemical impedance spectroscopy, without circuit fitting. In the revision, “Figure 10 shows the results of the electrochemical impedance spectroscopy (EIS) by using R (CR) circuit in ZSimDemo software” has been changed to "Figure 10 shows the test data of the electrochemical impedance spectroscopy (EIS)". (see line 337. highlighted in yellow). In view of this, we did not provide a circuit diagram.

 

8. Please specify the applied voltage for EIS studies.

Response: The applied voltage for EIS studies is 10 mV. We have added it in the revised manuscript, (see line 150-154. highlighted in yellow). Thanks very much.   

 

9. There are several typo and format errors please rectify in revision.

Response: In the revision, we revised all the issues raised above and the typo and format errors in the text.

 

We have also made editorial effort to improve the language of the manuscript. We would like to thank you again for reviewing the manuscript. Hope that the revised edition meets the publication requirements of the journal.

 

Regards,

Lixia Ying

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Editor,

The manuscript (coatings-1041628) reports a strategy for improvement of corrosion and friction resistance of epoxy coatings by employing PTFE and TiO2 nanoparticles. The work is interesting but there are several major concerns that should be addressed to render the work re-considerable for publication:

1- Materials and Methods; the name and details of the manufacturers of the chemicals should be included.

2- Page 3, line 115, where from the rotation speed has been obtained?

3- For SEM imaging, were the samples sputter coated with gold? If so, the coating details should be added.

4-FTIR result; any shift in the characteristic peak of TiO2 upon surface treatment can be recorded?

5- Figure 2, please remove black frame around the graphs and clearly define the axis units and names.

6-Figure 3, can the authors mark the different materials and phases in the SEM images?

7-Fig.4 and 5, instead of A-D simply write the compositions under each respective column.

8- What about brittleness of the materials, whether inclusion of modified TiO2 ends up with brittleness of related composite compared to the other compositions?

9- In general, the observations have not been sufficiently discussed, for instance, tribological properties of different compositions have been solely reported and not discussed. Why inclusion of modified TiO2 nanoparticles lowers friction coefficient? No reference is seen in the discussion part of the results, for instance, regarding interface strength of polymeric composites with inorganic inclusions and the effect of this parameter on mechanical properties of the resulting polymeric composite, the following references should be used in discussions and cited: (Journal of the European Ceramic Society 26 (3), 273-278, 2006; Journal of Materials Science: Materials in Medicine 15 (8), 853-858, 2004; Scientific Reports 10 (1), 1-11, 2020; Carbohydrate polymers 224, 115112, 2019).

10- Hydrophobic properties; seems the nanoparticles accumulate on the surface of the epoxy coating and thus contribute to its hydrophobicity/ hydrophilicity. Is it correct? If yes, why this is the case?

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Authors addressed all concerns

Reviewer 3 Report

Dear Editor,

My major comments have been addressed. I can suggest the paper for publication now.