The Effect of Coating Additives on the Properties of Hydrophobic Coatings with Low Infrared Emissivity
Round 1
Reviewer 1 Report
Publish as it is. No modification needed.
Author Response
It has been modified according to the requirements of the reviewer.
Reviewer 2 Report
This paper talks about the Effect of Coating Additives on Properties of Hydrophobic Coatings with Low Infrared Emissivity. The following points need to be clarified:
1. It is suggested that the authors should modify the last part of the introduction to: 1) clearly mention the goal and novelty of this work, 2) mention the methodology used and it is important to place the major hypothesis, 3) mention the structure of the paper or procedure of their work and expected results.
2. The authors should give more details regarding the strength and impact tests performed. Some figures showing the tests would help readers to understand the scope of the work.
3. In connection with the above point, the adhesion strength and impact strength results shown in Table 1 seems rounded. How are the sensitivity of the devices used? One would expect more accurate numbers.
4. Also the definitions for the grades describing the adhesion strength should be given. What strength values do the grades 1-5 correspond to?
5. The authors should compare the obtained results with those in the literature studying the amount of defoamer, adhesion enhancer on the properties of the coatings. Are they close to each other?
6. The paper lacks a discussion on the weakness and limitations of the present methodology proposed.
7. The authors should refrain from summarizing the work in the conclusion; instead, only the main findings should be placed.
Minor editing of English language required
Author Response
1.It is suggested that the authors should modify the last part of the introduction to: 1) clearly mention the goal and novelty of this work, 2) mention the methodology used and it is important to place the major hypothesis, 3) mention the structure of the paper or procedure of their work and expected results.
Now we have appropriately added relevant expressions at the end of the introduction according to the suggestions of reviewers.
2.The authors should give more details regarding the strength and impact tests performed. Some figures showing the tests would help readers to understand the scope of the work.
Now we have detailed the test method of mechanical properties in the revised draft.
3.In connection with the above point, the adhesion strength and impact strength results shown in Table 1 seems rounded. How are the sensitivity of the devices used? One would expect more accurate numbers.
Coating’s adhesion strength and impact strength testing techniques are not as sophisticated as other large compact instruments. They are a more intuitive evaluation method according to the relevant national standard methods, which can compare the relative mechanical properties of two coatings. But due to the limited level of testing, it's really not very detailed. However, the evaluation requirements of the mechanical properties of the coating can be achieved according to the relevant methods.
4.Also the definitions for the grades describing the adhesion strength should be given. What strength values do the grades 1-5 correspond to?
Now we have given the description of relevant test levels in the section of Test methods according to the suggestions of reviewers.
5.The authors should compare the obtained results with those in the literature studying the amount of defoamer, adhesion enhancer on the properties of the coatings. Are they close to each other?
Now we have added a comparison with the relevant references in the revised draft.
6.The paper lacks a discussion on the weakness and limitations of the present methodology proposed.
Now we have pointed out some shortcomings in the last part of the revised draft.
7.The authors should refrain from summarizing the work in the conclusion; instead, only the main findings should be placed.
According to the suggestions of reviewers, we have made appropriate modifications to the conclusion.
Reviewer 3 Report
Review
As the experience of the current Russian-Ukrainian war shows, it is extremely important for the military industry to design unknown aircraft and missiles. Therefore, the topic of the article is definitely relevant.
Based on the analysis of the literature and their own research experience, the authors proposed a recipe and manufacturing technology of a composite coating with high masking properties in the infrared section. The influence of the dispersant, adhesion promoter, and defoamer on the complex of reflective, mechanical, and hydrophobic properties of the coating was experimentally investigated.
Remarks
The strategy of the experiment (lines 97-105) is not justified.
The influence of three factors (dispersant, adhesion enhancer, defoamer) on five properties of the coating (emissivity, glossiness, adhesion strength, impact strength, and WCA ) is investigated. To reduce the number of experiments, a special motion trajectory is built in the 3-D factor space, which takes into account local extremums at the last change of each individual factor (others are fixed).
(1) Such a strategy does not provide complete information about the set of factors affecting the studied properties. There is a danger of missing the global extreme. The number of tests should be significantly increased or the mathematical planning of a multivariate experiment should be used.
(2) Even if you focus only on local extremes, you need to establish a quality criterion that includes 5 properties of the coating, or clearly appreciate that the minimum emissivity is the key requirement.
Conclusion
The article may be published after significant changes.
Author Response
The strategy of the experiment (lines 97-105) is not justified.
The influence of three factors (dispersant, adhesion enhancer, defoamer) on five properties of the coating (emissivity, glossiness, adhesion strength, impact strength, and WCA ) is investigated. To reduce the number of experiments, a special motion trajectory is built in the 3-D factor space, which takes into account local extremums at the last change of each individual factor (others are fixed).
(1) Such a strategy does not provide complete information about the set of factors affecting the studied properties. There is a danger of missing the global extreme. The number of tests should be significantly increased or the mathematical planning of a multivariate experiment should be used.
(2) Even if you focus only on local extremes, you need to establish a quality criterion that includes 5 properties of the coating, or clearly appreciate that the minimum emissivity is the key requirement.
As the reviewer said, the use of multi-factor test can indeed study more detailed. But that approach may not be very practical for low infrared emissivity coatings. Because the low infrared emissivity coating based on practical applications needs to consider various properties such as emissivity, mechanical properties, hydrophobicity, etc., it is difficult to fix a certain key performance, and all properties are equally important. Therefore, we use the single factor test method to study is more practical and efficient, and can also obtain the coating formula with superior comprehensive properties. According to experience, the single factor test method, which fixes other factors first and studies related factors one by one, is also a common research method in the field of functional coatings.
Reviewer 4 Report
Manuscript ID: coatings-2544377
Title: Effect of Coating Additives on Properties of Hydrophobic Coatings with Low Infrared Emissivity
Authors: Weigang Zhang *, Xiang Li, Dandan Lv
The manuscript explores the modification of the optical, mechanical, and hydrophobic properties of specialized coatings based on polyurethane and silicone oil for tin surfaces. The manuscript is well structured and easy to read. The purpose of the study is justified.
Changes required.
The margin of error is not reported for any of the experimentally measured quantities. What does the non-monotonicity of the change in glossiness in Table 2 mean? Is it due to a measurement error, is it a characteristic of that particular sample, or is it a reproducible change?
The authors often refer to the surface energy, but do not explain in any way how a slight change in the volume content of one or another ingredient of a mixture can have a significant effect on the surface energy.
Line 206. “However, the adhesion enhancer has little effect on the surface state of the coating, so the glossiness of the coating is almost unchanged.” This statement contradicts Figure 5.
Line 234. “Moreover, the addition of did not change the horizontal orientation state of flake Al and the dispersion state of nano-SiO2 in the coating.” Correct the sentence: the addition of the defoamer…
Part 3.3. What amount of adhesion enhancer was used in the studied samples? Is this the 4% sample?
Author Response
1. The margin of error is not reported for any of the experimentally measured quantities. What does the non-monotonicity of the change in glossiness in Table 2 mean? Is it due to a measurement error, is it a characteristic of that particular sample, or is it a reproducible change?
Now we have added the measurement error of relevant test data in the revised draft. Glossiness in Table 2 is a synthesis of test errors and actual differences. However, for such coatings, the glossiness below 10 is already a relatively low glossiness, so when the glossiness is 5-6, the glossiness of the coating is relatively superior. The difference of a few tenths actually has a very limited effect on coating performance.
2. The authors often refer to the surface energy, but do not explain in any way how a slight change in the volume content of one or another ingredient of a mixture can have a significant effect on the surface energy.
As the reviewer said, at present we are limited by the testing conditions and do not test the surface energy characteristics of the coating. However, there have been many reports confirming that the surface energy change of the coating can in turn be evidenced by the change of water contact angle. Therefore, the change rule of contact angle measured in this paper just verifies the change rule of coating surface energy, and the two rules can support each other.
3. Line 206. “However, the adhesion enhancer has little effect on the surface state of the coating, so the glossiness of the coating is almost unchanged.” This statement contradicts Figure 5.
Figure 5 refers to the water contact Angle of the coating. The water contact Angle is affected not only by the roughness of the coating surface, but also by the hydrophilicity of the coating surface itself. In this paper, because there are more hydrophilic polar groups in the molecular structure of the adhesion accelerator, the addition of them to the coating will inevitably increase the hydrophilicity of the coating surface, and thus reduce the contact Angle. So these are two different causes and there is no contradiction.
4. Line 234. “Moreover, the addition of did not change the horizontal orientation state of flake Al and the dispersion state of nano-SiO2in the coating.” Correct the sentence: the addition of the defoamer…
Thanks to the error found by the experts, we have made corresponding changes in the revised draft.
5. Part 3.3. What amount of adhesion enhancer was used in the studied samples? Is this the 4% sample?
It is the 4% sample. Now we have made a supplementary explanation in the corresponding position of the revised draft.
Round 2
Reviewer 2 Report
The points were corrected as requested.
Minor revision required.
Reviewer 3 Report
I agree with the authors' answer.
