Preparation and Molecular Dynamics Simulation of RDX/MUF Nanocomposite Energetic Microspheres with Reduced Sensitivity
Round 1
Reviewer 1 Report
This paper describes a particle coating technique and subsequent thermal and hazard analysis of the coated RDX particles. The coating methodology well design and interesting, but I 'm less convinced about the testing.
Overall the paper needs extensive editing to improve the english. It is very difficult to follow the narrative at times. There are just too many errors. Introduction was spelt incorrectly for instance.
Commenting on the style I recommend the authors look at the following:
1) Ensure each section is clearly defined. The results seems to contain experimental data and visa versa
2) Be precise in your wording. A certain amount of urea was added..is not enough detail in the experimental. What are the details of the hazard testing? Which countries national military standard did you use? Is there a reference?
3) When you make a statement ensure your data supports the statement. Where is your evidence for hydrogen bonding between RDX and MUF?
4) Images - please ensure you present fair comparisons. Figures 2 has images of varying resolution. Making it difficult to observe the effect of PhD. Use the same magnifcation!
5) Ensure you figures are clear. Figure 3 has a large circle which makes it very difficult to see the feature you are highlighting. Ensure you use appropriate terms - naked RDX is strange. Do you mean uncoated?
6) Figures: Please ensure you label what's important. Figures 5 -Please label the peak max so we can see if there are any problems with chemical incompatibility between RDX/MUF
7) Ensure you explain your thinking to thereader. What does quantum tunnelling have to do with this paper? Please explain and discuss?
8) I'm not convinced about the thermal explosion critical temperature theory equation. Where is the validation? The reference you provide has nothing to do with the equation.
9) Don't overstate your results. MUF has a remarkable effect on RDX - the results don't justify the word remarkable.
10) Check your references. There is no reference 24! Does reference 23 talk about hotspots? There are much better papers to reference.
Author Response
Dear Editors and Reviewers:
Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Preparation and characterization of RDX/MUF nanocomposite energetic microspheres with reduced sensitivity and excellent thermal stability”. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. We have highlighted the changes in the revised manuscript by using red text.
Please excuse us being unable to do some other experiments. We will give you some reasons why we can’t do this.
Reviewer 1
Comment 1: Ensure each section is clearly defined. The results seems to contain experimental data and visa versa.
Response: Thank you for your instructive suggestions. In the results section of the article, we analyzed the experimental data and explain the cause for these phenomena, such as the results of 4.4 safety performance.
It can be seen from Fig. 6 that MUF has a remarkable effect on RDX, among them, RDX/MUF-1 fabricated by the improved emulsion polymerization method has the best desensitization effect. Compared with the raw RDX, the H50 of the refined RDX, RDX/MUF-1 and RDX/MUF-2 increased from 29.32 cm to 44.5 cm, 82.4 cm, and 60.7 cm, respectively. The probability of frictional explosion decreased from 96% to 92%, 8%, and 60%, respectively, showing ideal desensitization effect with security performance efficiently improved. This can be explained by hotspot theory [23, 24]. The surface of the refined RDX particles tends to be smooth, and the internal defects gradually decrease, which increases the heat transfer rate between RDX particles, and hinders the formation of hot spots when encountering external stimuli, thus the security performance is improved.
Comment 2: Be precise in your wording. A certain amount of urea was added..is not enough detail in the experimental. What are the details of the hazard testing? Which countries national military standard did you use? Is there a reference?
Response: Thank you for your careful work. According to your request, we have added detailed experimental data and marked it in red in the original text. And the revised part is as follows: Preparation of urea-formaldehyde resin prepolymer. 0.62 g of urea and 1.87 g of formaldehyde solution (the concentration is 37 %) were mixed, and then the urea was sufficiently dissolved with a magnetic stirrer. As for the hazard testing, we mainly tested the impact sensitivity and the friction sensitivity in the article, and the test standard was in accordance with GJB772A-97 (already marked in the original text). Also, test techniques can refer to a large number of references [1-4].
Ji W, Li X, Wang J. Preparation and Characterization of CL-20/EPDM by a Crystal Refinement and Spray Drying Method[J]. Central European Journal of Energetic Materials, 2015, 12(4):831-840.
[2] Ye B, An C, Wang J. Preparation and Characterization of RDX-Based Composite with Glycidyl Azide Polymers and Nitrocellulose[J]. Journal of Propulsion & Power, 2016, 32(4):1035-1039
[3] Yang Z, Li H, Huang H. Preparation and performance of a HNIW/TNT cocrystal explosive[J]. Propellants, Explosives, Pyrotechnics, 2013, 38(4): 495-501.
[4] Wang Y, Song X, Song D. Synthesis, thermolysis, and sensitivities of HMX/NC energetic nanocomposites[J]. Journal of Hazardous Materials, 2016, 312:73-83.
Comment 3: When you make a statement ensure your data supports the statement. Where is your evidence for hydrogen bonding between RDX and MUF?
Response: Thank you for your careful reading of our manuscript. As you have suggested, we do have no evidence of the existence of hydrogen bonds. So in accordance with your scientific advice, with a rigorous academic attitude, we have removed this statement and thank you again for your professional advice.
Comment 4: Images-please ensure you present fair comparisons. Figures 2 has images of varying resolution. Making it difficult to observe the effect of PhD. Use the same magnification!
Response: Thank you very much for pointing out the magnification problem of the picture. According to your requirements, we have replaced Figure f and Figure i with the guaranteed magnification. We also tried to replace the SEM of other samples. However, due to the loss of the original sample, we are unable to make further replacements (We can see that the Fig. j - the Fig. o are clear enough by SEM, and the difference is obvious), so I hope to get your understanding, and thank you again for your guidance.
Comment 5: Ensure you figures are clear. Figure 3 has a large circle which makes it very difficult to see the feature you are highlighting. Ensure you use appropriate terms-naked RDX is strange. Do you mean uncoated?
Response: Yes, you are right. We are very sorry for not statement clearly. “Naked RDX” means that the RDX did not have a complete coating. For the coated composite particles, we usually use whether or not the particles are exposed as an intuitive basis for judging whether or not effective coating occurs.
Comment 6: Figures: Please ensure you label what's important. Figures 5-Please label the peak max so we can see if there are any problems with chemical incompatibility between RDX/MUF.
Response: Thank you for your instructive suggestions. We have corrected Figures 5 according to your comment.
Comment 7: Ensure you explain your thinking to the reader. What does quantum tunnelling have to do with this paper? Please explain and discuss.
Response: Thank you for your careful reading of our manuscript. The micron-sized RDX/MUF composite particles with obvious spherical effects prepared in this report have quantum size effect, surface effect and macroscopic quantum tunneling effect, resulting in a large surface area and many surface active centers, which have certain influence on the thermal decomposition process of composite particles.
Comment 8: I'm not convinced about the thermal explosion critical temperature theory equation. Where is the validation? The reference you provided has nothing to do with the equation.
Response: Thank you for your careful reading of our manuscript. Although the references provided in our article cannot directly demonstrate the process of the thermal explosion critical temperature theory equation, this theoretical equation is used in almost all thermal analysis processes in the field of energetic materials, such as thermal analysis in the following references [1-5].
[1] Wang Y, Song X, Song D, et al. Synthesis, thermolysis, and sensitivities of HMX/NC energetic nanocomposites[J]. Journal of Hazardous Materials, 2016, 312:73-83.
[2] Ye B, An C, Zhang Y, et al. One-Step Ball Milling Preparation of Nanoscale CL-20/Graphene Oxide for Significantly Reduced Particle Size and Sensitivity.[J]. Nanoscale Research Letters, 2018, 13(1):42-48.
[3] WANG Jing-yu, HUANG Hao, WANG Pei-yong, et al. Preparation and Characterization of high purity Nano HNS[J].Chinese Journal of Energetic Materials, 2008, 16(3): 258-261.
[4] Wang Y, Li X, Chen S, et al. Preparation and Characterization of Cyclotrimethylenetrinitramine (RDX) with Reduced Sensitivity.[J]. Materials, 2017, 10(8):1-10.
[5] Jia X L, Hou C H, Tan Y X, et al. Fabrication and Characterization of PMMA/HMX-based Microcapsules via in situ Polymerization[J]. Central European Journal of Energetic Materials, 2017, 14(3):559-572.
Comment 9: Don't overstate your results. MUF has a remarkable effect on RDX-the results don't justify the word remarkable.
Response: Thank you for your instructive suggestions. According to your comment, we have removed the “excellent thermal stability” from the title, corrected the inappropriate part about the thermal analysis section and marked it in red. Here, the RDX/MUF samples with the same MUF ratio were mainly compared, indicating that the thermal stability of RDX/MUF-1 was relatively improved. Thank you again for your help and guidance.
Comment 10: Check your references. There is no reference 24! Does reference 23 talk about hotspots? There are much better papers to reference.
Response: Thank you for your instructive suggestions. We are very sorry for our fault; We have corrected reference 23 according to your comment.
23. Barua A, Kim S, Horie Y, et al. Ignition criterion for heterogeneous energetic materials based on hotspot size-temperature threshold[J]. Journal of Applied Physics, 2013, 113(6):5794-5799.
Author Response File: 
Author Response.doc
Reviewer 2 Report
In this study, the authors presented a emulsion based method to prepare RDX/MUF composite and protect RDX. The polymerization is well studied and the overall presentation is in good quality. There are only a few comments:
The authors show a large amount of SEM images, but they are all in a low resolution. RDX and MUF cannot be distinguished from them. High-resolution SEM images are necessary.
A more detailed schame for the polymerization process in the emulsions is suggested to improve the quality of idea-presentaton.
Figure 1 is too blur, please improve the resolution.
The language needs to be polished.
Author Response
Dear Editors and Reviewers:
Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Preparation and characterization of RDX/MUF nanocomposite energetic microspheres with reduced sensitivity and excellent thermal stability”. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. We have highlighted the changes in the revised manuscript by using red text.
Please excuse us being unable to do some other experiments. We will give you some reasons why we can’t do this.
Reviewer 2
Comment 1: The authors show a large amount of SEM images, but they are all in a low resolution. RDX and MUF cannot be distinguished from them. High-resolution SEM images are necessary.
Response: Thank you for your careful reading of our manuscript. We are very sorry for our fault; According to your requirements, we have replaced Figure f and Figure i with the guaranteed magnification. We also tried to replace the SEM of other samples. However, due to the loss of the original sample, we are unable to make further replacements (We can see that the Fig. j - the Fig. o are clear enough by SEM, and the difference is obvious), so I hope to get your understanding, and thank you again for your guidance.
Comment 2: A more detailed schame for the polymerization process in the emulsions is suggested to improve the quality of idea-presentaton.
Response: Thank you for your instructive suggestions. According to your comment, we have made the following changes to this content and marked it in red in the original text.
(1) Preparation of RDX emulsion. 6 g of RDX was added to 35ml of deionized water, and 0.01 g of span-80 was dropwise added as an emulsifier. The mixture was emulsified and sheared at a rate of 7000 rad/min for 30 minutes until a stable explosive emulsion was formed. (2) Synthesis and modification of UF prepolymer. 0.62 g of urea and 1.87 g of formaldehyde solution (the concentration is 37 %) were mixed, and then the urea was sufficiently dissolved with a magnetic stirrer.
Comment 3: Figure 1 is too blur, please improve the resolution.
Response: Thank you for your careful work; according to your comment, we have improved it.
Comment 4: The language needs to be polished.
Response: Thank you very much for pointing out the sentence structure and grammatical issues in our manuscript. We have re-polished the grammar in the original text and marked it in red.
Once again, thank you for your valuable and thoughtful comments. We hope meet with your approval.
Sincerely
Xinlei Jia
Author Response File: Author Response.doc
Reviewer 3 Report
The manuscript discusses the reduced sensitivity of RDX using melamine-urea resin composites. Below are several questions and suggestions for authors:
The addition of MUF improves the thermal stability by only 3 degrees, but you are calling it "greatly enhancing the thermal stability (in abstract and conclusion), and also in the text. 3 degree is not "great enhancement" in fact it may lie in the sensitivity of the equipment. This is not worth mentioning, you can call it "thermal stability is not changed".
When using the Activation energy equations by Kissinger, Ozawa and Starink, please be consistent on letter assignment: In eq. 1 and 2 you have Ea, but in equation 3 you have E as activation energy, also in (2) you have function g(a) which is not explained what is it.
There is no indication how is RDX-MUF1 different from RDX-MUF2 (please provide percentages), also the experimental part is very vague (you mention "certain amounts of... please provide exact numbers with tables for each composition).
Before using acronyms, always give the definitions (PBX page 2 line 51) or MF (line 78) or HCL (page 3 line 122, is it HCl ?), why you suddenly mention RDX-PMMA-1 and 2 (is it PMMA Polymethyl metacrylate? You never mentioned about it, see page 11 line 359).
Please review the English for this manuscript (not "optimum" but "optimal", do not start sentences with "And" etc)
Author Response
Comment 1: The addition of MUF improves the thermal stability by only 3 degrees, but you are calling it "greatly enhancing the thermal stability (in abstract and conclusion), and also in the text. 3 degree is not "great enhancement" in fact it may lie in the sensitivity of the equipment. This is not worth mentioning, you can call it "thermal stability is not changed".
Response: Thank you for your instructive suggestions. According to your comment, We have removed the “excellent thermal stability” from the title, corrected the inappropriate part about the thermal analysis section to “slightly improving the thermal stability” and marked it in red.
Comment 2: When using the Activation energy equations by Kissinger, Ozawa and Starink, please be consistent on letter assignment: In eq. 1 and 2 you have Ea, but in equation 3 you have E as activation energy, also in (2) you have function g(a) which is not explained what is it.
Response: Thank you for your careful reading of our manuscript. We are very sorry for our fault; In fact, G(a) is the integral form of the reaction mechanism function. Besides, we have added and marked it in red in the original text, thank you again for your guidance.
Comment 3: There is no indication how is RDX-MUF1 different from RDX-MUF2 (please provide percentages), also the experimental part is very vague (you mention "certain amounts of... please provide exact numbers with tables for each composition).
Response: Thank you for your instructive suggestions. According to your comment, we have made the following changes to this part and marked it in red in the original text.
(1) Preparation of RDX emulsion. 6 g of RDX was added to 35ml of deionized water, and 0.01 g of span-80 was dropwise added as an emulsifier. The mixture was emulsified and sheared at a rate of 7000 rad/min for 30 minutes until a stable explosive emulsion was formed. (2) Synthesis and modification of UF prepolymer. 0.62 g of urea and 1.87 g of formaldehyde solution (the concentration is 37 %) were mixed, and then the urea was sufficiently dissolved with a magnetic stirrer.
The difference in the morphology of RDX/MUF-1 and RDX/MUF-2 particles can be visually seen through SEM, and the difference can be further observed through performance characterization. Moreover, the addition of detailed data of the experimental process and the poor quality before and after coating can prove that the mass of MUF is about 5% from the side.
Comment 4: Before using acronyms, always give the definitions (PBX page 2 line 51) or MF (line 78) or HCL (page 3 line 122, is it HCl ?), why you suddenly mention RDX-PMMA-1 and 2 (is it PMMA Polymethyl metacrylate? You never mentioned about it, see page 11 line 359).
Response: Thank you for your careful reading of our manuscript. We are very sorry for our fault; we will correct this fault when we upload the revised manuscripts.
Comment 5: Please review the English for this manuscript (not "optimum" but "optimal", do not start sentences with "And" etc)
Response: Thank you for your careful reading of our manuscript. According to your comment, We have modified the nonstandard details in the article.
Once again, thank you for your valuable and thoughtful comments. We hope meet with your approval.
Sincerely
Xinlei Jia
Author Response File: Author Response.doc
Round 2
Reviewer 3 Report
The manuscript quality has significantly improved and can be considered for publishing in present form
Author Response
Thank you for your approval of the article. Sincerely wish you good health, success in work, and family happiness!
