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  • George Pelin1,*,
  • George-Cătălin Cristea1 and
  • Cristina-Elisabeta Pelin1,*
  • et al.

Reviewer 1: Anonymous Reviewer 2: Sumbul Hafeez Reviewer 3: Anonymous

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper is of poor quality and fails to meet academic standards. The data presented raises serious concerns regarding its authenticity, and I recommend rejection. Furthermore, I request not to be assigned this manuscript for review again.

The abstract is unnecessarily divided into paragraphs and merely lists experimental procedures without presenting key results, let alone any discussion or analysis.

The introduction inappropriately labels 1500°C as an "ultra-high temperature," which does not align with the standard definition in the aerospace field, reflecting a lack of professionalism. Additionally, the structure is highly irregular, with some paragraphs consisting of only a single sentence—a flaw also evident in the Results and Discussion section. The introduction lacks a necessary review of existing research on polysiloxane-based thermal protection materials. Descriptions of reusable launch vehicles are irrelevant here, as this study focuses on disposable ablative materials. The introduction should clearly state the necessity and innovation of this work.

Figure 1 appears hastily prepared.

Figure 2 shows an unclear optical micrograph; scanning electron microscopy (SEM) images should be supplemented.

Figure 3 directly exports raw data from testing equipment without proper processing. Moreover, a significant portion of the data in this figure remains undiscussed.

Figure 4 has incomplete legends.

Figure 7 contains erroneous data. It is widely accepted in the field that the temperature of a butane flame does not exceed 1300°C, yet the authors claim it reached 1600°C.

Why was the oxyacetylene ablation test—the industry standard for evaluating ablation resistance—not used to assess the samples?

The conclusion is excessively lengthy, lacks focus, and fails to highlight the contributions of this work.

Author Response

1. This paper is of poor quality and fails to meet academic standards. The data presented raises serious concerns regarding its authenticity, and I recommend rejection. Furthermore, I request not to be assigned this manuscript for review again.
Authors' response: Thank you very much for your review and we sincerely regret that the scientific quality of our study did not meet your expectations. However, we will strive to meet the written requirements and thereby enhance the quality of our work.
2. The abstract is unnecessarily divided into paragraphs and merely lists experimental procedures without presenting key results, let alone any discussion or analysis. 
Authors' response: The abstract has been rewritten and updated with the key results of the study and added to our paper
3.The introduction inappropriately labels 1500°C as an "ultra-high temperature," which does not align with the standard definition in the aerospace field, reflecting a lack of professionalism. Additionally, the structure is highly irregular, with some paragraphs consisting of only a single sentence—a flaw also evident in the Results and Discussion section. The introduction lacks a necessary review of existing research on polysiloxane-based thermal protection materials. Descriptions of reusable launch vehicles are irrelevant here, as this study focuses on disposable ablative materials. The introduction should clearly state the necessity and innovation of this work. 
Authors' response: The expression used in the paper was "exceeding 1500°C". Indeed, the cited sources represent a temperature range between 1600-2200°C. We have modified the intended expression with "exceeding 1600°C", for better clarity. As you have probably noticed, in our study these materials were tested at temperatures exceeding 1600°C. The paragraph structure in our paper was rearranged and completed by rewriting the sentences. Sources and information regarding existing research on polysiloxane-based thermal protection materials have been introduced. Information on reusable launch vehicles was introduced in the introductory part to indicate the need for ablative composites, consumables that have a much lower price than reusable ones and are highly efficient in thermal protection.
4. Figure 1 appears hastily prepared. 
Authors' response: Figure 1 has been updated.
5. Figure 2 shows an unclear optical micrograph; scanning electron microscopy (SEM) images should be supplemented. 
Authors' response: Figure 2 has been updated. SEM images have been added.
6. Figure 3 directly exports raw data from testing equipment without proper processing. Moreover, a significant portion of the data in this figure remains undiscussed.
Authors' response:  Figure 3 has been upgraded. Table with data corresponding to DSC testing information and their commentary has been introduced.
7. Figure 4 has incomplete legends. 
Authors' response: Figure 4 has been updated.
8. Figure 7 contains erroneous data. It is widely accepted in the field that the temperature of a butane flame does not exceed 1300°C, yet the authors claim it reached 1600°C. 
Authors' response: Thank you very much for your observation. The term "Oxy Butane Flame" is a serious typo. In this study, the oxy-acetylene flame was used for thermal testing of ablative materials. The correction has been added to the work.
9. Why was the oxyacetylene ablation test—the industry standard for evaluating ablation resistance—not used to assess the samples? 
Authors' response: In this study, the oxy-acetylene flame was used for thermal testing of ablative materials. The correction has been added to the work.
10. The conclusion is excessively lengthy, lacks focus, and fails to highlight the contributions of this work. 
Authors' response: The conclusions have been re-edited and inserted into the paper

Reviewer 2 Report

Comments and Suggestions for Authors

Ref.:  Ms. No. applsci-3996889

The manuscript entitled “Development and characterization of new ablative materials based on polysiloxane resin and graphite felt”


The study introduces a new ablative thermal protection material using a high-performance polyxylan resin matrix, comparing its behavior to traditional phenolic-based ablatives. Thermal tests at 1100 °C and over 1500 °C, along with DSC and morphological analyses, were used to evaluate its resistance and structural changes. Results highlight the material’s performance under prolonged high-temperature exposure and intense flame conditions. While the manuscript presents a thoughtfully conducted study, its overall quality of writing requires improvement. I recommend that it be accepted for publication only after the authors have sufficiently addressed the following major points

  1. The authors should revise the entire abstract, as it currently lacks scientific clarity and does not read appropriately for a research manuscript.
  2. The author should rewrite the introduction as it currently lacks scientific clarity and coherence.
  3. The authors should revise the scale labelling in Figure 2, as the current version is difficult to read.
  4. In the Experimental section, the author should revise the 2.3 Measurement and combine as single paragraph.
  5. The authors should replot Figure 3, as figure 4 in its current presentation is not suitable for scientific publication.
  6. Author should incorporate the chemical characterization of starting materials and composites such as FTIR and XPS.
  7. The author should include a comparative table summarizing the current ablative materials with other commercially available ablative materials to benchmark performance.
  8. The authors should discuss the stability and recyclability of the current ablative materials.
  9. The author should provide the standard deviation for the figure 6.
  10. The author must provide the mechanical properties effect before and after heating of ablative materials.
  11. The authors should rewrite the entire conclusion, as it currently presents a general discussion rather than clearly highlighting the findings of the present study.
  12. The author reviews all the references to ensure that the missing details, such as page numbers, publication years, and volume numbers, are properly included.

Author Response

The manuscript entitled “Development and characterization of new ablative materials based on polysiloxane resin and graphite felt”
The study introduces a new ablative thermal protection material using a high-performance polyxylan resin matrix, comparing its behavior to traditional phenolic-based ablatives. Thermal tests at 1100 °C and over 1500 °C, along with DSC and morphological analyses, were used to evaluate its resistance and structural changes. Results highlight the material’s performance under prolonged high-temperature exposure and intense flame conditions. While the manuscript presents a thoughtfully conducted study, its overall quality of writing requires improvement. I recommend that it be accepted for publication only after the authors have sufficiently addressed the following major points
1.    The authors should revise the entire abstract, as it currently lacks scientific clarity and does not read appropriately for a research manuscript. 
Authors' response: The abstract has been rewritten and updated with the key results of the study and added to our paper
2.    The author should rewrite the introduction as it currently lacks scientific clarity and coherence. 
Authors' response: Thank you for the suggestion, the introductory part of the paper has been updated 
3.    The authors should revise the scale labelling in Figure 2, as the current version is difficult to read.
Authors' response: Thank you very much for the suggestion, we have made the change requested
4.    In the Experimental section, the author should revise the 2.3 Measurement and combine as single paragraph.
Authors' response: This suggestion has been taken into account and the paragraph has been updated.
5.    The authors should replot Figure 3, as figure 4 in its current presentation is not suitable for scientific publication. 
Authors' response: Thank you very much for the suggestion, we have made the change requested
6.    Author should incorporate the chemical characterization of starting materials and composites such as FTIR and XPS. 
Authors' response: FTIR analyses were introduced into the study
7.    The author should include a comparative table summarizing the current ablative materials with other commercially available ablative materials to benchmark performance. 
Authors' response: Thank you for the useful recommendation. A section including a table was added comparing the developed materials with two similar ablatives, showing the key indicators of the materials and how their performance differs from the commercially available alternatives. 

8.    The authors should discuss the stability and recyclability of the current ablative materials. 
Authors' response: Thank you for the recommendation. Recyclability is a high interest subject in our group; however, the current study focuses on the first stage involving these new materials, consisting of development and preliminary characterization and testing. Future studies involving the fully characterized materials will certainly include a stability and recyclability evaluation.

9.    The author should provide the standard deviation for the figure 6. 
Authors' response:  The precise percentages were added on the bars for each type of material. 
10.    The author must provide the mechanical properties effect before and after heating of ablative materials. 
Authors' response: A complementary subchapter on compression testing has been added. Mechanical compression tests were performed at ambient and +250 °C. Testing ablative materials after carbonization is difficult to perform due to thermal decomposition.
11.    The authors should rewrite the entire conclusion, as it currently presents a general discussion rather than clearly highlighting the findings of the present study.
Authors' response: The conclusions have been re-edited and inserted into the paper
12.    The author reviews all the references to ensure that the missing details, such as page numbers, publication years, and volume numbers, are properly included. 
Authors' response: Thank you very much for the suggestion. The bibliography has been updated with the information found. Articles published in the AIAA journal do not show the number of pages of the included articles.

Reviewer 3 Report

Comments and Suggestions for Authors
  1. Figure 2 currently labels the sub-images as (a) and (b) for both material systems, which may confuse readers. Since the figure includes four distinct micrographs, I recommend relabeling them sequentially as (a) to (d) and updating the caption accordingly to clearly distinguish each sub-panel. In addition, please revise the caption so that each label corresponds unambiguously to its respective sample and magnification (e.g., (a) GF/Isophen at 40×, (b) GF/Isophen at 100×, (c) GF/UHT at 40×, (d) GF/UHT at 100×).
  2. Figure 3 presents raw DSC output directly exported from the instrument, resulting in low readability and inconsistent style (font size, marker shapes, peak labels, noise, etc.). For publication-quality graphics, I strongly recommend re-plotting the DSC curves using a scientific plotting tool such as Origin, MATLAB, or Python, with unified formatting (line width, colors, axis scaling, and annotation style).
  3. The manuscript states that the UHT resin exhibits higher onset and end temperatures for the glass transition, suggesting a greater amount of heat released due to its chemical composition. However, the Tg peak temperatures reported for the two systems (442.3 °C vs. 441.7 °C) differ by less than 1 °C, which is within the typical experimental uncertainty of DSC measurements and therefore may not be sufficient to support the proposed interpretation. To justify this conclusion, I recommend providing additional quantitative evidence.
  4. In Table 1, the initial masses of the specimens differ considerably across samples (e.g., 5.28–7.49 g). For a fair comparison of mass loss under identical thermal exposure conditions, the initial mass should ideally be controlled or normalized, since the amount of absorbed heat is directly proportional to the specimen mass. Samples with larger initial mass inherently possess higher thermal inertia, which can reduce the apparent relative mass loss.
  5. The conclusion states that the GF/UHTR composite exhibits superior thermal properties and is a promising binder for passive thermal protection applications. However, this argument would be much stronger if the authors contextualized their results within the existing literature. I recommend adding a comparison table summarizing key performance indicators (e.g., mass loss, thermal stability, Tg, ablation rate, char yield, or thermal conductivity) of similar ablative composites reported in prior studies.

 

Author Response

1.    Figure 2 currently labels the sub-images as (a) and (b) for both material systems, which may confuse readers. Since the figure includes four distinct micrographs, I recommend relabeling them sequentially as (a) to (d) and updating the caption accordingly to clearly distinguish each sub-panel. In addition, please revise the caption so that each label corresponds unambiguously to its respective sample and magnification (e.g., (a) GF/Isophen at 40×, (b) GF/Isophen at 100×, (c) GF/UHT at 40×, (d) GF/UHT at 100×)
Authors' response: Thank you very much for the suggestion, we have changed the name of the optical images.
2.    Figure 3 presents raw DSC output directly exported from the instrument, resulting in low readability and inconsistent style (font size, marker shapes, peak labels, noise, etc.). For publication-quality graphics, I strongly recommend re-plotting the DSC curves using a scientific plotting tool such as Origin, MATLAB, or Python, with unified formatting (line width, colors, axis scaling, and annotation style).
Authors' response: Figure 3 has been upgraded. Table with data corresponding to DSC testing information and their commentary has been introduced.
3.    The manuscript states that the UHT resin exhibits higher onset and end temperatures for the glass transition, suggesting a greater amount of heat released due to its chemical composition. However, the Tg peak temperatures reported for the two systems (442.3 °C vs. 441.7 °C) differ by less than 1 °C, which is within the typical experimental uncertainty of DSC measurements and therefore may not be sufficient to support the proposed interpretation. To justify this conclusion, I recommend providing additional quantitative evidence.
Authors' response: The graphs were reanalysed and the values of the peak TG temperatures reported for the GF/UHT ablative material were reconsidered. The changes in the values and the related explanations were inserted in the paper.
4.    In Table 1, the initial masses of the specimens differ considerably across samples (e.g., 5.28–7.49 g). For a fair comparison of mass loss under identical thermal exposure conditions, the initial mass should ideally be controlled or normalized, since the amount of absorbed heat is directly proportional to the specimen mass. Samples with larger initial mass inherently possess higher thermal inertia, which can reduce the apparent relative mass loss.
Authors' response: Thank you very much for the suggestion. The normalized values have been added to the table. A graph and the related explanations have been introduced in the paper.
5.    The conclusion states that the GF/UHTR composite exhibits superior thermal properties and is a promising binder for passive thermal protection applications. However, this argument would be much stronger if the authors contextualized their results within the existing literature. I recommend adding a comparison table summarizing key performance indicators (e.g., mass loss, thermal stability, Tg, ablation rate, char yield, or thermal conductivity) of similar ablative composites reported in prior studies.

Authors' response: Thank you for the useful recommendation. A section including a table was added comparing the developed materials with two similar ablatives, showing the key indicators of the materials and how their performance differs from the commercially available alternatives. This information was added in the oxyacetylene test section, to avoid adding new additional information in the conclusion section.  

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

It can be accepted as it is.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

Thank you for your thorough revisions and detailed responses. They have significantly improved the readability and overall strength of the manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

The revised version is acceptable for publication in Applied Sciences.