Research on Fireproof and Anti-Corrosion Integrated Coatings for Modular Integrated Buildings

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Researchers in this study aim to develop fire- and corrosion-resistant integrated coatings for modular integrated buildings (MiC). I suggest that the researchers carefully consider the following points:

 

• Expand the abstract to encompass the entire paper and include some numerical data for support.
• Add an index of symbols and abbreviations, providing explanations at their first appearance.
• The introduction heavily relies on Chinese data; it offers limited connection to global research trends and international standards. Recent studies should also be included to broaden the perspective.
• The paper's uniqueness compared to others is not clearly stated. The original value that this work seeks to establish should be explicitly highlighted.
• In the materials and methods section, the synthesis is described using “equivalent,” but solvents are also assigned “equivalent” values (xylene 1.0 eq, chloroform 1.0 eq). This contradicts chemical stoichiometry principles, which base equivalents on molar functional groups, not solvents. This ambiguous expression hampers reproducibility.
• Details of catalyst loading are needed. Using DBU at 0.5 equivalents seems too high for a catalyst; it may be a typo or methodological error. The molar percentage should be clearly specified.
• Confirmation of the synthesis should include more data. IR spectra are provided, but essential information such as ^31P NMR for P–N bond analysis, elemental analysis (%P, %N), epoxy equivalent weight (EEW), viscosity at 25 °C, solid content (%NV), and GPC Mn/Mw are missing. Although IR peaks are listed (3303, 2939–2883, 1408, 1244 cm⁻¹), alone they are insufficient.
• Additional information on process safety is necessary, such as the total charge in g/mol, solvent quantities in g or mL, solid content, vacuum distillation conditions (temperature/pressure), and yield (%). Without these, full reproducibility is compromised.
• The title of Table 1 should be amended. For example, “mass fraction w/%” is used, but the sum exceeds 100% significantly (e.g., solvent 50–100, curing agent 10–40, flame retardant 40–65). This resembles “phr (parts per hundred resin),” but the base (resin=100) is not explicitly defined.
• Units are missing in Table 2 (PT1–PT5). The phrase “100 resin + 55 flame retardant + 26 charge agent + 38 blowing agent” appears to be phr, but units or basis are not indicated. Ratios for pigment, cure, and solvent should be based on solid and volume solids (PVC/CPVC, volume solids).
• The mixing conditions are vaguely described. Values of 800–2200 rpm are given, but details such as disc diameter, tip speed (m/s), viscosity and temperature control, vacuum or degassing steps, and temperature during mixing are absent.
• The application and curing procedures need detailing. Using “brush or airless” is mentioned, but specifics such as film thickness (DFT/NDFT), number of coats, inter-coat drying times, ambient temperature and humidity, and total curing schedule are missing. Steel surface preparation, described as “sanding,” lacks a standard reference (e.g., ISO 8501-1 Sa 2.5).
• For all samples and tests, the sample size, thickness (≤10.5 mm limit), number (n), and mean ± SD calculations are missing, which are essential for analysing stability and consistency.
• It is unclear whether all tests were conducted under the same dry film thickness (DFT). Variations in thickness could compromise the fairness of comparisons.
• The claim that 2540 hours of salt spray resistance is “much superior to existing coatings” lacks a detailed explanation of the underlying mechanism, potentially raising doubts among readers.
• While fire resistance is stated as 124 minutes, the lack of a critical temperature value leaves it uncertain if it meets relevant standards.
• The results are not directly compared with international studies. Including data such as LOI (35–40 range) and NSS (1000–1500 hours) from literature between 2022–2024 would highlight the distinctiveness of these findings evidentent.

Author Response

Thank you for pointing this out.  For the questions and responses of Reviewer1, please refer to the attachment "coverletter"

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article is suitable for publication in the journal Coatings, but the manuscript must be revised first.
Remarks
1. The Abstract section should indicate the fire resistance class of the material (HB, V0 or V1).
2. The Introduction section should justify the choice of epoxy binders for the manufacture of coatings and consider the areas of application of epoxy resins, methods of their modification to impart fire resistance (see, for example, Rybyan A.A. et al. Curing of DER-331 Epoxy Resin with Arylaminocyclotriphosphazenes Based on o-, m-, and p-methylanilines. Polymers. 2022; 14(24):5334).
3. The viscosity of the solution and the molecular weight of the epoxy resin and the n values ​​for the epoxy oligomer should be indicated. The epoxy number of the resulting modified epoxy resin should also be given.
4. The hardener used should be indicated.
5. The figures should be placed after they are mentioned in the text of the article.
6. The IR spectrum of the original epoxy resin and the IR spectrum of the phosphorus-containing resin should be provided for comparison.
7. The ISO standards used for testing the coating adhesion, fire resistance, and corrosion resistance should be indicated and the values ​​required for use in construction should be provided. A comparison of the properties obtained with other coatings should also be provided (lines 245-246).
8. A diagram of the mechanism of the fire-retardant effect of the resin during combustion should be provided.

Author Response

Thank you for pointing this out.  For the questions and responses of Reviewer2, please refer to the attachment "coverletter"

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript reports a phosphorous-nitrogen (P-N) modified epoxy binder combined with intumescent components and nanoplatelets (vermiculite, mica) to create an integrated fire-retardant/anticorrosive coating for modular integrated construction (MiC). The topic is compelling, and the preliminary performance is encouraging; however, the manuscript requires substantial clarification and additional data to be accepted for publication in the journal. The points of consideration are as follows:

1. The intro asserts most intumescent systems have <240 h salt spray; this seems dated/generalized. The authors should expand the review with recent international literature on dual-function intumescent/anticorrosive epoxies, nanoclay-modified IFR, and EIS-verified barrier coatings.
2. Table 1 lists “mass fraction w/%” but entries like “modified resin 100,” “solvent 50-100,” “flame retardant 40-65,” etc., cannot simultaneously be percent of the same basis. The authors should convert it to phr (parts per hundred resin) or present as wt% of total wet formulation to ensure the totals sum logically (solids vs VOC).
3. It is believed that for the salt spray and fire tests, dry film thickness (DFT) and the number of coats are mandatory. The authors are kindly requested to provide DFT targets and measured values (mean ± SD), as well as, for the intumescence, give as-applied thickness and expansion ratio.
4. The fire test methodology also needs engineering detail. The authors are kindly requested to specify the steel section, section factor (Hp/A), critical steel temperature, thermocouple positions, and heating curve. The authors are also requested to report time-temperature profiles instead of a single “124 min” number.
5. The authors are kindly requested to demonstrate the particle size distribution, aspect ratios, and surface treatments of the nanofillers used.
6. For MiC modulus, the authors are requested to include impact resistance, flexibility, abrasion, and hardness to know the mechanical durability.
7. The caption of Figure 4 refers to T1, but the text says “the film of T3 had great anti-corrosion capability”. The inconsistencies should be resolved by the authors.
8. There are several typographical errors. The manuscript needs careful editing.

Author Response

Thank you for pointing this out.  For the questions and responses of Reviewer3, please refer to the attachment "coverletter"

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

ŞuThank you for making the updates I mentioned to the authors. It is appropriate to publish the article as it is.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have taken the recommendations into account and made the appropriate changes to the manuscript. I believe the manuscript is ready for publication.

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript is improved after revisions and can be accepted for publication in its present form.