Development of Catalyst-Free Self-Healing Biobased UV-Curable Coatings via Maleate Monoester Transesterification
Lakshmi Priya Datta
Round 1
Reviewer 1 Report
In this study authors reported development of self-healing UV-cured tung oil based resins using maleate monoester transesterification. The study plan is well designed, and results associated to this study plan presented in an appropriate way. Some points to be addressed by the authors are as follows:
- PMETER abbreviation shall be given in open form at first appearance
- Authors must check the article for superscripts and subscripts for units and compounds.
- What is the R group in scheme 1? A definition on scheme or In caption is better be provided.
- It is better to present molar values and mass values in parentheses on Table 1.
- Is m0 in Cgel determination weighed in dry form?
- Any standards followed should be stated for the tests in 2.5.8 and 9.
- Rr in 2.5.11 and 12 shall be presented in different subscripts since they do not represent the same rates.
- Section 3 should be changed as “Results and Discussions”
- Depicted proton numbers in NMR spectra interferes with the numbers associated with the peak shifts.
- A brief explanation on how (da/dt) was obtained/calculated is better be provided.
- Is the graph on Figure 3d cropped at %16 strain? The break points are not observed on these graphs. Similarly on Figure 6d.
Author Response
Point 1: PMETER abbreviation shall be given in open form at first appearance
Response 1: Thank you for your comments. We have checked and corrected it in revised manuscript.
Point 2: Authors must check the article for superscripts and subscripts for units and compounds.
Response 2: Thank you for your comments. We have checked and corrected it in revised manuscript.
Point 3: What is the R group in scheme 1? A definition on scheme or In caption is better be provided.
Response 3: Thank you for your comments. The structure of tung oil is a triglyceride structure containing three identical fatty chain structures, and for convenience of representation, the remaining two fatty chains are denoted by R.
Point 4: It is better to present molar values and mass values in parentheses on Table 1.
Response 4: Thank you for your comments. The composition of the TOMAH/H samples is presented in Table 1, where HEMA is used as diluent and we present mainly different mass ratios of HEMA rather than molar ratios.
Point 5: Is m0 in Cgel determination weighed in dry form?
Response 5: Yes,it is. After curing, the samples were dried in an oven at 60°C for 24 hours and weighed accurately (denoted m0).
Point 6: Any standards followed should be stated for the tests in 2.5.8 and 9.
Response 6: Thank you for your comments. The stress relaxation curves in 2.5.8 were obtained from DMA tests, and the stress-strain curves in 2.5.9 were obtained from tests performed by a universal testing machine in accordance with ASTM D5402-06 standard, and the experimental conditions were described in the text.
Point 7: Rr in 2.5.11 and 12 shall be presented in different subscripts since they do not represent the same rates.
Response 7: Thank you for your comments.We have corrected it in revised manuscript.
Point 8: Section 3 should be changed as “Results and Discussions”
Response 8: Thank you for your comments. Section 3 has been changed to "Results and Discussion"
Point 9: Depicted proton numbers in NMR spectra interferes with the numbers associated with the peak shifts.
Response 9: Thank you for your comments. We have checked and corrected it in revised manuscript.
Point 10: A brief explanation on how (da/dt) was obtained/calculated is better be provided.
Response 10: Thank you for your comments. The polymerization rates of the UV-curable TOMAH/H resinscan be obtained by taking the first order derivative of the double bond conversion rate with respect to time “t”.
Point 11: Is the graph on Figure 3d cropped at %16 strain? The break points are not observed on these graphs. Similarly on Figure 6d
Response 11: Thank you for your comments. Yes, the break happened at around %16. All the samples broke without reaching yielding points, suggesting that they were rigid materials.
Reviewer 2 Report
In this paper, the authors present the obtaining of a UV crosslinkable biobased coating material with high temperature self-healing properties, as well as its characterization.
I am sure that the study deserves the attention of readers and can be considered for a possible publication in Coating; Please address the following points before accepting the paper for publication to improve the readability and clarity of the manuscript:
General aspects:
- the citations in the text must respect the format required by the journal;
- certain typographical errors need to be corrected: line 94: resultant; line 111: use Subscript for Mg2SO4; line 160: Soxhlet extraction; line 291: with the addition of Hema…etc.
Line 111: Please, clarify what does "elevated pressure" mean? Is pressure important for TOMA synthesis? The TOMAH synthesis seems to be similar, but here pressure is no longer used…
Lines 150-153: The authors are asked to specify the method of performing the FTIR analysis: transmission (how? KBr pellet method or thin film) or ATR?
Lines 159-165: The gel content is usually expressed as a percentage, therefore the calculation formula is:
Cgel (%) = (m1/m0)x100
Lines: 166-171: Certain aspects need to be clarified: Is the equipment Nicolet 5700 an FTIR spectrometer? I understand that the FTIR analysis was done in real time... How was the evaluation of the C=C conversion carried out? At the same point during UV exposure (did the sample remains motionless throughout the spectral acquisition?). If the ATR technique was used, it is important that the sample is fixed, because it is known that changing the pressure on the sample changes the intensity of the spectral bands. In this case, certain bands, which do not change during UV exposure, are used as the reference band (see the determination of the carbonyl index: https://doi.org/10.1515/epoly-2020-0041).
Lines 184-188: Was the DSC analysis performed in an inert atmosphere? In the manuscript, there are no references to the results of the DSC analysis...could it be removed from the M&M section?
Lines: 244-250 Please add some bibliographic references.
Lines 251-253 Theoretically it is true, in the spectral region 2500-3500, the strong and broad peak can be attributed to COOH, practically it is difficult to state this, especially when this band overlaps with the characteristic bands of CH stretching vibrations (~2800-3000 cm -1). In addition, the spectrum shown for TOMAH (Fig. 1a, blue) the existence of “Strong and broad” peak is imperceptible. I think that the presence of COOH can be evaluated better in the spectral region 1680-1730 cm-1. Therefore, the authors are asked to reformulate this paragraph.
Line 269: Is the NC=C value of 3.11 high or low? To what does this value refer? What are the NC=C values for TO or TOMA? For equation 4, a bibliographic reference must be presented.
Line 293: How was determined the Cbio? If there is a standard/reference, it must be specified.
Line 302: How the Tg is determined from tand (you can use a bibliographic reference)? Can the obtained Tg value be confirmed by DSC (or other technique)?
Lines 335-338 Could you provide some references?
Line 396: Fig. 5 (b) The self-healing mechanism is reversible?
Author Response
Point 1: the citations in the text must respect the format required by the journal
Response 1: Thank you for your comments. We have checked and corrected it in revised manuscript.
Point 2: certain typographical errors need to be corrected: line 94: resultant; line 111: use Subscript for Mg2SO4; line 160: Soxhlet extraction; line 291: with the addition of Hema…etc.
Response 2: Thank you for your comments. All typographical errors mentioned above and other typographical errors in the text have been corrected in revised manuscript.
Point 3: Line 111: Please, Clarify what does "elevated pressure" mean? Is pressure important for TOMA synthesis? The TOMAH synthesis seems to be similar, but here pressure is no longer used…
Response 3: Thank you for your comments. This is a clerical error by the author, who meant at 160°C, not under high pressure. We have check it and correct it in revised manuscript.
Point 4: Lines 150-153: The authors are asked to specify the method of performing the FTIR analysis: transmission (how? KBr pellet method or thin film) or ATR?
Response 2: Thank you for your comments. We have added the relevant methods to the revised manuscript.
Point 5: Lines 159-165: The gel content is usually expressed as a percentage, therefore the calculation formula is:Cgel (%) = (m1/m0)x100%
Response 5: Thank you for your comments. The corresponding correct format has been given in the revised version.
Point 6: Lines: 166-171: Certain aspects need to be clarified: Is the equipment Nicolet 5700 an FTIR spectrometer? I understand that the FTIR analysis was done in real time... How was the evaluation of the C=C conversion carried out? At the same point during UV exposure (did the sample remains motionless throughout the spectral acquisition?). If the ATR technique was used, it is important that the sample is fixed, because it is known that changing the pressure on the sample changes the intensity of the spectral bands. In this case, certain bands, which do not change during UV exposure, are used as the reference band (see the determination of the carbonyl index: https://doi.org/10.1515/epoly-2020-0041).
Response 6: Thank you for your comments.The equipment Nicolet 5700 is an FTIR spectrometer. Conversion rate of double bond (C=C) was determined by monitoring the intensity of the peak at 810 cm−1. When applying FT-IR using the attenuated total reflectance method to determine the conversion rate of C=C double bond, since the intensity of the absorption peak on the FT-IR spectrum is directly related to the amount and thickness of the sample during the determination process, in order to ensure the accuracy of the determination results and eliminate the influence of different operations on the results, the absorption peak with no change in absorption intensity before and after curing should be used as the internal standard in the calculation. In general, the absorption peak of C = O ( 1 717 cm-1 ) is used as the internal standard for the HEMA system[1].
Since the intensity of the absorption peak on the FT-IR spectrum can be expressed in terms of its area, the following equation is applied by choosing the area of the absorption peak of the group after determining the internal standard The conversion of the C=C double bond can be calculated by choosing the area of the absorption peak of the group.
Conversion rate of C=C =
R after curing = Absorption peak area of C=C after curing / Absorption Peak area of internal standard after curing
R before curing = Absorption peak area of C=C before curing / Absorption Peak area of internal standard before curing
This part of the experimental results is the data we obtained by sending the samples to an external testing facility for testing
[1]Cheng S S,Cui Y Y.Measuring the Conversion of Dental Composite Resin a Methodological Review[J] Materials Guide,2017, v.31(S2):194-197.
Point 7: Lines 184-188: Was the DSC analysis performed in an inert atmosphere? In the manuscript, there are no references to the results of the DSC analysis...could it be removed from the M&M section?
Response 7: Thank you for your comments. The DSC analysis section was a clerical error by the author, and we have removed it in the revised manuscript.
Point 8: Lines: 244-250 Please add some bibliographic references.
Response 8: Thank you for your comments. We have added the bibliographic references in the corresponding position in the revised manuscript.
Point 9: Lines 251-253 Theoretically it is true, in the spectral region 2500-3500, the strong and broad peak can be attributed to COOH, practically it is difficult to state this, especially when this band overlaps with the characteristic bands of CH stretching vibrations (~2800-3000 cm -1). In addition, the spectrum shown for TOMAH (Fig. 1a, blue) the existence of “Strong and broad” peak is imperceptible. I think that the presence of COOH can be evaluated better in the spectral region 1680-1730 cm-1. Therefore, the authors are asked to reformulate this paragraph.
Response 9: Thank you for your comments. We have checked it and corrected it in revised manuscript.
Point 10: Line 269: Is the NC=C value of 3.11 high or low? To what does this value refer? What are the NC=C values for TO or TOMA? For equation 4, a bibliographic reference must be presented.
Response 10: Thank you for your comments. The NC=C value represents the number of C=C per triglyceride involved in the reaction, and the NC=C valueof 3.11 is at an intermediate level.[1-2]
[1] Hu Y., Zhu G., Zhang J., Huang J., Yu X., Shang Q., An R., Liu C., Hu L., Zhou Y., Rubber Seed Oil-Based UV-Curable Polyurethane Acrylate Resins for Digital Light Processing (DLP) 3D Printing, Molecules 2021, 26.
[2] Wu Q., Hu Y., Tang J., Zhang J., Wang C., Shang Q., Feng G., Liu C., Zhou Y., Lei W., High-Performance Soybean-Oil-Based Epoxy Acrylate Resins: “Green” Synthesis and Application in UV-Curable Coatings, ACS Sustainable Chem. Eng. 2018, 6, 8340-8349.
Point 11: Line 293: How was determined the Cbio? If there is a standard/reference, it must be specified.
Response 11: Thank you for your comments. The United States Department of Agriculture defines the biobased content of a product as “the amount of biobased carbon in the material or product as a percent of the weight (mass) of the total organic carbon in the product”. According to this definition, the biobased content of the raw materials TO, MA and HEMA was 100%, 0%, 0%. We have added the relevant content in revised manuscript.
Point 12: Line 302: How the Tg is determined from tand (you can use a bibliographic reference)? Can the obtained Tg value be confirmed by DSC (or other technique)?
Response 12: For the DMA test, the glass transition temperature is generally expressed as the temperature corresponding to the peak of the loss factor curve.
Point 13: Lines 335-338 Could you provide some references?
Response 13: Thank you for your comments. We have added the bibliographic references in the corresponding position in the revised manuscript.
Point 14: Line 396: Fig. 5 (b) The self-healing mechanism is reversible?
Response 14: Thank you for your comments. Yes,the self-healing mechanism is reversible.
Reviewer 3 Report
Manuscript ID: coatings-2126916
Journal : coatings
Title: Development of catalyst-free self-healing biobased UV-curable coatings via maleate monoester transesterification
In this manuscript the authors have reported synthesis of a novel tung oil-based UV-curable oligomer and corresponding photo-copolymerization in presence of methacrylate to derive self-healing UV-curable materials. Although experimental sections are reported carefully, the result analysis part is very shortened. The authors are requested to explain more the results for better clarification of the data. Major revision is needed prior approval for publication.
Decision: Major revision
1. According to the experimental investigation and kinetic data, with increasing the percentage of HEMA, the crosslinking density of polymerization as well as coating properties are improved. It would be helpful if the authors explain why they have increased the HEMA percentage up to 30% only, not beyond that, for instance 50% or 75%?
2. Bare TOMAH, bare HEMA and TOMAH/H90% should be used as control systems to better compare the results.
Author Response
Point 1:According to the experimental investigation and kinetic data, with increasing the percentage of HEMA, the crosslinking density of polymerization as well as coating properties are improved. It would be helpful if the authors explain why they have increased the HEMA percentage up to 30% only, not beyond that, for instance 50% or 75%?
Response 1: Thank you for your comments. In the experiment, we found that when the content of diluent HEMA continued to increase, the self-healing efficiency of the coating first increased and then decreased, and when the content of HEMA was 20%, the self-repair effect of the coating was optimal, so we only increased the percentage of HEMA to 30%
Point 2:Bare TOMAH, bare HEMA and TOMAH/H90% should be used as control systems to better compare the results.
Response 2: Thank you for your comments. TOMAH prepolymer and diluent HEMA compound to get photosensitive prepolymer, by light curing are obtained self-healing light-curing coatings, HEMA itself no dynamic covalent bond, so do not do research. A similar approach can be found in the following literature.
[1] Huang J., Zhang J., Zhu G., Yu X., Hu Y., Shang Q., Chen J., Hu L., Zhou Y., Liu C., Self-healing, and high-performance, and high-biobased-content UV-curable coatings derived from rubber seed oil and itaconic acid, Prog. Org. Coat. 2021, 159.
[2] Zhang J., Huang J., Zhu G., Yu X., Cheng J., Liu Z., Hu Y., Shang Q., Liu C., Hu L., Zhou Y., Self-healing, recyclable, and removable UV-curable coatings derived from tung oil and malic acid, Green Chem. 2021, 23, 5875-5886.
Reviewer 4 Report
The manuscript is well structured and the results are clearly presented. A few grammatical errors need to be corrected throughout the manuscript.
Author Response
Point 1:The manuscript is well structured and the results are clearly presented. A few grammatical errors need to be corrected throughout the manuscript.
Response 1: Thank you for your comments. The author has corrected the grammatical and formatting errors that appear in the text.
Round 2
Reviewer 2 Report
The authors' answers are satisfactory. The manuscript can be accepted for publication in its current form.
