Preparation and Performance Study of Poly(1,3-propanediol) Ester/PLLA Blended Membrane
Round 1
Reviewer 1 Report
Preparation and Performance Study of Poly1, 3-propanediol Es-2 ter/PLLA Blended Membrane
Comments:
Yuan et al worked-on study of Poly1, 3-propanediol Ester/PLLA Blended Membrane and tested it via various physio-chemical tests.
The manuscript is in good shape and can be published after some changes as mentioned in the comments below:
- The Introductory section seems very short, research question, background and related studies must be explained discussed in detail
- Few related recent studies must be discussed and explain in lieu of present work
- In IR testing scanning rate is missing
- In line 135 the statement “Change the buffer every 48 h.” needs to be corrected
- In figure 2, the font in X-axis needs be updated as per the text in main body
- Please draw line on every main peak of IR graph, it would be easy for the readers to follow the results.
- Please either mention JCPDS file number or give reference spectra in the figure
- Error bars are missing in figure 8
- The conclusion needs to be re-written in light of obtained results.
- English Proof reading is required and authors are advised to use small sentences instead of large or longer sentences or paragraphs.
Author Response
March 18, 2023
Dear Sir/Madam,
Thank you for reviewing our manuscript and offering valuable advice. In accordance with your suggestions, we have made the following revisions to our manuscript:
- The Introductory section seems very short, research question, background and related studies must be explained discussed in detail
Response:Thank you very much for your valuable comments. According to your suggestion,We have rewritten the introduction, mainly introducing the research background and some recent work related to this article.
（2）Few related recent studies must be discussed and explain in lieu of present work
Response:Thank you very much for your valuable comments. According to your suggestion, we have added references in the introduction section, and introduced the recent work related to this article.
（3）In IR testing scanning rate is missing
Response:Thank you very much for finding this mistake. I have added the scanning rate for infrared testing to the "IR test" section.
（4）In line 135 the statement “Change the buffer every 48 h.” needs to be corrected
Response:Thank you very much for finding this mistake. I rewrote this sentence. Change the sentence "Change the buffer every 48 h" to "The buffer was renewed every 48 h"
- In figure 2, the font in X-axis needs be updated as per the text in main body
Response:Thank you very much for finding this mistake. I redraw Figure 2.
- Please draw line on every main peak of IR graph, it would be easy for the readers to follow the results.
Response:Thank you very much for your valuable comments. We have labeled the main infrared peaks in Figures 3 and 4.
（7）Please either mention JCPDS file number or give reference spectra in the figure
Response:Thank you very much for your valuable comments. We have added PLLA's JCPDS document number (49-2174) to the paper.
（8）Error bars are missing in figure 8
Response:Thank you very much for finding this mistake. I have added error bars to Figure 8.
- The conclusion needs to be re-written in light of obtained results.
Response:Thank you for your suggestion. I have rewritten the conclusion section.
（10）English Proof reading is required and authors are advised to use small sentences instead of large or longer sentences or paragraphs.
Response:Thank you for your suggestion. I have rewritten some of the long sentences in the manuscript.
Reviewer 2 Report
Manuscript ID: coatings-2267961
Author reported the paper entitled “Preparation and Performance Study of Poly1, 3-propanediol Ester/PLLA Blended Membrane”. After reading it, I think that the contents of scientific finding are fine, but it is not much polished. Hence, I suggest a major revision.
- Polymer’s nomenclature: Except for several cases, Authors should follow a regular way. e.g., Poly1, 3-propanediol => Poly (1, 3-propanediol)
- Authors should follow the abbreviation rule
e.g., Abstract: Without introducing a full name for PO3G-PA/PLA, Authors used it. (Line 13)
- Line 19: 0 => 0%
- English should be improved. Currently, it is not smooth.
- Experimental Section: Write again (Lines 64-73). Current style should be rejected.
(Also, in this part, Authors may introduce 1H NMR, SEM, etc.)
- Line 68: Fourier infrared => Fourier transform infrared
- Line 97: CDCl3 (subscript needed)
- Line 100: The scanning range was 400–4000 cm−1. => The scanning range was 4000–400 cm−1
- Line 113: (Question: Why ΔHcc deduction is needed? Add references and explain it)
(Why crystallinity changes, you may explain it scientifically)
- Line 116: 93.6 Jg => 93.6 J/g
- Line 24: You can use “SEM” instead of its full name. (Check all the other places, if you have a similar problem)
- Line 139 and 154: 1H NMR
- Line 156 and Line 165: FTIP => FTIR
- Line 179: Figure’s caption: FTIR spectra
- Line 180: TGA should be introduced correctly (Maybe, in the experimental section)
- Figure 9: y-axis’s title: Weight loss (%) => Weight (%)
(Note, although the physical meaning is weight loss, the title should be weight (%))
- Physical parameter should be italic, e.g., Tg , Tm, etc. (Check All)
- Figure 6 (Authors should show the DSC curve for a pure PO3G–PA , and mention its Tg also) (In addition, please add the 1st cooling curve in the supporting information)
- Figure 6: Around ~15-20 oC, we can see some small peaks, explain it.
- Table 1: Physical parameters should be italic. (Check Xc, crystallinity calculation and formula. Also, what about Xc calculation based on 1st heating curve because here there is no cold crystallization and compare it with the 2nd heating curve’s results) (Also notify the Tg of pure PO3G–PA and their mixture from the Tg of PO3G–PA)
- Line 210: Table 2.1 => Table 1. (Did you copy and paste your thesis’ chapter 2? Also delete "thesi"s word in the manuscript, Line 51)
- Figure 7: PLA => PLLA (inside of the Figure)
- Figure 8: For reader-friendly, not only color but also "two arrows" are needed for notifying which curve is which.
- Figure 9: This figure also needed a scale bar. (Note: Without scale bar, it is not science)
- Figure 12: y-axis: Please check the maximum should be 100 instead of 1.
Overall, there are too many errors, which should be fixed. In addition, some scientific explanation should be improved. For example, two polymers are usually phase-separated. In this condition, when two polymers are mixed together, why crystallinity can be improved here. Authors may explain it in a better way. Also, in a phase-separated sample, usually, there are two Tg. Here also, authors can explain it. Finally, check again your manuscript one-by-one, and improve it extensively.
Author Response
March 18, 2023
Dear Sir/Madam,
Thank you for reviewing our manuscript and offering valuable advice. In accordance with your suggestions, we have made the following revisions to our manuscript:
- Polymer’s nomenclature: Except for several cases, Authors should follow a regular way.e.g., Poly (1, 3-propanediol)=> Poly (1, 3-propanediol)
Response:Thank you very much for finding this mistake. I have corrected this error in my manuscript.
(2)Authors should follow the abbreviation rule
e.g., Abstract: Without introducing a full name for PO3G-PA/PLA, Authors used it. (Line 13)
Response:Thank you very much for finding this mistake. I have corrected this error in my manuscript.
- Line 19: 0 => 0%
Response:Thank you very much for finding this mistake. I have corrected this error in my manuscript.
(4)English should be improved. Currently, it is not smooth.
Response: Sorry for the inconvenience caused to your reading due to my insufficient English proficiency. I have carefully checked the grammar of the paper and revised some long sentences that are not accurately expressed.
Experimental Section:
- Write again (Lines 64-73). Current style should be rejected.
(Also, in this part, Authors may introduce 1H NMR, SEM, etc.)
Response:Thank you very much for finding this mistake. I have rewritten this section. SEM and NMR were introduced.
(6)Line 68: Fourier infrared => Fourier transform infrared
Line 97: CDCl3 (subscript needed)
Line 100: The scanning range was 400–4000 cm−1. => The scanning range was 4000–400 cm−1
Response: Thank you very much for pointing out these mistakes. I have made corrections in the manuscript.
(7)Line 113: (Question: Why ΔHcc deduction is needed? Add references and explain it)
(Why crystallinity changes, you may explain it scientifically)
Response: Thank you for your insightful comment.
Materials that are not fully crystallized at room temperature may undergo recrystallization when heated to a temperature near the crystallization temperature. A portion of the final melting peak is the melting of the recrystallized portion, which needs to be deducted from the area in order to calculate the crystallinity of the material at room temperature.
References
[1] Tabi, T.,Wacha, A. F.,Hajba, S..Effect of D-lactide content of annealed poly(lactic acid) on its thermal, mechanical, heat deflection temperature, and creep properties[J]Journal of Applied Polymer Science.2019, 136, 47103
[2] Noémi Petrovics, Csaba Kirchkeszner, Antónia Patkó, Tamás Tábi, Norbert Magyar, Ilona Kovácsné Székely, Bálint Sámuel Szabó, Zoltán Nyiri, Zsuzsanna Eke, Effect of crystallinity on the migration of plastic additives from polylactic acid-based food contact plastics, Food Packaging and Shelf Life, 2023, 36, 101054.
We conducted an in-depth analysis of the changes in the crystallinity of the material. Line223-239.
(8)Line 116: 93.6 Jg=>93.6 J/g
Line 24: You can use “SEM” instead of its full name. (Check all the other places, if you have a similar problem)
Line 139 and 154:1H NMR
Line 156 and Line 165: FTIP => FTIR
Line 179: Figure’s caption: FTIR spectra
Line 180: TGA should be introduced correctly (Maybe, in the experimental section)
Figure 9: y-axis’s title: Weight loss (%) => Weight (%)
(Note, although the physical meaning is weight loss, the title should be weight (%))
Response: Thank you very much for pointing out these mistakes. I have made corrections in the manuscript.
(9)Physical parameter should be italic, e.g., Tg , Tm, etc. (Check All)
Figure 6 (Authors should show the DSC curve for a pure PO3G–PA , and mention its Tg also) (In addition, please add the 1st cooling curve in the supporting information)
Response: Thank you very much for pointing out these mistakes. I have made corrections in the manuscript.
The DSC curve of a pure PO3G-PA has been added to figure 6. The 1st cooling curve has been added to the supporting information.
(10)Figure 6: Around ~15-20 oC, we can see some small peaks, explain it.
Table 1: Physical parameters should be italic. (Check Xc, crystallinity calculation and formula. Also, what about Xc calculation based on 1st heating curve because here there is no cold crystallization and compare it with the 2nd heating curve’s results) (Also notify the Tg of pure PO3G–PA and their mixture from the Tg of PO3G–PA)
Response: Thank you for your insightful comment.
(1)The small peak around 15-20℃ is the melting peak of PO3G-PA.
(2)I have changed Tc, Tg, Xc, etc. to italics.
(3)Xc calculation based on 1st heating curve as follows：
|
Sample |
Tm(℃) |
ΔHm(J/g) |
Xc(%) |
|
Pure PLLA |
168.9 |
31.45 |
33.60 |
|
5PO3G–PA/PLLA |
168 |
30.29 |
34.06 |
|
10PO3G–PA/PLLA |
168.6 |
28.83 |
34.22 |
|
15PO3G–PA/PLLA |
167.9 |
27.95 |
35.13 |
|
20PO3G–PA/PLLA |
168.2 |
28.37 |
37.89 |
|
25PO3G–PA/PLLA |
169.3 |
23.23 |
33.09 |
Compared with A, it can be seen that the crystallinity of the original PLLA/PO3G-PA film is relatively large. This may be due to the fact that the thin film is prepared by natural slow cooling, and the PLLA chain segment has sufficient crystallization time. However, the change trend of Xc in both cases is consistent.
(11)Line 210: Table 2.1 => Table 1. (Did you copy and paste your thesis’ chapter 2? Also delete "thesi"s word in the manuscript, Line 51)
Figure 7: PLA => PLLA (inside of the Figure)
Figure 8: For reader-friendly, not only color but also "two arrows" are needed for notifying which curve is which.
Response: Thank you very much for pointing out these mistakes. I have made corrections in the manuscript.
(12)Figure 9: This figure also needed a scale bar. (Note: Without scale bar, it is not science)
Response: Thank you very much for your valuable comments. I have added a scale bar to Figure 9.
- Figure 12: y-axis: Please check the maximum should be 100 instead of 1.
Response: Thank you very much for pointing out these mistakes. I have made corrections in figure 12.
(14)Overall, there are too many errors, which should be fixed. In addition, some scientific explanation should be improved. For example, two polymers are usually phase-separated. In this condition, when two polymers are mixed together, why crystallinity can be improved here. Authors may explain it in a better way. Also, in a phase-separated sample, usually, there are two Tg. Here also, authors can explain it. Finally, check again your manuscript one-by-one, and improve it extensively.
Response:Your review comments have been very helpful to me. I have revised the manuscript one by one based on your comments, and have carefully reviewed and revised some inappropriate statements in the manuscript. Thank you again for your valuable suggestions on the manuscript.
Reviewer 3 Report
The present article is devoted to establishing the possibility of using PO3G-PA for the plasticization of polylactide (PLLA). A fairly short introduction, however, provides sufficient background and clearly sets the research goal. The experiments, especially the elongation at break and tensile strength tests, clearly show that the proposed plasticizer can significantly improve the performance of the polymer film. However, in this edition, the article contains many shortcomings that need to be corrected before publication.
1. The process of preparing a solution for casting films is not described clearly enough. The nature and amount of the solvent are not specified. One can only guess that the concentrations of the plasticizer are relative to polylactide.
2. The phase state of the prepared films is unclear. Thus, in the comments on the results of infrared spectroscopy (lines 172-176) the authors say that the polylactide and the plasticizer are "physically blended" at all the studied plasticizer concentrations. At the same time, the results of DSC (Table 1), according to the authors, show that the transition from 20% to 25% of PO3G-PA leads to a deterioration in the compatibility of the polylactide and the plasticizer. Also, the extreme dependence of elongation at break on the plasticizer concentration shows a "crack phase between PO3G–PA and PLLA". However, in the comments to Figure 10, the authors conclude that there is no significant phase separation. In general, it turns out that the samples were studied using a whole series of methods, but a comparative analysis of the results was not carried out.
3. Figure 11 shows that the obtained samples are porous and are characterized by a complex structure of connected pores. However, the authors do not say anything about this. If the plasticizer causes pore formation, this point is very important. It is also possible that the porosity of the samples depends on the drying rate of the films. In the opinion of the reviewer, additional experiments are absolutely necessary to clarify this issue.
4. The authors do not explain why the dependence of the sample decomposition rate on the plasticizer concentration is non-monotonic in an acidic medium but monotonous in an alkaline one.
5. Elongation to break values are given with an accuracy of hundredths of a percent (lines 226-227). What are the experimental errors?
6. In Figure 10 nothing is visible at all.
7. English should be greatly improved. In particular, the word "moreover" is used incorrectly (see lines 182, 248).
Author Response
March 18, 2023
Dear Sir/Madam,
Thank you for reviewing our manuscript and offering valuable advice. In accordance with your suggestions, we have made the following revisions to our manuscript:
- The process of preparing a solution for casting films is not described clearly enough. The nature and amount of the solvent are not specified. One can only guess that the concentrations of the plasticizer are relative to polylactide.
Response: Thank you very much for pointing out these mistakes. We have rewritten this section. A solution with a mass fraction of 20% was prepared using PLLA/PO3G-PA mixtures with PO3G content of 0%, 5%, 10%, 15%, 20%, and 25% as the solute and 1,4-Dioxane as the solvent.
- The phase state of the prepared films is unclear. Thus, in the comments on the results of infrared spectroscopy (lines 172-176) the authors say that the polylactide and the plasticizer are "physically blended" at all the studied plasticizer concentrations. At the same time, the results of DSC (Table 1), according to the authors, show that the transition from 20% to 25% of PO3G-PA leads to a deterioration in the compatibility of the polylactide and the plasticizer. Also, the extreme dependence of elongation at break on the plasticizer concentration shows a "crack phase between PO3G–PA and PLLA". However, in the comments to Figure 10, the authors conclude that there is no significant phase separation. In general, it turns out that the samples were studied using a whole series of methods, but a comparative analysis of the results was not carried out.
Response: Thank you very much for your valuable comments. The meaning we want to express is that when the content of PO3G-PA in the film exceeds 20%, the concentration of PO3G-PA in PLLA tends to aggregate due to excessive concentration, resulting in a decline in Xc and mechanical properties. We have corrected inappropriate statements in the manuscript based on your suggestions.
- Figure 11 shows that the obtained samples are porous and are characterized by a complex structure of connected pores. However, the authors do not say anything about this. If the plasticizer causes pore formation, this point is very important. It is also possible that the porosity of the samples depends on the drying rate of the films. In the opinion of the reviewer, additional experiments are absolutely necessary to clarify this issue.
Response: Thank you very much for your valuable comments.According to your suggestion, we have carefully observed the film surface and tensile section through SEM and found that there are no holes on all film surfaces, while the section containing PO3G-PA has holes. This indicates that the pores are formed due to stretching and the presence of PO3G-PA.
Due to the flexibility of PO3G-PA, it undergoes large deformation as a stress concentration point during the tensile process, overcoming the interfacial adhesion and absorbing a large amount of energy during the process of detaching from the substrate. Therefore, a large number of holes oriented along the tensile direction appear on the tensile surface. Pure PLA can produce thin necks at low strain rates, but the thin necks are still transparent and smooth without holes. Therefore, the rod-shaped holes in the tensile surface of PLLA/PO3G-PA blends are caused by the dispersed phase, which deforms the modifier along the tensile direction. The dispersed phase changes from spherical to ellipsoidal, and both ends of the ellipsoidal form energy absorption points. During the fracture process, the PLA matrix in the middle of the modifier becomes more prone to movement, resulting in shear yielding.
- The authors do not explain why the dependence of the sample decomposition rate on the plasticizer concentration is non-monotonic in an acidic medium but monotonous in an alkaline one.
Response: Thank you very much for your valuable comments. According to your suggestion, we have explained this phenomenon in the manuscript.
Both acids and bases can catalyze the hydrolysis of PLLA, so the degradation rate of the material under acidic and alkaline conditions is faster than under neutral conditions. Due to the faster hydrolysis rate of PO3G-PA under alkaline conditions than under acidic conditions, the presence of PO3G-PA will greatly accelerate the invasion of the solution into the interior of the film. Therefore, the degradation rate of the film under alkaline conditions is proportional to the content of PO3G-PA.
- Elongation to break values are given with an accuracy of hundredths of a percent (lines 226-227). What are the experimental errors?
Response:Thank you very much for finding this mistake. I have added error bars to Figure 8.
- In Figure 10 nothing is visible at all.
Response:Thank you very much for finding this mistake. I enlarged Figure 10 for easy reading.
- English should be greatly improved. In particular, the word "moreover" is used incorrectly (see lines 182, 248).
Response: Sorry for the inconvenience caused to your reading due to my insufficient English proficiency. I have carefully checked the grammar of the paper and revised some long sentences that are not accurately expressed.
Round 2
Reviewer 1 Report
The following are the comments.
1. Sentences should be smaller
2. I or We or Us etc. should be removed, nothing personalized.
3. Abstract & Conclusions should only contain the findings not the experimental details, please correct and modify accordingly.
Author Response
- Sentences should be smaller
Response:Thank you very much for your valuable comments. According to your suggestion, we rewrote some long sentences.
- I or We or Us etc. should be removed, nothing personalized.
Response:Thank you very much for your valuable comments. According to your suggestion, I rewrote the sentences in the article that contain I, We, Us, etc.
- Abstract & Conclusions should only contain the findings not the experimental details, please correct and modify accordingly.
Response:Thank you very much for your valuable comments. According to your suggestion, I deleted the content related to the experimental details in Abstract & Conclusions.
Reviewer 2 Report
The manuscript looks partially improved. However, the quality of presentation (both English and explanation) should be improved more. In addition, as I mentioned in the 1st report, in the TGA data, the y-axis title should be "Weight (%)", not "Weight Loss (%).
For example, if y-axis title is weight loss (%), Authors started the experiment at 100 % of weight loss, which is nonsense. Therefore, the y-axis title should be simply "Weight (%)" in the TGA data.
Author Response
The manuscript looks partially improved. However, the quality of presentation (both English and explanation) should be improved more. In addition, as I mentioned in the 1st report, in the TGA data, the y-axis title should be "Weight (%)", not "Weight Loss (%).
For example, if y-axis title is weight loss (%), Authors started the experiment at 100 % of weight loss, which is nonsense. Therefore, the y-axis title should be simply "Weight (%)" in the TGA data.
Response:Thank you very much for your valuable comments. According to your suggestion, we made changes to Figure 5 and Figure12 and rewrote some of the explanation.
Reviewer 3 Report
Please see my comments in the attached file
Comments for author File: 
Comments.doc
Author Response
3.Figure 11 shows that the obtained samples are porous and are characterized by a complex structure of connected pores. However, the authors do not say anything about this. If the plasticizer causes pore formation, this point is very important. It is also possible that the porosity of the samples depends on the drying rate of the films. In the opinion of the reviewer, additional experiments are absolutely necessary to clarify this issue.
Response: Thank you very much for your valuable comments.According to your suggestion, we have carefully observed the film surface and tensile section through SEM and found that there are no holes on all film surfaces, while the section containing PO3G-PA has holes. This indicates that the pores are formed due to stretching and the presence of PO3G-PA.
Due to the flexibility of PO3G-PA, it undergoes large deformation as a stress concentration point during the tensile process, overcoming the interfacial adhesion and absorbing a large amount of energy during the process of detaching from the substrate. Therefore, a large number of holes oriented along the tensile direction appear on the tensile surface. Pure PLA can produce thin necks at low strain rates, but the thin necks are still transparent and smooth without holes. Therefore, the rod-shaped holes in the tensile surface of PLLA/PO3G-PA blends are caused by the dispersed phase, which deforms the modifier along the tensile direction. The dispersed phase changes from spherical to ellipsoidal, and both ends of the ellipsoidal form energy absorption points. During the fracture process, the PLA matrix in the middle of the modifier becomes more prone to movement, resulting in shear yielding.
I really appreciate the additional SEM experiments and the new data obtained, especially the information that pure PLA can produce thin necks, and the necks are still transparent and smooth without holes. However, explanations of the pore formation mechanism are not clear enough. What is dispersed phase (spherical or ellipsoidal)? What is modifier? Thus, the question again comes down to the structure of the modified polymer, its internal structure. This issue should be carefully considered.
Response:Thank you very much for your valuable comments. I apologize for not clearly stating our views. We have rewritten the content of this section.
From Figure 10 (c) (d) (e) (f), we can clearly see the spherical or ellipsoidal dispersed phase of PO3G-PA. Modifier refers to PO3G-PA. We have changed the word ‘modifier’ to ‘PO3G-PA’ in the text.
4.The authors do not explain why the dependence of the sample decomposition rate on the plasticizer concentration is non-monotonic in an acidic medium but monotonous in an alkaline one.
Response: Thank you very much for your valuable comments. According to your suggestion, we have explained this phenomenon in the manuscript.
Both acids and bases can catalyze the hydrolysis of PLLA, so the degradation rate of the material under acidic and alkaline conditions is faster than under neutral conditions. Due to the faster hydrolysis rate of PO3G-PA under alkaline conditions than under acidic conditions [???], the presence of PO3G-PA will greatly accelerate the invasion of the solution into the interior of the film. Therefore, the degradation rate of the film under alkaline conditions is proportional to the content of PO3G-PA.
The above explanations are logical, but references to the comparison of the rates of autocatalysis in acidic and alkaline media are necessary.
Response: Thank you very much for your valuable comments. According to your suggestion, we have added relevant references.
[1] Tsuji H., Ikada Y.: Properties and morphology of poly(l-lactide) 4. Effects of structural parameters on long-term hydrolysis of poly(l-lactide) in phosphate-buffered solution. Polymer Degradation & Stability, 2000, 67, 179-189.
[2] Tsuji H., Ikarashi K.: In vitro hydrolysis of poly(l-lactide) crystalline residues as extended-chain crystallites: III. Effects of pH and enzyme. Polymer Degradation and Stability, 2004, 85, 647-656.
5.Elongation to break values are given with an accuracy of hundredths of a percent (lines 226-227). What are the experimental errors?
Response:Thank you very much for finding this mistake. I have added error bars to Figure 8.
Changing the Figure is not enough. It is necessary to remove excessively precise values from the text.
Response: Thank you very much for your valuable comments. According to your suggestion, We removed the excessively precise values in this section.
6.In Figure 10 nothing is visible at all.
Response:Thank you very much for finding this mistake. I enlarged Figure 10 for easy reading.
The changes in the Figure are not noticeable. It is necessary to reduce the size of the visible area of the samples. In this case, the features of the structure can be considered.
Response: Thank you very much for your valuable comments. According to your suggestion, We have partially zoomed in on Figure 10.
