Effects of Bio-Based Polyelectrolyte Complex on Thermal Stability, Flammability, and Mechanical Properties Performance Utilization in PLA/PBS Composites

Round 1

Reviewer 1 Report (Previous Reviewer 2)

The authors are claiming that the flame resistance properties of P/15B biocomposites were significantly improved by incorporating bio-based flame retardants (PA-PEI and PA-Arg) into the complexes. There were also comparisons done between the different impacts of monomeric type and polymeric phytate amine complexes on the flame retardancy and mechanical properties of the materials which could be insightful and useful for further studies.

The article is in a good shape for publishing overall with well structured content and relatively clear data presentations, however, the reviewer believes that a few minor concerns should be addressed before acceptance:

1) Quality of presentation:

- The figure quality should be improved for Fig 1, and Fig 5. Especially for Fig 5, the scale bars should be clearly presented and readable to the audience.

- Misalignment of Table 5.

- Line 351, it should be either thermal decomposition is faster or the decomposition temperature is lower.

- Line 377-378, Table 4 has nothing to do with combustion. Please double-check and reassign the correct table number here.

 

2) Contradicting claims:

- The authors showed faster thermal decomposition of PA-PEI and PA-Arg compared to bare PEI and Arg respectively. However, the authors were trying to claim the high thermal stability of PA-PEI and PA-Arg contributed to the high flame retardancy of P/15B integrated composites. The claim here also does not explain the observed higher char residues in PA-PEI or PA-Arg-containing P/15B biocomposites compared to neat P/15B.

- The authors made claims in both the abstract and conclusions that the thermal stability of P/15B/PA-PEI series and P/15B/PA-Arg series biocomposites is improved compared to neat P/15B. This is not consistent with the thermal decomposition data shown in Table 3.

- Line 340-342, the authors claimed that the P/15B/15PA-Arg biocomposite demonstrates the highest char residues percentage (10.4%) among all tested P/15B biocomposites, which is not the case shown in Table 5.

 

Please comment on the above-mentioned concerns or make changes accordingly.

 

Thank you.

Author Response

Detailed responses to each of the review’s comments are given below. Reviewer comments are in black, and the responses to the reviewer comments are in blue.

1) Quality of presentation:

- The figure quality should be improved for Fig 1, and Fig 5. Especially for Fig 5, the scale bars should be clearly presented and readable to the audience.
Response: The figure quality Fig 1, and Fig 5 were changed to higher1200 dpi, and the scale bars of Fig 5 was corrected to right alignment.

- Misalignment of Table 5.
Response: The Table 5 was corrected to right alignment.

- Line 351, it should be either thermal decomposition is faster or the decomposition temperature is lower.
Response: Thank you for your very careful review of our paper, and for the comments. Line 351 was corrected as Such phenomes have been ascribed to the fact that the thermal decomposition temperature of PA-Arg is lower than PA-PEI,..”in line 354.

- Line 377-378, Table 4 has nothing to do with combustion. Please double-check and reassign the correct table number here.
Response:  Line 377-378, " In Table 4, the .." was corrected to Line 378~379 "In Table 5, the...."

2) Contradicting claims:

- The authors showed faster thermal decomposition of PA-PEI and PA-Arg compared to bare PEI and Arg respectively. However, the authors were trying to claim the high thermal stability of PA-PEI and PA-Arg contributed to the high flame retardancy of P/15B integrated composites. The claim here also does not explain the observed higher char residues in PA-PEI or PA-Arg-containing P/15B biocomposites compared to neat P/15B.

- The authors made claims in both the abstract and conclusions that the thermal stability of P/15B/PA-PEI series and P/15B/PA-Arg series biocomposites is improved compared to neat P/15B. This is not consistent with the thermal decomposition data shown in Table 3.
Response: Thank you for your very careful review of our paper, and for the comments. In abstract, line 18~19 ” enhance the thermal stability and char residues in these P/15 biocomposites.” was corrected as line 19 “enhance the char residues in these P/15B biocomposites” . And Line 253~255 “ This may due to the high thermal stability of PA-PEI and PA-Arg both makes it possible to obtain high flame retardancy in P/15B biocomposites.”was corrected as Line 253~ 257 “This may due to the faster thermal decomposition of PA-PEI and PA-Arg at relative lower temperature, and then phosphorus-containing elements from PA  promoted the dehydration and carbonization of P/15B polymer matrix to form stable carbon layers [19], which had positive effect to enhance the flame retardancy in P/15B biocomposites.”. In conclusion, Line 392 "the thermal stability of P/15B/PA-PEI series.. " was crrected as Line 394 "the char residues of P/15B/PA-PEI series..

- Line 340-342, the authors claimed that the P/15B/15PA-Arg biocomposite demonstrates the highest char residues percentage (10.4%) among all tested P/15B biocomposites, which is not the case shown in Table 5.
Response: Thank you for your very careful review of our paper, and for the comments. As we checked the experiment results, and we corrected the char residues in Table 5, and the P/15B/15PA-Arg biocomposite demonstrates the highest char residues percentage (10.4%).

Reviewer 2 Report (Previous Reviewer 3)

I have two small remarks

1) abbreviation descriptions should be given at the first mention in the text (see abstract line 19)

2) the articles need to be checked

Author Response

Detailed responses to each of the review’s comments are given below. Reviewer comments are in black, and the responses to the reviewer comments are in blue.

1) abbreviation descriptions should be given at the first mention in the text (see abstract line 19)
Response: Thank you for your very careful review of our paper, and for the comments. The line 19 was corrected “the P/15 polymer enhance the thermal stability and char residues in these P/15 biocomposites.” in to “the P/15B polymer enhance the thermal stability and char residues in these P/15B biocomposites.”

2) the articles need to be checked
Response: Thank you for your very careful review of our paper, and for the comments. The articles were checked again, and the corrected portion was red marked in the new manuscripts

Thank you.

Reviewer 3 Report (New Reviewer)

The flammability of polymeric materials is a very current topic. The risk of fire causes huge losses in infrastructure and people. The development of new materials with increased fire resistance is one of the main research directions.

1.       The purpose of the work was well defined. The title of the manuscript corresponds to its content. The literature is up to date and well chosen.

2.       It would be worth a bit to expand the information on the conducted research, it is about extending the description of the methodology.

3.       The obtained results are interesting, it would be worth specifying the flammability criteria that the material must meet and where it can be used.

4.       It would be worth supplementing the manuscript with the tensile test results. Very often flame retardants significantly deteriorate these material properties.

5.       Conclusions are well worded.

Author Response

Detailed responses to each of the review’s comments are given below. Reviewer comments are in black, and the responses to the reviewer comments are in blue.

 

1. The purpose of the work was well defined. The title of the manuscript corresponds to its content. The literature is up to date and well chosen.
   Response: Thank you for your very careful review of our paper, and for the comments.
2. It would be worth a bit to expand the information on the conducted research, it is about extending the description of the methodology.
   Response: Thank you for your very careful review of our paper, and for the comments.
3. The obtained results are interesting, it would be worth specifying the flammability criteria that the material must meet and where it can be used.
   Response: Thank you for your very careful review of our paper, and for the comments.
4. It would be worth supplementing the manuscript with the tensile test results. Very often flame retardants significantly deteriorate these material properties.
   Response: Thank you for your very careful review of our paper, and for the comments.
5. Conclusions are well worded.
   Response: Thank you for your very careful review of our paper, and for the comments.

Thank you.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Major

1. The manuscript should be revised in terms of English. Some sentences are very confusing. For instance, in the abstract authors wrote: “In order to improve the flame retardancy of the polylactic acid/polybutylene succinate biocomposites (P/15B), the chemical structure and thermal stability of PA-PEI and PA-Arg were characterized by Fourier-transform infrared spectroscopy (FTIR) and Thermogravimetric analysis (TGA).” Did you perform an analysis in order to improve flame retardancy???
2. Temperature above 170 °C but according to TGA PE-Arg and PA-PEI slightly degrade at this temperature. This point needs to be considered while the composite manufacturing and result & discussion.
3. Since thermal stability and flame retardancy is the study’s primary objective, TGA and flame retardancy sections must be significantly improved.
4. Poor discussion of mechanical properties as well.

Minor 

 

1. Section material. Detailed information about PLA and PBS must be added.
2. What is the role of SDE in composite? The additive also affects the properties of the composite. Please describe it. 
3. Section 2.3.5. The proper method must be described.
4. After which test does the images shown in Figure 5?
5. Table 4. How can composite reach HB rate without being tested in horizontal dimension???

Reviewer 2 Report

The author demonstrated that the fire resistance performance of a P/15B-based bio-composites was enhanced by incorporating polymeric type PA-PEI or the monomeric type PA-Arg into the P/15B matrix. The authors established the arguments in a systematic fashion and most of the conclusions were supported by the evidence. However, in my opinion, there is one key data set of P/15B/15PA-PEI missing from the article, and may the authors please address the following comments/questions as well:

 

1. In section 2.2.3, why were only P/15B/PA-Arg made with different wt% (10 and 15wt%) of the flame retardant additives? In line 227, the author also claimed that higher content of PA-PEI was also used, but where is the data?

2. Can section 2.3.4 and 2.3.6 be combined together if they are essentially the same?

3. In section 3.3. for the XRD analysis, why weren't PLA peaks presented in the composites but only PBS peaks?

4. Compare Fig 2(c) and Fig 3(a), why did PA-PEI showed higher carbon residue level than PA-Arg if not integrated in to P/15B composites but it was the opposite after the integration?

5. Line 311 to 313, I would not claim the concentration effect just based on the graphs. As for THR, P/15B/15PA-Arg is clearly higher than P/15B/10PA-Arg. It would be nice to add data from P/15B/15PA-PEI here if available.

6. English grammar: line 39, the sentence is out of order.

7. Formatting and typos: line 133, cubic meter symbol; line 210, TG missing A; line 242, missing a degree symbol for 19; line 285, the title of Table 4 is wrong; line 317, this should be Table 5; line 311, what is DTGA?; line 330, should be Table 5. Please check the article thoroughly as there might be more errors.

 

Thank you.

Reviewer 3 Report

This article is very breakthrough and the material being developed has a good potential for commercialization. It certainly deserves to be published, but I have a few questions and small comments:

1 Please add the MW of the used polymers in Materials and Methods section, this information is very important.

2 How the amounts of PLA and PBS for composite synthesis (Table1, 85/15, 66/15) have been chosen?

3 I didn't understand very clearly, what is the point of using several compositions and comparing their effects with each other, as they have very different structures (X-ray diffraction data)? Doesn't the structure of a material determine its properties?

4 The authors conclude: “In contrast with the neat P/15B, the thermal stability of P/15B biocomposites is moderately improved with the incorporation of PA-PEI or PA-Arg”. How does this follow from FTIR measurements?

5 The authors should cite the next article as it deals with the same flame retardant material (DOI 10.1007/s10570-018-1866-4)

6 There is a typo, check the Line124: tempera-ture