Biocomposite Films of Amylose Reinforced with Polylactic Acid by Solvent Casting Method Using a Pickering Emulsion Approach

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript entitled “Biocomposite films of amylose reinforced with polylactic acid by solvent casting method using a Pickering emulsion approach” studies different compositions of amylose, polylactic acid, cellulose, and glycerol to produce a biocomposite. The topic studied in the manuscript is of academic and industrial interest. The manuscript is well-written and reflects good technical quality; however, some sections need to be improved. Suggestions:

1 - Add more bibliographical references in the Introduction. For example, in the sentence of the line 69. Please revise the text to introduce more references if necessary.

2 - Line 120-123, this sentence seems to be discussing results of the work. I suggest moving it to the 'discussion' section. Use the Introduction section to show the state of the art in relation to the topic.

3 – Line 131, can 12% be considered a low percentage of PLA? Explain why these values were chosen. However, perhaps introduce the information in the materials and methods section.

4 - In the last paragraph, improve the involvement of the innovation of the work. The main objectives of the work should also be highlighted.

5 - In general, the introduction needs to be improved so that it is more coherent. Please review this section.

6 – Methods section: Explain/relate biocomposite with the use of solvents such as methanol, toluene, DCM. Shouldn't the use of these solvents be restricted or reduced? What is the impact of their use? How do you ensure that the product is free from contamination by these solvents? It is important for the authors to clarify this issue.

7 - Line 163: Specify how many washes are carried out (volume spent?) and why.

8 - Line 177: Describe the variables used and the units.

9 - Table 1 or section 2.2.3: Explain why the mass of glycerol was fixed for all tests. Specify which and volume of solvent used for each production (perhaps add columns in the table to add the information).

10 - Line 226: This looks like the water removal procedure (moisture content), why were different temperatures used for the tests?

11 - Line 228: Explain/improve how the drying was done.

12 - Line 234 / 225: Place the constant dimension units throughout the manuscript. Please review the manuscript for uniformity.

13 - Line 262-264: It is suggested that the authors improve the description.

14 - Line 284 / 231: “…developed on 3 %PLA, 6% PLA and 12 PLA.” Please uniformise.

15 – Please avoid using abbreviations as titles/subtitles.

16 - Figure 3a - Having a line across the graph tracing the control point would help the interpretation of the points.

17 - Suggestion: show images of the films produced. It would be interesting for readers to have access to this information in order to visualize the film produced.

18 - Section 3.7 unformatted.

19 - Section 3.8: Improve the discussion of the results in this section. Explain the impact of the formulation on wettability / contact angle.

20 - Line 473 - please describe CA - Contact angle.

21 - Throughout the article: the statistical treatment has been applied to the results but the authors do not consider it in their discussion of the results. It is suggested that this be improved and applied throughout the manuscript.

Author Response

For research article

 

 

Response to Reviewer 1 Comments
1. Summary
Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions highlighted in red in the re-submitted files.
3. Point-by-point response to Comments and Suggestions for Authors

Comment 1:- Add more bibliographical references in the Introduction. For example, in the sentence of the line 69. Please revise the text to introduce more references if necessary.

Response 1: Thank you for this comment. More references are added in the introduction and reference no. (9) has been added to the mentioned part, page 3-line 72.

 

Comment 2: Line 120-123, this sentence seems to be discussing results of the work. I suggest moving it to the 'discussion' section. Use the Introduction section to show the state of the art in relation to the topic.

Response 2: Thank you for your valuable comment on structuring the text. We agree with this comment, therefore, we moved this part to the discussion section 3.6, page 14 lines 409-411.

 

Comment 3: Line 131, can 12% be considered a low percentage of PLA? Explain why these values were chosen. However, perhaps introduce the information in the materials and methods section.

Response 3: Thank you for pointing this out. We agree that additional information is required, hence,  we explained the rationale of using lower percentages of PLA, on pages 4, lines: 151-155 as follows: "Few studies have examined the integration of starch-based bioplastics with minimal amounts of PLA. Our objective is to develop highly compostable blends of PLA and AM-based bioplastic, utilizing low PLA concentrations (0, 3, 6, and 12%) to regulate the biodegradation process of polysaccharides.”

 

Comment 4: In the last paragraph, improve the involvement of the innovation of the work. The main objectives of the work should also be highlighted.

Response 4: We agree with your comment. The main objective has been emphasized as follows, on page 4, lines 147-162: ‘’Binary and ternary blends, consisting of AM, PLA, CNF, and g-CNF, were prepared using the Pickering emulsion approach and dried at 50°C. Given the limited exploration of lower concentrations of AM and PLA, our objective is to investigate a bioplastic blend based on PLA and AM using the Pickering emulsion approach with low per-centages of PLA (0, 3, 6, and 12%). Few studies have examined the integration of starch-based bioplastics with minimal amounts of PLA. Our objective is to develop highly compostable blends of PLA and AM-based bioplastic, utilizing low PLA con-centrations (0, 3, 6 and 12%) to regulate the biodegradation process of polysaccha-rides. By our approach using grafted starch, compatibility between starch and PLA is enhanced, requiring less CNF and g-CNF were incorporated into the bioplastic composites, and the produced materials were characterized by physical, mechanical, hydrophobicity, and morphological observations. The overarching goal of this research is to use pure, bulk AM to develop a novel ternary blend of AM/CNF/PLA, and AM/g-CNF/PLA using a Pickering emulsion solvo-casting method. Film properties were assessed after drying at moderate temperatures, eliminating the need for heat-intensive processing methods.’’

 

Comment 5: In general, the introduction needs to be improved so that it is more coherent. Please review this section.

Response 5: Thank you for your valuable comment. The introduction has been extended, updated and modified to be more streamlined. Highlighted in red.

 

Comment 6: Methods section: Explain/relate biocomposite with the use of solvents such as methanol, toluene, DCM. Shouldn't the use of these solvents be restricted or reduced? What is the impact of their use? How do you ensure that the product is free from contamination by these solvents? It is important for the authors to clarify this issue.

Response 6: Thank you for pointing this out. We have thus taken care of such potential contamination and environmental issues mentioned in the method section the volume used which is less 5 times the water content, as this is the minimum amount required for the emulsion, page 5- lines: 201-203. The evaporation of the solvent volumes overnight and FTIR spectra shows the removal of the used solvents.

Comment 7: Line 163: Specify how many washes are carried out (volume spent?) and why.

Response 7: Thank you. Volumes and washing numbers are now included in section 2.2.2, pages 5&6- lines: 190-202, highlighted in red.

 

Comment 8 - Line 177: Describe the variables used and the units.

Response 8: Variables used the equation are now described. Pages 6 lines: 210-212.

Grafted yield= ((m_g-CNF- m_CNF)/m_CNF)*100

Where m_g-CNF is the mass of the g-CNF produced in grams after washing with DCM and drying, and m_CNF is the mass of original CNF in grams.

 

 Comment 9: Table 1 or section 2.2.3: Explain why the mass of glycerol was fixed for all tests. Specify which and volume of solvent used for each production (perhaps add columns in the table to add the information).

Response 9: The mass of glycerol was fixed for all tests based on polysaccharide weight % to avoid brittle matrices. The wt% is based on our previous experience in references (20) on page 6, lines213-214.

 

Comment 10: Line 226: This looks like the water removal procedure (moisture content), why were different temperatures used for the tests?

Response 10: Important comment. Thank you. The water removal in moisture content held on temperature at 105 ˚C, but for measuring the swelling and solubility, we used different temperatures based on previous knowledge and work (33) due to the hydrophilic nature of polysaccharides.

 

Comment 11 - Line 228: Explain/improve how the drying was done.

Response 11: Thank you pointing this out. The method of drying is now explained; carried until constant weight. page 7-line 250.

 

Comment 12 - Line 234 / 225: Place the constant dimension units throughout the manuscript. Please review the manuscript for uniformity.

Response 12: Thank you for your comment. The manuscript is now revised with respect to uniform units.

 

Comment 13 - Line 262-264: It is suggested that the authors improve the description in page 8-lines:

Response 13: Thank you for pointing this out, more explanation has been added to this part.

 

Comment 14: - Line 284 / 231: “…developed on 3 %PLA, 6% PLA and 12 PLA.” Please uniformise.

Response 14: Thank you for having identified this typo. 12 PLA has been changed to 12% PLA.

 

Comment 15: Please avoid using abbreviations as titles/subtitles.

Response 15: Thank you for your comment. We removed all the initials in the subtitles and titles.

 

Comment 16: - Figure 3a - Having a line across the graph tracing the control point would help the interpretation of the points.

Response 16: Thank you for your suggestion. A dotted indication line has been included to trace the control point in Fig- 3a page 12.

 

Comment 17 - Suggestion: show images of the films produced. It would be interesting for readers to have access to this information in order to visualize the film produced.

 

Response 17: Thank you for your valuable comment. Images of films have been included to help the reader’s data interpretation by visualization.

 

Comment 18 - Section 3.7 unformatted.

Response 18: Thank you. 3.7 has been formatted on page 13.

 

Comment 19 - Section 3.8: Improve the discussion of the results in this section. Explain the impact of the formulation on wettability / contact angle.

Response 19: Agree with your comment. Therefore, we have described the impact of the formulation on wettability on page 16- lines 486-499.

 

Comment 20 - Line 473 - please describe CA - Contact angle.

Response 20: Thank you for your valuable comment. CA has been described in more detail with reference no. (34) mentioned on page 16- lines 486-491.

Comment 21 - Throughout the article: the statistical treatment has been applied to the results but the authors do not consider it in their discussion of the results. It is suggested that this be improved and applied throughout the manuscript.

Response 21: Thank you for pointing this out. The results have been discussed and updated based on the statistical outcomes.

 

 

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

"The following points should be reviewed before publication:

1. Line 161 – The time unit should be expressed in "h" instead of hour;
2. The FTIR spectra should be resized to allow for better resolution in peak analysis. Relevant peaks should be marked in the figures. The authors claim that the peak at 1650 cm-1 (line 271) is related to water absorption; however, this relationship seems unsubstantiated to me. Therefore, the authors should cite references that confirm the relationship between the peaks and the chemical groups presented in the spectra, especially the chemical groups related to the peak at 1650 cm-1.
3. The SEM micrographs do not have a scale bar.
4. The contact angle results should be used to calculate the material's surface energy, using the Fowkes Model, which will allow for a more appropriate discussion of the results obtained."

 

Comments on the Quality of English Language

Minor editing of English language required.

Author Response

For research article

 

 

Response to Reviewer 2 Comments
1. Summary
Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions highlighted in red in the re-submitted files.
2. Point-by-point response to Comments and Suggestions for Authors

1. Comment 1: Line 161 – The time unit should be expressed in "h" instead of hour;

Response 1: Thank you ‘’ hour ‘’ has been changed and updated to ‘’h’’ on page 4- line172.

 

1. Comment 2: The FTIR spectra should be resized to allow for better resolution in peak analysis. Relevant peaks should be marked in the figures. The authors claim that the peak at 1650 cm-1 (line 271) is related to water absorption; however, this relationship seems unsubstantiated to me. Therefore, the authors should cite references that confirm the relationship between the peaks and the chemical groups presented in the spectra, especially the chemical groups related to the peak at 1650 cm-1.

Response 2: Thank you for your comment. FTIR spectra are updated by highlighting the main peaks. Additional references no. (35)&(36) have been added to confirm starch characteristic peaks specially with 1644 cm^-1 on page 8-line 341.

 

1. The SEM micrographs do not have a scale bar.

Response 3: Thank you for commenting on this. Scale bars have been added to Figure 4 page 16.

 

1. The contact angle results should be used to calculate the material's surface energy, using the Fawkes Model, which will allow for a more appropriate discussion of the results obtained."

Response 4: Thank you for your suggestion. However, due to the limited resources it was difficult to obtain results with Fawkes model in addition it requires to use three different solvents which is hardly to measure.

 

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manusript introduces a ternary biocomposite consisting of AM/PLA and g-CNF or CNF. I think the manuscript should be rejected and perhaps resubmitted after a major revision, especially regarding the interpretation of the data. The following issues are suggested for consideration: 

(1)Line 51-53 “Starch with a high content of AM poses challenges in forming entangled matrices due to the presence of amylopectin, resulting in short segments that form stable double helical junction zones” This statement requires citation of relevant references.

(2)Grammatical error in line 69-71 (missing a period after ‘parameter’?) “Crystallinity is also a desirable parameter this is because pure PLA has higher amorphous phase compared to the crystalline phase, which facilitate gas permeability [8].”

(3)Line 71-74 “Consequently, various approaches have been proposed to enhance its properties, including the blending of PLA with other materials as a straightforward and cost-effective strategy to address shortcomings, such as the incorporation of silicates and 1, 3, 5-benzene tricarboxyamide (BTA) [9,10].” : It would be helpful if you can clarify the role of the fillers silicates and BTA (e.g., nucleating agent? Impact modifier? Chain extenders? Compatibilizers? Just reinforcing fillers?)

(4)Line 367-368 “Blending AM with PLA decreased the tensile while it increases by increasing the content of PLA to 12%.” : What is it that increases with increasing the PLA content to 12%? Is it relative crystallinity? This needs to be clarified. Also, from Table 2, it can be seen that the EAB of AM/PLA composites are decreasing from 28.2 to 8.9 (12% of PLA) in proportion of increasing PLA, although you state exactly the opposite in line 369-370. The same kind of misinterpretation of Table 2 also appears in line 370-371 (“It is showed that adding PLA can raise tensile strength and decrease the EAB.”): Adding PLA decreases both tensile strength and EAB. Plus, it is very difficult to grasp any correlation between the effects of g-CNF that has on improving mechanical properties as compared to non-grafted counterpart.

 

(5)All the other data should be re-organized such that they reveal the correlation or the effects that adding g-CNF has on the overall improvement of macroscopic properpties of the composites (e.g. In Figure 5, what kind of structure-property relation are you trying to emphasize?)

Comments on the Quality of English Language

English editing is highly recommended. 

Author Response

For research article

 

 

Response to Reviewer 3 Comments
1. Summary
Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions highlighted in red in the re-submitted files.
2. Point-by-point response to Comments and Suggestions for Authors

Line 51-53 “Starch with a high content of AM poses challenges in forming entangled matrices due to the presence of amylopectin, resulting in short segments that form stable double helical junction zones” This statement requires citation of relevant references.

Response 1: Thank you for your comment. A reference (4) has been included to substantiate theses effects on page 2-line 60.

(2)Grammatical error in line 69-71 (missing a period after ‘parameter’?) “Crystallinity is also a desirable parameter because pure PLA has higher amorphous phase compared to the crystalline phase, which facilitate gas permeability [8].”

Thank you for your comment.  It has been correct and updated in the text as follows:“ Crystallinity is also a desirable parameter. PLA has a higher amorphous phase compared to the crystalline phase, which facilitates gas permeability [8].”

(3)Line 71-74 “Consequently, various approaches have been proposed to enhance its properties, including the blending of PLA with other materials as a straightforward and cost-effective strategy to address shortcomings, such as the incorporation of silicates and 1, 3, 5-benzene tricarboxyamide (BTA) [9,10].” : It would be helpful if you can clarify the role of the fillers silicates and BTA (e.g., nucleating agent? Impact modifier? Chain extenders? Compatibilizers? Just reinforcing fillers?).

Response 3: Thank you for this comment. The role of the fillers on PLA matrix have been clarified on page 3, lines 81-93 as follows:

‘’The physical properties of PLA-layered silicate nanocomposites are sensitive to large-scale chain movements; silicates restrict the mobility of the surrounding poly-mer chains. The effect could be improved by compatalization using modifiers. [11]. 

Another approach for reducing the rigidity of PLA-based materials consists in its plasticization that can be achieved simply by blending the PLA matrix with low mo-lecular weight additives or another miscible polymer. A series of 1, 3, 5-trialkyl-benzenetricarboxylamides (BTA-Rs) with different side-chain lengths of n-alkyl are synthesized to use as nucleating agents of poly (lactic acid) (PLA). It is found that 0.8 wt % is the optimal weight fraction of BTA-nBu to improve the crystallization of PLA the nucleation efficiency can reach up to 91%with no effect of crystal-line structure [12].’’

 (4)Line 367-368 “Blending AM with PLA decreased the tensile while it increases by increasing the content of PLA to 12%.” What is it that increases with increasing the PLA content to 12%? Is it relative crystallinity? This needs to be clarified.

Also, from Table 2, it can be seen that the EAB of AM/PLA composites are decreasing from 28.2 to 8.9 (12% of PLA) in proportion of increasing PLA, although you state exactly the opposite in line 369-370. The same kind of misinterpretation of Table 2 also appears in line 370-371 (“It is showed that adding PLA can raise tensile strength and decrease the EAB.”): Adding PLA decreases both tensile strength and EAB. Plus, it is very difficult to grasp any correlation between the effects of g-CNF that has on improving mechanical properties as compared to non-grafted counterpart.

Response 4: Thank you for your feedback. The sentence has been changed and updated on pages 14.

We also agree with your comment that g-CNF did not improve the mechanical properties due to low dispersity in the ternary matrix, which consists by SEM image.

 

(5)All the other data should be re-organized such that they reveal the correlation or the effects that adding g-CNF has on the overall improvement of macroscopic properties of the composites (e.g. In Figure 5, what kind of structure-property relation are you trying to emphasize?).

Response 5: Thanks for your comment. We are trying to see the structure of the composites and see if there is a phase separation and or heterogeneity between the polysaccharide and the PLA. We anticipated that g-CNF should display a more homogenous composite but we found no significant effect compared to CNF.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

No additional comments. The authors responded to questions and changed the manuscript when necessary.

Reviewer 2 Report

Comments and Suggestions for Authors

Accept in the present form.

Comments on the Quality of English Language

Minor editing of English language required.

Reviewer 3 Report

Comments and Suggestions for Authors

Line 51-53, "Both are polysaccharides and ... less hydrophilic.": it would be better off with a relevant reference cited herein. The authors may consider citing the following article reporting on a Pickering emulsion-based approach to combine PLA and polysaccharide nanofibers, which would help support the authors' idea and conclusion; 'Wholly bio-based, ultra-tough, transparent PLA composites reinforced with nanocellulose and nanochitin', Composites Part B: Engineering, 281, 111563 (2024) (https://doi.org/10.1016/j.compositesb.2024.111563)

For the rest, the authors have addressed most of the issues raised, and therefore I recommend publishing the manuscript in the journal. 

Comments on the Quality of English Language

The quality of English is on an appropriate level.