Plasma Treatment of Different Biodegradable Polymers: A Method to Enhance Wettability and Adhesion Properties for Use in Industrial Packaging

Round 1

Reviewer 1 Report

1.       I would like to suggest the authors providing some extended details on alternative polymers plasma-treated, e.g. PHB. It is known that plasma provides unique opportunity to modulate surface wetting behavior.

2.       I would recommend providing more details on polymer chains cleavage due to energetic particle exposure.

3.       Surface ageing is an important point to be addressed in case of plasma-treatment of polymers. In addition, different polymers may experience different rate of surface properties ageing after plasma treatment. Thus, some approaches addressing this issue should be discussed.

4.       I would like the authors pointing some specific details in SEM-images, otherwise some of them look similar and can be omitted or moved to the supplementary file.

5.       Alongside with surface wetting behavior, surface energy plays an important role and is usually also calculated based on WCA measurements of 2 or more fluids.

6.       I would also recommend providing some details if droplet evaporation might have affected the WCA-values.

7.       I would recommend providing all the data as average and standard deviation. Otherwise the significance of the obtained difference is not obvious.

8.       Could the ration between amorphous and crystalline phases of the polymers be defined? In particular could the effect of the plasma treatment be derived on the ratio between the phases.

9.       I would recommend paying attention only to the results obtained, thus moved any references to the main body of the manuscript. Comparison or referring to the literature is very good while discussing the results obtained.

10.   It would also be good to provide some details on possible mechanical properties changes of materials due to plasma effect on surface or bulk properties of the treated polymers.

Author Response

Dear Referee,

The authors thank for time and expertise in reviewing of our manuscript entitled “Plasma treatment of different biodegradable polymers: a method to enhance wettability and adhesion properties for use in industrial packaging”.

The suggestion and comments were taken into consideration and included in the manuscript.

Please find attached below our point-by-point replies (normal script in red) to specific comments (normal script) and the revised manuscript with marked corrections in the original text.

On behalf of all the authors,

Espedito Vassallo

Author Response File: Author Response.docx

Reviewer 2 Report

Plasma activation of biodegradable plastics, particularly those that might be used in food, is studied based on a two-step oxygen followed by argon low-pressure plasma. Except for the polymer selection, there is not much new information in the paper. The plasma conditions have previously been optimized, the characterization mainly shows that bulk properties are not affected. Aging might be reduced bit no reference is shown.

In its current state the paper has thus no high value for readers. It might be reconsidered only after major changes.

It is an asymmetric plasma with treatment at the grounded electrode. Where was the position of the Langmuir probe?

Considering the high bias, the plasma potential might be on the order of just a few tens of volt. Thus the potential drop to the substrates can be assumed to be small, which should not result in sputtering effects at 10 Pa. Please comment and revise the discussion on substrate heating and sputtering. As stated later in the manuscript there might be no morphological damage. The etching rate might be measured to further comment on the plasma etching using the applied plasma gases.

It is stated that optimized conditions have been applied. To see its potential, plasma treatment with only O2 as well as only Ar following their aging should be added.

FTIR mainly indicates that the bulk properties were not altered. For chemical characterization of the surface, ATR-FTIR or XPS should be used following aging.

okay

Author Response

Dear Referee,

The authors thank for time and expertise in reviewing of our manuscript entitled “Plasma treatment of different biodegradable polymers: a method to enhance wettability and adhesion properties for use in industrial packaging”.

The suggestion and comments were taken into consideration and included in the manuscript.

Please find attached below our point-by-point replies (normal script in red) to specific comments (normal script) and the revised manuscript with marked corrections in the original text.

On behalf of all the authors,

Espedito Vassallo

Author Response File: Author Response.docx

Reviewer 3 Report

The author studied and reported the changes in the biodegradable polymers  using gas-phase plasma treatment. The study is interesting and useful for practical use. The manuscript should be accepted after adding the following information. 

1. The chemical reactions during plasma treatment on biodegradable polymers should be added to provide a clear understanding of plasma treatment on materials. 

2. The calculation methods/equations of the plasma parameters should be provided, as well as a discussion on how these parameters relate to the change of products. 

The quality of English is good, but there are a few mistakes. Please carefully check again. 

Author Response

Dear Referee,

The authors thank for time and expertise in reviewing of our manuscript entitled “Plasma treatment of different biodegradable polymers: a method to enhance wettability and adhesion properties for use in industrial packaging”.

The suggestion and comments were taken into consideration and included in the manuscript.

Please find attached below our point-by-point replies (normal script in red) to specific comments (normal script) and the revised manuscript with marked corrections in the original text.

On behalf of all the authors,

Espedito Vassallo

Author Response File: Author Response.docx

Reviewer 4 Report

For the following reason the manuscript should be rejected:

Based on the same FTIR data the authors draw highly contradictory conclusions:

line 266-268: plasma treatment enhances the breaking of C-H bonds, favouring the formation of C=O and C-O functional groups on the sample surface

line 254-255: for all treated BP, the plasma process does not produce the formation of any new chemical functional group on the surface

Comments for a possible revision / resubmission:

Every symbol should be explained when it appears in the text for the first time (PBS, PBAT, PLA, SEM, AFM, DSC, XRD, …)

The terms plastic and polymer are used as synonyms throughout the text. In a scientific publication polymer should be used.

Error bars should be added to Fig. 4. Alternatively, experimental uncertainties should be discussed in the text.

The presentation of WCA results should be improved by including the case of zero post crosslinking.

The experimental setup is introduced as an ‘asymmetric parallel electrode configuration’. However, this is not clear in Fig. 1. Possibly, the metallic chamber is part of the grounded electrode? In this case the self bias potential mentioned in Table 1 appears at the powered electrode while the sample is placed on the grounded electrode.

In the discussion of FTIR data it should be considered, that the expected depth of modification is smaller by orders of magnitude compared to the sample (foil) thickness. For that reason most studies of low pressure plasma polymer modification employ surface selective characterization techniques like XPS.

Author Response

Dear Referee,

The authors thank for time and expertise in reviewing of our manuscript entitled “Plasma treatment of different biodegradable polymers: a method to enhance wettability and adhesion properties for use in industrial packaging”.

The suggestion and comments were taken into consideration and included in the manuscript.

Please find attached below our point-by-point replies (normal script in red) to specific comments (normal script) and the revised manuscript with marked corrections in the original text.

On behalf of all the authors,

Espedito Vassallo

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have respoded well on comments and the manucript can be accepted.

Author Response

The authors would like to thank the reviewer for all useful and helpful comments on our manuscript. 

Sincerely yours,

E. Vassallo

Reviewer 2 Report

The authors managed to substantially improve the quality of their manuscript which is now fine for publication.

acceptable

Author Response

The authors would like to thank the reviewer for all useful and helpful comments on our manuscript. 

Sincerely yours,

E. Vassallo

Reviewer 4 Report

My previous concerns were largely considered in the revised manuscript.

Author Response

The authors would like to thank the reviewer for all useful and helpful comments on our manuscript. 

Sincerely yours,

E. Vassallo