Surface Functionalization of a Polyurethane Surface via Radio-Frequency Cold Plasma Treatment Using Different Gases
Round 1
Reviewer 1 Report
The manuscript is about PU films treated by low-temperature RF plasma in O2, N2, Ar, air and mixtures. Surface changes were investigated. Highly hydrophilic behavior of PU was observed after plasma treatment.
The study is well structured and the spectrum of analysis is impressive. Nevertheless, I have some concerns about the results.
I would like to point out that the study lacks a clear aim. Plasma treatment of polymers is now a mature field and changing the polymer and observing the same trends lacks novelty. Why is improved hydrophilicity of PU important and where exactly could we benefit from it?
Overall, the results of gas mixtures offer very little additional insights.
English grammar must be improved. For example, lines 16, 27, 29, 33, 38, 41, 44, 55 etc.
Here are some of the other lines that need improvement:
Line 20, O2 is missing. Please list the gases in the exact order every time you mention them. This goes also for the figures. Unify the symbols too (fig 2,7,8,13).
Line 48, "plasma deposition" should be replaced by "plasma treatment"
Line 68-71, There is no explanation of why N2 is used. Please elaborate.
Line 84, Ethanol was probably not used as a CA testing liquid but is mentioned as such.
Line 93, "vacuum pressure" should be replaced by "low-pressure"
Line 98, "vacuum level" should be replaced by "pressure"
Line 99, Out of curiosity, did you measure the pressure after gas flow was applied? What was it, approx.?
Line 100, How, and why did you treat the film from both sides?
Line 137, AFM offers not only Ra but also Sa roughness information, why did you decide for Ra when you could compare the Sa from AFM to Sa from profilometer? Areas for both are similar enough to offer a comparison.
Line 171, "water contact angle" instead of "contact angle water"
Line 176-180 Do you have a reference for this claim?
Line 185 Figures with graphs would benefit from a dot-line-dot configuration, dots only are sufficient for Fig 1 but not Fig 2, 3, 4, 5, 7…
Line 192, Plasma parameters missing, 80W and 180s I guess?
Line 196 O2/Ar above and Ar/O2 below are confusing, I suggest O2 100% - 0% above and Ar 0% - 100% below. This goes for Fig. 4 and 5 also.
Line 213 is not in agreement with Fig. 6, air seems to be better than Ar. The explanation in line 213 is also a bit vague.
Line 219-222, unnecessary long run-on sentence.
Line 224, How were the aged CA measured, on the same aged sample over time or on a fresh, aged sample every time?
Line 230, Fig. 7, consider another break in the "Aging time" axis to properly show the shorter aging times or maybe consider a logarithmic scale.
Line 250, Fig. 8, I cannot find a result for Ar after 500 h?
Line 279, Untreated sample is usually presented first for comparison/reference. Air and the untreated sample have a sum different than 100%.
Line 283 is not in agreement with Table 1.
Line 288, 15,9 to 16,6 cannot be called a noticeable increase
Line 311, I strongly suggest consulting a specialist for roughness measurements! Sa is not "root mean square"!
How many roughness analyses were performed on different areas of one sample? What is the standard deviation?
Line 330, Ra is not surface roughness!
Line 336, Do you have a reference for this claim?
Lines 352, 355, What is the standard deviation of these measurements?
Line 358, Fig 15a and 16a are not like lines 140-142 suggest. I understand it is difficult to observe polymers with SEM, but maybe you should try different magnification to obtain high resolution images. These two images are useless.
Line 363, Ra is not "root mean square"!
I have serious doubts about the efficiency of your plasma system and the results concerning oxygen being the least appropriate for hydrophilicity improvement.
Author Response
The manuscript is about PU films treated by low-temperature RF plasma in O2, N2, Ar, air and mixtures. Surface changes were investigated. Highly hydrophilic behavior of PU was observed after plasma treatment.
The study is well structured and the spectrum of analysis is impressive. Nevertheless, I have some concerns about the results.
I would like to point out that the study lacks a clear aim. Plasma treatment of polymers is now a mature field and changing the polymer and observing the same trends lacks novelty. Why is improved hydrophilicity of PU important and where exactly could we benefit from it?
Reply: The authors thank you reviewer for valuable comments and suggestions. The extended statement about improved hydrophilicity has been included in revised manuscript: “This paper provides a prerequisite study to properly quantify the effect of plasma treatment on the surface hydrophilicity and surface structural changes of polyurethane films at optimum operating conditions and to properly demonstrate the underlying causes of the aforementioned modifications applicable in various applications where improved wettability and adhesion is required.” Improved hydrophilicity of PU is important for example, for better adhesion for preparation of laminates, sealant or better printability.
Overall, the results of gas mixtures offer very little additional insights.
Reply: The use of gas mixture was used to analyze their potential synergic effect on the surface and adhesion properties of PU, such as treatment in air (mixture of gases), which showed the best performance. Moreover, these studies confirmed that the presence of oxygen in gas mixtures deteriorated wettability.
English grammar must be improved. For example, lines 16, 27, 29, 33, 38, 41, 44, 55 etc.
Reply: The English grammar was checked by professional editing company. However, typos and grammar have been corrected.
Here are some of the other lines that need improvement:
Line 20, O2 is missing. Please list the gases in the exact order every time you mention them. This goes also for the figures. Unify the symbols too (fig 2,7,8,13).
Reply: The authors agree with the reviewer and the comment has been rectified accordingly throughout the revised manuscript.
Line 48, "plasma deposition" should be replaced by "plasma treatment"
Reply: It has been corrected as suggested.
Line 68-71, There is no explanation of why N2 is used. Please elaborate.
Reply: The use of N2 introduces nitrogen-containing functional such as –NH2, =NH, and ≡N groups into the polymeric matrix which produces stationery polarities, resulting in hydrophilic surface properties: "Plasma activation is typically performed using various gases (Ar, O2, He, CO2, N2, NH3, H2, CF4, SF4, C4F8, or air) and their choice depends on the expected effects of surface modification. Fluoride plasmas are typically used if the purpose of activation is to reduce chemical activity or to induce release properties. The main goal of this work is to increase the surface hydrophilicity of the surface through introducing new surface functionalities on the polymeric surface during plasma activation including reactive groups including but not limited to hydroxyl (–OH), carboxylic (–COOH), an amine (–NH2). This requires the use of oxygen-containing gas medias such as air, oxygen, and Nitrogen. Ar gas, on the other hand can be utilized to produce radicals that will react with oxygen or water in the air to form oxygen functionalities, which will be able to enhance the surface hydrophilicity. Therefore, in this study O2, N2, air, and Ar discharges and their mixtures were used as plasma gases.''
Line 84, Ethanol was probably not used as a CA testing liquid but is mentioned as such.
Reply: This mistake has been corrected and the paragraph under ''materials section'' has been rectified accordingly.
Line 93, "vacuum pressure" should be replaced by "low-pressure"
Reply: It has been corrected as suggested.
Line 98, "vacuum level" should be replaced by "pressure"
Reply: It has been corrected.
Line 99, Out of curiosity, did you measure the pressure after gas flow was applied? What was it, approx.?
Reply: Before plasma discharge ignition, the chamber pressure has been stabilized during gas flow (in and out) and kept constant during plasma treatment process (~27 Pa).
Line 100, How, and why did you treat the film from both sides?
Reply: The RF plasma system generates homogeneous plasma discharge in the whole reactor allowing treatment of 3D materials from each side. Therefore samples were treated from both sides. However, in fact that only the top surface layer was homogeneously treated because of the sample holder contains holes on which films were placed. The statement that film was treated from both sides was omitted in revised manuscript.
Line 137, AFM offers not only Ra but also Sa roughness information, why did you decide for Ra when you could compare the Sa from AFM to Sa from profilometer? Areas for both are similar enough to offer a comparison.
Reply: By our knowledge, our AFM can provide only information about Ra (arithmetical mean height of a line) or Rq (root mean square deviation) value. Ra is as resulting information from the arithmetic average of the absolute values of the profile height deviations from the mean line, recorded within the evaluation length (particular line paths of the tip cantilever over the projected surface in line). On the other hand, profilometry is able to analyze Sa (arithmetical mean height) according Surface ISO 25178.
Line 171, "water contact angle" instead of "contact angle water"
Reply: It has been corrected as suggested.
Line 176-180 Do you have a reference for this claim?
Reply: This observation has been reported in several studies. References that support this claim have been added to line 180.
Line 185 Figures with graphs would benefit from a dot-line-dot configuration, dots only are sufficient for Fig 1 but not Fig 2, 3, 4, 5, 7…
Reply: The dot-line-dot configuration would be probably confusing because it would not indicate the real trend (fitting).
Line 192, Plasma parameters missing, 80W and 180s I guess?
Reply: The information about plasma parameters was included in the revised manuscript.
Line 196 O2/Ar above and Ar/O2 below are confusing, I suggest O2 100% - 0% above and Ar 0% - 100% below. This goes for Fig. 4 and 5 also.
Reply: The Figures have been changed as suggested.
Line 213 is not in agreement with Fig. 6, air seems to be better than Ar. The explanation in line 213 is also a bit vague.
Reply: Ar was a typo and has been changed to air accordingly. Moreover the explanation has been extended in the revised manuscript: “The latter is due to the formation of polar-containing groups, which resulted in the highest wettability and therefore the bonding strength between the contacting substrates (PU/Scotch tape) increased as well. Moreover, the highest surface roughness was observed for PU plasma treated in air, which also contributed to the peel resistance increase.”
Line 219-222, unnecessary long run-on sentence.
Reply: This sentence briefly should introduce the reader to the objective of the section. However the authors agree with the reviewer that the sentence is too long and therefore it has been shortened: “The contact angle of water was measured over a month-long period for samples in ambient air conditions to study the stability of the introduced polar groups.”
Line 224, How were the aged CA measured, on the same aged sample over time or on a fresh, aged sample every time?
Reply: This CA has been measured on the same aged (stored) sample but every time from different surface area that was not affected by previous measurement.
Line 230, Fig. 7, consider another break in the "Aging time" axis to properly show the shorter aging times or maybe consider a logarithmic scale.
Reply: Figure 7 has been updated with detailed Figure showing shorter aging times (from 1 to 24 hrs).
Line 250, Fig. 8, I cannot find a result for Ar after 500 h?
Reply: Authors thank you for this notice. The missing value of peel resistance has been included in Figure 8.
Line 279, Untreated sample is usually presented first for comparison/reference. Air and the untreated sample have a sum different than 100%.
Reply: Table 1 has been rectified accordingly. The incorrect sum of the atomic percentages caused by number rounding has been corrected.
Line 283 is not in agreement with Table 1.
Reply: This typo has been rectified.
Line 288, 15,9 to 16,6 cannot be called a noticeable increase
Reply: The sentence was corrected: “The percentage of oxygen atoms noticeably increased after plasma treatment for all the gases used except N2 (slightly increase), which indicated that the number of oxygen-containing functional groups increased relative to that of the untreated sample.”
Line 311, I strongly suggest consulting a specialist for roughness measurements! Sa is not "root mean square"!
Reply: The incorrect interpretation of Sa has been corrected with “arithmetical mean height.”
How many roughness analyses were performed on different areas of one sample? What is the standard deviation?
Reply: Before each measurement, the sample was carefully screened from different surface areas to ensure sample homogeneity in different surface areas and the roughness was than evaluated from related representative images. The following statement has been included in revised manuscript: “Different locations were first carefully analyzed and then the representative images of the samples were captured.”
Line 330, Ra is not surface roughness!
Reply: Surface roughness was corrected with “surface roughness parameter.”
Line 336, Do you have a reference for this claim?
Reply: This statement was made based on general assumption that higher roughness and microstructures allow better penetration of liquid resulting in higher wettability.
Lines 352, 355, What is the standard deviation of these measurements?
Reply: The Sa values were evaluated from the representative images of individual samples.
Line 358, Fig 15a and 16a are not like lines 140-142 suggest. I understand it is difficult to observe polymers with SEM, but maybe you should try different magnification to obtain high resolution images. These two images are useless.
Reply: There was not possible to obtain better resolution even after gold sputtering because of non-conductive polymer substrate. The SEM images have been omitted.
Line 363, Ra is not "root mean square"!
Reply: The incorrect interpretation of Ra has been corrected with “arithmetical mean height of a line.”
I have serious doubts about the efficiency of your plasma system and the results concerning oxygen being the least appropriate for hydrophilicity improvement.
Reply: This phenomenon was observed also for gas mixtures, while a presence of O2 caused the wettability decrease. Moreover, the same trend was observed also for treatment of polyethylene in our previous study.
Reviewer 2 Report
This work described some results with regards to the surface functionalization of polyurethane by means of cold plasmas in different gas mixtures. This work has certain practical interest and, indeed, it can be interesting for some engineers, who are looking for cheaper and more efficient methods for surface modifications of PU.
However, this work has certain issues that must be solved:
1) XPS. Authors reported only elemental compositions changes, without standard deviations and descriptions how they did measured and calculated these values. I mean that it seems that you used wide scans for elemental quantification, but the errors for such method is very large, especially when you want to see the differences of 0.1-0.5 at.%. You need to do High-Resolution spectra for C1s, N1s and O1s (or report if you did and put Figs in main text or Support info). Please look at the changes of carbon and nitrogen environments. That is very important! And if you want to see so tiny changes in concentration of nitrogen, please measure 3 times each sample.
2) FT-IR. Fig9 is not informative, I cannot see anything from those spectra that are nearly merged one to another
3)Overal. Too many Figures, 18!!! Many pf them are not informative (e.g. abundant AFM and SEM).
4) There are some typos and some errors. E.g. Line 261 Error with Refs
Author Response
This work described some results with regards to the surface functionalization of polyurethane by means of cold plasmas in different gas mixtures. This work has certain practical interest and, indeed, it can be interesting for some engineers, who are looking for cheaper and more efficient methods for surface modifications of PU.
However, this work has certain issues that must be solved:
1) XPS. Authors reported only elemental compositions changes, without standard deviations and descriptions how they did measured and calculated these values. I mean that it seems that you used wide scans for elemental quantification, but the errors for such method is very large, especially when you want to see the differences of 0.1-0.5 at.%. You need to do High-Resolution spectra for C1s, N1s and O1s (or report if you did and put Figs in main text or Support info). Please look at the changes of carbon and nitrogen environments. That is very important! And if you want to see so tiny changes in concentration of nitrogen, please measure 3 times each sample.
Reply: The authors thank reviewer for his valuable comments. Unfortunately, high-resolution spectra for C1s, N1s, O1s were not obtained. Each sample was measured only once and therefore no SD was provided. However, the RF generated plasma is homogeneous and therefore we believe that PU samples were treated homogeneously (small SD from wettability measurement). The reproducibility of XPS results for RF plasma treated polymeric samples was previously proven.
2) FT-IR. Fig9 is not informative, I cannot see anything from those spectra that are nearly merged one to another
Reply: Figure 9 has been modified to be more visible. The most important are changes in the peek area associated with urethane group.
3)Overal. Too many Figures, 18!!! Many pf them are not informative (e.g. abundant AFM and SEM).
Reply: SEM images have been omitted in revised manuscript because of lacking high resolution.
4) There are some typos and some errors. E.g. Line 261 Error with Refs
Reply: Typos and errors have been corrected. Error in this line was corrected as well.
Reviewer 3 Report
Dear authors,
The manuscript coatings-984167-peer-review-v1, entitled ‘Surface functionalization of a polyurethane surface via radio-frequency cold plasma treatment using different gases’ presents the possibility and limitations of improving the hydrophobic surface properties of polyether-based polyurethane (PU) films (~200 µm thick, American Polyfilm, USA) by medium-pressure (~30 Pascal) low-temperature and low power (50-120W) RF plasma treatment, with special attention on the plasma-gas composition (air, O2, Ar, N2 and mixture of them). The authors attention was directed to parameters that critically alter the surface wettability (such as: surface energy, morphology, surface chemistry), and long-term aging studies were performed to analyze the stability of this plasma treatment polymeric surfaces.
Characterization methods, such as: static contact angle measurements (SCA), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) analyses, optical microscopy profilometry, atomic force microscopy (AFM), scanning electron microscopy (SEM), and peel adhesion tests were used by the authors of the manuscript for verifying the successful functionalization of the plasma treated polyurethane.
The results are presented well, supported by adequate images and graphs (with good resolution) revealing the infos needed to sustain the conclusions drown by the authors.
Overall, the manuscript is well written, with many techniques / methods described for the characterization of the plasma-treated polymer films, with good correlation between the obtained results.
However, there are some clarifications that MUST be made in the experimental set-up / working conditions part of the manuscript:
- on page 3, first paragraph: ‘2.2. Plasma treatment of PU films’ some infos upon the plasma polymer treatment conditions MUST be made:
- a) a schematic with the plasma reactor should be inserted in order to visualize the plasma region for polymer exposure
- b) the total / partial working pressure MUST be mentioned, as the sentence on the lines 98-99: ‘The chamber was evacuated to a vacuum level of about 27 Pa, and the treatment time 98 was applied from 10 s up to 180 s at 50-120 W of nominal power and 10 cm3 min-1 of gas flow. ’is rather confusing. What was the total pressure during the plasma treatment process?
- c) the flow rate of all gases was identical: ~10 sccm? How was the mixing of gases made? A mass flow controller or a mixing system was used?
- d) The gas / gas mixture flow in the reactor chamber was during the whole experiment, eg 10s- 180s, or the discharge chamber was filled with gas and till a certain pressure and then the treatment was performed? What is the discharge type? Is it a glow discharge? Please put these infos into the manuscript.
- e) What about the discharge temperature? Was the temperature measured during the plasma treatment process and if so, were it was measured? Is it near the polymer sample, or in the chamber? Please specify this aspect.
The above information’s must be added, since starting with the title of the manuscript authors have plasma polymer treatment.
- Moreover, the following figures should be remade to ensure better visualization to the reader:
- a) on page 11, figures 11 and 12, concerning the morphology resulted from optical profilometry, should be properly tilted in order for the reader to clearly view the 3D details on the surface.
- b) on pages 13 – 14 - 15, figures 15 and 16, the SEM figures, I notice the ‘bad’ signal to noise ratio and poor focus, making rather hard for the reader ( if he is not familiar with this technique) to draw the same conclusion as the authors.
- c) on pages 15 – 16, figures 17 and 18, the AFM 3D topography images, also are not on the best ‘view angle’ displayed. A ‘regular’ reader would not see much differences between them. Please change the angle or switch to another program for visualizing the images ( eg. Gwyddion , http://gwyddion.net/).
The conclusions are in brief but sustained (most of the conclusions) by the experimental findings, BUT THEY ARE ‘VERY’ BRIEF AND GENERAL. The authors should rewrite the conclusions ( extend them)
In the end, based on their experimental findings, the authors concluded that the plasma treatment led to surface morphological / topography changes that featured notable textured structures on the outer layer of the PU film. Their experimental findings revealed considerable changes in the surface roughness indicating the effect of etching due to ion bombardment (from the plasma) on the film interface.
I propose that this manuscript can be accounted for publishing after MINOR REVISIONS in the journal COATINGS.
Author Response
The manuscript coatings-984167-peer-review-v1, entitled ‘Surface functionalization of a polyurethane surface via radio-frequency cold plasma treatment using different gases’ presents the possibility and limitations of improving the hydrophobic surface properties of polyether-based polyurethane (PU) films (~200 µm thick, American Polyfilm, USA) by medium-pressure (~30 Pascal) low-temperature and low power (50-120W) RF plasma treatment, with special attention on the plasma-gas composition (air, O2, Ar, N2 and mixture of them). The authors attention was directed to parameters that critically alter the surface wettability (such as: surface energy, morphology, surface chemistry), and long-term aging studies were performed to analyze the stability of this plasma treatment polymeric surfaces.
Characterization methods, such as: static contact angle measurements (SCA), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) analyses, optical microscopy profilometry, atomic force microscopy (AFM), scanning electron microscopy (SEM), and peel adhesion tests were used by the authors of the manuscript for verifying the successful functionalization of the plasma treated polyurethane.
The results are presented well, supported by adequate images and graphs (with good resolution) revealing the infos needed to sustain the conclusions drown by the authors.
Overall, the manuscript is well written, with many techniques / methods described for the characterization of the plasma-treated polymer films, with good correlation between the obtained results.
However, there are some clarifications that MUST be made in the experimental set-up / working conditions part of the manuscript:
- on page 3, first paragraph: ‘2.2. Plasma treatment of PU films’ some infos upon the plasma polymer treatment conditions MUST be made:
- a) a schematic with the plasma reactor should be inserted in order to visualize the plasma region for polymer exposure
Reply: The authors thank reviewer for all valuable comments. The scheme of plasma system, which was already published, has been referred in the revised manuscript. Moreover, some additional information has been included as well: “This equipment is consisted of a cylindrical chamber made of aluminum (25 cm in diameter and 28 cm deep). A capacitive parallel plate design allows generating nominal power with a maximum of 120 W. All the operational parameters are fully controllable by the PC software, such as treatment time, nominal power, gas flow, gas mixture flow, for achieving an optimal plasma treatment process of the samples.”
- b) the total / partial working pressure MUST be mentioned, as the sentence on the lines 98-99: ‘The chamber was evacuated to a vacuum level of about 27 Pa, and the treatment time 98 was applied from 10 s up to 180 s at 50-120 W of nominal power and 10 cm3 min-1 of gas flow. ’is rather confusing. What was the total pressure during the plasma treatment process?
Reply: The total pressure during the plasma treatment was 27 Pa. There was continuous gas flow in and out during plasma treatment and the system regulates pressure automatically to keep it constant during plasma treatment process. The text has been updated with: “The working pressure was about 27 Pa,… .”
- c) the flow rate of all gases was identical: ~10 sccm? How was the mixing of gases made? A mass flow controller or a mixing system was used?
Reply: This plasma system contains gas flow controller allowing setting up flow rate by the software.
- d) The gas / gas mixture flow in the reactor chamber was during the whole experiment, eg 10s- 180s, or the discharge chamber was filled with gas and till a certain pressure and then the treatment was performed? What is the discharge type? Is it a glow discharge? Please put these infos into the manuscript.
Reply: The gas flow in the reactor was kept constant during the whole plasma treatment. Discharge type is capacitively coupled radio-frequency plasma (glow discharge). It has been included in the revised manuscript: “This equipment generates capacitively coupled radio-frequency plasma (glow discharge) and it is consisted of a cylindrical chamber made of aluminum (25 cm in diameter and 28 cm deep). A capacitive parallel plate design allows generating nominal power with a maximum of 120 W. All the operational parameters are fully controllable by the PC software, such as treatment time, nominal power, gas flow, gas mixture flow, for achieving an optimal plasma treatment process of the samples.”
- e) What about the discharge temperature? Was the temperature measured during the plasma treatment process and if so, were it was measured? Is it near the polymer sample, or in the chamber? Please specify this aspect.
Reply: Unfortunately, we don’t have probe (Langmuir) to monitor the discharge temperature in our system. However, the temperature in the reactor is about 40-50 °C as was evaluated based on the treatment of polyethylene wax whith specific melting points.
The above information’s must be added, since starting with the title of the manuscript authors have plasma polymer treatment.
- Moreover, the following figures should be remade to ensure better visualization to the reader:
- a) on page 11, figures 11 and 12, concerning the morphology resulted from optical profilometry, should be properly tilted in order for the reader to clearly view the 3D details on the surface.
Reply: Profilometry images have been modified for better clarity.
- b) on pages 13 – 14 - 15, figures 15 and 16, the SEM figures, I notice the ‘bad’ signal to noise ratio and poor focus, making rather hard for the reader ( if he is not familiar with this technique) to draw the same conclusion as the authors.
Reply: The Figure 15 and 16 have been omitted because of not adequate quality.
- c) on pages 15 – 16, figures 17 and 18, the AFM 3D topography images, also are not on the best ‘view angle’ displayed. A ‘regular’ reader would not see much differences between them. Please change the angle or switch to another program for visualizing the images ( eg. Gwyddion , http://gwyddion.net/).
Reply: The angle of AMF images has been changed for better clarity.
The conclusions are in brief but sustained (most of the conclusions) by the experimental findings, BUT THEY ARE ‘VERY’ BRIEF AND GENERAL. The authors should rewrite the conclusions ( extend them)
Reply: The conclusions have been extended.
In the end, based on their experimental findings, the authors concluded that the plasma treatment led to surface morphological / topography changes that featured notable textured structures on the outer layer of the PU film. Their experimental findings revealed considerable changes in the surface roughness indicating the effect of etching due to ion bombardment (from the plasma) on the film interface.
I propose that this manuscript can be accounted for publishing after MINOR REVISIONS in the journal COATINGS
Round 2
Reviewer 1 Report
I would like to thank the authors for considering my suggestions. I recommend the new manuscript to be accepted for publication.
In the future please keep in mind:
R - line-profile roughness
S - surface roughness
a - mean height
q - root mean square
...
Kind regards
Author Response
I would like to thank the authors for considering my suggestions. I recommend the new manuscript to be accepted for publication.
In the future please keep in mind:
R - line-profile roughness
S - surface roughness
a - mean height
q - root mean square
Reply: The authors thank reviewer for his valuable comments, which resulted in correction of these mistakes.
Reviewer 2 Report
Very unfortunately, authors did not provide High Resolution spectra and standard deviations for their measurements of XPS.
In this case please refere to literature and provide refs where you confirmed the reliability of your treatments and surface compositions. Second, please add disclaimer that all your changes are withing error margin of the measuerement, This is absolutely necessary unless you provide data with standard deviations.
Author Response
Very unfortunately, authors did not provide High Resolution spectra and standard deviations for their measurements of XPS.
In this case please refere to literature and provide refs where you confirmed the reliability of your treatments and surface compositions. Second, please add disclaimer that all your changes are withing error margin of the measuerement, This is absolutely necessary unless you provide data with standard deviations.
Reply: The XPS results regarding plasma treatment reliability have not been published but for example at.% of O1s and N1s for plasma treated polyethylene measured from different spots was 20.32±0.49 and 3.54±0.54, respectively. The following statement was included in revised manuscript: "The chemical composition was obtained from one measurement of each sample and therefore the chemical composition is within an error margin of the measurement."
