Experimental Study on the Surface Properties of Nanoalumina-Filled Epoxy Resin Nanocomposites

Round 1

Reviewer 1 Report

The MS reports some interesting results but it needs a strong revision to improve its quality before publication.

In particular:

- Fig 2 b and fig 3 are not necessary and they can be removed

- Correlation between roughness and wettability has been reported for other bionanocomposites and the e results can be compared here (see: New J. Chem. 2018, 42 (11), 8384–8390. https://doi.org/10.1039/C8NJ01161C; ACS Appl. Mater. Interfaces 2017, 9 (20), 17476–17488. https://doi.org/10.1021/acsami.7b04297.)

- In conclusion the authors’ discus on materials “reinforced with alumina” but mechanical measurements are missed.

Author Response

The authors want to express their gratitude to the reviewer for the relevant and helpful comments. In the revised manuscript, changes and text corrections are highlighted using yellow colour.

 

 

Reviewer´s comment: “The MS reports some interesting results but it needs a strong revision to improve its quality before publication.”

Authors' reply: The author appreciates the reviewer´s comments.

 

Reviewer´s comment: “Fig 2 b and fig 3 are not necessary and they can be removed”

Authors' reply: The referred figures were removed in the revised manuscript. Consequently, the figures were renumbered.

 

Reviewer´s comment: “Correlation between roughness and wettability has been reported for other bionanocomposites and the e results can be compared here (see: New J. Chem. 2018, 42 (11), 8384–8390. https://doi.org/10.1039/C8NJ01161C; ACS Appl. Mater. Interfaces 2017, 9 (20), 17476–17488. https://doi.org/10.1021/acsami.7b04297.)”

Authors' reply: A brief and additional discussion was added in the revised manuscript. Please see new paragraph right before the conclusions section. Also, the referred studies were added in the reference list.

 

Reviewer´s comment: “In conclusion the authors’ discus on materials “reinforced with alumina” but mechanical measurements are missed”

Authors' reply: The aim of this article was to study only the surface properties of the produced epoxy resin nanocomposites (EPNCs). The mechanical properties of other samples made from the same produced EPNC where presented by the authors in previous articles (see references [1,2,28]).

 

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors should indicate the number of nanoparticles measured to produce the size distribution in figure 1.   In equation (1), I believe the sum of deviations from the average Z height would equal zero for all samples. The equation is missing the "absolute" or "modulus" function (mod x = ¦x¦) which would avoid this problem.   There is evidence of AFM tip damage or contamination in the images in figure 6 and 7, which causes the features in the image to have a triangular shape. The authors should comment on this and ensure it does not affect their measured roughness values significantly.   The authors explain their results in terms of "tougheners thermosetting". Tougheners are usually thermoplastic or elastomer particles dispersed in the epoxy matrix. What tougheners were used in these samples, and could the authors elaborate on the proposed effect on the roughness/hydrophilicity of their samples?   It may also be useful for the authors to consider the "lotus effect", the increase in contact angles on surfaces with nanoscale roughness as an explanation for their observations (see eg https://en.wikipedia.org/wiki/Lotus_effect or Nature Materials, Volume 2, Issue 7, pp. 457-460 (2003)).

Author Response

The authors want to express their gratitude to the reviewer for the relevant and helpful comments. In the revised manuscript, changes and text corrections are highlighted using yellow colour.

 

 

Reviewer´s comment: “The authors should indicate the number of nanoparticles measured to produce the size distribution in figure 1.”

Authors' reply: The size distribution presented in Figure 1 for the NPs was given by the supplier. The authors don´t have information about the number of NPs used to obtain the presented sized distribution. In the revised manuscript, the sentence related with Figure 1b was reviewed to clarify this aspect.

 

Reviewer´s comment: “In equation (1), I believe the sum of deviations from the average Z height would equal zero for all samples. The equation is missing the "absolute" or "modulus" function (mod x = ¦x¦) which would avoid this problem.”

Authors' reply: The authors agree with the reviewer. Eq. (1) was corrected in the revised manuscript.

 

Reviewer´s comment: “There is evidence of AFM tip damage or contamination in the images in figure 6 and 7, which causes the features in the image to have a triangular shape. The authors should comment on this and ensure it does not affect their measured roughness values significantly.”

Authors' reply: Thank you for your remark. As referred in Section 2.3, the surface of the samples was not polished, only cleaned. For this reason, the observation of some features in the images was already expected. However, from the several images obtained for each sample, some of them were disregarded because they presented pronounced atypical shapes in the images, probably due to contamination (AFM does not damage the polymer surface). Also, there was a certain carelessness in choosing the images to exemplify the results from AFM. Therefore, the images in Figures 6 and 7 (Figures 5 and 6 in the revised manuscript) where substituted by other ones which were effectively used to compute the average amplitude parameters. Despite some natural features are still observed in the new images, they didn´t affect significantly the results. To sustain this, the values for the coefficient of variation were added in Table 1. As it can be seen, the obtained values are in general below 20%, which can be considered acceptable. The paragraph right before Figure 5 was revised to discuss this aspect.

 

Reviewer´s comment: “The authors explain their results in terms of "tougheners thermosetting". Tougheners are usually thermoplastic or elastomer particles dispersed in the epoxy matrix. What tougheners were used in these samples, and could the authors elaborate on the proposed effect on the roughness/hydrophilicity of their samples?”

Authors' reply: Thank you for your remark. In fact, the term “tougheners thermosetting” was misused in the paragraph before Figure 8 (Figure 7 in the revised manuscript). Instead, it should refer to the “curing agent”. The referred paragraph was revised to correct this error.

 

Reviewer´s comment: “It may also be useful for the authors to consider the "lotus effect", the increase in contact angles on surfaces with nanoscale roughness as an explanation for their observations (see eg https://en.wikipedia.org/wiki/Lotus_effect or Nature Materials, Volume 2, Issue 7, pp. 457-460 (2003)).”

Authors' reply: Thank you for your suggestion. The paragraph right before Figure 8 (Figure 7 in the revised manuscript) was revised to incorporate this additional discussion. The referred article was also added in the reference list.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Revised version is suitable for publication