Composite High-k Films Based on Polyethylene Filled with Electric Arc Furnace Dust and MWCNT with Permittivity Synergetic Effect

Round 1

Reviewer 1 Report

In this paper, the author studied and fabricated composite films based on a widely used polyethylene polymer matrix and metallurgical production waste as a filler. The idea is good but some improvements.

1.       The introduction section is too basic, it should be revised with some latest and relevant literature. Also, please make a maximum of 4 to 5 paragraphs in this section.

2.       In the experimental section, relevant references are required for each used general statement.

3.       In table 1, the “S” value should be corrected.

4.       In figure 3, please label the relevant XRD peaks for a better understanding of these spectra.

5.       In Figures 4, 5, and 6 please use units in brackets.

6.       The conclusion part is too generic, please revise it with key findings.

7.       The article is full of grammatical and typo mistakes and hard to understand. English corrections are necessarily required. 

Comments for author File: Comments.pdf

Author Response

In this paper, the author studied and fabricated composite films based on a widely used polyethylene polymer matrix and metallurgical production waste as a filler. The idea is good but some improvements.

Point 1: The introduction section is too basic, it should be revised with some latest and relevant literature. Also, please make a maximum of 4 to 5 paragraphs in this section.

Response 1: Thank you for your comment. Latest and relevant literature was added and 5 paragraphs were made in Introduction.

Point 2: In the experimental section, relevant references are required for each used general statement.

Response 2: Thank you for your comment. It was corrected. (in red)

Point 3: In table 1, the “S” value should be corrected.

Response 3: Thank you for your comment. The “S” value was corrected. (in red)

Point 4: In figure 3, please label the relevant XRD peaks for a better understanding of these spectra.

Response 4: Thank you for your comment. Label the relevant XRD peaks was added.

Point 5: In Figures 4, 5, and 6 please use units in brackets.

Response 5: Thank you for your comment. It was corrected.

Point 6: The conclusion part is too generic, please revise it with key findings.

Response 6: Thank you for your comment. The conclusion part was corrected. (in red)

Point 7: The article is full of grammatical and typo mistakes and hard to understand. English corrections are necessarily required.

Response 7: Thank you for your comment. English corrections were done. (in red)

Author Response File: Author Response.docx

Reviewer 2 Report

The reuse of industrial waste including EAFD as reinforcement in metal matrix composites is not widely explored although it has shown a potential to improve mechanical properties, such as hardness and mechanical strength. The authors have used this material as a filler to improve the dielectric permittivity with some additions of MWCNTs. The most broadly used conductive fillers are carbon nanotubes (CNTs), metal particles, and graphene derivatives. Among all the Single-wall CNTs commercially available on the market. In the submitted work to Coatings/MDPI by the authors Kuznetsov et al, it has been demonstrated that higher dielectric permittivity can be improved through conductive filler / special additives. The article itself is written OK and supported with data but the main concern of this is the novelty part (being not extensively explained in appropriate sections), and the areas that require clarification are given below.

 ·         The importance of MWCNTs and their novelty must be well demonstrated in the last paragraph of the introduction. Otherwise, it leaves an impression as though it is routine work without any original ideas.

·         In the section introduction lines 81 – 84, a long sentence and the intended meaning are unclear.

·         The nature and the mechanism of the synergistic effect must be clearly articulated.

·         What is “EAFD reduced”?

·         Figure 3 the XRD peaks must be labelled.

·         Why using LDPE rather than HDPE must be discussed.

·         Are the composites prepared in this work significantly outperform the known literature data for

·         the polymer/carbon-nanotubes systems with the same SW/MWCNT content?

·         What is the conductivity of the composites?

·         In the literature (such as doi.org/10.1016/j.electacta.2014.06.039; doi.org/10.1021/ie502615w) it is reported that the increase in conductivity through the addition of the ceramic fillers inhibits the recrystallization of the polymer that enhances the conductivity. Please include these citations and discuss the synergistic effect of the composite polymer material.

·         What are the values of the imaginary part of the dielectric permittivity?

·         The clarity of Figure 1 can be improved.

·         The presence of zinc iron oxide in the XRD peaks must be referred to the XRD database (ideally good) or at least reported work earlier (such as doi.org/10.1016/j.electacta.2010.09.011).

·         What are the shiny particles seen in SEM micrographs in Fig 2b corresponds to?

·         In Figure 4, why the permittivity of the sample LDPE 25% with reduced dust 75 wt.% is significantly higher than the other samples? This trend appeared for all the samples in the presence and absence of additives.

·         Figure 6a has been shown without any explanation.

Author Response

The reuse of industrial waste including EAFD as reinforcement in metal matrix composites is not widely explored although it has shown a potential to improve mechanical properties, such as hardness and mechanical strength. The authors have used this material as a filler to improve the dielectric permittivity with some additions of MWCNTs. The most broadly used conductive fillers are carbon nanotubes (CNTs), metal particles, and graphene derivatives. Among all the Single-wall CNTs commercially available on the market. In the submitted work to Coatings/MDPI by the authors Kuznetsov et al, it has been demonstrated that higher dielectric permittivity can be improved through conductive filler / special additives. The article itself is written OK and supported with data but the main concern of this is the novelty part (being not extensively explained in appropriate sections), and the areas that require clarification are given below.

Point 1: The importance of MWCNTs and their novelty must be well demonstrated in the last paragraph of the introduction. Otherwise, it leaves an impression as though it is routine work without any original ideas.

Response 1: Thank you for your comment. It was added information about importance of MWCNTs and their novelty in the last paragraph of the introduction. (in red)

Point 2: In the section introduction lines 81 – 84, a long sentence and the intended meaning are unclear.

Response 2: Thank you for your comment. A long sentence was split into two sentences. (in red)

Point 3: The nature and the mechanism of the synergistic effect must be clearly articulated.

Response 3: The nature and the mechanism of the synergistic effect are difficult for discussion, because the filler is multiphase materials. That’s why in this work the possibility of a synergistic effect for the studied systems is only mentioned.

Point 4: What is “EAFD reduced”?

Response 4: Thank you for your comment. It was added information about this in section of Materials and Methods. (in red)

Point 5: Figure 3 the XRD peaks must be labelled.

Response 5: Thank you for your comment. The XRD peaks were labeled.

Point 6: Why using LDPE rather than HDPE must be discussed.

Response 6: Thank you for your comment. It was added information about this in Introduction. (in red)

Point 7: Are the composites prepared in this work significantly outperform the known literature data for the polymer/carbon-nanotubes systems with the same SW/MWCNT content?

Response 7: Thank you for your comment. The comparison of dielectric characteristics of the composites prepared in this work with the known literature data was added. (in red)

Point 8: What is the conductivity of the composites?

Response 8: Thank you for your comment. The information about conductivity of the composites was added. (in red)

Point 9: In the literature (such as doi.org/10.1016/j.electacta.2014.06.039; doi.org/10.1021/ie502615w) it is reported that the increase in conductivity through the addition of the ceramic fillers inhibits the recrystallization of the polymer that enhances the conductivity. Please include these citations and discuss the synergistic effect of the composite polymer material.

Response 9: Before the percolation threshold, the conductivity value changes insignificantly; after the percolation threshold, it increases by an order of magnitude. In this work, it is difficult to associate this with the recrystallization of the polymer; most likely, this is due to the contribution of the filler.

Point 10: What are the values of the imaginary part of the dielectric permittivity?

Response 10: The values of the imaginary part of the dielectric permittivity can be calculated from the ratio of the real part of the permittivity and the dielectric loss tangent. The authors decided not to show these values separately in the text of the manuscript.

Point 11: The clarity of Figure 1 can be improved.

Response 11: Thank you for your comment. The clarity of Figure 1 was improved.

Point 12: The presence of zinc iron oxide in the XRD peaks must be referred to the XRD database (ideally good) or at least reported work earlier (such as doi.org/10.1016/j.electacta.2010.09.011).

Response 12: Thank you for your comment. The XRD peaks were labeled.

Point 13: What are the shiny particles seen in SEM micrographs in Fig 2b corresponds to?

Response 13: The shiny particles seen in SEM micrographs in Fig 2b corresponds to metal phase of reduced dust.

Point 14: In Figure 4, why the permittivity of the sample LDPE 25% with reduced dust 75 wt.% is significantly higher than the other samples? This trend appeared for all the samples in the presence and absence of additives.

Response 14: This is due to the fact that this concentration of the filler is above the percolation threshold for polymer composites.

Point 15: Figure 6a has been shown without any explanation.

Response 15: Thank you for your comment. The explanation of Figure 6a was added. (in red)

Author Response File: Author Response.docx

Reviewer 3 Report

1) Kindly please enhance the language standard

2) Line 28 and 110, the unit should be provided after '130'

3) The key finding can be provided at the end of the abstract

4) Introduction may be further strengthened. The addition of EAFD can be justified with comparing existing procedure i.e. including conventional reinforcement in the polymer matrix. You may refer the follow. Thermal and mechanical behaviour of sub micron sized fly ash reinforced polyester resin composite; Multi Response Optimization on Mechanical Properties of Silica Fly Ash Filled Polyester Composites Using Taguchi-Grey Relational Analysis

5) The novelty can be given at the end of the introduction section.

6) Figure 1 quality may be improved

7) Kindly refine the conclusion section 

8) Provide reasoning for " forming larger agglomerates" would affect the characteristics.

9) Provide a suitable application which can be suited for the proposed material specimen.

Author Response

Point 1: Kindly please enhance the language standard.

Response 1: Thank you for your comment. It was corrected. (in red)

Point 2: Line 28 and 110, the unit should be provided after '130'

Response 2: Thank you for your comment. It was corrected. (in red)

Point 3: The key finding can be provided at the end of the abstract

Response 3: Thank you for your comment. It was corrected. (in red)

Point 4: Introduction may be further strengthened. The addition of EAFD can be justified with comparing existing procedure i.e. including conventional reinforcement in the polymer matrix. You may refer the follow. Thermal and mechanical behaviour of sub micron sized fly ash reinforced polyester resin composite; Multi Response Optimization on Mechanical Properties of Silica Fly Ash Filled Polyester Composites Using Taguchi-Grey Relational Analysis

Response 4: Thank you for your comment. It was corrected. (in red)

Point 5: The novelty can be given at the end of the introduction section

Response 5: Thank you for your comment. It was corrected. (in red)

Point 6: Figure 1 quality may be improved

Response 6: Thank you for your comment. Figure 1 quality was improved.

Point 7: Kindly refine the conclusion section 

Response 7: Thank you for your comment. It was corrected. (in red)

Point 8: Provide reasoning for "forming larger agglomerates" would affect the characteristics

Response 8: The formation of agglomerates inevitably reduces the area of the filler–matrix interface. This effect reduces the contribution of the Maxwell-Wagner polarization to the dielectric properties of the composites.

Point 9: Provide a suitable application which can be suited for the proposed material specimen

Response 9: Thank you for your comment. The information about a potential application for the proposed materials was added. (in red)

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The author answeres my queries, thus I am supportive of its publication in its current form. 

Reviewer 3 Report

My comments have been addressed