Processing and Properties of Wood-Plastic Composite Containing Alkali-Treated Birch Wood Shavings and Bioadditive Obtained by Biorefinery of Birch Bark

Round 1

Reviewer 1 Report

Dear authors,

The topic presented in your manuscript counts with a great interest for the readers, since it is related to the reclycing and the introduction of renewable filler in plastic composites. However, several points should be corrected and/or improved:

-In the abstract, what does SAs  acronym stand for?

-Authors should review the manuscript and correct some format, spelling and grammar mistakes.

-Authors should revise sentence "The usage of plastics... chemical properties. The meaning of this sentence is not clear.

-In the introduction section the objective should be described more in detail and more clearly

-In section 2.1.1 it would be of great help for the readers if a diagram of the process is included.

-On which basis was selected the ratio 95/5 rPP/PLA? Why PP alone was not used?

-Authors should improve figure 4. To which sample makes reference curve in red. This curve shows signals with negative absorbance, which is usually related to a poor background. I suggest that this spectra is reanalyzed and corrected. Moreover, the discussion of FTIR results should be ameliorated.

-Figure 7 should be corrected in terms of size and resolution. Both graphs could be inserted in the same graph for comparison purposes. Figure 8 should also be corrected concerning resolution and size.

-Regarding the discussion of TGA analysis, how it was possible that the lignocellulosic material had between 18-26% of hemicellulose (treated and untreated) and then the weight LOSS due to hemicellulose degradation was between 40-45%.

 The shift of te Tmax could be also due to cellulose and lignin that were partially degraded during the process. Either that or the structure of the lignin was changed, owing to activation, to a state more susceptible to thermal degradation.

-The authors should improve the figure 9 by using a graph based on the plots of the machine, rather thant a screeshot of the machine curves.

-Concerning the torque analysis of the composite, if the addition of the lubricant and MBS was aiming enhancements in the compatibility of the phases and procesability, then the torque should be lower, ather than higher. Authors should explain this behavior. In fact in figure 11, the reduction was not very significant.

-In table 4, standard deviation should be presented with (average) ± (standard deviation)

-In the conclusions section, it should be specified that with the adition of the lubricant, the reduction of the torque is ocurring regarding the minimum torque. But this results are not showed for the maximum value.

Should these points be improved.

Regards,

In general terms the quality of the English is good and it can be understood without big problems. Authors should though pay attention to some words that should be separated and some sentences that should be rephrase for a better understanding.

Author Response

      We would like to thank our reviewers for their valuable remarks and notes, concerning our article. We have really found all the comments, notes and remarks very useful for its approval. We would like also to apologize for the delay with our replies that was caused by both the time needing for approval of the article and vacation time.

Author Response File: Author Response.docx

Reviewer 2 Report

The authors tend to improve the process of extruding WPC. It is interesting to try new lubrication agent. However, the article need to further improved.

 Abstract: what does SA mean?

Introduction:

The authors tried to explain the challenge in compatibility, extrusion lubrication, and plastic recycle. And  rPP/PLA matrix was proposed in the end. It is obvious that the authors did not logically tie these issues together and the Introduction needs to improve.

Why do the authors put PP/PLA together, one is recycable and one is bio-degradable. In addition, they are not compabible and PLA will make the composite brittle. 

“the samples with an overall length of 63.0 mm, an overall width of 9.4 mm, a narrow section length of 9.4 mm, a narrow section width of 3.15 mm, and a thickness of 3.15 mm were for the tensile test, and the samples with a length of 80 mm, a width of 10.0 mm and a thickness of 4.0 mm for bending test were prepared.” This long sentence is confusing. It is suggested to sepereate it into two sentences.

The marking axis in the figures is not clear

In Fig. 12, what’s the content of SAs? How about the case of 7% content of SAs?

The authors used much higher content of SA lubrication agent to get better processing performance, and the whole treatment process to wood powder is so complicated. Wood powder has to be treated with NaOH, washed, and dried for a long time. It is not a practical approach. Actually, when combined with thermoplastic, no water is preffered.

If the SAs is really effective, it is suggested to add into untouched wood powders.  

Finally, it is suggested to do statistic analysis for those mechanical propterty testing. 

English language is OK. 

Author Response

      We would like to thank our reviewers for their valuable remarks and notes, concerning our article. We have really found all the comments, notes and remarks very useful for its approval. We would like also to apologize for the delay with our replies that was caused by both the time needing for approval of the article and vacation time.

Author Response File: Author Response.docx

Reviewer 3 Report

1. The abstract can be improved, please state short introduction before you put your objective and method.

2. Some formatting error need to be corrected like spacing (refer manuscript)

3. Figure 12 is blur

4. why Znst not mention earlier? what the function of Znst? as comparison?

5. Suggest to put figure of contact angle

7. Details comment has been noted in manuscript

Comments for author File: Comments.pdf

In general, English is fine and acceptable

Author Response

      We would like to thank our reviewers for their valuable remarks and notes, concerning our article. We have really found all the comments, notes and remarks very useful for its approval. We would like also to apologize for the delay with our replies that was caused by both the time needing for approval of the article and vacation time.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Dear authors,

I thank you for taking into considerations the points I raised in the previous review. You have mostly covered in an adequate way, so I estimate the article could be considered for publication. However, before that a couple of points should be clarified:

-Point 7 was already clarified by the authors but it should be pointed out. Line 327, "by  the diferential FTIR spectrum (curve in red)". Also in line 337, correct figure 4, since now it is figure 5.

-In point 8, the authors removed previous figure 7 and include a brief paragraph in lines 389-393. I still consider  it could be attached to supplementary information the figure shown in the previous version of the manuscript with the zeta potentials. In this case it should be referenced at the end of line 393.

Author Response

Please see the attachment

Author Response File: Author Response.doc