A Study on the Susceptibility of PLA Biocomposites to Drilling
, Radosław Auriga 1, Jacek Wilkowski 1, Alicja Auriga 2, Adrian Trociński 3 and Lee Seng Hua 4
Round 1
Reviewer 1 Report
This manuscript is novel, well-structured, and informative. Authors are required to make a minor revision to render the paper publishable. The following comments must be addressed:
1) Citations should b double-checked. Some references do not seem to be correct. For example, reference 11 in line 47 is double-written.
2) Please add high-quality photos of the samples (panels) to the materials and methods.
3) Methods for statistical comparison should be added to materials and methods.
4) Results of the present research must be compared with the findings of previous studies and similarities and differences have to be discussed.
Author Response
This manuscript is novel, well-structured, and informative. Authors are required to make a minor revision to render the paper publishable. The following comments must be addressed:
1) Citations should be double-checked. Some references do not seem to be correct. For example, reference 11 in line 47 is double-written.
Thank you for that remark, the citation has been reviewed and correct in the whole manuscript.
2) Please add high-quality photos of the samples (panels) to the materials and methods.
Photos of the specimens has been placed in section Materials and Methods according to the Reviewer’s suggestion (Figure 1, pg 3)
3) Methods for statistical comparison should be added to materials and methods.
Statistical methods has been added to the Materials and Methods section.
4) Results of the present research must be compared with the findings of previous studies and similarities and differences have to be discussed.
The test results are related to the literature data as far as it is possible. It is not possible to compare the results of drilling samples to a large number of findings, as the literature is very limited in the scope of the studies presented.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Dear Authors, I find your work entitled ``A study on the susceptibility of PLA biocomposites to drilling`` interesting and suitable for the Journal, I think it can be published after addressing some minor comments listed below:
Line 14: please define the acronyms the first time they appear in the text, even if it is in the abstract
Abstract: I suggest to include some numerical results in the abstract
Line 47: please remove one of the two “11”
Introduction: please add the research hypotheses or research questions at the end of introduction section
M &M section: please add a sub-section reporting the description of the statistical analysis
Please change the name of the section from ``Results” to “Results and Discussion”
Figure 4 should be Figure 3, please correct
Author Response
Dear Authors, I find your work entitled ``A study on the susceptibility of PLA biocomposites to drilling`` interesting and suitable for the Journal, I think it can be published after addressing some minor comments listed below:
Line 14: please define the acronyms the first time they appear in the text, even if it is in the abstract
Thank you for that comment, all the acronyms have been defined according to the Reviewer’s suggestion.
Abstract: I suggest to include some numerical results in the abstract
The sentence: “Regardless of the composite formulation, composites based on PLA had a 25 to 56% higher axial forces during drilling than HDPE …” has been introduced into abstract.
Line 47: please remove one of the two “11”
Thank you, it has been removed.
Introduction: please add the research hypotheses or research questions at the end of introduction section
The following phrase has been added: Based on the available literature the hypothesis that the drilling process will be affected by the composition of WPC composites was formed.
M &M section: please add a sub-section reporting the description of the statistical analysis
Fixed according to the Reviewr’s comment.
Please change the name of the section from ``Results” to “Results and Discussion”
Changed according to the Reviewr’s comment.
Figure 4 should be Figure 3, please correct
Thank you for this remark, all Figures have been checked and corrected.
Author Response File: Author Response.docx
Reviewer 3 Report
Dear authors,
It is an interesting work, but the explanations are not clear and consistent. I suggest improving the content of Results and Conclusions chapters taking into consideration the remarks from the report. The abstract must also be modified according to the results obtained.
Comments for author File: 
Comments.pdf
Author Response
It is an interesting work, but the explanations are not clear and consistent. I suggest improving the content of Results and Conclusions chapters taking into consideration the remarks from the report. The abstract must also be modified according to the results obtained.
peer-review-23921402.v1.pdf
Line 15: Please add after conifer bark: …… with different size (large and small). (Or add some dimensions of these particles!)
The sentence has been rewritten according to the Reviewer’s comment.
Line 16: Replace or with and
The sentence has been rewritten according to the Reviewer’s comment.
Line 16: Add 3% :… the addition of 3% additives …
The sentence has been rewritten according to the Reviewer’s comment.
Line 17: Add density profile ….were examined for the density profile and their susceptibility to drilling….
The sentence has been rewritten according to the Reviewer’s comment.
Line 19: Please, reformulate. Add also density. The matrix had influence on density and as a consequence on drilling….
The sentence has been rewritten according to the Reviewer’s comment.
Lines 24-25: Please reformulate. The statistical analysis indicated that the additives had greater influence on HDPE than PLA….
The sentence has been rephrase according to the Reviewer’s comment.
Keywords: Please add: HDPE, lignocellulosic filler, density
The keywords have been changed according to the Reviewer’s comment.
Line 34: Please, try to add another reference avoiding self-citation
The authors would like to emphasize that the self-citation results from the limited literature in the context of emerging citation. However, a new reference has been added in the text: doi:10.3390/ma9060435.
Lines 36-38: To be convincing, it is good to add that the composite materials with PLA are ecological also due to the fact that the filling material is made of: wood fibers, shredded post-consumer wood materials……….
The following has been added: “The composite materials with PLA are ecological also due to the fact that the filling material is made of wood fibers”.
Line 54: Add other references if possible, to avoid self-citation. Please add other references about machining of composites made with PLA since this is the subject of your research
Mention first that most of studies are on physical, mechanical or biological properties of these kind of composites (and add some references like : https://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2019000400599
or https://www.sciencedirect.com/science/article/pii/S2238785422002423
https://www.researchgate.net/publication/280287142_Biocomposites_of_Wood_Flour_and _Polylactic_Acid_Processing_and_Properties
and there are just few related to machining:
see: https://www.researchgate.net/publication/273632494_Hole_making_in_natural_fiber-reinforced_polylactic_acid_laminates_An_experimental_investigation
https://www.tandfonline.com/doi/abs/10.1080/15440478.2020.1764435?journalCode=wjnf 20
It should be noted that the literature on the mechanical processing of this type of composite is limited. Of the publications cited by the Reviewer, only one deals with the subject of machining. The others describe only the properties of composites. Nevertheless, we are grateful for pointing out the position regarding drilling. The relevant paragraph regarding this publication has been added to the manuscript.
"Bajpai et al. (2015) studied the drillability of laminates based on PLA and natural fiber (sisal and Grewia optiva fiber). The authors indicated a significant impact on the quality and efficiency of machining drill types and cutting parameters. At the same time, the tests did not show the influence of the type of natural fibers on the cutting forces”
Lines 68-72: Here you have to explain clearly the objective of the work.
Please, change the sentence: e.g….Based on the research carried out so far, and due to the fact that the drilling is the most important machining operation in the processing of wood based materials intended for use in the furniture industry…, the authors consider necessary to study the behavior to drilling of WPC composites with polylactic acid (PLA) and high-density polyethylene (HDPE)..
The sentence has been rewritten according to the Reviewer’s comment.
- MATERIALS AND METHODS
Line 83: Please, mention here the size obtained.
‘ >35 and 10-35 mesh’ has been added.
Table 1: Check the size of mesh! Which is the difference between small and large particles, since you have <35 and 10-35 mesh???
Thank you for that remark, there was a mistake in the manuscript (table 1 and 2; it supposed to be ‘>35 mesh’) which has been improved in the text now.
Line 89:….probably … the granules obtained (not granulate!)
Corrected.
Line 112: Please, add a scheme with the points of drilling in a plate.
Appropriate information has been included in Materials and Methods.
In this chapter it should be mentioned the method used for statistical analysis.
Appropriate information has been added in the section.
- RESULTS
Line 118: Please, reformulate. You cannot say that it is no effect. There are in case of PLA, increases of density with 3-10% (when compare large bark particles with sawdust large particles e.g in table 3). It is better, slight influence, since it is a small influence of bark large particles on the density of PLA compared to sawdust large particles even in those with additive. 3
The sentence has been rewritten according to the Reviewer’s comment.
Lines 129-130: Please, explain what means this difference of 100 kg/m3 or 200 kg/m3 (between faces and core…!? ) In which type of board is greater? This density profile was obtained by others researchers? Add some references.
Differentiation of density on the cross-section occurs in traditional wood-based panels. It can amount to several hundred kg/m3. In the case of WPC composites, this variation is much smaller and amounts to max. 200 kg/m3. It is difficult to identify the inner and outer layers in this type of composites.
Line 132: Please, add another reference if possible to avoid self-citation
These studies are pioneers, therefore, literature is very limited.
Line 137: It is better, slight influence (see line 118 explanations!)
The sentence has been rephrase according to the Reviewer’s comment.
Lines 141-142: Please, reformulate based on the results presented in fig 2. There are values of axial force of around 15 N in HDPE and between 20 N and 35 N for PLA! More homogenous values for HDPE and high variation for PLA! Why ?
The reason might be that PLA is more brittle and HDPE is more flexible .
In line 148 you discussed that there are differences and these differences are related to the density!
Where is Figure 3?
The numbers of figures have been fixed.
Line 150: Please, reformulate. In HDPE axial forces are smaller than PLA. How smaller are?? Give values in %. What determined these increases in HDPE? From fig 4 the values of HDPE are more homogenous than in case of PLA!! Can explain this?
Again, it might be related to the materials’fitures: PLA is more brittle and HDPE is more flexible . The authors also notice mistake in results interpretation, the axial forces in HDPE did not increase but decreased.
There is a contradiction in your statement between line 118, line 137 and lines 167-168. They don’t have effect on density but had effect on axial forces! Please, be more clear in your explanations and consistent.
There are no contradictions at all in the statements described in the article. In lines 118 and 137 the authors discuss the tested factors in terms of the density of the produced boards. In line 167-168, the influence of the tested factors on the axial forces during drilling is discussed.
In the case of WPC, density should not be directly combined with axial forces during drilling. The properties of the matrix (PLA or HDPE) will have a much greater impact than density.
Lines 173-174: What means thicken? Please, reformulate.
The ‘thicken’ has been change to ‘compacted’. This term is related to mechanical compaction.
- CONCLUSIONS
Line 222: Based on Fig 5 values of axial forces are greater in samples with additives for PLA compared to HDPE.
Thus, it is important to emphasize that this increase in the case of PLA is due to other factors, not because of the presence of additives. In the case of HDPE, additives had a greater contribution in increasing the values of axial forces than other non-studied factors.
Conclusion 4 has been corrected: “The increase in axial forces in the case of PLA was due to other factors than the presence of additives. In the case of HDPE, additives had a greater contribution in increasing the values of axial forces than other non-studied factors.”
Author Response File: Author Response.docx
