Use of Thymus Plants as an Ecological Filler in Urea-Formaldehyde Adhesives Intended for Bonding Plywood
, Zineb El Montassir 2, Ayoub Ainane 2, Said Gharby 3, El Hassan Sakar 4, Ali Merito 1, Jalludin Mohamed 1 and Tarik Ainane 2
Round 1
Reviewer 1 Report
77 What parts of the plant were used should be better described. Was the whole plant used?
12 Did you measure the density with a hydrometer? Please, define the device better. Viscometer was not at all describe.
Please, could you describe better of Statistical Analysis. How many samples were measured?
19 Are you sure DTA and GTA thermal analysis is the good name of paragraph? GTA or TGA? Please edit the entire section. Figure 4 of thermogravimetric Analysis (TGA) is weakly described in the text.
21 Figure 5 has a bad descripion. It is not TGA but FITR.
Why did you decide to use medicinal plants?
Author Response
Dear Reviewer,
First of all, we thank you for the comments and remarks that you have given us. really, they gave added value to our work.
Below, you find all the answers to your comments.
In a favorable response, please accept our sincere greetings.
C1. What parts of the plant were used should be better described. Was the whole plant used?
For this work, for each plant, the aerial part which has been used as filler. (line74)
C2. Did you measure the density with a hydrometer? Please, define the device better. Viscometer was not at all describe.
We have added the description of the devices used for the measurement of viscosity and density (lines 117 and 122)
C3. Please, could you describe better of Statistical Analysis. How many samples were measured?
we used 3 replicates for each test.
a sentence was added at the beginning of this paragraph (line 139)
C4. Are you sure DTA and GTA thermal analysis is the good name of paragraph? GTA or TGA? Please edit the entire section. Figure 4 of thermogravimetric Analysis (TGA) is weakly described in the text.
We have corrected the title of this paragraph.
We have corrected the abbreviation for thermogravimetric analysis (TGA) throughout the manuscript.
C5. Figure 5 has a bad descripion. It is not TGA but FITR.
We have corrected the title of figure 5.
C6. Why did you decide to use medicinal plants?
In the context of minimizing the consumption of fillers intended for the wood industries, we had the idea of using natural substances that can replace chemical products. In this regard, medicinal plants play a very important role in various industrial applications, moreover, they are rich in secondary metabolites which can introduce into the mechanisms involved in the preparation of adhesives.
The choice of this type of plants of the Thymus genus comes down to the availability of biomass, which is less expensive.
According to the results obtained, it should be noted that these natural substances can replace the other chemical substances included in this preparation and can also reduce the emission of formaldehyde.
Reviewer 2 Report
Very interesting and actual study comprising several thymus species as additive in the UF adhesive formulation to scavenger free formaldehyde. However, the accessibility and costs of the plants should be taken into account and described better in the introduction of the manuscript. The study demonstrates that, replacing 15% of starch filler in UF formulation by thymus powder, only one meaningful benefit is achieved – free formaldehyde content decreased by 0.1% that is not big improvement in spite of statistical significance approved. To enrich the study and to get the full picture of the thymus plant impact on the formaldehyde behavior, it would be also very worth to detect the formaldehyde emission rate in the panels bonded with the elaborated AFs.
Abstract: “In the lab, adhesive formulations made using urea-formaldehyde resin and based on medicinal plants have been elaborated”. Please use the right English sentence structure that could be more understandable, e.g., “An innovative adhesive formulations have been laboratory-elaborated based on urea-formaldehyde resin modified with the addition of medicinal plants”. Please take into account, that the elaborated adhesive is not based on thymus, because of it contain only 15% of thymus in the adhesive formulation. However, it could be said that modification of UF resin was made based on addition of thymus plants powder.
The second sentence in the Abstract is not clear.
Please use the united Italic style of thymus along the manuscript since it is the scientific name of botanical plants.
Keywords: “filler” and “medicinal plant” could be jointed to one, e.g., “plant filler”. I suggest also to change “adhesive characterization” instead of “characterization” and “plywood properties” instead of “mechanical properties”.
Introduction The objective of the study should include the purpose and therefore should be clarified since there is not clear why the thymus species were added to the adhesive formulations.
The sentence in the Row 36 is meaningless.
Row 48-50 The sentence should be clarified since urea, melamine and phenol are not fillers, but basic components of the adhesives. Please use “wheat flour” instead of “wheat”.
Row 54-63 The paragraph could be skipped or at least narrowed to some 3 references since it is not highly related to the topic of the manuscript and all the cited references include self-citation. You can maintain e.g., the last two sentences of the paragraph including a citation of at least one appropriate review article of independent authors.
Section 2.2.2: please give a justification for used the amount of adhesive (373 g/m2) which is very high. For example, the industry uses 140-240 g/m2 depending on adhesive, wood species and surface smoothness of the veneer. As well, the plywood industry uses hot-pressure of about 1 MPa that is 10 bars instead of 50 bars you used. The pressing time you used also differs from the used in the industry (3 min/4 mm plywood). So, please clarify your choice of the parameters. As well, please indicate the panels number fabricated per each AF.
Section 2.3 It is suggested to clarify the title as “AFs and plywood characterization techniques”.
Section 2.3.1 It is suggested to use the title “Determination of AFs Properties” instead of “Properties determination of AFs”.
Section 2.3.3 It is suggested to use the title “Determination of Plywood Properties” instead of “Mechanical properties measurements”. It is not clear why only three specimens were tested per each mechanical property since the dimensions of the panel were large. Please indicate the place of the specimens in the panel sample tested for the mechanical properties.
Section 3.1 It is suggested to supplement the title as “Physical-Chemical Properties of AFs.
Section 3.2 It is suggested to supplement the title as “Characterization of AFs”. Please use the “μm” instead of “m” to characterize the SEM resolution. The thymus powder content (15%) in AFBS is high enough you used. Was the presence of thymus not observed in the SEM images? Does it mean that the plant powder was fully solved in UF adhesive system?
Section 3.2.3 It is enough to mention only “Thermal Analysis” in the title instead of “Thermal analysis DTA and TGA”. The both denominations include the words of “thermal” and “analysis”, therefore, there is not necessary to use, e.g., “DTA thermal analysis”. Use “TGA” instead of “GTA” (Row 191, 198).
Row 194-197 Please supplement the statement providing the temperature ranges for formaldehyde polymerization of the samples and highlighting the differences between the samples of reference (SAF) and AFBP, these are evident above 240℃ in Figure 3.
Row 198-200 Please supplement the paragraph highlighting the differences between the samples of SAF and AFBP, these are evident at temperature range of ~300 - 400℃ in Figure 4.
Row 226-228 The statement is not correct since the replacement of one eco-friendly filler (starch) by another (thymus) does not make a sense especially if the properties of plywood are not improved.
Section 3.3 It is suggested to rename the title to e.g., “Mechanical Properties of Plywood”. It is suggested to supplement the section by evaluation of mean apparent cohesive failure of plywood samples after the shear strength test according to the standard EN 314-1.
Tables 2 and 3. Please add the letter evaluation according to the comment below the tables “Different letters in the same row indicate significant differences according to Tukey's test (p < 0.05)”.
Figures 2, 3 and 5: please include all designations of the samples represented in the figures. It is suggested to add endo/exo directions or zero line at the Y-axis of the Figure 3.
Discussion It is suggested to supplement the section by comparison of your study and achieved data with other similar studies contributed to modification of UF adhesives for application in plywood manufacture.
References The references 22 and 23 are the same.
Author Response
Dear Reviewer,
We are lucky that you have given us relevant remarks, and to this end our team would like to thank you for your scientific quality.
You will find attached a WORD document which contains the details of the responses to all the comments proposed.
In anticipation of a positive response, please accept our best regards.
Author Response File: 
Author Response.pdf
Reviewer 3 Report
Line 20, 190, 198, 252 - What is GTA?
Line 52 - Flour as a filler in adhesives does not "waste" grain resources, because the flour used is not food grade and cannot be used as food.
Line 103 - What is "cheese essence veneer"?
Line 105 - Gluing is not clear. Is 373g/m2 the amount on each piece of veneer or on two pieces of veneer?
Figures 2, 3, and 5 have curves that are not identified. Figure 5 is not thermogravimetric analysis.
Line 195 - How does DTA identify a "high quantity formaldehyde?"
Line 198 - Why are the endothermic peaks by DTA and mass losses by TGA important? Especially since the temperatures at which they occur are above the bonding temperature, so the adhesives are never exposed to these temperatures.
Line 213 - Are these results for phenol? If so, they are irrelevant.
Line 227 - Why does adding Thymus plants instead of flour make the adhesive eco-friendly? Flour is also from a plant.
Line 258 - Thymus plants may be easy to obtain, but not in the quantity needed as a filler for adhesives.
Line 264 - A reduction of only 28% in the free formaldehyde is not minimizing the formaldehyde.
Author Response
Dear Reviewer,
Following the comments and questions that you have proposed, you will find below, all the answers.
We thank you for your scientific quality that we have helped to represent the manuscript in good ways.
In a favorable continuation, please accept our most respectful greetings.
C1. Line 20, 190, 198, 252 - What is GTA?
We have corrected the abbreviation in the text. This is TGA (thermogravimetric analysis).
C2. Line 52 - Flour as a filler in adhesives does not "waste" grain resources, because the flour used is not food grade and cannot be used as food.
In some local industries, they use flour seized by specialist government administrations "(Customs or fraud") and in some cases they use flour of cereal origin for the preparation of adhesives.
C3. Line 103 - What is "cheese essence veneer"?
We have corrected the sentence, it is: Okoume wood veneer
C4. Line 105 - Gluing is not clear. Is 373g/m2 the amount on each piece of veneer or on two pieces of veneer?
For each piece of veneer.
C5. Figures 2, 3, and 5 have curves that are not identified. Figure 5 is not thermogravimetric analysis.
The requested corrections have been made. The title of Figure 5 has been changed.
C6. Line 195 - How does DTA identify a "high quantity formaldehyde?"
During the analysis of DTA, the existence of formaldehyde may give another exothermic peak in the range (200 - 300°C), the absence of a peak proves the total reaction of formaldehyde with urea.
C7. Line 213 - Are these results for phenol? If so, they are irrelevant.
Phenol: is corresponding to the part of the phenolic compounds that exist in the fillers (plants).
We did a rewrite of the sentence
C8. Line 227 - Why does adding Thymus plants instead of flour make the adhesive eco-friendly? Flour is also from a plant.
indeed, the two substances give ecological adhesive, but the plants of the genus Thymus have other advantages: rich in molecules which can react and reduce the formaldehyde.
C9. Line 258 - Thymus plants may be easy to obtain, but not in the quantity needed as a filler for adhesives.
Currently in the local market, this type of plant is available in reasonable quantities.
C10. Line 264 - A reduction of only 28% in the free formaldehyde is not minimizing the formaldehyde.
Even though, this value that was obtained is low, but it has an advantage for the preparation of adhesives
Round 2
Reviewer 1 Report
Thanks for the correction and clarification. Your article is interesting for future research in this area.
Author Response
Dear Reviewer,
We thank you for the comments that have given added value to our work.
In a favorable response, please accept our sincere greetings.
cdly.
Reviewer 2 Report
For comments and suggestions to the authors please download the prepared PDF file.
Comments for author File: Comments.pdf
Author Response
Dear Reviewer,
You will find attached the comments of all the remarks and questions proposed.
In a favorable response, please accept our sincere greetings.
Author Response File: Author Response.pdf
Reviewer 3 Report
Several changes have not been made. If the answers in the response to reviewers were made, I could have approved the article, but I cannot.
C3. What is "cheese essence veneer" for the face veneers?
C4. It is still not clear if 373 g m-3 is the amount on each piece of veneer or the total for two pieces of veneer.
C6. DTA not showing formaldehyde was not adequately explained in the article.
The paragraph in lines 53-62 is about the properties of medicinal plants and has nothing to do with adhesives. It should be removed along with the references cited.
Author Response
Dear Reviewer,
you find the answers below.
C3. What is "cheese essence veneer" for the face veneers?
it is an internal plating model developed in the industry according to a food plating model. For these reasons, we have reformulated the paragraph in a simple manner. (lines 108-117)
C4. It is still not clear if 373 g m-3 is the amount on each piece of veneer or the total for two pieces of veneer.
the amount made of 373 g/m3 is the amount made on each piece of veneer.
C6. DTA not showing formaldehyde was not adequately explained in the article.
We added a paragraph which gives more explanations on the thermal analyzes more precisely on the free formaldehyde.
The paragraph in lines 53-62 is about the properties of medicinal plants and has nothing to do with adhesives. It should be removed along with the references cited.
We have removed the paragraph and quotes included within.
Round 3
Reviewer 2 Report
Dear authors,
the work still needs to be improved for the publication in Processes.
My comments are filled in the attached file.
Comments for author File: Comments.pdf
Author Response
Dear Reviewer,
We have made all the responses about your comments.
You will find attached a document which contains all the details
In a favorable result, please accept our sincere greetings.
Author Response File: 
Author Response.docx
Reviewer 3 Report
C4. was still not made in the manuscript, as was claimed in the response. It is still ambiguous if 373 g m-2 is the amount of adhesive on two pieces of veneer or one. This is probably the one most important number because the important strength data depends on it. This will make it difficult for someone to try to replicate the results, and if the results cannot be replicated, the research will not be taken seriously.
Author Response
Dear Reviewer,
On behalf of my team, I thank you for the interest and the time you have given to our manuscript.
Below are the responses to your comments:
C4. was still not made in the manuscript, as was claimed in the response. It is still ambiguous if 373 g m-2 is the amount of adhesive on two pieces of veneer or one. This is probably the one most important number because the important strength data depends on it. This will make it difficult for someone to try to replicate the results, and if the results cannot be replicated, the research will not be taken seriously.
We corrected the sentence to make it easier to read (lines 96-97):
The veneers were glued using a roller gluer, with a grammage of 373 g/m2 of the AFs which were distributed on both sides of core veneer.
Round 4
Reviewer 2 Report
Dear authors, please find the comments in the attachment.
Comments for author File: Comments.pdf
Author Response
Dear reviewer,
We have redone most of the suggestions requested. You will find attached a document which contains the answers to the questions asked as well as the corrections requested on the manuscript.
In a favorable response, please accept our sincere greetings.
Author Response File: Author Response.docx
