Inorganically modified particles FeAl-LDH@SiO2 as reinforcement in poly (methyl) methacrylate matrix composite

Silica particles were obtained from rice husk to which layered double hydroxide particles were deposited (weight ratio 1 : 1). Fe2+-Al3+ layered double hydroxides (FeAl-LDH) were synthesized by co-precipitation with ratios Fe : Al of 3 : 1 in the presence of SiO2 particles from the rice husk. Characterization of the synthesized FeAl-LDH@SiO2 particles was performed by X-ray diffraction, Fourier transforms infrared spectroscopy (FTIR) and scanning electron microscopy with EDS. Prepared FeAl-LDH@SiO2 particles were used as reinforcing agents in 1, 3 and 5 wt% quantity in poly (methyl) methacrylate matrix. The aim of this study was to examine whether FeAl-LDH@SiO2 particles affect the mechanical properties of polymer composite materials. The morphology of the composites was examined using a field emission scanning electron microscope. Microindentation, tensile and impact testing determined the mechanical properties of the obtained composites.

XRD pattern of LDH should appear in the mixture. This can be an indication that a very small amount of LDH was deposited. This information should be given in the text by using proper analysis since EDS is not quantitative. 19-Pg. 8 -Line 24 -crystal structure remains non crystalline. This is really strange, if crystals exist, the material is crystalline. 20-Pg. 8 -Line 27 -no crystalline layer of LDH. This is unlikely to be true, particles were observed with layered morphology, consequently LDH must be in the sample and crystalline material. 21-Pg. 8 -Line 33 -The absorption peaks. FTIR spectra preset bands, not peaks. Please correct all the text.

22-
Pg. 8 -Line 47 -The FeAl-LDH@SiO2 particles are randomly dispersed in the PMMA matrix, as seen in images of the composite's fracture surface. This is really to see in the images, a higher magnification and mapping the elements would give better information in this sense.

Do you have any ethical concerns with this paper? No
Have you any concerns about statistical analyses in this paper? No

Recommendation?
Accept with minor revision (please list in comments)

Comments to the Author(s)
The manuscript can be published after considering all the comments in the attached file (see Appendix A).

Decision letter (RSOS-210835.R0)
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Once again, thank you for submitting your manuscript to Royal Society Open Science and I look forward to receiving your revision. If you have any questions at all, please do not hesitate to get in touch. ********************************************** RSC Associate Editor: Comments to the Author: (There are no comments.) RSC Subject Editor: Comments to the Author: (There are no comments.) ********************************************** Reviewers' Comments to Author: Reviewer: 1 Comments to the Author(s) Royal Society Open Science -Manuscript ID RSOS-210835 The manuscript reports the purification of rice husk silica, deposition of LDH on the silica surface and use these materials as filler into PMMA. The topic is interesting and deserves publication but many corrections need to be implemented in the text before acceptance. Recommendations/changes/suggestions: 1-Pg. 1 -Line 46 -are lamellar compounds. Better to say: layered compounds 2-Pg. 1 -Line 47 -exchangeable anions. Recently it was reported that LDH can also exchange cations and even cations/anions simultaneously, please update this information. 3-Pg. 1 -Line 50 -In LDH, the metal ions must have an ionic radius similar to Mg2+ (0.65 A). The interlayer anions are carbonates, chlorides, nitrates and sulfates. The first information is not correct and the second is incomplete, organic and inorganic anions can be intercalated, please correct. 4-Pg. 3 -Line 47 -f Fe-Al LDH. A reason should be given for choosing this composition and also for the 3:1 molar ratio, which is very uncommon. 5-Pg. 3 -Line 48 -remove the pollution. Better to say: remove the contaminants. 6-Pg. 3 -Line 56 -were synthesized by a co-precipitation method. This information is incomplete, there are many different co-precipitations procedures, please explain details of the procedure. 7-Pg. 3 -line 60 -2.93 g of FeCl2·4H2O and 1.07 g of Al2(OH)5Cl·2,5 H2O. In chemistry the amounts should be given in mols, not in masses. Please convert the numbers. 8-Pg. 4 -Line 4 -The suspension. The correct term is dispersion. 9-Pg. 4 -Line 5 -6000 rpm for 10 minutes. The centrifugal force should be provided. Also, the filtering method is not a good method to avoid contaminants, better to centrifuge, remove the solution, dispersed the slurry with an ultrasound bath and repeated this procedure at least 5 times. 10-Pg. 4 -Line 18 - Figure 1 should be removed; it is too basic for this level of journal. 11-Pg. 4 -Line 20 -The set consisted of the prepolymerized powder and the monomer liquid. The complete information about these Chemical should be given to allow any reader reproduction. 12-Pg. 5 -Line 48 - Figure 2. FE-SEM micrographs of fillers a) SiO2 particles, b) FeAl-LDH and c) FeAl-LDH@SiO2. Where is Figure 2C???? 13-Pg. 5 -All the figures need to be replaced due to the low quality. 14-Pg. 5 -It is recommended that all the discussion come after each figure otherwise it is difficult to follow in the text. Use the topic results and discussion 15-Pg. 7 -Line 4 -related to the SEM images, better magnifications would better support the comments in the text. 16-Pg. 7 -Line 12 -The Fe/Al/Si ratio confirms that the majority of LDHs are found on the surface of silica particles. How the authors explain the composition of the EDS if the ratio LDH: Silica was of 1:1? This proportion is far in the analysis and no comments are provided in the text. 17-Pg. 8 -Line 19 -The XRD diffraction peaks should be indicated in interplanar distances after the position of the peaks in 2 theta and the basal distance calculated by the higher order peak possible, never the first one. The sizes of the crystalline domains can be calculated by Scherrer equation, the a and b cell parameters from the 110 peak. Which is intercalated anion? 18-Pg. 8 -Line 22 -In pattern FeAl-LDH@SiO2 from figure 3 there are no characteristic peaks of LDH structure because FeAl-LDH was synthesized in the presence of amorphous SiO2 and broad peaks of SiO2 obscured them. This is not correct, if the proportion used is true, the XRD pattern of LDH should appear in the mixture. This can be an indication that a very small amount of LDH was deposited. This information should be given in the text by using proper analysis since EDS is not quantitative. 19-Pg. 8 -Line 24 -crystal structure remains non crystalline. This is really strange, if crystals exist, the material is crystalline. 20-Pg. 8 -Line 27 -no crystalline layer of LDH. This is unlikely to be true, particles were observed with layered morphology, consequently LDH must be in the sample and crystalline material. 21-Pg. 8 -Line 33 -The absorption peaks. FTIR spectra preset bands, not peaks. Please correct all the text. 22-Pg. 8 -Line 47 -The FeAl-LDH@SiO2 particles are randomly dispersed in the PMMA matrix, as seen in images of the composite's fracture surface. This is really to see in the images, a higher magnification and mapping the elements would give better information in this sense.

Do you have any ethical concerns with this paper? No
Have you any concerns about statistical analyses in this paper? No

Recommendation?
Accept with minor revision (please list in comments)

Comments to the Author(s)
Changes to be processes based on the previous recommendations: 2-Pg. 1 -Line 47 -exchangeable anions. Recently it was reported that LDH can also exchange cations and even cations/anions simultaneously, please update this information. As it was requested, the information that LDH can only exchange anions is not correct. In 2019 a paper was published in the journal JACS indicating that LDH with a special composition can also exchange cations and even both simultaneously. This information needs to be included in the text. 4-Pg. 3 -Line 47 -Fe-Al LDH. A reason should be given for choosing this composition and also for the 3:1 molar ratio, which is very uncommon. This is not the explanation why the authors decided to use the molar ration of 3:1. The most favorable molar ratio is 2:1 and not 3:1 of 4:1, please explain as requested. 9-Pg. 4 -Line 5 -6000 rpm for 10 minutes. The centrifugal force should be provided. Also, the filtering method is not a good method to avoid contaminants, better to centrifuge, remove the solution, dispersed the slurry with an ultrasound bath and repeated this procedure at least 5 times. The centrifuga force was included. Accepted or not by the authors, filtering is definitively not the best method to remove soluble impurities. There are a lot of references using filtration, but these references should be avoided since they are using an equivocal method of purification. Authors are always using references to support the data, but they should have in mind that many papers are published with wrong data and these cannot be used as references to justify doubtfully results. When referencing use always references groups working in the area, being recognized as experts in the area and journals of high impact factors.

Recommendation?
Accept as is

Comments to the Author(s)
The authors have replied to all questions and comments. The current version of manuscript has been modified very well and it can be considered for publication as it is.

Decision letter (RSOS-210835.R1)
We hope you are keeping well at this difficult and unusual time. We continue to value your support of the journal in these challenging circumstances. If Royal Society Open Science can assist you at all, please don't hesitate to let us know at the email address below.
Dear Dr Vuksanovic: Title: Inorganically modified particles FeAl-LDH@SiO2 as reinforcement in PMMA matrix composite Manuscript ID: RSOS-210835.R1 Thank you for submitting the above manuscript to Royal Society Open Science. On behalf of the Editors and the Royal Society of Chemistry, I am pleased to inform you that your manuscript will be accepted for publication in Royal Society Open Science subject to minor revision in accordance with the referee suggestions. Please find the reviewers' comments at the end of this email.
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Once again, thank you for submitting your manuscript to Royal Society Open Science. The chemistry content of Royal Society Open Science is published in collaboration with the Royal Society of Chemistry. I look forward to receiving your revision. If you have any questions at all, please do not hesitate to get in touch. ************************************* RSC Associate Editor: Comments to the Author: (There are no comments.) RSC Subject Editor: Comments to the Author: (There are no comments.) ************************************** Reviewer comments to Author: Reviewer: 2 Comments to the Author(s) The authors have replied to all questions and comments. The current version of manuscript has been modified very well and it can be considered for publication as it is.
Reviewer: 1 Comments to the Author(s) Changes to be processes based on the previous recommendations: 2-Pg. 1 -Line 47 -exchangeable anions. Recently it was reported that LDH can also exchange cations and even cations/anions simultaneously, please update this information.
As it was requested, the information that LDH can only exchange anions is not correct. In 2019 a paper was published in the journal JACS indicating that LDH with a special composition can also exchange cations and even both simultaneously. This information needs to be included in the text. 4-Pg. 3 -Line 47 -Fe-Al LDH. A reason should be given for choosing this composition and also for the 3:1 molar ratio, which is very uncommon. This is not the explanation why the authors decided to use the molar ration of 3:1. The most favorable molar ratio is 2:1 and not 3:1 of 4:1, please explain as requested. 9-Pg. 4 -Line 5 -6000 rpm for 10 minutes. The centrifugal force should be provided. Also, the filtering method is not a good method to avoid contaminants, better to centrifuge, remove the solution, dispersed the slurry with an ultrasound bath and repeated this procedure at least 5 times. The centrifuga force was included. Accepted or not by the authors, filtering is definitively not the best method to remove soluble impurities. There are a lot of references using filtration, but these references should be avoided since they are using an equivocal method of purification. Authors are always using references to support the data, but they should have in mind that many papers are published with wrong data and these cannot be used as references to justify doubtfully results. When referencing use always references groups working in the area, being recognized as experts in the area and journals of high impact factors.
Author's Response to Decision Letter for (RSOS-210835.R1) Decision letter (RSOS-210835.R2) We hope you are keeping well at this difficult and unusual time. We continue to value your support of the journal in these challenging circumstances. If Royal Society Open Science can assist you at all, please don't hesitate to let us know at the email address below.
Dear Dr Vuksanovic: Title: Inorganically modified particles FeAl-LDH@SiO2 as reinforcement in PMMA matrix composite Manuscript ID: RSOS-210835.R2 It is a pleasure to accept your manuscript in its current form for publication in Royal Society Open Science. The chemistry content of Royal Society Open Science is published in collaboration with the Royal Society of Chemistry.
The comments of the reviewer(s) who reviewed your manuscript are included at the end of this email.
Please see the Royal Society Publishing guidance on how you may share your accepted author manuscript at https://royalsociety.org/journals/ethics-policies/media-embargo/. After publication, some additional ways to effectively promote your article can also be found here https://royalsociety.org/blog/2020/07/promoting-your-latest-paper-and-tracking-yourresults/. This study investigates the effect of adding novel biobased fillers on mechanical properties of PMMA polymers. The investigators have presented results of materials characterization and mechanical assessment results to indicate the variations in behavior of composite specimens. The content of manuscript is interesting with very good potential for future research. However, the context of manuscript must be modified before publication and novelty of research should be signified more of authors. The comments of reviewer are given below. These minor comments must be resolved before publication. Page5-line 17: you have mentioned that test samples were standard. Which standard did you use?
Page 9-line44-57: Please increase the quality of SEM images, since the details you have discussed are not clearly seen for reader.
Page 8 (last paragraph) and Page 9 (first paragraph) : you have reported dual values for the increase of hardness with addition of 3% and 5% FeAl-LDH@SiO2 fillers. Please correct this ambiguity.
Page 9-line7: You have specified that addition of fillers increases young modulus. Does it mean that addition of 50% filler materials will also result in extremely high elastic modulus? Is there a optimum number for addition of filler material to PMMA material.
The same question goes for hardness increase due to addition of filler to PMMA.
Page 9-line 15: The term "static loading experiments" does not seem to be applicable to your research since you have performed test by varying load over time with a constant speed of 0.5mm/min. Please clarify if you have done tests under quasi-static loading (constant increase of load over time) or fixed load over specific time intervals.
Page 9-line 16: what do you mean by ability of material to deform? Does it mean ductility? Failure strain? Table 3: what do you mean by σ, K and ε? Please define them in the text.

Appendix A
There is contradiction in authors' statements in last paragraph of section 5 (discussion). At the beginning they say at low deformation rates (tensile tests) the material deformability with addition of fillers decreases, on the other hand they state that at high strain rates (impact) material loses deformability with addition of filler material. So, at both loading scenarios the material loses deformability with increase of the filler content. There seems to be no material behavior varying with change of loading rate. And How is this issue similar to the behavior of thixotropic materials?

Dear reviewer,
The authors would like to thank the reviewer comments and suggestions. All the questions made us revising the paper and obtaining a more complete form of our work, and we are very grateful for your suggestions. In this document, the answers follow your remarks.

Reviewer: 1
The manuscript reports the purification of rice husk silica, deposition of LDH on the silica surface and use these materials as filler into PMMA. The topic is interesting and deserves publication but many corrections need to be implemented in the text before acceptance. Recommendations/changes/suggestions: 1-Pg. 1 -Line 46 -are lamellar compounds. Better to say: layered compounds Answer: It is corrected in the text.

2-Pg. 1 -Line 47 -exchangeable anions. Recently it was reported that LDH can also exchange cations and even cations/anions simultaneously, please update this information. Answer: In these hydroxide layers some of the M 2+ cations are isomorphy substituted with M 3+ thereby generating a positive charge. The higher (excess of) charge is compensated by the hydrated anions located in interlayer gallery. These layered configurations give them the ability to extensive use as anion-exchanging materials (adsorption, polymerization, catalysis, photochemistry, electrochemistry, biomedical and environmental application etc). LDH also has the ability of cation-exchange, which has been the subject of many researchers in recent years (photocatalysis…) [Parida K, Mohapatra L, Baliarsingh N. Effect of Co 2+ Substitution in the Framework of Carbonate Intercalated Cu/Cr LDH on Structural, Electronic, Optical, and Photocatalytic Properties. J Phys Chem C [Internet]. 2012 Oct 25;116(42):22417-24. Available from: https://pubs.acs.org/doi/10.1021/jp307353f].
This was added to the text.
3-Pg. 1 -Line 50 -In LDH, the metal ions must have an ionic radius similar to Mg2+ (0.65 A). The interlayer anions are carbonates, chlorides, nitrates and sulfates. The first information is not correct and the second is incomplete, organic and inorganic anions can be intercalated, please correct.

This is added to the text in introduction.
4-Pg. 3 -Line 47 -f Fe-Al LDH. A reason should be given for choosing this composition and also for the 3:1 molar ratio, which is very uncommon.

Answer: The common ratios vary from 2 to 4 if the LDH structure is favored. Other ratios are producing other phases and sometimes lead to formation mostly of divalent ion oxides, in this case it would produce the oxide phase of ferrous ion. [M.V. Bukhtiyarova, A review on effect of synthesis conditions on the formation of layered double hydroxides, Journal of Solid-State Chemistry, Volume 269 (2019) 494-506].
Thus, this was the choice. This is added to the introduction as explanation of the chosen ionic ratio 5-Pg. 3 -Line 48 -remove the pollution. Better to say: remove the contaminants.

Answer: It is corrected in the text.
6-Pg. 3 -Line 56 -were synthesized by a co-precipitation method. This information is incomplete, there are many different co-precipitations procedures, please explain details of the procedure.

Answer: FeAl-LDH (molar ratio Fe: Al = 3: 1) were synthesized by the method of coprecipitation from aqueous solutions under atmospheric conditions. FeCl2·4H2O (0.015 mol) and Al2(OH)5Cl·2.5 H2O (0.005 mol) were dissolved in 100 ml of deionized water each. Silica particles were added to the glass beaker, which was placed on a magnetic stirrer, and aqueous solutions of FeCl2·4H2O and Al2(OH)5Cl·2.5 H2O were prepared. The mass ratio of silica: LDH was 1:1. The aim of this synthesis is to form a precipitate layer (FeAl-LDH) on the present silica particles which are inert to the co-precipitation reaction. 1 mol/L NaOH was added dropwise to the solution until the pH reached 10 when the experiment was stopped. The dispersion was allowed to stand for 24 hours, then centrifuged at 6000 rpm for 10 minutes and then washed with water until the pH of the effluent solution was neutral. The solid with filter paper was dried at 80 °C for 24 hours to give FeAl-LDH@SiO2 particles.
7-Pg. 3line 60 -2.93 g of FeCl2·4H2O and 1.07 g of Al2(OH)5Cl·2,5 H2O. In chemistry the amounts should be given in mols, not in masses. Please convert the numbers. Answer: It is corrected in the text.

8-Pg. 4 -Line 4 -The suspension. The correct term is dispersion. Answer: It is corrected in the text.
9-Pg. 4 -Line 5 -6000 rpm for 10 minutes. The centrifugal force should be provided. Also, the filtering method is not a good method to avoid contaminants, better to centrifuge, remove the solution, dispersed the slurry with an ultrasound bath and repeated this procedure at least 5 times.

The filtration procedure was accepted from literature data as a standard one that enables the preparation of clean LDH particles after precipitation. [Zongxue Yu, Xiuhui Li, Yixin Peng, Xia Min, Di Yin and Liangyan Shao, MgAl-Layered-Double-Hydroxide/Sepiolite Composite Membrane for High-Performance Water Treatment Based on Layer-by-Layer Hierarchical Architectures, Polymers 2019, 11(3), 525; https://doi.org/10.3390/polym11030525]. The procedure you mentioned will be applied in further research and compared to the existing one.
10-Pg. 4 -Line 18 - Figure 1 should be removed; it is too basic for this level of journal.

Answer: It is corrected in the text. Figure 1 is removed from the text. Other images are renumbered.
11-Pg. 4 -Line 20 -The set consisted of the prepolymerized powder and the monomer liquid.
The complete information about these Chemical should be given to allow any reader reproduction.

Answer: All denture base materials consist of two components one is the methyl methacrylate monomer and the powder is the polymerized PMMA. The powder that usually contains the initiator is dissolved in the monomer and after that the rest of the monomer polymerizes. This one is auto polymerizing material without cadmium which is required for the use in dentistry. The material is declared to be conform to the ISO 1567 class I type II.
12-Pg. 5 -Line 48 - Figure 2. FE-SEM micrographs of fillers a) SiO2 particles, b) FeAl-LDH and c) FeAl-LDH@SiO2. Where is Figure 2C???? Answer: It is corrected in the text.
13-Pg. 5 -All the figures need to be replaced due to the low quality. Answer: All the figures provided are in 600 dpi and this is the best possible performance we can obtain from the SEM. We observed that in text downloaded from the site the quality was poor, so it seems to be the problem with image processing.
14-Pg. 5 -It is recommended that all the discussion come after each figure otherwise it is difficult to follow in the text. Use the topic results and discussion.

Answer: It is corrected in the text.
15-Pg. 7 -Line 4related to the SEM images, better magnifications would better support the comments in the text.

Answer: The best selected images are given and they represent the observed structure. The higher magnification induced the melting of the polymer matrix and this is why we could not obtain higher magnifications of composites structures.
16-Pg. 7 -Line 12 -The Fe/Al/Si ratio confirms that the majority of LDHs are found on the surface of silica particles. How the authors explain the composition of the EDS if the ratio LDH: Silica was of 1:1? This proportion is far in the analysis and no comments are provided in the text.

Answer: The deposition took place on the surface of the silica particles and most of the process was at that place. The EDS confirms the composition of the layer that was on the surface of silica particles. The excess of LDH was deposited probably in the space between particles and is visible as individual hexagonal particles on the image. That corresponds partly to some images of as deposited and formed LDH@SiO2. [Xuqiang Ji 1, Wenling Zhang 1, Lei Shan 2, Yu Tian 2, Jingquan Liu, Self-assembly preparation of SiO2@Ni-Al layered double hydroxide composites and their enhanced electrorheological characteristics, Sci Rep [Internet]. 2015 Dec;5:18367. Doi/ 10.1038/srep18367].
17-Pg. 8 -Line 19 -The XRD diffraction peaks should be indicated in interplanar distances after the position of the peaks in 2 theta and the basal distance calculated by the higher order peak possible, never the first one. The sizes of the crystalline domains can be calculated by Scherrer equation, the a and b cell parameters from the 110 peak. Which is intercalated anion?

Answer: The Scherrer formula could be applied only to the pure LDH particles as only there we are able to observe clear peeks resulting from crystal structure. In the LDH@SiO2 structure the peeks are difficult to observe, as the layer of deposited LDF is very thin and the crystal structure could not be identified using this method, and only the result of the interaction of an amorphous phase is visible. The similar result was observed in the paper [Xuqiang Ji 1, Wenling Zhang 1, Lei Shan 2, Yu Tian 2, Jingquan Liu, Self-assembly preparation of SiO2@Ni-Al layered double hydroxide composites and their enhanced electrorheological characteristics, Scientific Reports Volume 5 (2015) 18367. DOI: 10.1038/srep18367] where another type of LDH was deposited on silica particles having the similar structure as particles produced in this research. So, for particles used in this research this calculation could not be performed.
18-Pg. 8 -Line 22 -In pattern FeAl-LDH@SiO2 from figure 3 there are no characteristic peaks of LDH structure because FeAl-LDH was synthesized in the presence of amorphous SiO2 and broad peaks of SiO2 obscured them. This is not correct, if the proportion used is true, the XRD pattern of LDH should appear in the mixture. This can be an indication that a very small amount of LDH was deposited. This information should be given in the text by using proper analysis since EDS is not quantitative.

Answer: Obviously, the EDS analysis indicate that the ratio of elements present on the surface correspond to the situation where the layer deposited on the surface is retaining the structure present in the precursor solution, and that the process didn't result in the deposition of all the LDH on the surface of the particles. This observation would be presented in the paper as follows:
The results from the EDS are suggesting that the layer of deposited LDH has the ratio of 3/1 of ions used in the preparation of the modifying layer. This crystal structure does not built the crystals that are easily recognizable from the XRD pattern. From available analysis it is possible to establish the layer of the inorganic material on the surface of the silica particles having predetermined ionic ratio. 20-Pg. 8 -Line 27 -no crystalline layer of LDH. This is unlikely to be true, particles were observed with layered morphology, consequently LDH must be in the sample and crystalline material. 22-Pg. 8 -Line 47 -The FeAl-LDH@SiO2 particles are randomly dispersed in the PMMA matrix, as seen in images of the composite's fracture surface. This is really to see in the images, a higher magnification and mapping the elements would give better information in this sense.

Reviewer: 2
Page 2-line 49: It will be better if authors explained why in LDH, the metal ions must have to possess an ionic radius similar to Mg2+ (0.65 A)? Page 3-line 24 to 35: Authors must give more details about their state of art and importance of their research in the final paragraph of introduction.

This is added in the introduction of the paper
Page 5-line 11-15: please revise the sentence about the measurement positions on each sample as you have mentioned twice that six positions were used for measurements.

Answer: the test is replaced and instead
During the measurements force, time and depth data were recorded. Because of the possibility of inhomogeneity in the sample, microindentation measurements were performed on six positions for each sample to obtain more results that are accurate and reduce the influence of possible inhomogeneity microindentation measurements were performed on six positions for each sample.

We replaced with The measurement was done using the indenter having round tip with a diameter of 6mm. The machine enables the fine measurement of the force applied on the surface of the material and the measurements of the indentation depth, similar process as it is in nanoindentation. The process is repeated on six positions at the surface of the specimen and the data obtained are the mean of six measurements.
Page5-line 17: you have mentioned that test samples were standard. Which standard did you use?

Answer: ASTM International. ASTM E384-16, Standard Test Method for Micro indentation Hardness of Materials. West Conshohocken, PA. 2016. That reference is added in the text.
Page 5-line 33: Revise the sentence.
Answer: It is corrected in the text. Figure 1 shows the morphology of synthesized silica particles and those with deposited LDH on the surface as revealed by FE-SEM analysis of the synthesized particles.
Page 9-line44-57: Please increase the quality of SEM images, since the details you have discussed are not clearly seen for reader. Answer: The authors observed that the images are of poor quality when downloaded from the site so we suppose that the problem is in image processing. We changed the images for the correct visibility and hope that it will be better when it comes to you.
Page 8 (last paragraph) and Page 9 (first paragraph) : you have reported dual values for the increase of hardness with addition of 3% and 5% FeAl-LDH@SiO2 fillers. Please correct this ambiguity.

Answer: Page 8 (last paragraph) shows the Vickers hardness, and page 9 (first paragraph talks about the hardness obtained by Micro indentation on Texture Analyzer EZ LX, Shimadzu. Additional clarification was added to the manuscript.
Page 9-line7: You have specified that addition of fillers increases young modulus. Does it mean that addition of 50% filler materials will also result in extremely high elastic modulus? Is there a optimum number for addition of filler material to PMMA material? The same question goes for hardness increase due to addition of filler to PMMA.

Answer: The addition of filler leads to an increase in hardness and modulus of elasticity, but the addition of 50 wt. % of filler does not lead to an extreme increase. With the increase of the filler content, agglomeration of the filler occurs and heavier mixing leads to a decrease in the elasticity modulus. 5 wt. % filler in our case is the optimal value to which the hardness and Young's modulus of elasticity increase. From the previous research the maximum improvement is reached before the content of the filler exceeds 10%. Usually optimal performance is obtained when the content is about 3%. At those amounts the structure profits from the interaction over interphase matrix-reinforcement. Larger quantities of reinforcement provide the possibility of particle -particle interaction and this is not beneficial for material mechanical properties.
Page 9-line 15: The term "static loading experiments" does not seem to be applicable to your research since you have performed test by varying load over time with a constant speed of 0.5mm/min. Please clarify if you have done tests under quasi-static loading (constant increase of load over time) or fixed load over specific time intervals.
Answer: This is actually the quasi-static loading of the material. We corrected this in the paper.

The quasi static loading means that the load is increased over time with constant increase. The real dynamic increase of the load is when the impact testing is performed. This is done in the impact testing machine where the speed of the impact is controlled.
Page 9-line 16: what do you mean by ability of material to deform? Does it mean ductility? Failure strain?
Answer: This is considered to be the maximum deformation during the tensile test. Table 3: what do you mean by σ, K and ε? Please define them in the text. Table 3.

Answer: It is corrected in the text. Meanings are added below
There is contradiction in authors' statements in last paragraph of section 5 (discussion). At the beginning they say at low deformation rates (tensile tests) the material deformability with addition of fillers decreases, on the other hand they state that at high strain rates (impact) material loses deformability with addition of filler material. So, at both loading scenarios the material loses deformability with increase of the filler content. There seems to be no material behavior varying with change of loading rate. And how is this issue similar to the behavior of thixotropic materials?

Answer: All the text in the paper is corrected and the statements are clarified. From the results it was obvious that the addition of the reinforcement in quasi static loading is decreasing the deformation of the specimen and increases the strength. If the energy absorbed during this test is calculated as the integration under the stress-strain curve it reveals that the energy degreases with addition of the reinforcement. This is in accordance with the literature for similar particulate reinforced polymer and this is cited in the paper. On the other hand when the specimen undergoes the high speed impact test the data about total energy that is transferred to the material is obtained in function to time. The total of the energy transferred to the material during the experiment increased with the addition of the reinforcements. The rate of load transfer to the material was proven to be the one of the most important parameters both for micro and nano composite materials and this confirms our observations. So in accordance to
all of this the text in the discussion is changed to reflect those changes.