Fused Filament Fabrication Based on Polyhydroxy Ether (Phenoxy) Polymers and Related Properties

Round 1

Reviewer 1 Report

Dear Authors,

 

The article is interesting but has to be improved in many sections:

1. State of the art in the introduction is very poor, based on the fact that your research is focus on a new type of material. I recommend to improve it and add references such as (but it might be something else), related to rheology and mechanical properties of FFF and FDM. Moreover, you could describe more about FDM technology and progress in this method. e.g. electrospinning what allow for composites.

• Evaluation of the rheological properties of photopolymers used in Polymer Jetting technology, DOI: 10.1051/matecconf/201925407001
• The Influence of Selected Selective Laser Sintering Technology Process Parameters on Stress Relaxation, Mass of Models, and Their Surface Texture Quality, DOI: 10.1089/3dp.2019.0036 
• Stabilization of Electrospun Nanofiber Mats Used for Filters by 3D Printing, DOI: 10.3390/polym11101618

2. Figures 2 and 3 need more explanation below it to better understand it by readers.

3. Fig 7 should be divided into a b and c. 

4. There is no discussion about figure 9, please add information about micrographs.

5. In conclusion you should remove tables and move it to the discussion (you should create point 5 discussions). I would recommend doing short conclusion  and show a few most important points, now it looks like part of the paper, not the most important results.

Kind regards,

Reviewer

 

Author Response

Dear Reviewer,

We would like to thank you for your time and effort for reviewing our article. Thanks as well for the valuable comments which helped us to improve our article. Based on your comments we have added further experimental trails, rewritten different section and have done a English editing by MPDI. Some detailed comments we have answered in the attchment.

We hope on your positive review

With best regards,
Delal Arslan, Christian Brauner, Marco Küng and Christoph Maurer

Author Response File: Author Response.pdf

Reviewer 2 Report

This manuscript deals with the possibility of applying the polyhydroxy ether polymers to fused filament fabrication, the processing parameters involved for filament extrusion, and the mechanical propoerities with comparison with injection samples with the same materials. However, the presentation makes hard to follow because the manuscripts has numerous errors and the explanation of the presented results are not comprehensive. The authors should improve the description and the state of the art of the problem reported. In consequence, I am afraid that the work does not merit publication in its current form.
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1. Section 1.

1.1 The authors have mentioned several statements with numerical data. However, it is suggested to indicate the references for these statements.

1.2 ‘ Therefore, the component strengths depend on the orientation of the deposited layers and the stress.’ Beside the orientation of the deposited layers and the stress, there are several more factors affecting the bonding strength, like the temperature profile, feed forces, and processing parameters involved. Please refer to some references, like Luo, C.; Mrinal, M.; Wang, X.; Hong, Y. Bonding widths of Deposited Polymer Strands in Additive Manufacturing. Materials 2021, 14, 871.

1.3 ‘It was developed in the early 1960s --- by Huntsman Advanced Materials’, which is not necessary material in the introduction section.

1.4 It is suggested to give the advantages and disadvantages for the application of the phenoxy polymers. Since the authors mentioned that it is the first-time application of the polyhydroxy ether polymer, so why these polymers are not used before? The authors had better emphasis the importance of the work.

2. Section 2.

2.1 Section 2.1. What does ‘The curves of the first heating differ in the temperature of the glass transition temperature and in the shape of the glass transition temperature.’ mean?

2.2  Section 2.2. What is the reason for the first stage of mass losing? And what is the meaning of the lines in bule in Figure 3? The explanation for the presented results is missing.

2.3 ‘In the FFF process, the mean viscosity depends on the nozzle temperature, the nozzle diameter and the printing speed.’ First, for the given Equation (1), I do not see the temperature parameter. Second, the volume flow is assumed as the extrusion speed * the area of the nozzle diameter. Please clarify the volume flow here. And what is the meaning of the velocity (v), printing speed, extrusion speed?

       2.3.1 For Figure 4, feed rates and printing speeds are two different concepts. Please clarify the concepts here. Shear rate is also assumed as a function of temperature as well. While the results presented in Figure 4 is ignoring the effect.

       2.3.2 ‘It can also be observed that, as the temperature rises, the viscosity also decreases.’, from Figure 5, when temperature increase from 190 degree to 200 degree, instead of decreasing, viscosity increases. So how can the authors get the conclusion?

3. Section 3.

3.1 Please state manufacturer, city and country from where equipment has been sourced.

3.2 For Figure 6 and Table 1, it is suggested to offer an illustration for the Extruder zone or close view of the extruder with labels, Extruder zone 1, 2 and so on. This figure should be rebuilt for the better clarity of the reader. And why 195 degree is selected for the extruder temperature?

3.3 The authors have used a filament with a diameter of 1.75 mm. However, many FFF 3D printers use filaments with a diameter of 2.85. So, we think that authors should have indicate the possibility of the dimension?

4. Section 4.

4.1 Figure 8 is not mentioned in main text.

4.2 What is the strategy for printing the tensile bars? The first way, second way or the last way described in Figure 8?

4.3 Figure 10, the line styles are not consistent. Dash lines and solid lines.

4.4 The influence of the printer’s nozzle temperature on the tensile strength? For the tested samples, any heat treatment carried on?

4.5 what does ‘This means a reduction by the factor of 5.3 rep. 4.5.’ mean?

4.6 Five tensile bars (injection molding) and three tensile bars (printed) are compared that are not consistent logically.

4.7 Table 4. What are the Yield Stress and Yield Stress? Why they are not offered for the printed samples? One more typo, the Yield Strain instead of Yield Stress for the second column of the table.

4.8 ‘Figure 13 shows a comparison between a 3D printed and an injection-molded specimen.’ Figure 12 instead of Figure 13 should be stated here. And the quality of the figure is poor. What is the meaning of the black curves?

4.9 It would be necessary to include tensile and flexural tests, in order to characterize the mechanical behaviour of samples printed with the polymers considered in this work.

5. Section 5.

5.1 The value of ‘The Fracture strain in printing direction’ offered in the Table 5 is in the X-direction, it is so confused to judge the statement.

Author Response

Dear Reviewer,

We would like to thank you for your time and effort for reviewing our article. Thanks as well for the valuable comments which helped us to improve our article. Based on your comments we have added further experimental trails, rewritten different section and have done a English editing by MPDI. Some detailed comments we have answered in the attchment.

We hope on your positive review

With best regards,
Delal Arslan, Christian Brauner, Marco Küng and Christoph Maurer

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear Author,

I recommend the article for publication in presented form.

Kind regards,

Reviewer

Author Response

thank you

Reviewer 2 Report

The authors revised the manuscript well, and the responds are correct generally. While ignoring some points on the previous comments.

1. Section 1.

For the first paragraph in the Introduction, the authors have mentioned several statements with numerical data. It is suggested to indicate the references for these statements。

2. Section 2.

2.2 What happens to the bule lines in Figure 3? It needs explanation.

2.3 The authors changed the statement of ‘In the FFF process, the mean viscosity depends on the nozzle temperature, the nozzle diameter and the printing speed.’ to ‘In the FFF process, the apparent shear rate on the wall depends on the nozzle diameter and the printing speed.’, and tried to ignore the effect of temperature, which is still unclear to me. Please modify the model.

The volume flow is assumed as the extrusion speed * the area of the nozzle diameter. ‘the extrusion velocity which corresponds to the printing speed ’The printing speed and extrusion speed are two different concepts. Please clarify the model.

       2.3.1 For Figure 4, feed rate and extrusion velocity are two different concepts. Shear rate is also assumed as a function of temperature as well. Please offer the explanation. Refer to https://doi.org/10.1016/j.addma.2020.101361

4. Section 4.

4.2 What is the strategy for printing the tensile bars, in y direction horizontally or vertically? And the presented results for the following tables and figures are based on which samples? 

4.3 Figure 10, the line styles are not consistent. The experimental results are in ‘solid lines’, while the labels are in ‘dash lines’.

4.7 Table 4. Why  the Yield Stress and Yield Stress are not offered for the printed samples?

4.9 ‘Tensile tests have been performed in several material direction and a comparison to injected moulded material was performed. In literature most of the time bending / flexure properties are not missing in data sheet or publications. We do not see a benefit of flexural test because there is a non-uniaxial stress state applied and therefore for a design of a structural part, they are not relevant.’ Since this work is the first-time application of the polyhydroxy ether polymer, beside the tensile tests, the flexural test results may also needed. If the tensile tests are offered somewhere, the authors should indicate that.

Author Response

Dear Reviewer,

We would like to thank you for your time and effort for reviewing our article. Thanks as well for the valuable comments which helped us to improve our article. Based on your comments we have added further experimental trails, rewritten different section. Some detailed comments we have answered below.

We hope on your positive review

With best regards,

Delal Arslan, Christian Brauner, Marco Küng and Christoph Maurer

Author Response File: Author Response.pdf

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

I have initially read the manuscript with interest. However, fairly quickly into the manuscript, it became apparent that not only was it rather poorly written, it was also essentially partially an advertisement campaign for a product of the chemical industry. There is a whole paragraph dedicated to the history of the particular company making the polymer the writers are trying to present and not nearly enough discussion of polymer properties and the implication of these properties on incorporation of the polymer into 3D printing and the types of advantages the polymer provides that are not attainable by the use of other polymers. While the breadth of basic polymer physical properties is rather wide, it does not address or translate into the critical parameters of the printers that would be necessary for the incorporation of the polymer into desktop printing. The measured data is provided often without replicates or standard deviations. Where replicates are made, e.g. in tensile test results, it is not immediately clear why sample 3 was skipped. The methods and results are communicated poorly, with numerous mistakes that probably stem from poor translation of the manuscript. These mistakes vary from adorable nuisances, e.g. "Nozel temperature" in Table 2, "Glastransition temperature" in Table 3, "in summery" on page 12 to things that make it genuinely difficult to understand what was done, e.g. Figure 6 caption that proudly reads " TGA characterization to derive drying time related to 80°C for 6h." - I have no idea what is meant here and how one derives drying time related to 80 degrees Celcius. Finally, some items may have been nearly or completely plagiarized by reproduction in nearly unaltered state without explicit author permission, e.g. Figure 2. I am not sure what the journal policies are with regards to such reproductions, but in most journals such reproduction is considered plagiarism, even where the completely copied content is cited, and is not accepted practice. The rest of the manuscript is rather sloppily assembled with rather poor quality and inattention (e.g. all headings are numbered 1). I cannot, with clear conscience, recommend this work for publication.

Reviewer 2 Report

This manuscript describes a study on evaluating using the polyhydroxy ether(phenoxy) polymer as a candidate for 3D printing materials for Fused Filament Fabrication (FFF). However, there are a lot of issues with the study design and data collection, and it was difficult to understand the significance of this study. Below is a list of issues/concerns regarding this manuscript:

1. Manuscript formatting and grammar: all the numbering s of the sections in this manuscript were incorrect; a lot of typos and grammar mistakes and seemed like the authors have not done a thorough proofreading before submitting
2. Page 3 DSC: how many specimens per sample were tested? The results should be presented at “average ± standard deviation”. The difference of the two DSC cycles were very minor; it is difficult to convince people if the result was from one single sample run.
3. Page 3 Figure 4: can the authors explain the enthalpy relaxation difference in the two cycles of the DSC?
4. Page 4 TGA: for the sample drying to get rid of the water, the drying temperature was only 80 °C, while the polymer’s T_g was 95–97 ° Have the authors considered the possibility that without heating up the sample above the T_g, the water molecules might be trapped in the polymer network? Can the authors add a TGA with higher drying temperature?
5. Figure 7: where was this figure from? Where did the authors get the data to plot Figure 7? Please add the reference here.
6. Page 5 last paragraph: what is “shear dilution”? Can the authors put a definition (or reference) here? Or did the authors mean “shear thinning”?
7. Page 7 under “FFF manufacturing and characterization”: the definition of FFF in this page was confusing and inaccurate. Can the authors review some more papers focused on FFF printing and re-word the definition here? And please add reference.
8. Page 8: too few citations/reference here when mentioned the anisotropy. There was only reference [5] for the entire section.
9. Figure 11 right: missing scale bars
10. Page 9 tensile test: what is the minimum sample quantity for test that follows DIN 527-1? 4 samples seemed to be an odd sample quantity.
11. Page 9 tensile test: the printing direction vs the tensile direction on all the samples were confusing and difficult to understand from the current Figure 13. Can the authors review some more papers which have done similar studies on the anisotropy in the FFF printed samples and follow what worked for them?
12. Page 9 tensile test: again all the results should be presented as “average ± standard deviation”
13. Figure 14: missing scale bar in the embedded picture
14. Page 10 DMA: can the authors explain why would they choose to use “drop in loss [sic] modulus” as their way to identify the T_g? What was the reason not using the peak of tan delta?
15. Page 10 DMA: the authors said in the text that the “drop in loss modulus” but in the figure 15, only storage modulus was presented in the figure. Which one is correct?
16. Page 12 Table 3: can the authors note in the manuscript about when were the data presented in the Table 3 published? Were they up to date? This matters when you compare the prices.
17. Page 12 Table 3: there are a lot of different grades of PLA and ABS. Which grades were the authors trying to compare with phenoxy? The Young’s moduli for all these materials should not be a discrete number; at least they should be a range, and best to be presented in “average ± standard deviation” with an indication of the manufacture and the grade of the material
18. Page 12 summary
    1. Up to this point, it was still difficult to understand why would anyone use phenoxy in the FFF printing. Is it better price/property ratio? If so, the paper did not show any superior properties of this new material that can beat the other existing ones.
    2. The authors claimed that the phenoxy “reduces warpage due to amorphous characteristic” but there were no discussion or measurements in the manuscript to support this; at least printing some parts with phenoxy and ABS, then compare the warpage/shrinkage of these two
    3. The authors claimed that “potential application for this polymer might be as well interesting by reviewing the applications in which the material is already used”, but can the authors speak more specifically? Like what exactly the potential application they are talking about here? What are the “applications in which the material is already used”?
19. The summary did not touch the anisotropy at all on the phenoxy printed samples. Please summarize and compare with the other existing FFF printing materials

In conclusion, the study presented in this manuscript was not well designed and needed a lot of re-testing and extra experiments. The scope of this study was also very narrow and insignificant. Until these concerns fully addressed, this manuscript in my opinion does not qualify for publication.