An Investigation to Reduce the Effect of Moisture on Injection-Molded Parts through Optimization of Plasticization Parameters

Round 1

Reviewer 1 Report

The manuscript presents a study in the field of injection moulding. The manuscript has a series of weaknesses that need to be resolved prior to the acceptance of the manuscript. 

There are a series of grammatical and syntactical errors on the manuscript.

The motivation of the study is around moisture content and the effect of said moisture on the quality of the injection moulded parts, however none of the control variables is relating to moisture in the feedstock therefore the title and motivation are not in line with the research.

The presentation of the results is very weak. The authors state that there was a series of runs per parameter. one would expect that the st. deviation and spread of the repeat trials would be presented in order to support the findings of the paper.

The conclusions are too generic and need to be focused on the motivation findings and the advancement of the state of the art in the field 

Author Response

Dear Sir,

We thank you for highlighting those mistakes and all those comments have indeed helped us to improve the quality of the paper. Furthermore, the reviewer's comment encourage us to do another experiment with different moisture content, this helped us in adding more conceptual clarity to the paper to highlight the aim and novelty, please see the attachment.

Thanking you

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper relates a study about the consequences of moisture in the appearance of bubbles after injection moulding in hygroscopic polymers, takin as a model thermoplastic polyurethane (TPU). For this purpose, the authors apply a factorial design and statistically evaluate the effect of temperature, screw rate and back pressure.

Even though the technological application of this study is interesting, I suggest rejection for the publication of the present document in Applied Sciences. In particular, issues on the introduction, experimental and results and discussion sections must be addressed. Indeed, there is a lack of discussion of most of the results.

Moreover, the overall writing of the document must be taken care of. There are many sentences in the article with punctuation marks usually misused and the capital letters inappropriately used. Therefore, a deep re-examination of the writing of the manuscript is required.

Divided by sections, comments are:

Title:

1. The title refers to the evaluation of moisture. However, the authors did not assess the moisture of the selected model polymer, nor prior nor after injection moulding. Therefore, other titles such as “An Investigation into the Effect of Temperature, Screw Rate and Back Pressure on the Plasticization Stage during Injection Moulding Process of Hygroscopic Thermoplastic Polymers” would be more appropriate.

Graphical abstract:

2. A graphical abstract is encouraged to capture the attention of the readers.

Abstract

3. In the abstract, the authors talk about moisture absorption, and subsequently refer to the absorbed moisture as “condensed moisture on the surface”. In this sense, they are confusing different concepts, such as the absorption of water in bulk, with surface condensation, caused by other phenomena influenced by the difference in temperature or pressure. This is a crucial confusion, which determines the focus of the entire study.

Keywords

4. The name of the used software is not relevant, and the authors should avoid mentioning “Minitab” or “AutoCAD” in the keywords.

Introduction:

5. The authors refer to the traditional injection moulding manufacturing process as the most widely used technology. Supporting with updated data is highly encouraged.
6. The plasticization of the plastic pellets into the molten state is due to the effect of external heat together with the contribution of shear during screw rotation. The authors may have this in consideration, and not only describe plasticization as the effect of the action of shear heat.
7. Along the introduction, the factors that determine the final quality of a given product are referenced repeatedly in different paragraphs. As well, the consequences of unsatisfactory processing strategy are also repeated during the introduction. In this regard, the authors should avoid repetition and go through the specific contribution of factors that promote particular consequences. Given the evaluation of the temperature, screw rate and back pressure in this study, the particular effect of this factors must be especially introduced and referenced with appropriate references to other studies in the literature.
8. Although references from the literature are well described from lines 94 to 120, the authors must go further and deeper on the results of such studies, especially those relevant for supporting the findings of the current investigation.
9. The aim and novelty should be therefore highlighted in the introduction, giving importance to the contribution of the current study to the field of injection moulding of thermoplastic hygroscopic polymers.

Materials and methods:

10. In section 2.1, the description of TPU given from line 134 to 139 must be moved to the introduction section, motivating the selection of TPU as a model material. In addition, this section should contain the information about the moisture content of the TPU pellets. In this regard, the use of TPU with different moisture content would enrich the study and significantly increase its quality and usefulness. If applied, the drying procedure must be described.
11. Section 2.2, must be properly named. For instance, “Injection moulding conditions” could be used. As well, when defining the parameter “Screw rpm”, the unit is defined as “%”. In this sense, the reviewer wonders about how rpm represents this percentage. Are these screw rotation conditions applicable to other injection moulding machines? Moreover, authors defined two levels for each factor. However, for visualizing the tendency or pattern of a given factor, three levels are usually applied.
12. Lines 162 to 170 in section 2.3 must be included into the introduction section, motivating the benefits of factorial design analysis for this study.
13. Moreover, lines 180 to 186 should also be moved to the introduction section, as it justifies the generation of air bubbles, which is the base for selecting such indicator for assessing the effect of temperature, screw rotation rate and back pressure.
14. Figure 1 in section 2.3 is useless and can be omitted.
15. From line 207 to 228 should be moved to the results and discussion section. All the information shown in Figure 2 and Figure 3 are results obtained after applying the described injection moulding procedure. For a proper visualisation, the several runs could have been assessed as an average plus standard deviation.

Results and discussion:

16. The visual appearance of representative samples showing bubbles for the different injection moulding conditions could be complementarily included for supporting the obtained results.
17. Although the authors evaluated the bubble area and bubble number, they focus their statistical study only on the bubble area. In this line, the bubble number could also have been included. Are there other defects due to the contribution of moisture that could be monitored?
18. During the whole study, the authors did not motivate or discuss the contribution of the selected factors temperature, screw rotation rate and back pressure on the bubble area or number. They have just described the obtained results, but avoided discussing the reasons behind the perceived performance.
19. The study of the remnant humidity on the injection moulded samples, immediately after processing, could be a complementary indicator of the effect of the initial moisture content of the pellets, considering the different processing conditions.

Conclusions

20. The text in the conclusion section is clear and well written. However, it should be more concise and avoid doing a summary of the obtained results.

Comments for author File: Comments.pdf

Author Response

Dear Sir,

We thank you for highlighting the mistakes, and all those comments have indeed helped us to improve the quality of the paper. Furthermore, your comment encourage us to do another experiment with different moisture content, this helped us in adding more conceptual clarity to the paper to highlight the aim and novelty. 

Thanking you

Author Response File: Author Response.pdf

Reviewer 3 Report

There are some weaknesses through the manuscript which need improvement. Therefore, the submitted manuscript cannot be accepted for publication in this form, but it has a chance of acceptance after a major revision. My comments and suggestions are as follows:

1- Abstract gives information on the main feature of the performed study, but some details about the obtained results must be added.

2- Authors must clarify necessity of the performed research. Objectives of the study must be clearly mentioned in introduction.

3- The literature study must be enriched. In this respect, authors must read and refer to the following papers: (a) https://doi.org/10.1007/s10845-019-01481-0 (b) https://doi.org/10.1016/j.polymertesting.2020.106748 and other research works.

4- It would be nice, if authors could add some figures to show concept and some conditions. In addition, some references are required for the presented values.

5- Figures must be illustrated in a high quality. For example, numbers and legend in Fig. 2 and3  are illegible.

6- Statistical study must be presented in details. Moreover, factor regression analysis is presented in Table 4. It is necessary to add its details to the manuscript.

7- Standard deviation is the presented results must be discussed. In addition, error in calculation must be considered and discussed.

8- In its language layer, the manuscript should be considered for English language editing. There are sentences which have to be rewritten.

9- The conclusion must be more than just a summary of the manuscript. List of references must be updated based on the proposed papers. Please provide all changes by red color in the revised version.

 

 

Author Response

Dear Sir,

We thank you for highlighting those mistakes and all those comments have indeed helped us to improve the quality of the paper. Furthermore, the reviewer's comment encourage us to do another experiment with different moisture content, this helped us in adding more conceptual clarity to the paper to highlight the aim and novelty, please see the attachment.

Thanking you

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have addressed a number of comments made by this and the other reviewers. Moreover, they have included a complementary study on the consequences of moisture level on the glossiness of polycarbonate-based specimens.

However, even though the technological application of this study may be interesting, the overall quality of the document must be still improved. The structure of the manuscript must be clarified. The selection of materials must be justified. Most of the figures still show mistakes in the units, the size of the fonts or in the identification of results.

Overall, this study shows a great experimental work, with a good hypothesis and a large number of results, but with a drafting and strategy for the presentation and discussion of results still with a wide margin for improvement.

Author Response

Sir,

we thank you for those comments, this helped us in adding more conceptual clarity to the paper to highlight the aim and novelty. Sir, please see the attachment.

Thanking you

Author Response File: Author Response.pdf

Reviewer 3 Report

In response to the third comments, although authors mentioned that suggested papers "helped them to improve the quality of the paper" they didn't refer to these papers. So, I recommend to cite both relevant papers.

Author Response

Sir,

we thank you for those comments, we rearranged the introduction part, and we added two references (reference no 15 & 16) to denote the effect of plastcization parameters thus most of the paragraphs in the introduction part in the revised manuscript is changed. 

Thanking you