Secondary Treatment Facilitating the Mechanical Recycling of Film-Coated Waste Automobile Bumpers
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis manuscript presented a study about the treatment of waste automobile bumpers and its effects on mechanical recycling and mechanical properties of recycled material. The work has potential. However, some points listed below need to be improved.
Abstract: please add numerical results to the abstract to better quantify the changes in mechanical properties.
Section 2: please add how the scanning electron microscopy was performed.
Section 2: the author must add some statistical analysis to better evaluated the mechanical properties results.
Section 3.1: compare the obtained results with others from the literature. In addition, better discuss the results presented in Figure 6.
Figure 5 and Figure 6: I suggest identified in both figures the main bands discussed in the text. It will be better if x axis initiating in 3900 cm-1 instead of 400 cm-1.
Table 1: please add the standard deviation for the values presented in Table 1. In addition, add the statistical analysis evaluation. It is not possible evaluate if the effect of primer and other effects are significant on the mechanical results without a statistical analysis.
Table 2: please add the standard deviation and statistical analysis also for the values presented in Table 2.
Author Response
Manuscript ID: Recycling-3535187
Title: Secondary treatment to contribute to mechanical recycling of waste automobile bumpers with coating film
Authors: Tetsuo Takayama *, Toshiyki Niiyama, Tadao Tanabe, Jeongsoo Yu
Thank you for your interest in reviewing this paper. I would like to respond to your suggestions and questions raised below.
Abstract: please add numerical results to the abstract to better quantify the changes in mechanical properties.
I appreciate you bringing this to my attention.
We have taken the liberty of including the numerical results in the abstract.
Section 2: please add how the scanning electron microscopy was performed.
I appreciate you bringing this to my attention.
It appears that an explanation of the scanning electron microscope was omitted from the experimental method. We have taken the liberty of adding this explanation as 2.9. We would like to thank you again for your careful review of this paper.
Section 2: the author must add some statistical analysis to better evaluated the mechanical properties results.
I appreciate you bringing this to my attention.
We have taken the liberty of adding explanations regarding standard deviation and analysis of variance to the descriptions of the 3-point bend test, tensile test, and Charpy impact test.
Section 3.1: compare the obtained results with others from the literature. In addition, better discuss the results presented in Figure 6.
I appreciate you bringing this to my attention.
We have taken the liberty of including it as a reference that can be used to identify the composition from the FT-IR results. Additionally, we have taken the liberty of including a description of the main bands as depicted in Figure 5, which we have appended to the description of Figure 6.
Figure 5 and Figure 6: I suggest identified in both figures the main bands discussed in the text. It will be better if x axis initiating in 3900 cm-1 instead of 400 cm-1.
I appreciate you bringing this to our attention.
First, we have changed the starting point of the abscissa axis to 3900 cm-1. In addition, in Figures 5 and 6, we have indicated the regions of the main bands discussed in the text with arrows and added a brief description of each region.
Table 1: please add the standard deviation for the values presented in Table 1. In addition, add the statistical analysis evaluation. It is not possible evaluate if the effect of primer and other effects are significant on the mechanical results without a statistical analysis.
I appreciate you bringing this to my attention.
We have taken the liberty of including the standard deviation results in Table 1 and the analysis of variance results in the text.
Table 2: please add the standard deviation and statistical analysis also for the values presented in Table 2.
I appreciate you bringing this to my attention.
We have taken the liberty of including the standard deviation results in Table 2 and the analysis of variance results in the text.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThis is an excellent work that addresses one of the most common problems in the field of plastic recycling.
This problem is the presence of impurities in plastic recycling, in the case of automotive parts coating
The description of the problem is correct.
In the case of identification, using only the infrared technique can lead to errors. I recommend that a differential calorimetry test be performed. This allows the IR results to be confirmed.
In the experimental section it talks about tensile properties, but then it talks about bending. It doesn't make sense
Regarding the analysis of the mechanical properties, the removal of the coating improves the impact properties, as is logical. On the other hand, it seems that removing the coating improves the flexural properties. This requires a better explanation.
You says:“The tensile strength of the welding zone is referred to as weld strength, which, as reported by the authors, is equivalent to the interfacial strength between the fiber and the base material in short-fiber- reinforced thermoplastic composites”
Does the material contain fiber? How much? Why can't you see it in the SEM? Does it make sense on uncoated material?
But the presence of the primer is beneficial. This requires a better explanation. How much primer is there? What is the composition of the primer?
This sentence is confusing: “The coating was applied by means of a spray gun at a distance of approximately 20 to 30 centimeters, and the materials were allowed to dry for 30 minutes”.
Differentiating between original and added coating
Author Response
Manuscript ID: Recycling-3535187
Title: Secondary treatment to contribute to mechanical recycling of waste automobile bumpers with coating film
Authors: Tetsuo Takayama *, Toshiyki Niiyama, Tadao Tanabe, Jeongsoo Yu
Thank you for your interest in reviewing this paper. I would like to respond to your suggestions and questions raised below.
In the case of identification, using only the infrared technique can lead to errors. I recommend that a differential calorimetry test be performed. This allows the IR results to be confirmed.
I appreciate you bringing this to my attention.
We performed additional DSC and were unable to identify a clear base shift in the temperature range where glass transition of PMMA occurs. This suggests that the primer is applied in such a manner that it is below the level that can be detected by DSC. Therefore, we decided to discuss the composition of the primer in this paper based on the FT-IR results alone, without adding the DSC results.
In the experimental section it talks about tensile properties, but then it talks about bending. It doesn't make sense
I appreciate you bringing this to my attention.
The tensile tests in this paper were performed on welded specimens to evaluate the interfacial strength of the coating film and base material. As you astutely noted, the flexural results were intended to assess the mechanical properties of the molded product in its entirety. In hindsight, it would have been more logical to present this information first. In light of your valuable feedback, we have made a few changes to the structure of the paper. We have rearranged the order of the results to make it more logical and easier to understand. Additionally, we concluded that including the weld results without coating was not essential to achieve the clarity we sought.
Regarding the analysis of the mechanical properties, the removal of the coating improves the impact properties, as is logical. On the other hand, it seems that removing the coating improves the flexural properties. This requires a better explanation.
I appreciate you bringing this to my attention.
As you can see in Table 1, the flexural strength and flexural modulus are both higher for the coated material than for the uncoated material. Therefore, we respectfully disagree with the reviewer's assessment.
You says:“The tensile strength of the welding zone is referred to as weld strength, which, as reported by the authors, is equivalent to the interfacial strength between the fiber and the base material in short-fiber- reinforced thermoplastic composites”
Does the material contain fiber? How much? Why can't you see it in the SEM? Does it make sense on uncoated material?
But the presence of the primer is beneficial. This requires a better explanation. How much primer is there? What is the composition of the primer?
Thank you for pointing this out.
The bumpers used in this study do not contain fibers. The sentence you pointed out was used to explain the interface between the coating film and the base material. After the series of explanations, we included an explanation replacing the fibers with the paint film, which we believe will mislead the reader. Therefore, to avoid misunderstanding, we have added an explanation of replacing the fiber with the coating in the main text after the indicated sentence.
As for the composition of the primer, as explained in Figure 5, it is thought that the coating component has a PMMA-like composition. As for the amount of primer applied, we measured the weight of the primer before and after coating and found that it was a very small amount, about 0.1 wt%. This explanation has been added to 2.2.
This sentence is confusing: “The coating was applied by means of a spray gun at a distance of approximately 20 to 30 centimeters, and the materials were allowed to dry for 30 minutes”.
Differentiating between original and added coating
Thank you for pointing this out.
We have revised the wording to avoid any misunderstanding.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThis paper investigates the “Secondary treatment to contribute to mechanical recycling of waste automobile bumpers with coating film.” It is well-structured and addresses an interesting research subject. However, the manuscript could be further improved according to the following suggestions.
- What is the main contribution of this paper? What is the novelty shown in this study?
- A comparison with other studies is necessary; however, this content is missing from the manuscript.
- The language should be improved.
The language should be improved.
Author Response
Manuscript ID: Recycling-3535187
Title: Secondary treatment to contribute to mechanical recycling of waste automobile bumpers with coating film
Authors: Tetsuo Takayama *, Toshiyki Niiyama, Tadao Tanabe, Jeongsoo Yu
Thank you for your interest in reviewing this paper. I would like to respond to your suggestions and questions raised below.
- What is the main contribution of this paper? What is the novelty shown in this study?
I appreciate you bringing this to my attention.
The primary focus of this study is to illustrate the potential for enhancing the mechanical properties of bumpers through the application of coating film in conjunction with additional treatments, without the need for removal of the existing coating. We believe that primer coating is applicable in this study. We believe that primer coating is a particularly novel aspect of this research, as it has not been considered in other academic papers.
- A comparison with other studies is necessary; however, this content is missing from the manuscript.
他の研究との比較が必要であるが、原稿にはこの内容が欠けている。
I appreciate you bringing this to my attention.
In an effort to address this concern, we have included a comparison citing relevant literature in the results section of this paper.
- The language should be improved.
We appreciate you bringing this to our attention.
We have requested an English review and have made efforts to improve the English.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsAfter corrections the manuscript reads well. I suggest publication in its current form.
Reviewer 2 Report
Comments and Suggestions for Authors After the modifications made by the authors, I consider that the article has improved, and therefore is suitable for publication.