Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The main objective of this study is to evaluate the adhesive strength between etched PI and overmolded biopolymers before and after surface modifications. Three different types of etched copper polyimide (PI) foils were used as the substrate of electronic components. Two bio-based and biodegradable polymers of polylactic acid (PLA) and polyhydroxybutyrate (PHB) served as the overmolding material. Four different surface pretreatments: drying, polydopamine (PDA) coating, oxygen plasma, and 3-aminopropyltriethoxysilane (APTES), were applied to the PI surface before the overmolding process to investigate the influence on the adhesive strength. A thermoplastic polyurethane (TPU) adhesive layer was introduced via vacuum lamination to improve adhesion further. Various issues need to be resolved before further consideration.

 

1. Line 169. Most studies have indicated that the pH value for dopamine to form polydopamine on different substrates needs to be slightly basic, such as 8.5, as pointed out in Polymers 16(4) (2024), Appl Surf Sci 626 (2023), and Annu Rev Mater Res 41 (2011) 99-132. and references within these three. Although the authors have argued that a uniform PDA coating was formed, it may not be (see comment six below). The authors should provide a rationale to support their selection of the pH value of the PDA surface modification solution.
2. Line 238. Statistical analysis. As the authors indicated that the t-test is appropriate for comparing two groups, the t-test might not be suitable to determine the differences among three or four groups in this study, such as Table 4. The ANOVA analysis, followed by an ad-hoc Tukey test, would be more appropriate for Table 4.
3. Table 4. Figure 4. What does the “pristine” mean here? Does it indicate the PI was completely etched as indicated in Lines 115-118? If so, it is no wonder that the WCA of pristine Pyralux and Shengyi were higher since the adhesive layer on these two PIs could not be completely removed with the etching solution shown in Lines 115-118. These residual adhesives might be the contaminants pointed out in Line 271.
4. Figure 4 caption. How many samples were analyzed in each group? The authors only indicate that 5 measurements were done in each group.
5. Figure 6. The binding energy assignment for each deconvoluted peak should be properly referenced from earlier publications. That meant the authors should provide references for the binding energy assignment. In addition, the authors are advised to prepare a Table to summarize the area percentage and the chemical structure associated with the deconvoluted peak shown in Figure 6.
6. Line 339-352 and Line 424. The C/O/N ratio shown in Table 5-7 didn’t show good agreement with the C/O/N for the polydopamine in Line 342. The authors should reexamine their arguments about the PDA coating uniformity and thickness.
7. Line 425. O2 plasma. Should it be “an increase of hydrophilicity” or “a decreased WCA”?
8. Line 497. The authors have argued that epoxy resin is better matched for the PHB. This indicated that the previous comment about the existence of epoxy compound after the so-called “completely etched” process in comment 3.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The introduction should discuss related research examples below:

1. Adhesion Optimization between Incompatible Polymers through Interfacial Engineering", Polymers 2021, 13(24), 4273; https://doi.org/10.3390/polym13244273. "The studied treatments include PI surface preparation by cleaning, plasma activation, and roughness modification by abrasion, adhesive bonding by the deposition of an adhesive nanocoating on PI, and the welding of PLA by heating against PI. The use of a nanocoating adhesive such as polydopamine (PDA), known as a universal adhesive, is expected to better transmit the thermoplastic matrix strain level to the sensor"

1. 2. Engineering of Adhesion at Metal-Poly(lactic acid) Interfaces by Poly(dopamine): The Effect of the Annealing Temperature, 2023, DOI: 10.1021/acsapm.3c00672

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

In this manuscript, the authors report the results of their evaluation of the adhesion properties of various polyimides and biopolymers. 

The authors' evaluation of adhesion properties is an interesting study that examines the adhesion properties of versatile polyimides and biopolymers based on various surface characteristics, thereby expanding our understanding of heterogeneous polymer interfaces.

The authors' manuscript is well-structured, the references are well-chosen, and the examples of their work are presented with plenty of specificity, but contain the following major issues that could be improved.

 

1. The authors should provide a detailed explanation for their selection of the specific polyimides examined in this manuscript. This should include the scientific rationale for their choices and an explanation of how these polyimides adequately address the objectives of their study.
2. The authors should thoroughly describe the molecular structures of the polyimides and biopolymers utilized in their research. Including chemical structures, relevant functional groups, and structural features will aid readers in comprehending the scientific basis of their study.
3. The authors should discuss the correlation between the molecular structures of polyimides and biopolymers and their resulting surface properties, substantiating their discussion with citations from relevant peer-reviewed studies.
4. The authors should examine the relationship between the surface microstructure of each polymer and its adhesion properties, supporting their analysis with references to pertinent scientific literature.
5. The authors should analyze the correlation between molecular structure and surface adhesion properties, referencing FTIR spectral data collected from polymer surfaces before and after each treatment to support their conclusions.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have revised the manuscript in accordance with the previous comments.

Reviewer 3 Report

Comments and Suggestions for Authors

As shown in the revised manuscript, the reviewer's suggested issues have been resolved.

The reviewer believes the authors' findings will contribute to advancing the science of the coatings field.

The reviewer recommends accepting the revised manuscript for publication in “Coatings."