Comparative Study of Seal Strength and Mechanical Behavior of Untreated and Corona-Treated Polymer Films
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis manuscript addresses a highly relevant topic in the packaging and polymer processing industry. Understanding how corona treatment affects both seal strength and mechanical properties of different polymer films is not only scientifically interesting but also practically important for optimizing packaging performance and process reliability. The comparative analysis across multiple films under different corona power levels offers valuable insights that could guide industrial parameter selection.
In the abstract, it is recommended to briefly include information on the experimental design. Overall, the abstract is sufficient.
The introduction section provides fundamental background well; however, it does not clearly highlight which specific research gap this study addresses. In particular, please explicitly state which aspect of the effect of corona treatment on seal strength has not been previously investigated and how this study addresses it.
In the materials and methods section, the film production methods (e.g., blown, cast, biaxially oriented) should be specified, as they can influence the effects of corona treatment.
The selection of the 100 W and 300 W power levels should be justified (based on literature or industrial practice).
The suitability of the heat-sealing conditions (temperature, time, pressure) with industrial standards or the need for optimization for each film type should be discussed.
In the results and discussion section:
FTIR findings should be supported with quantitative data (e.g., peak area ratios).
Correlation analyses explaining the relationships between surface free energy, mechanical properties, and seal strength should be added.
Unexpected mechanical behaviors (e.g., the fluctuating elongation at break in OPP1) should be discussed in the context of polymer structure or morphological changes.
Conclusions and Practical Recommendations:
The conclusion section should go beyond summarizing the findings. Practical, application-oriented recommendations should be provided, such as the optimal corona treatment ranges for each film type or specific conditions to avoid.
Author Response
C1: This manuscript addresses a highly relevant topic in the packaging and polymer processing industry. Understanding how corona treatment affects both seal strength and mechanical properties of different polymer films is not only scientifically interesting but also practically important for optimizing packaging performance and process reliability. The comparative analysis across multiple films under different corona power levels offers valuable insights that could guide industrial parameter selection.
Ans: Thank You, we appreciate this comment
C2: In the abstract, it is recommended to briefly include information on the experimental design. Overall, the abstract is sufficient.
Ans: Thank you for this remark. We have revised the abstract to briefly describe the experimental design, including the treatment conditions and the types of analyses performed.
C3: The introduction section provides fundamental background well; however, it does not clearly highlight which specific research gap this study addresses. In particular, please explicitly state which aspect of the effect of corona treatment on seal strength has not been previously investigated and how this study addresses it.
Ans: We thank the Reviewer for this insightful comment. While the effects of corona treatment on surface energy and mechanical properties of fossil-based and biodegradable polymers are well documented, the relationship between treatment intensity and seal strength—particularly in the context of different polymer types—has not been systematically explored. There are only a few papers dealing with this problem. Those are:
Ref 13: Das, B.; Chakrabarty, D.; Guha, C.; Bose, S. Effects of Corona Treatment on Surface Properties of Co-Extruded Transparent Polyethylene Film. Polym. Eng. Sci. 2021, 61, 1449–1462, doi:10.1002/PEN.25663.
Ref 26: Farley, J.M.; Meka, P. Heat Sealing of Semicrystalline Polymer Films. III. Effect of Corona Discharge Treatment of LLDPE. J. Appl. Polym. Sci. 1994, 51, 121–131, doi:10.1002/APP.1994.070510113.
These references have been mentioned by us in our paper. However, we have rewritten the introduction section to clarify this focus.
C4: In the materials and methods section, the film production methods (e.g., blown, cast, biaxially oriented) should be specified, as they can influence the effects of corona treatment.
Ans: We appreciate the Reviewer’s observation and fully agree that the production method of polymer films can influence their response to corona treatment. However, the films used in this study were provided by an industrial partner under non-disclosure terms. Therefore, we were not allowed to disclose specific details regarding their manufacturing processes. We have clarified this limitation in the Materials and Methods section.
C5: The selection of the 100 W and 300 W power levels should be justified (based on literature or industrial practice).
Ans: We appreciate the Reviewer’s comment. The choice of 100 W and 300 W was based on preliminary trials and practical considerations. Higher power levels (higher than 300 W) were found to cause visible surface degradation, which affects material integrity. Additionally, it is important to note that the electrode passed over the film surface twice (forward and backward), effectively doubling the exposure. Considering the film width and line speed, the resulting energy densities were approximately 99 and 297 W·min·m⁻² for the 100 W and 300 W settings, respectively.
Two sentences were added to section 3.2.2.
C6:
The suitability of the heat-sealing conditions (temperature, time, pressure) with industrial standards or the need for optimization for each film type should be discussed.
Ans: Thank You for this valuable remark. The primary goal of this study was to investigate the influence of surface free energy on the sealability of the polymer (OPP and BOPP) films. To isolate this effect, we focused on three levels of corona treatment: no treatment, 100 W, and 300 W. Considering additional variables such as sealing temperature, time, or pressure would have complicated the analysis and potentially obscured the relationship between surface energy and sealing performance.
Nevertheless, we agree that optimizing sealing parameters for each film type could be an interesting direction for future research. Techniques such as Design of Experiments (DoE) and Response Surface Methodology (RSM) could be employed to systematically explore these variables.
We have added a note regarding this consideration in the Materials and Methods section (lines 181 – 184).
C7: FTIR findings should be supported with quantitative data (e.g., peak area ratios).
Ans: Thank you for your comment. We acknowledge the importance of quantitative FTIR analysis. However, in this study, FTIR was used primarily to confirm the presence of functional groups introduced by corona treatment, not on the quantitative FTIR analysis. Although FTIR analysis confirmed the presence of polar functional groups after corona treatment, we did not observe a distinct and sharp peak corresponding to C=O stretching vibrations, as reported by other authors. Despite the substantial increase in surface free energy, the spectral changes remained subtle and consistent, supporting a qualitative interpretation. Therefore, we chose not to include peak area ratios, as the FTIR data served primarily to confirm the presence of functional groups rather than quantify their abundance.
C8: Correlation analyses explaining the relationships between surface free energy, mechanical properties, and seal strength should be added.
Ans: Thank You for this remark. We have provided the results of Pearson and Spearman correlation.
C9: Unexpected mechanical behaviors (e.g., the fluctuating elongation at break in OPP1) should be discussed in the context of polymer structure or morphological changes.
Ans: Thank you for your thoughtful comment. We have expanded the discussion and add few sentences to explain the changes in elongation at break observed in OPP1.
C10: The conclusion section should go beyond summarizing the findings. Practical, application-oriented recommendations should be provided, such as the optimal corona treatment ranges for each film type or specific conditions to avoid.
Ans: Thank you for this remark. In response, we have revised the conclusion section to highlight the practical, application-oriented recommendations regarding optimal corona treatment of plastic films. We hope the updated version meets your expectations.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe introduction provides an adequate overview of the industrial context of polymer packaging films, highlighting the challenges associated with low surface free energy and the role of corona treatment in overcoming them. The literature cited covers both fundamental studies and recent work (2020–2025) - demonstrates awareness of current developments. The research gap is also well identified, namely the lack of systematic analysis of treatment power on sealing performance. On this basis, the introduction provides sufficient background and includes the relevant references.
The experimental design is suitable for addressing the stated research question. Multiple polymer films were studied under controlled corona treatment conditions at two power levels. This comparative approach allows material-specific effects to be distinguished, which directly serves the stated aim. the design is appropriate to answer the research question.
The methods section describes film selection, corona treatment, contact angle, SFE, FTIR, and seal strength testing. While sufficient for understanding the general procedure, certain details (e.g., exact operating parameters of corona treatment, sample size for statistical robustness, calibration details for instrumentation) could be expanded to ensure full reproducibility. The methods are fundamentally sound, but they can be improved with additional detail.
The results are organized logically, progressing from surface free energy to chemical characterization (FTIR) and then to sealing strength. Figures and data are consistent with the textual discussion. Results are clearly presented.
The conclusions appropriately reflect the experimental outcomes. The proportional relationship between surface free energy and seal strength is well substantiated. Material-specific responses to corona treatment are discussed with sufficient nuance. Conclusions are supported by the results.
Figures are generally informative, but in some cases, formatting could be improved (axis labels, resolution, removal of extraneous line numbers). Tables are clear and consistent with the narrative. Figures and tables are usable, they can be improved in presentation quality.
The English is overall clear and professional. Minor improvements in conciseness and reduction of repetitive phrasing would further enhance readability. English could be improved but does not contain major errors.
The study provides new insight by linking corona treatment intensity with sealing performance, which is not widely addressed in the literature.
Findings have direct industrial relevance, particularly for optimizing packaging processes. The structure is coherent, but improvements in figure clarity and removal of formatting inconsistencies are needed. The experimental work is methodologically reliable and the interpretation consistent with the data. Researchers and practitioners in packaging science, polymer processing, and surface engineering will find the work relevant. The paper makes a valuable contribution to the field.
The references are largely appropriate and up to date. However, some duplication exists (e.g., Chen et al. cited twice) and certain entries include metadata errors that should be corrected. The references are relevant but require careful revision for formatting accuracy.
Comments on the Quality of English LanguageThe English is overall clear and professional. Minor improvements in conciseness and reduction of repetitive phrasing would further enhance readability. English could be improved but does not contain major errors.
Chapter 2 has subchapters 3.xxx - line 96, 103, 106, 119, 129, 149, 165
Author Response
C1: The methods section describes film selection, corona treatment, contact angle, SFE, FTIR, and seal strength testing. While sufficient for understanding the general procedure, certain details (e.g., exact operating parameters of corona treatment, sample size for statistical robustness, calibration details for instrumentation) could be expanded to ensure full reproducibility. The methods are fundamentally sound, but they can be improved with additional detail.
Ans: Thank you for your helpful comment. We have expanded material section to ensure reproducibility. We hope these additions enhance the clarity and completeness of the experimental procedure.
C2: Figures are generally informative, but in some cases, formatting could be improved (axis labels, resolution, removal of extraneous line numbers). Tables are clear and consistent with the narrative. Figures and tables are usable, they can be improved in presentation quality.
Ans: We have revised all figures to improve clarity and presentation quality.
C3: The English is overall clear and professional. Minor improvements in conciseness and reduction of repetitive phrasing would further enhance readability. English could be improved but does not contain major errors.
Thank You for this remark, we have carefully edited to enhance conciseness and eliminate repetitive expressions. We believe these changes improve the overall readability and flow of the text.
C4: The references are largely appropriate and up to date. However, some duplication exists (e.g., Chen et al. cited twice) and certain entries include metadata errors that should be corrected. The references are relevant but require careful revision for formatting accuracy.
Ans: Thank You for this remark, we have reviewed and corrected the reference list.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript is devoted to the study of the effect of corona treatment on the properties of polyethylene and polypropylene films.
Corona treatment increases the free surface energy, which leads to an increase in surface wettability, as demonstrated in this paper by measuring the water contact angle.
On the other hand, corona treatment can sometimes lead to a decrease in strength characteristics. The paper demonstrates the selection of optimal treatment conditions that do not affect strength characteristics. The change in phase composition during corona treatment was investigated using FTIR spectroscopy.
There are no significant drawbacks in the paper.
It is advisable to decipher the abbreviations OPP, BOPP.
Author Response
C1: There are no significant drawbacks in the paper.
Ans: We thank the Reviewer for the positive and encouraging evaluation of our manuscript
C2: It is advisable to decipher the abbreviations OPP, BOPP.
Ans: We have updated the manuscript to include the full forms of the abbreviations at their first occurrence.
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsMost of the requested revisions have been adequately addressed. However, the point regarding the production method of the films (blown, cast, biaxially oriented, etc.) remains unclear. The authors explain that disclosure is restricted due to industrial confidentiality. While this explanation is understandable, the limitation should be explicitly acknowledged in the Materials and Methods section, and the potential impact on the generalizability of the findings should be clearly stated.
Author Response
Comment 1: Most of the requested revisions have been adequately addressed. However, the point regarding the production method of the films (blown, cast, biaxially oriented, etc.) remains unclear. The authors explain that disclosure is restricted due to industrial confidentiality. While this explanation is understandable, the limitation should be explicitly acknowledged in the Materials and Methods section, and the potential impact on the generalizability of the findings should be clearly stated.
Answer: Thank you for your valuable comment. We acknowledge the importance of specifying the production method of the films. However, due to industrial confidentiality constraints, we are unable to disclose this information. To address this limitation, we have explicitly acknowledged it in the Materials and Methods section. We hope this clarification is satisfactory. We have higlithed the comment with yellowe.
