Exploring the Potential of Post-Consumer Agroindustrial Subproducts for Nanocellulose-Biobased Adhesives

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript investigates the incorporation of cellulose nanofibers into a polymer-based system with the aim of improving mechanical and adhesive performance. The topic is relevant to the field of sustainable polymer materials, and the experimental work appears to be conducted with reasonable effort. However, in its current form, the manuscript suffers from several fundamental issues that significantly limit its scientific impact and reliability. Most notably, the novelty of the work is not sufficiently established in relation to existing CNF-based systems, and the positioning of the study within the broader literature remains unclear. Several key claims, particularly regarding the role of CNFs in regulating polymerization behavior and network formation, are not adequately supported by direct experimental evidence. In addition, the experimental design lacks critical control groups, and some essential characterizations are either qualitative or insufficiently detailed, raising concerns about the robustness and reproducibility of the conclusions. Furthermore, the discussion tends to overgeneralize the applicability of the proposed system without a rigorous comparison to alternative processing strategies reported in recent literature. As a result, the current conclusions appear premature and require substantial revision and additional experimental support.

1. The manuscript mainly focuses on the performance enhancement of a PVA-based adhesive system through the incorporation of TEMPO-oxidized CNFs combined with APTES modification. However, similar strategies involving CNF/PVAc systems or silane-modified nanofibers have been extensively reported in the literature. The authors do not clearly articulate the substantive innovation of the present work relative to these prior studies, particularly at the mechanistic level, where the discussion remains largely qualitative. How does the strategy proposed in this work compare with recent dissolving-based approaches for cellulose nanomaterials reported in the literature?

The authors are strongly encouraged to consider and discuss recent advances in this area, for example the comprehensive review published in Cellulose (2024, 31: 27–60), and to clearly clarify the positioning and unique contribution of the present study within the broader research context.

2. The authors repeatedly emphasize that CNFs not only act as reinforcing fillers but also actively regulate the heterogeneous polymerization process and network structure. However, the supporting evidence is largely indirect, relying mainly on rheological behavior and macroscopic mechanical performance. Direct experimental evidence—such as monomer conversion kinetics, particle size evolution during polymerization, or chemical bonding analysis—is absent. The lack of such data significantly weakens the credibility of this key claim.

3. The effectiveness of APTES modification is confirmed only qualitatively by FTIR analysis, which is insufficient to evaluate the degree of grafting, surface coverage, or reproducibility. Given that silane modification is presented as a critical factor contributing to performance enhancement, the absence of quantitative characterization (e.g., XPS, elemental analysis, or nitrogen content determination) makes it difficult to establish a clear causal relationship between surface modification and property improvements.

4. Both TOCNF-APTES and SDS are introduced simultaneously into the polymerization system, yet their individual contributions to particle size distribution, rheological behavior, and adhesive strength are not systematically distinguished. The current experimental design does not rule out the dominant influence of the surfactant. At a minimum, control systems without CNFs (SDS-only) and without SDS (CNF-only) should be included. Without these controls, the conclusions remain ambiguous.

5. The adhesive performance is evaluated solely through ASTM D905 shear strength testing under a single condition. Important performance metrics, such as water resistance, durability under humid or thermal aging conditions, and failure mode analysis, are not addressed. For a study claiming a “high-performance and sustainable wood adhesive,” the current level of mechanical evaluation is insufficient, and the application-oriented conclusions appear overstated.

6. Several key experimental steps—such as the energy input during TEMPO oxidation, the efficiency of APTES modification, and polymerization conversion—lack error analysis or discussion of batch-to-batch variability. Moreover, certain experimental parameters (e.g., ultrasonication energy and shear history) are known to be highly sensitive yet are not adequately controlled or reported. These issues limit the reproducibility of the study and reduce its value as a reference for future research or potential scale-up.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

1. The abstract lacks the description of the experimental data, which makes it impossible to directly present the experimental results.
2. The introduction section lacks logical coherence. The methods described in the text and the expected conclusions from the experiments do not have sufficient correlation.
3. The lignin content of rice husks and olive pomace mentioned in Section 3.1 is different from the data shown in Table 2. Is it necessary to verify the accuracy of the data?
4. The article states that the viscosity of the apple pomace TOCNF suspension is very high, but no relevant data is provided, making it impossible to assess its impact on the subsequent processing and the sufficiency of choosing rice husks TOCNF for the subsequent research. It is suggested to provide the viscosity data of the apple pomace TOCNF suspension or to explain in more detail why rice husks TOCNF was chosen for the subsequent study.
5. CNFs were prepared using rice husk and apple pomace as the main raw materials. However, it was mentioned that the viscosity of the TOCNF suspension made from apple pomace was high, so the analysis was mainly focused on the rice husk. Can the conclusions drawn from the single raw material be applied to other raw materials?
6. The list of 8 raw materials mentioned in the selection process, however, applies to all other raw materials as well (such as tomato pomace). Could you please further explain the advantages of choosing rice husk and apple pulp as raw materials, or the shortcomings of other raw materials?
7. The final prepared adhesive only lists the bonding performance, lacking tests for other properties and application conditions, and is insufficient to demonstrate the advantages of the prepared adhesive; it can be compared with the performance of commonly used adhesives on the market to prove the superiority or inferiority of the performance?
8. After being stored for two weeks, the PVA-TOCNF-APTES emulsion exhibited phase separation, indicating that the nanofibers were insufficiently stable as stabilizers at the interface between the PVA polymer and water. For practical adhesive applications, long-term stability is of crucial importance. It is recommended to discuss the mechanism of emulsion phase separation and explore strategies to enhance its long-term stability.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

In this paper the authors describe the preparation and characterization of  bio-based wood adhesives, through the valorization of agro-industrial residues as sources of functional polysaccharides.

The Introduction part is too large in my opinion, with an unusual high number of references. I recommend to reduce them.

The Materials and Methods sections are well described and the provided information is complete and sufficient for another user to replicate the experiment.  

The Results and Discussion part is clearly presented, and no scientific errors were identified in the manuscript. A comparison with currently bio-based or commercial PVA adhesives is needed.

Conclusions are supported by the experimental data.

The manuscript is scientifically correct and very well written. Therefore, I recommend it for publication.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The author has revised the article as required and it can be accepted.

Author Response

We appreciate the time and effort invested in evaluating our work. 

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript has been improved.

I recommend it for publication.

Author Response

We appreciate the time and effort invested in evaluating our work.