Experimental Tests on Solvent Solutions for the Recycling of Coated Polypropylene in Food Packaging

Round 1

Reviewer 1 Report

The paper Experimental tests on solvent solutions for the recycling of food packaging coated polypropylene approaches a topic of experimental research in a field of major importance for the environmental protection. I appreciate and respect the experimental work of the authors, the instrumental analysis and the effort of editing the manuscript. The instrumental analyzes and the experimental results obtained in the investigations are relevant for the aim proposed by the authors.

To be published, I believe that it is absolutely necessary to improve or clarify the following aspects:

1. The authors justified the aim of the research in removing the coating from the polypropylene film, without affecting the mechanical properties, for the purpose of recycling.  The Introduction refers too much to plastic benefits for food packaging but it does not mention recycling techniques that require preserving the mechanical properties of the plastic waste. I recommend completing the paper with some aspects regarding current techniques for recycling and valorizing plastic waste. Why the authors consider it necessary to test a technique aimed at preserving mechanical property, knowing that the energetic and material valorization implies just the chemical/mechanical transformation of the material.

2. How the plastic film freed from the coating may be further used? It is obvious that in recycling the plastic waste will undergo a major transformation, if not abandoned in the environment. If the goal is not recycling, but reuse, what would be the potential applications of these foils from which the coating has been removed? Could this option be feasible and safe? This information should be clarified in the Introduction.

3. From the references studied, are there any authors who have addressed the problem of removing the coating from plastic foils for recycling or reuse, caring to preserve the mechanical properties too? What is the status of the research in this issue? I recommend a better argumentation of the aim of the research for removing the acrylic or aluminum layer in the light of the real applicability of the proposed technique.

4. Page 3: Replace <samples were obtained called basic film>, with <the samples obtained were called basic film>

5. Page 4: Please mention 99.9 methanol solvent, but not solution. Only KOH 1M is a solution in this case.

6. Which is the standardized method(s) used in 2.2 Selective dissolution? Or are these methods taken from other researches? Please cite the reference.

7. The authors argue the selection of methanol (an extremely toxic solvent, subject to strict regulations) only because it has already been used to remove the non-polymeric layers from the film, by manual scrubbing, at the factory. But the method used by the authors, of immersing the samples in the solvent, under mechanical stirring, for 15 min., generates very toxic vapors, and the operator is exposed to inhalation of methanol vapors. I believe that for practical application another solvent, effective but less toxic, will have to be selected and tested.

8. Conclusions should be elaborated in more detail based on the experimental results, without repeating the theoretical information from the introduction. Also, the applicability of the proposed method should be pointed out, in which recycling techniques or in what kind of reuse applications this technique can be capitalized, which does not require mechanical transformation.

The manuscript has important gaps and ambiguities; requires major changes, which I mentioned in the report.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

This work is potentially interesting and although the article is interesting, there are problems with the authors' style, which, in places, is a little tedious and not engaging for the reader. Therefore, the authors need to carefully read the paper and make the necessary corrections and changes to promote reader engagement. There are 11 figures and 7 tables in the article, I think they took half of the place in the draft. Some figures can be combined. I feel there are more figures, tables and fewer explanations. I would be happy to see the TGA data before and after removing the layer.

There are a lot of formatting errors in the paper; please revise carefully.

For example, please define LWIR.

You said in the text  Tab. 10, Fig. 12, Fig. 13 but t there is no Table 10 and fig. 12 in the manuscript.

All figures for ATR have different line widths; please keep the same in all figures.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors answered in evidence to all the aspects for which I asked for clarification in the first round review. The manuscript was completed with relevant information; the content is much improved.