Recent Trends of Recycling and Upcycling of Polymers and Composites: A Comprehensive Review

Round 1

Reviewer 1 Report

In this review, the authors summarize many recycling technologies for thermoset and thermoplastic polymers, detailing some experimental procedures.

The manuscript is rich and well written, and an almost exhaustive bibliography is added. However, I believe a few points require minor revisions to strengthen the quality of the work.

Below are my thoughts and some detailed comments that might help revise the manuscript.

1. A few sentences have to be rephrased more clearly: For example, “Carbon Fibre Reinforced Polymers (CFRP) are extremely strong and light-weight materials that possess significant advantages over conventional isotropic materials such as steel and aluminium counterparts.” (page 1, lines 42-44). The sentence “This comprehensive review combines all recent recycling technologies for thermoset and thermoplastic polymers, sharing details about existing experimental procedures and comparing the effectiveness of each methodology.” is not correct.

On page 3, lines 113-114, the manuscript is named Chapter, but this is not a book. Sentences on page 28, lines 1262-1264 are not useful.

2. There are no comparative tables among different techniques.

3. SEM in Figure 1 are original images? Reference to related published articles is not reported.

4. There is a little confusion about thermosets and composite materials: not all thermosets are composite, so the separation of the reinforcement cannot be the only discriminant.

5. More recent studies about CAN are not included.

6. Language needs minor revision. Many typing errors in spacing between numbers and measurement units, and some chemical formulas require corrections.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

This is an interesting study on the upcycling of various polymers and composites. However, several problems are contained.

1) Various types of fillers are added to each polymer to make composite materials, but the introduction should explain in detail what drawbacks the inclusion of fillers may have for recycling.

2) The content should be divided into sections for each polymer, and a brief description of the polymer-specific structure and properties derived from the polymerization method should be added at the beginning of each section.

3) Pyrolysis, the main method of composite material recycling, is mentioned in the text, but not enough is made of it.

a) Equipment for pyrolysis should be described in detail.

b) Pyrolysis mechanism of a typical polymer should be shown.

c) The influence of the presence of filler (fiber) on the pyrolysis mechanism should also be shown with a representative example.

4) Cases of microplastics during recycling should be mentioned and introduced.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Corrections are confirmed.