Investigation of the Substitutability of Rubber Compounds with Environmentally Friendly Materials
Round 1
Reviewer 1 Report
The manuscript has been significantly improved by revision.
For example, it should be prominently mentioned in the abstract that this paper is only about replacing some components with environmentally friendly and sustainable products.
Even the title is not quite correct in the linguistic usage of elastomer technology, since polymers and fillers are not referred to as "additives" here.
It should also be mentioned that all three rubber polymers considered are the same product "Natural Rubber" based on polyisoprene, but only of different biological origin.
When mentioning silica as the most important filler for tire treads, it is totally wrong to associate them with "sand or rock". The silica used as a filler has absolutely nothing to do with it, except for the chemical formula. It is not crystalline SiO2 but amorphous precipitated silica in the form of well-defined aggregates of almost monodisperse spheres on nanometer scale.
The introduction of silica as a filler in the 1970s was only possible through the use of compatibilizing sulfur silanes, which make the polar silica compatible with the nonpolar rubber matrix. This technology, which is in use in industry for almost 50 years now, can and must also be used for polar biogenic fillers, e.g. there are recent papers describing the use of lignin or cellulose with silanization and describing a considerable improvement of the elastomer material. This effect must also be discussed for the biogenic polar fillers discussed in the paper.
When discussing substitute fillers, it should also be discussed for which potential applications they are suitable, and whether a complete or partial replacement of silica or carbon black is intended.
The sentence " Since silica is a highly corrosive substance, manufacturers often use it by mixing it with carbon black. " is simply nonsense!
Author Response
We thank the reviewer for their careful reading of the manuscript and their constructive remarks.
We have taken the comments on board to improve and clarify the manuscript.
Please find the attachment for detailed point-by-point response to all comments.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
We would like to thank your addressing all our reviewed comments to the best of your ability.
Author Response
We would like to thank you for your time spent on reviewing our manuscript and your comments helping us improving the article.
Round 2
Reviewer 1 Report
The authors dit the necessary changes to the manuscript. It can be accepted.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
According to its title, this manuscript deals with "Investigation of the Substitutability of Rubber Additives with Environmentally Friendly Materials”.
The Introduction chapter contains more than 3 pages of outdated textbook knowledge on elastomers and rubber. Natural rubber is introduced and it is mentioned that there are also synthetic rubbers. Nothing is said about the specifics of why which rubber is used in the compounding of special parts, including safety-relevant parts such as car tires.
This continues with the mention of fillers, where only carbon black is sufficiently discussed; today's most important filler in the tire industry, silica, is only mentioned in a short list between completely insignificant fillers such as calcium carbonate or talc. It is the fillers that control the most important properties of e.g. car tires, the most important elastomer product: rolling friction (fuel consumption), tire adhesion (safety) and wear (longevity). These three key targets of rubber compounding will not be mentioned or discussed here or in the subsequent course of the manuscript.
The second chapter (“Materials and Methods”) only gives a textbook-like description of the used Analytical Hierarchy Process (AHP) method - a citation would have been quite sufficient instead of the detailed exhaustive textbook-like explanation.Other methods are not discussed or a reason given why the authors chose AHP-method.
In the "Application" section, various natural rubber sources, very idiosyncratically selected fillers and oils of biological origin are discussed without it having been demonstrated that they are suitable for the intended applications of the rubbers.
It follows that the results of the AHP analysis also do not yield any useful recommendations for the rubber compound developer. Especially in the application for tire treads, an adoption of these recommendations would be useless at best, and a dangerous safety risk at worst.
Reviewer 2 Report
See the attachment.
Comments for author File: Comments.pdf
