SNOPKOVÁ, M. Hodnocení kvality vstupního polyethylenterftalátu pro výrobu recyklovaného regranulátu potravinářské kvality [online]. Brno: Vysoké učení technické v Brně. Fakulta chemická. 2023.

Posudek vedoucího

Kučerík, Jiří

The submitted diploma thesis "Evaluation of the quality of polethylene terephtalate flakes for the production of food grade recycled regranulate” addresses the problems associated with mechanical recycling of PET and upgrading it to a food-grade quality. In particular, the quality of the “raw material” i.e. PET flakes is variable, which can influence both recycling chain and the quality of the PET regranulate. Mrs. Martina Snopková approached the problem methodically by testing the quality of the flakes from various providers from different parts of Europe, from countries differing in the collection systems. The obtained data are unique and applicable for improvements (both technological and legislative) of the PET mechanical recycling system. Mrs. Martina Snopková has been working on her diploma thesis since the 4th year, which is reflected in the amount of experimental data and variability of tested approaches. She presented the results of her research on 90 pages of her diploma thesis, she evaluated the obtained data in a readable, careful, and often original way. Although the subject of the thesis is more technological then fundamental, she worked very well with literary sources (a total of 143 relevant citations). Therefore, it can be stated that the assignment of the work was fulfilled. I would also like to highlight diligence and patience in the elaboration of the work, independence and innovative approach to evaluation. Last but not least, it can be mentioned that the student frequently consulted her data with supervisor and mainly with the consultant and always managed to use it maximally. For this reason, my evaluation of the work is very positive resulting in an overall grade of "A".

Posudek oponenta

Melčová, Veronika

The diploma thesis by Bc. Martina Snopková addresses the issue of the quality of PET flakes from a total of 18 suppliers from different EU countries, which are intended for recycling and subsequent production of PET bottles. The chosen topic is highly relevant due to EU regulations regarding the content of recyclates in PET bottles, and the thesis provides a valuable overview of the European market that has not been conducted before. In the theoretical part, the student showed an overview not only in the research articles on the subject but also in relevant legislation, and thanks to the collaboration with companies in the field since her bachelor's thesis, there is also evident insight into industrial practice in the text. The experimental part consists of approximately 40 pages and includes a brief description of the methods used, obtained results, and a discussion of individual analyses (entrance quality control, spectrophotometry, viscosity measurement, and contamination) conducted on up to 158 batches of PET flakes. My only objection is that it is unclear from the thesis which experiments were performed directly by the student and by the lab technicians mentioned in the text. For each studied parameter, basic descriptive statistics, a thorough discussion of the results, and recommendations/non-recommendations of individual PET flake suppliers are provided. The student also relates the results to the geographic location of the supplier (east/west) and the local type of PET bottle collection (mono/collective), which is a topic continuously discussed in the Czech Republic. The thesis includes innovative approaches to the PET flake quality analysis, such as using the lightness parameter L* instead of visual evaluation and viscosity measurement using a capillary rheometer. All observed trends are verified at the end by correlation analysis. The thesis has a total of 90 pages, is clearly divided into four chapters, and is highly above average in terms of citations, with a total of 143 references to scientific articles, standards, and other relevant sources. It is written in English, without apparent grammatical errors, and is very readable. The thesis fulfils the assignment, and I recommend it for defence.

eVSKP id 148944