Recycling plastic parts from discarded, post-consumer products is of paramount importance to reach a sustainable economy. Although mechanical recycling of plastics has been successfully employed for decades, the utilization of plastics in a closed-loop perspective may be compromised by the limited quality of the recycled materials, which usually present a certain level of degradation and contamination. Degradation of the polymers’ macromolecules during the lifetime of plastic parts may occur due to, e.g., exposition to heat, oxygen, and ultraviolet (UV) light. In turn, post-consumer plastics usually contain a certain content of contaminants such as other polymers, paints, or fillers.

There are many different types of stabilizers commercially available aiming to prevent (or retard) polymer degradation. However, for durable goods (with a long lifetime – greater than five years) containing plastic parts, one may expect a certain degree of degradation of the polymeric materials even with the use of stabilizers. It is known that aged plastics may present thermal-oxidative and(or) photochemical degradation, typically leading to chain breaks and the formation of new chemical structures, primarily on the surface of the plastic parts.

Limitations in the disassembling process, as well as in the efficiency of conventional sorting technology employed for post-consumer plastics recycling usually lead to contamination of the sorted materials. Although the presence of a small content of contaminants – such as other types of polymers, inks, and inorganic fillers – is acceptable for low-end applications, it normally impedes closed-loop recycling for high-end products.

Currently, the effects of the combination of degraded molecules and contaminants on the properties of recycled thermoplastics are essentially unknown. In this study, the Ph.D. candidate will analyze the state-of-the-art regarding polymers’ aging, their degradation, and stabilization, and then assess the (anti-)synergistic effects among aged plastics and certain contaminants found in recycled plastics. The scientific basis of the observed effects and their interactions will be investigated and discussed. Later, strategies to improve the quality of the recycled materials will be proposed and analyzed. These strategies may involve the use of additives, (chemical) modifiers, compatibilizers, etc., as well as changes in the recycling process such as sorting and de-inking, among others.

One of the aims of the present research is to indicate possible strategies to improve the quality and the recyclability of post-consumer recycled plastics widely used in durable goods. Polypropylene (PP) is an essential material for this study, but other polymers will also be investigated.

The topic is highly relevant and it is part of several projects with industrial partners. The results will also be coupled with the group's larger work on Recycling Quality (RQ). This Ph.D. topic is meant to go deep into polymer science, to then be translated to the more applied nature of the RQ work (not necessarily by the Ph.D. candidate studying this topic).

• You hold an M.Sc. in one of these fields: Polymer Engineering, Polymer Science, Chemical Engineering, Materials Science – specialized polymers. Candidates without one of these degrees will not be considered.
• Excellent knowledge of structure-property-processing relations in polymers, and polymer characterization methods.
• While we are not looking for a chemist, you have a sufficient grasp of chemistry to understand how polymers may be degraded, stabilized, and chemically modified.
• Experience with polymer processing machinery is a bonus but not required.
• Dedicated to sustainability. Contributing to the circularity of plastics is part of your personal ambition.

• We offer a rewarding career at a young university in the heart of Europe, with a distinct global perspective and a strong focus on innovative research and education;
• You’ll work in an international interdisciplinary team with cutting-edge equipment and a leading academic position in the field of plastics recycling;
• The terms of employment of Maastricht University are set out in the Collective Labour Agreement of Dutch Universities (CAO). Furthermore, local UM provisions also apply. For more information look at the website www.maastrichtuniversity.nl > About UM > Working at UM.
• We offer a full-time employment contract for a period of 1 year, which will be extended for another 3 years after positive evaluation. Remuneration will be according to standard salary levels for PhD candidates starting with a salary of € 2.541,- with a yearly growth to € 3.247,- gross a month (based on a full-time appointment of 38 hours per week). Each year the standard salary is supplemented with a holiday allowance of 8% and an end-of-year bonus of 8.3% of the yearly gross income.
• We offer an attractive package of fringe benefits such as reduction on collective health insurance, substantial leave arrangements, optional model for designing a personalised benefits package and application for attractive fiscal arrangements for employees from abroad.

Maastricht University

Maastricht University is renowned for its unique, innovative, problem-based learning system, which is characterized by a small-scale and student-oriented approach. Research at UM is characterized by a multidisciplinary and thematic approach, and is concentrated in research institutes and schools. Maastricht University has around 22,000 students and about 5,000 employees. Reflecting the university's strong international profile, a fair amount of both students and staff are from abroad. The university hosts 6 faculties: Faculty of Health, Medicine and Life Sciences, Faculty of Law, School of Business and Economics, Faculty of Science and Engineering, Faculty of Arts and Social Sciences, Faculty of Psychology and Neuroscience.

Eager to learn more? Take our virtual campus tour to get a sense of our university culture, the city of Maastricht, and your potential working environment.

Faculty of Science and Engineering
The Faculty of Science and Engineering (FSE) is home to several outstanding departments and institutions covering education and research in Science, Technology, Engineering and Mathematics (STEM) as well as the liberal arts and sciences.

Department of Circular Chemical Engineering; Circular Plastics research group

The Circular Plastics research group is part of the newly created Department of Circular Chemical Engineering in the Faculty of Science and Engineering at Maastricht University. Our research group is uniquely situated in the heart of the Dutch chemical industry at the Brightlands Chemelot campus, 20 km north of Maastricht. Our strong links with industry give excellent opportunity to build collaborations and partnerships, giving good prospects for a future career in industry. Our group has a strong expertise in plastics recycling, polymer processing, characterization and multi-scale structure-property-processing relationships in plastics. The chair is widely recognized as a European leader in plastics recycling research.  We have excellent international connections with esteemed laboratories, and we therefore expect the applicant will have the opportunity to work abroad during their PhD.

To learn more about our department, please visit our website: https://www.maastrichtuniversity.nl/research/circular-chemical-engineering