Role of PFAS substances in the plastic manufacturing process

Abstract

The aim of this thesis was to study the significance of per- and polyfluoroalkyl substances (PFASs), such as their sources and possible alternatives in plastic food packaging. In addition, efforts were made to clarify, for example, the PFASs testing methods for the packaging materials. The thesis was commissioned by a client company that uses extrusion processes to manufacture plastic films from raw materials containing polymeric PFASs for example for the food packaging industry. The subject was relevant for the company as the pending proposal for PFAS restriction measures in Europe includes the ban of all polymeric PFASs, which would affect the composition of the raw materials used. The entry into force of the proposed restrictions would mean that there should be alternative raw materials for polymeric PFAS-based raw materials. In addition, their performance in high volume manufacturing processes should be guaranteed. The research methods used in the thesis can be divided into a literature and an experimental part. The experimental part included a survey to raw material suppliers, total organic fluorine (TOF) analysis of granulates and a product development interview. A questionnaire sent to suppliers (the response rate was 90 %) of raw materials collected additional information on the link between granulates and PFASs. TOF analyses carried out in external laboratories were used to determine the fluorine content of granulate samples. The survey results indicated both positive and negative aspects. The TOF analysis showed large variation between different raw materials and laboratories. Based on the laboratory tests, TOF analysis cannot be considered a reliable method for determining the PFAS content of plastic granulates. One factor affecting this was the small number of material samples. The interview showed that polymer processing aid (PPA) has an essential impact on the plastic manufacturing process, on the extrusion, regarding for example the film quality and production flow. The interview seemed to strengthen the theoretical basis offering answers for the remaining questions. In the future, a larger sample for analysis is proposed to build a more comprehensive response. Testing of finished plastic films is also recommended to investigate possible contaminants transferred from the extrusion machinery to the sample. Moreover, trial production runs without polymer processing aid and metallocene polymers with PPA are recommended to investigate the effect on polymer flow, production efficiency and flexibility, as well as on the quality of the plastic film.