Design of temperature resistant recycled PET/PBT bead foams and clarification of structure-property-relationships when foaming and welding.

• Applicant: Professor Dr.-Ing. Holger Ruckdäschel, since 2/2023
• Subject Area: Plastics Engineering
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 456088221

The long-term objective of the joint project between the Polymer Engineering department of the University Bayreuth and the Metallurgical and Materials Engineering department of the Istanbul Technical University is to develop innovative bead foaming technology for three-dimensional shaped recycled poly(ethylene terephthalate) (rPET)/poly(butylene terephthalate (PBT) (not established yet) foam products with ultra-low density, using an environment-friendly blowing agent, CO2. This is while the effect of crystallization kinetics and rheological properties of the developed polymers and blend systems with and without the use of different chain extenders (CE) on the processability and the foaming mechanisms of the developed foamed beads will be extensively investigated. Although bead foaming of rPET/PBT blends could be very advantageous for various technical applications (where high temperature resistance is required) due to their miscibility and crystallization temperature differences, the bead foams of these blends have not been introduced yet. The proposed technology will combine four steps: (1) formulation development for bead foams and fundamental studies on the rheological, molecular and thermal properties of the materials, (2) batch-based foaming with an autoclave foaming process and fundamental studies on the effect of material formulations and processing parameters (i.e. saturation pressure, temperature and time) on the foaming behavior of the samples (final cell nucleation and expansion behavior of the foamed samples). Results from these fundamental studies will be utilized to manufacture beads with the pilot scale continuous bead foaming using extrusion process equipped with underwater pelletizer and characterization of the bead foams, and (4) sintering/molding with a steam chest molding process and exploring the final quality of the sintering or cohesion of the molded bead foam parts. The fundamental scientific aim is to control the crystallization behavior of rPET/PBT blends during the bead foaming process using an underwater pelletizer and to work out correlative relationships with the final foaming and welding results. The use of rPET products is of a great importance for environmental protection and provides an effective and efficient means of recapturing and reusing the energy and resources of its raw materials. However, extrusion foaming of recycled PET and PBT is creating several challenges due to their low melt strength and hence they have to be chemically modified to improve the processability. Therefore, rPET/PBT blends will be systematically chemically modified with different chain extenders improving the rheological properties and hence the melt properties of these polymers. Blending of rPET and PBT derives from the idea that two polymers with different crystallization kinetics can affect crystallization behavior and the desirable formation of a double melting peak which could be benefical for the fusion behavior of bead foams.

• DFG Programme: Research Grants
• International Connection: Turkey
• Partner Organisation: TÜBITAK The Scientific and Technology Research Council of Turkey
• Cooperation Partner: Professor Dr. Reza Nofar
• Ehemaliger Antragsteller: Professor Dr.-Ing. Volker Altstädt, until 1/2023