Project Details
Projekt
Influence of topology of well-defined branched polymers on foam extrusion and mechanical properties of polymer blends
Subject Area
Polymer Materials
Term
since 2024
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 553369617
Topology and tacticity of homopolymers strongly influence their processing and end-use properties. Polymers with a so-called pom-pom architecture (two stars which are covalently linked by a linear chain, pom-pom polymers) have exactly two branching points which yield pronounced strain-hardening in melt elongation. Consequently, pom-pom polymers are ideally suited to tailor processing by means of film blowing and foam extrusion if they are used as an additive. In particular, closed cell polymer foams with a very low density (xi < 0.04 g/cm3) can be prepared with low additive concentrations of these branched polymers. In this project, the influence of topology of self-synthesized well-defined branched polystyrenes (PS) on the processing of polymer blends by means of foam extrusion and on the mechanical properties is studied. The branched polymer (concentration < 3 wt%) is the minority component of the blends with a chemically identical linear homopolymer (atactic and syndiotactic PS, respectively). Consequently, the branched polymers can be used as additive for recycled polymers and their up-cycling. A main objective is the up-scaling of the synthesis of well-defined branched polymers by means of anionic polymerization with a yield in the range of more than 100 g for engineering applications. Furthermore, we investigate in detail the influence of well-defined branched polymers on the thermal, rheological and mechanical properties of polymer blends and of the extruded foams. The rheological properties will be modelled using the pom-pom and the molecular stress function models to predict strain-hardening based on linear shear rheology and polymer topology. We focus on the influence of topology (pom-pom, barbed wire, Cayley-tree) and the molecular parameters (number and molar mass of arms and of backbone) on (I) the thermal transitions (glass transition, melting and crystallization temperature) and (II) on the rheological properties under loading with a physical blowing agent. In addition, the influence of concentration of blowing agent on foam extrusion with carbon dioxide (III) as well as the mechanical properties of foams under uniaxial, quasi-static loading (IV) will be investigated. The objective of this project is to establish structure-processing-properties relationships between molecular structure (topology, tacticity) of both blend components and the foam properties (processing/mechanical properties as well as morphology and foam density). The fundamental understanding gained based on the PS model systems shall be transferred to polylactide for a few, specially chosen topologies. The results will promote the development of high-performance additives for the production of closed cell polymer foams and will enhance up-cycling of polymer recyclates.
DFG Programme
Research Grants
International Connection
Belgium
Cooperation Partner
Professorin Evelyne Van Ruymbeke, Ph.D.
