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Investigations on the Foaming Behaviour of a Toughness Modified Recyclable, Amourphous Polymer

This work presents the influence of core-shell particles as toughness modifier for recyclable, amorphous polymers and their influence on the foaming behaviour. As matrix materials, two amourphous polymers, a styrene-acrylate-copolymer (SACP) and polystyrene (PS) were investigated. The toughness modification of brittle, amorphous polymers like PS, PMMA and PC is already well known in literature, nevertheless the foam properties were not studied yet.

The present results in the field of fracture mechanics show the optimized fracture toughness of the modified SACP. In this work foaming of SACP in correlation with increasing core-shell-rubber content was carried out for the first time. Therefore, different foaming techniques like batch foaming, foam extrusion and bead foaming were investigated. The foaming of the toughness modified compounds showed innovative results. The incorporation and selection of the core-shell particles resulted in varying foam structures. Varying the amount of core-shell particles and the compounding technique resulted in different cell sizes, densities and open cell contents. Using a twin screw extruder resulted in network-like structures by increasing rubber content. These structures resulted in completely open-cell structures by choosing ideal parameters for batch foaming.

Foam extrusion didn't result in completely comparable results, but partially open cell structures were achieved. A transfer to technical scale and calibration of the foams was possible and resulted in low density calibrated foam boards with homogeneous, microcellular cell structures. It is also possible to prepare bead foams with the SACP polymer by adding higher rubber contents. Especially short chain alkanes as foaming agents are suitable for bead foaming of the polymer. The rubber leads to increasing diffusion rates of the foaming agent and therefore especially foaming of the compounds with high amounts of core-shell particles is possible. First investigations on the foaming with an underwater-pelletizer to produce foamed beads was successful. Enclosed block moulding of the foamed beads on a bead moulding machine was working quite well. Furthermore it is possible to recycle the polymer in an easy and innovative way by using NaOH and regaining the neat polymer by changing the pH-value.

Lesen Sie die deutsche Zusammenfassung auf Kunststoffe.de
Author
 Marieluise Lang

Marieluise Lang
Lehrstuhl für Polymere Werkstoffe
Universität Bayreuth

Information

Free keywords: styrene-acrylate-copolymer, polystyrene, core-shell-particles, toughness modifier, Buss cokneader, batch foaming, foam extrusion, bead foams, recyclability, microcellular
Institute / chair: Fakultät für Ingenieurwissenschaften der Universität Bayreuth
Language: German
Technical consultant for expert services: Prof. Dr.-Ing. Volker Altstädt (Betreuer), Prof. Dr. Axel Müller
Publication year: 2014
Provider: Wissenschaftlicher Arbeitskreis Kunststofftechnik (WAK) / Kunststoffe.de

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