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Foaming and Powderisation of Selected Biopolymers

The foaming of biopolymers with pressurised carbon dioxide was investigated by using two different procedures. Three polyesters were chosen as model substances. They were based on biological substances and/or biologically degradable. All polymers were characterised via differential scanning calorimetry and rheology. Their carbon dioxide induced melting behaviour was investigated, too.

The first foaming procedure consists of three steps, powderisation, encapsulation of a blowing agent and foaming. Both powderisation and encapsulation were accomplished via PGSS-process (particles from gas saturated solutions). First, the polymers were sprayed separately without any blowing agent in order to determine adequate process parameters. The obtained powder was characterised, e.g. because of particle size and morphology. Once water as model substance for a blowing agent is encapsulated, the process parameters need to be adjusted.

As second procedure, a direct foaming process was established. The polymer granules were filled into porous moulds and saturated with pressurised carbon dioxide at elevated temperatures. The gas dissolves into the polymer. Due to the subsequent expansion of the system, the volume of polymer is enhanced. Hence, stabile foams are created. Appropriate foaming parameters were identified for each polymer up to pressures of 30 MPa. The samples were characterised by using compression strength tests.

The PGSS-process yields important knowledge about the behaviour of the polymers being sprayed in presence of water. The direct foaming procedure was easier to handle and yields foams in only one step.

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Author
 Sulamith Frerich

Sulamith Frerich
Lehrstuhl für Verfahrenstechnische Transportprozesse
Ruhr-Universität Bochum

Information

Free keywords: Biopolymers, carbon dioxide, PGSS-process, molding, foam
Institute / chair: Fakultät für Maschinenbau der Ruhr-Universität Bochum
Language: German
Technical consultant for expert services: Prof. Dr.-Ing. E. Weidner (Betreuer), rof. Dr.-Ing. M. Petermann
Publication year: 2011
Provider: Wissenschaftlicher Arbeitskreis Kunststofftechnik (WAK) / Kunststoffe.de

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