Regensburg 2007 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 2: Polymer Physics I
CPP 2.9: Talk
Monday, March 26, 2007, 12:15–12:30, H40
How to stop ageing of biosynthetic PHB - 'melt irradition' — •Antje Bergmann1,2 and Anthony Owen1 — 1Fakultät für Physik, Universität Regensburg — 2Fakultät für Physik, Universität Karlsruhe (TH)
Bacterially processed polyhydroxybutyrate (PHB) is a semicrystalline polymer. Its properties are similar to those of some conventional plastics such as polyethylene (PE). Unfortunately, it undergoes an ageing process, which is characterised by an increasing embrittlement while stored at room temperature. Using various structural analysis methods and comparing the results with those obtained by mechanical measurements we investigated the mechanisms of ageing and found that both a progressive crystallisation process and physical ageing are responsible for the ageing phenomenon.
On the basis of that knowledge we tried out different treatments on the samples in order to prevent the progressive embrittlement. Whereas annealing treatments and the use of plastizisers were not suitable to stop the ageing process completely, irradiation of amorphous PHB with electrons turned out to be a successful method - we call this procedure 'melt irradiation'. An elastic network can be established within the amorphous regions, even though the samples are highly crystalline. This new PHB morphology shows the desired elastic mechanical properties, and the samples are no longer prone to ageing.