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# Preparation, characterisation and secondary crystallisation of PHB based copolymers and carbohydrate blends

Fitzgerald, Annabel Victoria Lucy (2017)
Ph.D. thesis, University of Birmingham.

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## Abstract

Poly(hydroxybutyrate) copolymers are sustainable and biodegradable, but they are known to exhibit secondary crystallisation, which severely reduces the ductility of these materials, thus hindering their current commercial use. Therefore, the main focus of this research was to explore a number of strategies to control the secondary crystallisation behaviour of two Poly(hydroxybutyrate) based copolymers.

Blends of P(HB-co-HV)(3 wt % HV) with carbohydrate molecules of varying chain lengths were prepared by melt blending, characterised, and monitored over time to assess their capability to reduce secondary crystallisation. Additives were found to hinder the secondary crystallisation process, demonstrated by a reduction in the percentage change of mechanical properties as the concentration and chain length increased.

The effect of storage temperature on the secondary crystallisation behaviour of P(HB-co-HHx)(33 % HHx) was also reported. Samples were stored at a range of storage temperatures and the effects on thermal, chemical and mechanical properties discussed. Increasing storage temperature caused the secondary process to occur to a greater extent, with greater increases in the melting temperature recorded in samples stored at 100 $$^∘$$C (128 $$^∘$$C - 135 $$^∘$$C) compared to samples stored at 7 $$^∘$$C (128 $$^∘$$C –
128 $$^∘$$C). Sub-melting point degradation of the material was also noted.

Type of Work: Ph.D. thesis. Jenkins, Mike Colleges (2008 onwards) > College of Engineering & Physical Sciences School of Metallurgy and Materials TN Mining engineering. Metallurgy University of Birmingham 7474
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