Thesis-2011-Zhang.pdf (6.23 MB)
Development of polyhydroxybutyrate based blends for compostable packaging
thesis
posted on 2011-02-14, 15:03 authored by Min ZhangIn this research, three polymers have been blended with polyhydroxybutyrate:
poly(ethylene glycol), maize starch and polylactic acid. Their morphology, structure,
thermal, rheological, mechanical properties and biodegradation behaviour have been
studied.
Blends of PHB and PEG, at three different concentrations (2, 5 and 10 wt %) were
prepared by solvent-casting. For these blends the glass transition temperature and
crystallization temperature decreased with increasing PEG content, while the addition of a
low level of PEG (2% and 5%) did not change the thermal stability of the blends.
Blends of PHB with maize starch (72% amylopectin), at different weight ratios of 100/0,
90/10, 80/20, 70/30, 60/40 and 50/50, respectively, were prepared by melt compounding.
The physical properties were found to be optimum at a 70/30 ratio. Blends of PHB with
two types of maize starch (28% amylose and 70% amylose) were prepared at a ratio of
70/30. The starch granules act as a filler and nucleating agent for PHB. Intermolecular
hydrogen bonding was observed in the PHB/starch blends. Hydrogen bonding was found
to be stronger between PHB and high amylose content starch. Thus the PHB/70%
amylose starch blends showed greater improvement in thermal stability, melt viscosity and
mechanical properties compared with the PHB/28% amylose starch blends.
Blends of PHB and PLA at a number of different weight ratios (100/0, 75/25, 50/50, 25/75,
0/100) were prepared by melt compounding. The results indicate that PLA/PHB blends
are immiscible but exhibit some molecular interaction. PHB is highly crystallisable and it
enhances the recrystallization of PLA and results in an increase in the heat distortion
temperature. Adding PLA to PHB improves the mechanical properties of PHB. In fact,
blending with PHB is also a viable approach to improve the mechanical properties of PLA
because the PLA/PHB 75/25 blend exhibits significantly improved tensile properties
compared with pure PLA. This is due to the finely dispersed PHB crystals acting as a filler
and nucleating agent in PLA. The biodegradability of the blends, studied by weight change
measurement at room temperature, improved with increasing PHB content.
History
School
- Aeronautical, Automotive, Chemical and Materials Engineering
Department
- Materials
Publisher
© Min ZhangPublication date
2011Notes
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.EThOS Persistent ID
uk.bl.ethos.551500Language
- en