Biodegradable poly (hydroxyalkanoates) : melt, solid, and foam
Abstract/Contents
- Abstract
- Plastic materials have a huge impact to the environment. EPA statistics shows that less than 7% of the plastic products are being recycled, and many of the rest are sent to landfills or, in worse scenarios, end up in our natural environment. Poly(hydroxyalkanoates) (PHAs), a family of biodegradable polyesters that can be produced by microbes fed on renewable carbon substrates, can be used as a "green" substitute to conventional plastics and help solve this environmental problem. However, difficulties remain for using PHAs at a sizable scale. Besides the high production cost, weaknesses in material properties, including narrow thermal processing window and insufficient melt elasticity, are also limiting the application of PHAs. Recent progress in PHA syntheses has resulted in new copolymers in the PHA family which are expected to possess improved properties. In this thesis, the melt properties of a series of one such copolymer, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB-co-3HHx), with varying 3HHx content, were investigated. Results suggested that the presence of the propyl side groups on 3HHx increases the steric hindrance of the P3HB-co-3HHx chains, thus resulting in increased entanglement density, and subsequently, the melt elasticity. Solid-state properties of P3HB-co-3HHx were also studied, and the effects on biodegradability of thin films of P3HB-co-3HHx were investigated. Results show that varying copolymer composition in combination with modifying the crystalline morphology through heat treatment may enable control over biodegradation rates for PHAs materials. In addition, biodegradable cellular foams made of PHAs were synthesized through extrusion foaming, a standard melt processing for thermoplastics. A commercial PHA copolymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB-co-3HV), was used and evaluated for its foamability. Another naturally-derived polymer, cellulose acetate butyrate (CAB), was chosen to blend with P3HB-co-3HV to enhance its melt properties and processability. It was found that blending significantly improved the thermal processing window and enhanced melt elasticity. Results showed that selectively combining two types of bio-based renewable polymer could be an effective way to tune the melt properties and crystallinity and thus the processability.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2010 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Liao, Qi |
|---|---|
| Associated with | Stanford University, Department of Chemical Engineering |
| Primary advisor | Frank, C. W |
| Thesis advisor | Frank, C. W |
| Thesis advisor | Billington, Sarah L. (Sarah Longstreth), 1968- |
| Thesis advisor | Criddle, Craig |
| Advisor | Billington, Sarah L. (Sarah Longstreth), 1968- |
| Advisor | Criddle, Craig |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Qi Liao. |
|---|---|
| Note | Submitted to the Department of Chemical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2010. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2010 by Qi Liao
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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