Dissertation
INVESTGATION OF PHOSPHATE ESTER CURED EPOXY SYSTEM: CURING KINETICS, MECHANICAL, PROPERTIES, DEGRADATION, AND APPLICATIONS
Doctor of Philosophy (PhD), Washington State University
01/2017
Handle:
https://hdl.handle.net/2376/111754
Abstract
In this study, the prepolymers based on phosphate monoesters were used as curing agents for cure epoxy compounds to form three-dimensional network polymers. The potential biomedical application of the crosslinked polymers with phosphate ester linkages was investigated.
The P-OH groups of phosphate ester play an important role in the system. The curing reaction of phosphate ester and epoxy could proceed at room temperature without the presence of solvent and catalyst, which was due to the high reactivity of the P-OH group of phosphate ester. The mechanism of phosphate ester reaction with epoxy group was studied, and the reactivity was influenced by the P-OH proton activity. The reactivity of phosphate diester was the highest compared to phosphate monoester and phosphoric acid. On the other hand, the P-OR ester bonds are subject to hydrolytic cleavage under basic or acid condition, resulting in degradation of the crosslinked polymers.
The curing kinetics was measured by differential scanning calorimetry (DSC) and chemorheometry. The curing activation energies were calculated and the values were significantly lower than that of the reactions of epoxy with amine or anhydride type curing agents, suggesting that the phosphoesters were more reactive when reacting with epoxies.
The mechanical properties of the cured systems were manipulated by varying the structures of phosphate ester and epoxys, stoichiometric ratio, and molecular weight of the prepolymer used for the preparation of phosphate ester. By varying the chain softness/rigidity of the curing agent or epoxy in the resin system, the spectrum of mechanical properties of the crosslinked polymer was manipulated greatly. The molar ratio of P-OH/epoxy also exhibited great influence on the crosslink density of the cured resin. When the P-OH/epoxy molar ratio was 2:3, the system had the highest crosslink density, consequently resulting in highest mechanical properties.
One of the important advantages of the phosphate ester crosslinked polymers is the in vitro degradability. In vitro cytotoxicity tests of the crosslinked polymers with phosphate linkages were conducted, and the results suggested that this type of crosslinked polymers had great potential to be used in biomedical field, such as drug delivery, tissue engineering, and scaffold.
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Details
- Title
- INVESTGATION OF PHOSPHATE ESTER CURED EPOXY SYSTEM: CURING KINETICS, MECHANICAL, PROPERTIES, DEGRADATION, AND APPLICATIONS
- Creators
- Jia Cheng
- Contributors
- Jinwen Zhang (Advisor)Ming Xian (Committee Member)Kerry Hipps (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Materials Science and Engineering Program
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 172
- Identifiers
- 99900581829801842
- Language
- English
- Resource Type
- Dissertation