| Author: | Yung, Kin-on Brian |
| Title: | Preparation and characterization of biodegradable PLLA fibers for orthopedics applications |
| Degree: | M.Sc. |
| Year: | 2000 |
| Subject: | Polymers in medicine -- Biodegradation Polymers in medicine -- Mechanical properties Orthopedic implants Hong Kong Polytechnic University -- Dissertations |
| Department: | Multi-disciplinary Studies Jockey Club Rehabilitation Engineering Centre |
| Pages: | xi, 65, [30] leaves : ill. ; 30 cm |
| Language: | English |
| Abstract: | The objective of this MSc thesis is to prepare biodegradable PLLA fibers under various fiber forming conditions and to measure their mechanical properties. Biodegradable PLLA fibers with different molecular weights have been prepared in this study by a two-step melt-spinning process, i.e., melt-extrusion and hot-drawing. After melt-extrusion, the as-spun PLLA fibers did not exhibit sufficient mechanical properties for applications in bond repairs. They exhibited low tensile strength and low modulus, which were difficult for further processing. In order to improve the mechanical properties, the method hot-drawing was applied to these fibers. By optimizing hot-drawing parameters like draw temperature, draw ratio, fiber feeding speed and fiber taking-up speed, PLLA fiber with 500 MPa tensile strength and 6 GPa Young's modulus could be obtained. In this study, a hot-drawing apparatus was designed and fabricated. Heat plates were installed in a thermally insulated metal casing and the heating profile throughout the 600mm hot-drawing path has been recorded. Draw temperature from 110C to 160C was applied to PLLA with molecular weight 150,000 (PLLA-帢); draw temperature from 110C to 150C was applied to PLLA with molecular weight 112,900 (PLLA-帣). After the hot-drawing operation, all the fiber samples were heat-treated at 120C for l0mins. The samples were then tested in a Hounsfield machine to obtain their tensile strength, Young's modulus, yield strength, percentage of elongation at break and the maximum draw ratio. The relationship between the tensile strength and draw temperature at maximum draw ratio was studied using a linear regression. |
| Rights: | All rights reserved |
| Access: | restricted access |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| b15289254.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 3.15 MB | Adobe PDF | View/Open |
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