Date of Award

Spring 2003

Document Type

Thesis

Degree Name

Master of Science in Chemical Engineering - (M.S.)

Department

Chemical Engineering

First Advisor

Marino Xanthos

Second Advisor

Costas G. Gogos

Third Advisor

Michael Chien-Yueh Huang

Abstract

In attempts to address the growing need of materials with controlled degradation characteristics and good mechanical properties for tissue engineering applications, composites based on biodegradable polymers and a potentially bioactive novel inorganic synthetic filler were produced and characterized. Composites were produced by solution mixing of a commercial polylactic acid, as well as a biodegradable thermoplastic polyester based on butylene adipate/succinate, with synthetic magnesium/aluminum carbonate minerals, known as hydrotalcites. Two types of hydrotalcites, at 30 wto/o filler level, were used: surface coated and uncoated. Composites were also melt-mixed in a twin-screw extruder for comparison.

Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and Melt Rheology were used to characterize the unfilled polymers and their composites. Results of long-term degradation data in vitro in a PBS solution are also presented. The polylactic acid composites showed significant differences compared to the unfilled polymers and the copolyester composites. The copolyester composites showed only slight thermal and hydrolytic short and long-term degradation. By contrast, hydrotalcites appear to promote in all cases degradation of the matrix in the polylactic acid composites. During the course of long-term degradation of the polylactic acid and its composites, Elemental Analysis for released Mg and Al ions was performed, as well as measurement of pH changes. Scanning Electron Microscopy was also used to study morphological changes of the composites. Further investigation is needed involving degradation experiments in vivo for the most promising polylactic acid/hydrotalcite composites.

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